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Filed Pursuant to rule 424(b)(4)
Registration Nos. 333-203267 and 333-203887

PROSPECTUS

11,250,000 American Depositary Shares

Representing 67,500,000 Ordinary Shares

Adaptimmune Therapeutics plc

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              This is Adaptimmune Therapeutics plc's initial public offering. We are selling American Depositary Shares, or ADSs. Each ADS represents 6 ordinary shares, par value £0.001 per share.

              The initial public offering price is $17.00 per ADS. Currently, no public market exists for the ADSs or ordinary shares. We have received approval to list the ADSs on the Nasdaq Global Select Market under the symbol "ADAP."

              We are an "emerging growth company" as that term is used in the Jumpstart Our Business Startups Act of 2012 and, as such, have elected to comply with certain reduced public company reporting requirements for this prospectus and future filings.

              Investing in our ADSs involves risks that are described in the "Risk Factors" section beginning on page 12 of this prospectus.

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              The underwriters may also exercise their option to purchase up to an additional 1,687,500 ADSs from us, at the public offering price, less the underwriting discount, for 30 days after the date of this prospectus.

              Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

              The ADSs will be ready for delivery on or about May 11, 2015.

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Joint Book-Running Managers

Lead Manager

Guggenheim Securities

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The date of this prospectus is May 5, 2015

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              Neither we nor the underwriters have authorized anyone to provide you with information other than that contained in this prospectus or in any free writing prospectus prepared by or on behalf of us or to which we have referred you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give to you. We are offering to sell our ADSs, and seeking offers to buy our ADSs, only in jurisdictions where offers and sales are permitted. The information contained in this prospectus is accurate only as of the date of this prospectus, regardless of the time of delivery of this prospectus or any sale of our ADSs.

              Neither we nor the underwriters have taken any action to permit a public offering of our ADSs or the possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than the United States. You are required to inform yourself about and to observe any restrictions relating to this offering and the distribution of this prospectus.

              Through and including May 30, 2015 (the 25^th day after the date of this prospectus), all dealers effecting transactions in these securities, whether or not participating in this offering, may be required to deliver a prospectus. This is in addition to the dealers' obligation to deliver a prospectus when acting as an underwriter and with respect to an unsold allotment or subscription.

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              Adaptimmune has a U.K. trademark for "Adaptimmune" and has filed trademark applications for the Adaptimmune logo. The Adaptimmune logo and other trademarks or service marks of Adaptimmune Therapeutics plc appearing in this prospectus are the property of Adaptimmune. Trade names, trademarks and service marks of other companies appearing in this prospectus are the property of their respective owners.

ABOUT THIS PROSPECTUS

              On April 1, 2015, we completed the corporate reorganization described under "Corporate Reorganization." Pursuant to this reorganization, on February 23, 2015, Adaptimmune Limited became a wholly-owned subsidiary of Adaptimmune Therapeutics Limited, a recently formed holding company with nominal assets and liabilities, which has not conducted any operations prior to this offering other than acquiring Adaptimmune Limited. On April 1, 2015, pursuant to the final step in our corporate reorganization, Adaptimmune Therapeutics Limited re-registered as a public limited company and our name was changed from Adaptimmune Therapeutics Limited to Adaptimmune Therapeutics plc.

              Unless otherwise indicated or the context otherwise requires, all references in this prospectus to "Adaptimmune Limited," "Adaptimmune Therapeutics Limited," "Adaptimmune Therapeutics plc," the "Company," "we," "our," "ours," "us" or similar terms refer to (i) Adaptimmune Limited and its subsidiary prior to the acquisition of Adaptimmune Limited by Adaptimmune Therapeutics Limited, (ii) Adaptimmune Therapeutics Limited and its subsidiaries after the acquisition of Adaptimmune Limited by Adaptimmune Therapeutics Limited, and (iii) Adaptimmune Therapeutics plc and its subsidiaries after the re-registration of Adaptimmune Therapeutics Limited as a public limited company. See "Corporate Reorganization."

PRESENTATION OF FINANCIAL INFORMATION

              All references in this prospectus to "$" are to U.S. dollars and all references to "£" are to pounds sterling. Solely for the convenience of the reader, unless otherwise indicated, all pounds sterling amounts as of and for the year ended June 30, 2014 and the six months ended December 31, 2014 have been translated into U.S. dollars at the rate of £1.00 = $1.5578, which was the exchange rate at December 31, 2014. These translations should not be considered representations that any such amounts have been, could have been or could be converted into U.S. dollars at that or any other exchange rate as of that or any other date.

              We have historically conducted our business through Adaptimmune Limited and its subsidiary, and therefore our historical financial statements present the results of operations of Adaptimmune Limited. Following this offering, and after the consummation of the transactions described under "Corporate Reorganization," our financial statements will present the consolidated results of operations of Adaptimmune Therapeutics plc.

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RISK FACTORS

              Investing in the ADSs involves a high degree of risk. You should carefully consider the following risk factors as well as all the other information contained in this prospectus, including our consolidated financial statements, before making an investment decision regarding our securities. If any of these risks materialize, our business, results of operations or financial condition could suffer, the price of the ADSs could decline and you could lose part or all of your investment.

Risks Related to Our Financial Condition and Capital Requirements

We are a clinical-stage biopharmaceutical company with no commercial products and prediction of future performance is very difficult.

              We are a clinical-stage biopharmaceutical company focused on novel cancer immunotherapy products. We have no products or therapeutics approved for commercial sale and have not generated any revenue from product supplies or royalties. Our therapeutic candidates are based on engineered T-cell receptors, or TCRs, and are new and largely unproven. Our limited operating history, particularly in light of the rapidly evolving cancer immunotherapy field, may make it difficult to evaluate our current business and predict our future performance. Investment in biopharmaceutical product development is highly speculative because it entails substantial upfront capital expenditures and significant risk that any potential product candidate will fail to demonstrate adequate effect or an acceptable safety profile, gain regulatory approval and become commercially viable. Our inability to address these risks successfully would have a materially adverse effect on our business and prospects.

We have incurred net losses every year since our inception and expect to continue to incur net losses in the future.

              We have generated losses since our inception in 2008, during which time we have devoted substantially all of our resources to research and development efforts relating to our TCR therapeutic candidates, including engaging in activities to manufacture and supply our TCR therapeutic candidates for clinical trials in compliance with current good manufacturing practices, or cGMP, conducting clinical trials of our TCR therapeutic candidates, providing general and administrative support for these operations and protecting our intellectual property. We do not have any products approved for sale and have not generated any revenue from product supplies or royalties. Based on our current plans, we do not expect to generate product or royalty revenues unless and until we obtain marketing approval for, and commercialize, any of our TCR therapeutic candidates.

              For the years ended June 30, 2013 and 2014, we incurred net losses of £5.6 million and £7.5 million, respectively. As of June 30, 2014, we had an accumulated deficit of £18.9 million. We expect to continue incurring significant losses as we continue with our research and development programs and to incur general and administrative costs associated with our operations. The extent of funding required to develop our product candidates is difficult to estimate given the novel nature of our TCR therapeutic candidates and their un-proven route to market. Our profitability is dependent upon the successful development, approval, and commercialization of our TCR therapeutic candidates, successfully achieving GlaxoSmithKline, or GSK, milestones and achieving a level of revenues adequate to support our cost structure. We may never achieve profitability, and unless and until we do, we will continue to need to raise additional cash.

We have never generated any revenue from sales of our TCR therapeutic candidates and our ability to generate revenue from sales of our TCR therapeutic candidates and become profitable depends significantly on our success in a number of factors.

              We have no TCR therapeutic candidates approved for commercial sale, have not generated any revenue from sales of our TCR therapeutic candidates, and do not anticipate generating any revenue

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from sales of our TCR therapeutic candidates until some time after we receive regulatory approval, if at all, for the commercial sale of a TCR therapeutic candidate. We intend to fund future operations through milestone payments under our collaboration and license agreement with GSK and through additional equity financings. Our ability to generate revenue and achieve profitability depends on our success in many factors, including:

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completing research regarding, and preclinical and clinical development of, our TCR therapeutic candidates;



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obtaining regulatory approvals and marketing authorizations for our TCR therapeutic candidates for which we complete clinical trials;



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developing sustainable and scalable manufacturing and supply processes for our TCR therapeutic candidates, including establishing and maintaining commercially viable supply relationships with third parties and establishing our own commercial manufacturing capabilities and infrastructure;



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launching and commercializing TCR therapeutic candidates for which we obtain regulatory approvals and marketing authorizations, either directly or with a collaborator or distributor;



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obtaining market acceptance of our TCR therapeutic candidates as viable treatment options;



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addressing any competing technological and market developments;



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identifying, assessing, acquiring and/or developing new TCR therapeutic candidates;



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maintaining, protecting, and expanding our portfolio of intellectual property rights, including patents, trade secrets and know-how; and



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attracting, hiring and retaining qualified personnel.

              Even if one or more of our TCR therapeutic candidates is approved for commercial sale, we anticipate incurring significant costs associated with commercializing any approved TCR therapeutic candidate. Our expenses could increase beyond expectations if the U.S. Food and Drug Administration, or the FDA, or any other regulatory agency requires changes to our manufacturing processes or assays, or for us to perform preclinical programs and clinical or other types of trials in addition to those that we currently anticipate. If we are successful in obtaining regulatory approvals to market one or more of our TCR therapeutic candidates, our revenue will be dependent, in part, upon the size of the markets in the territories for which we gain regulatory approval, the accepted price for the TCR therapeutic candidate, the ability to get reimbursement at any price, and whether we own the commercial rights for that territory. If the number of our addressable disease patients is not as significant as we estimate, the indication approved by regulatory authorities is narrower than we expect, or the reasonably accepted population for treatment is narrowed by competition, physician choice or treatment guidelines, we may not generate significant revenue from sales or supplies of such TCR therapeutic candidates, even if approved. If we are not able to generate revenue from the sale of any approved TCR therapeutic candidates, we may never become profitable.

If we fail to obtain additional financing, we may be unable to complete the development and commercialization of our TCR therapeutic candidates.

              Our operations have required substantial amounts of cash since inception. We expect to continue to spend substantial amounts to continue the development of our TCR therapeutic candidates, including future clinical trials. If we receive approval for any of our TCR therapeutic candidates, we will require significant additional amounts in order to launch and commercialize these therapeutic candidates.

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              As of December 31, 2014, we had $101.5 million of cash and cash equivalents and $24.8 million of short-term deposits. We estimate that our net proceeds from this offering will be approximately $175.7 million, based on the initial public offering price of $17.00 per ADS. We expect to use the net proceeds from this offering to advance and accelerate the clinical development of our MAGE A-10 TCR therapeutic candidate, to further develop and enhance our manufacturing capabilities and secure a commercially viable manufacturing platform for all of our TCR therapeutic candidates, to advance additional TCR therapeutic candidates into preclinical testing and progress such TCR therapeutic candidates through to clinical trials as quickly as possible and to fund working capital, including other general corporate purposes. We believe that such proceeds, our existing cash, and cash equivalents together with milestone payments to us under the GSK collaboration and license agreement will be sufficient to fund our operations for the foreseeable future, including for at least the next 24 months. However, changing circumstances beyond our control may cause us to increase our spending significantly faster than we currently anticipate. We may require additional capital for the further development and commercialization of our TCR therapeutic candidates and may need to raise additional funds sooner if we choose to expand more rapidly than we presently anticipate.

              We cannot be certain that additional funding will be available on acceptable terms, or at all. We have no committed source of additional capital and if we are unable to raise additional capital in sufficient amounts or on terms acceptable to us, we may have to significantly delay, scale back or discontinue the development or commercialization of our TCR therapeutic candidates or other research and development initiatives. Our license and supply agreements may also be terminated if we are unable to meet the payment obligations under these agreements. We could be required to seek collaborators for our TCR therapeutic candidates at an earlier stage than otherwise would be desirable or on terms that are less favorable than might otherwise be available or relinquish or license on unfavorable terms our rights to our TCR therapeutic candidates in markets where we otherwise would seek to pursue development or commercialization ourselves. Any of the above events could significantly harm our business, prospects, financial condition and results of operations and cause the price of our ADSs to decline.

Risks Related to the Development of Our TCR Therapeutic Candidates

Our business is highly dependent on our lead NY-ESO TCR therapeutic candidate, which will require significant additional clinical testing before we can seek regulatory approval and begin commercialization of any of our TCR therapeutic candidates.

              There is no guarantee that any of our TCR therapeutic candidates will achieve regulatory approval or proceed to the next stage of clinical programs. The process for obtaining marketing approval for any candidate is very long and risky and there will be significant challenges for us to address in order to obtain marketing approval, if at all.

              There is no guarantee that the results obtained in current clinical trials for our NY-ESO TCR therapeutic candidate will be sufficient to plan one or more pivotal clinical trials and obtain regulatory approval or marketing authorization. Negative results in this lead clinical program of our NY-ESO TCR therapeutic candidate may also impact our ability to obtain regulatory approval for other TCR therapeutic candidates, either at all or within anticipated timeframes because, although the TCR therapeutic candidate may target a different cancer peptide, the underlying technology platform, manufacturing process and development process is the same for all of our TCR therapeutic candidates. Accordingly, a failure in any one program may affect the ability to obtain regulatory approval to continue or conduct clinical programs for other TCR therapeutic candidates.

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We may not be able to submit INDs, or the foreign equivalent outside of the United States, to commence additional clinical trials for our MAGE A-10 or any other TCR therapeutic candidates on the timeframes we expect, and even if we are able to, the FDA or comparable foreign regulatory authorities may not permit us to proceed with planned clinical trials.

              We are currently undergoing preclinical development of our TCR therapeutic candidate targeting MAGE A-10. Progression of this TCR therapeutic candidate or any other TCR therapeutic candidate into clinical trials is inherently risky and dependent on the results obtained in preclinical programs, the results of other clinical programs and results of third-party programs that utilize common components, such as production of the lentiviral vector lot used for production and administration of our TCR therapeutic candidate. If results are not available when expected or problems are identified during therapy development, we may experience significant delays in development of pipeline products and of existing clinical programs, which may impact our ability to receive regulatory approval. This may also impact our ability to achieve certain financial milestones and the expected timeframes to market any of our TCR therapeutic candidate. Failure to submit further INDs or the foreign equivalent and commence additional clinical programs will significantly limit our opportunity to generate revenue.

Our TCR therapeutic candidates being developed may have potentially fatal cross-reactivity to other peptides or protein sequences within the body.

              One of our prior TCR therapeutic candidates, designed to target a MAGE-A3 cancer-specific peptide, recognized another unrelated peptide from a protein called TITIN, expressed within normal cardiac and other muscle tissues in patients. As a result of this cross-reactivity to the TITIN protein in the heart, two patients died during our MAGE-A3 clinical program, the program was put on pause, then formally placed on hold by the FDA, after which we abandoned the program. We subsequently developed a preclinical safety testing program that identifies potential cross-reactivity risks that has not yet been used for our existing TCR therapeutic candidates, and accordingly, there may be gaps or other problems detected in the testing program at a later date. Even with the use of this testing program, there can be no guarantee that the FDA will permit us to begin clinical trials of any additional TCR therapeutic candidates or that other off-target cross-reactivity will not be identified or present in any patient group. Failure to develop an effective preclinical safety testing program will prevent or delay clinical trials of any TCR therapeutic candidate. Detection of any cross-reactivity will halt or delay any ongoing clinical trials for any TCR therapeutic candidate and prevent or delay regulatory approval. Given that the underlying technology platform, manufacturing process and development process is the same for all of our TCR therapies, issues pertaining to cross-reactivity for one TCR therapeutic candidate may impact our ability to obtain regulatory approval for other TCR therapeutic candidates undergoing development and clinical trials, which would significantly harm our business, prospects, financial condition and results of operations.

              Cross-reactivity or allo-reactivity (binding to peptides presented on other Human Leukocyte Antigen, or HLA, types) could also occur where the affinity-enhanced engineered TCR resulting from administration of our TCR therapeutic candidate binds to peptides presented by HLAs other than the HLA type for which the relevant TCR was developed. We have also developed a preclinical screening process to identify allo-reactivity risk and have identified such allo-reactivity for one rare allele in the case of our MAGE A10 TCR therapeutic candidate. Any allo-reactivity or other cross-reactivity that impacts patient safety could materially impact our ability to advance our TCR therapeutic candidates into clinical trials or to proceed to market approval and commercialization. In addition, there is no guarantee that exclusion of patients with the allo-reactive allele will successfully eliminate the risk of allo-reactivity, and serious side effects for patients may still exist. Given that the underlying technology platform, manufacturing process and development process are the same for all of our TCR therapeutic candidates, issues pertaining to allo-reactivity for one TCR therapeutic candidate may impact our ability to obtain regulatory approval for other TCR therapeutic candidates undergoing development

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and clinical trials, which would significantly harm our business, prospects, financial condition and results of operations.

Our T-cell therapy, which is a type of cell therapy that uses gene therapy technology, represents a novel approach to cancer treatment that could result in heightened regulatory scrutiny, delays in clinical development, or delays in or our inability to achieve regulatory approval or commercialization of our TCR therapeutic candidates.

              Use of our TCR therapeutic candidates to treat a patient requires the use of gene therapy technology, which involves combining the patient's T cells with our lentiviral delivery vector containing the gene for our affinity-enhanced engineered TCR. This is a novel treatment approach that carries inherent development risks. We are therefore constantly evaluating and adapting our TCR therapeutic candidates following the results obtained during development work and the clinical programs. Further development, characterization and evaluation may be required, depending on the results obtained, in particular where such results suggest any potential safety risk for patients. The need to develop further assays, or to modify in any way the protocols related to our TCR therapeutic candidates to improve safety or effectiveness, may delay the clinical program, regulatory approval or commercialization, if approved at all, of any TCR therapeutic candidate. Consequently, this may have a material impact on our ability to receive milestone payments and/or generate revenues from our TCR therapeutic candidates.

              In addition, given the novelty of our TCR therapeutic candidates, the end users and medical personnel require a substantial amount of education and training in their administration of our TCR therapeutic candidates. Regulatory authorities have very limited experience with commercial engineered cell therapies and TCR therapeutic candidates for the treatment of cancer. As a result, regulators may be more risk adverse or require substantial dialogue and education as part of the normal regulatory approval process for each stage of development of any TCR therapeutic candidate. To date, no gene therapy products have been approved in the United States and only one has been approved in the European Union under exceptional circumstances. Consequently, it is difficult to predict and evaluate what additional regulatory hurdles may apply to the development of our TCR therapeutic candidates and whether additional investment, time or resources will be required to overcome any such hurdles.

              Additionally, because our technology involves the genetic modification of patient cells ex-vivo using a viral vector, we are subject to many of the challenges and risks of gene therapy, including the following challenges:

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Regulatory requirements governing gene and cell therapy products have changed frequently and may continue to change in the future. To date, no products that involve the genetic modification of patient cells have been approved in the United States and only one has been approved in the European Union, or EU.



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Random gene insertion associated with retrovirus-mediated genetically modified products, known as insertional oncogenesis, could lead to lymphoma, leukemia or other cancers, or other aberrantly functioning cells. Insertional oncogenesis was seen in early gene therapy studies conducted outside of the United States in 2003. In those studies, insertional oncogenesis resulted in patients developing leukemia following treatment with the relevant gene therapy, with one patient dying. As a result of the data from those studies, the FDA temporarily halted gene therapy trials in the United States. The previous trials involved modification of stem cells rather than T cells and utilized a murine gamma-retroviral vector rather than a lentiviral vector. We cannot guarantee that insertional oncogenesis resulting from administration of our TCR therapeutic candidates will not occur.

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Although our viral vectors are not able to replicate, there may be a risk with the use of retroviral or lentiviral vectors that they could undergo recombination and lead to new or reactivated pathogenic strains of virus or other infectious diseases.



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There is the potential for delayed adverse events following exposure to gene therapy products due to persistent biological activity of the genetic material or other components of products used to carry the genetic material. In part for this reason, the FDA recommends a 15-year follow-up observation period for all surviving patients who receive treatment using gene therapies in clinical trials. We may need to adopt such an observation period for our therapeutic candidates; however, the FDA does not require that the tracking be complete prior to its review of the Biologics License Application, or BLA.



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Clinical trials using genetically modified cells conducted at institutions that receive funding for recombinant DNA research from the U.S. National Institutes of Health, or NIH, are subject to review by the NIH Office of Biotechnology Activities' Recombinant DNA Advisory Committee, or RAC. Although the FDA decides whether individual protocols may proceed, the RAC review process can delay or impede the initiation of a clinical trial, even if the FDA has reviewed the study and approved its initiation.

              If adverse events of the type described above were to occur, further advancement of our clinical trials could be halted or delayed, which would have a material adverse effect on our business and operations. In addition, heightened regulatory scrutiny of gene therapy product candidates may result in delays and increased costs in bringing a product candidate to market, if at all. Delay or failure to obtain, or unexpected costs in obtaining, the regulatory approval necessary to bring a potential product to market could decrease our ability to generate revenue in the future.

T-cell therapy is a novel approach to cancer treatment that creates significant increased risk in terms of side-effect profile, ability to satisfy regulatory requirements associated with clinical trials and the long-term viability of administered TCR therapeutic candidates.

              Development of a pharmaceutical or biologic therapy or product has inherent risks based on differences in patient population and responses to therapy and treatment. The mechanism of action and impact on other systems and tissues within the human body following administration of our TCR therapeutic candidate is not completely understood, which means that we cannot predict the long-term effects of treatment with our TCR therapeutic candidates.

              We are aware that certain patients do not respond to our TCR therapeutic candidates and that other patients may relapse or cease to present the peptide being targeted by such TCR therapeutic candidates. The percentage of the patient population in which these events may occur is unknown, but the inability of patients to respond and the possibility of relapse may impact our ability to conduct clinical trials, to obtain regulatory approvals, if at all, and to successfully commercialize any TCR therapeutic candidate.

              Our clinical trials are still in the early stages, and it is difficult to predict the results that will be obtained in ongoing clinical trials or the next phase or phases of any clinical program. There is a significant risk at each stage that serious adverse events or low efficacy, as well as less favorable safety profiles, will prevent our TCR therapeutic candidates from proceeding further. Events that have been reported in more than 15% of patients and considered at least possibly related to our NY-ESO TCR therapeutic candidate include diarrhea, rash, fever, fatigue, disturbed liver function tests, nausea and anemia. Our NY-ESO TCR therapeutic candidate itself has been well tolerated with relatively few related adverse events above grade 3. Several events have been classified as serious adverse events. Related serious adverse events occuring in more than one patient include neutropenia, pyrexia, Cytokine-Release Syndrome, Graft Versus Host Disease and dehydration. Graft Versus Host Disease, which impacts the gastrointestinal tract, has only been reported in our myeloma transplant study

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involving auto-SCT. We have also seen a suspected unexpected serious adverse reaction of grade 4 supraventricular tachycardia, or SVT, in one patient.

              The utility of our TCR therapeutic candidates may depend on persistence and potency of the modified T cells within a patient's body following administration of our TCR therapeutic candidate. The duration of persistence and the factors affecting such persistence and potency are not completely understood which presents an additional risk to the ongoing development and use of our TCR therapeutic candidates.

              Because administration of our TCR therapeutic candidates is patient-specific, the process requires careful handling of patient-specific products and fail-safe tracking, namely the need to ensure that the tracking process is without error and that patient samples are tracked from patient removal, through manufacturing and re-administration to the same patient. It is difficult to predict the investment in appropriate mechanisms and systems that will be required to ensure such fail-safe tracking and there is always a risk of a failure in any such system. Inability to develop or adopt an acceptable fail-safe tracking methodology and handling regime may delay or prevent us from receiving regulatory approval.

Validation of our TCR therapeutic candidates requires access to human samples but there is no guarantee that such samples can be obtained or, if they can be obtained, that the terms under which they are provided will be favorable to us.

              Certain of the steps involved in validating and carrying out safety testing in relation to our TCR therapeutic candidates require access to samples (e.g., tissues samples or cell samples) from third parties. Such samples may be obtained from universities or research institutions and will often be provided, subject to satisfaction of certain terms and conditions. There can be no guarantee that we will be able to obtain samples in sufficient quantities to enable development of and use of the full preclinical safety testing program for all TCR therapeutic candidates undergoing development. In addition, the terms under which such samples are available may not be acceptable to us or may restrict our use of any generated results or require us to make payments to the third parties.

Our TCR therapeutic candidates and their application are not fully scientifically understood and are still undergoing validation and investigation.

              Our TCR therapeutic candidates and their potential associated risks are still under investigation. For example, there is a potential risk that, given that the TCR chains are produced separately and then assembled within patient T cells into full TCRs, the TCR chains from both transduced and naturally occurring T cells could be assembled into an unintended end TCR due to mis-pairing of TCR chains, which could create unknown recognition and cross-reactivity problems within patients. Although this phenomenon has not been reported in humans, it remains a theoretical risk for our TCR therapeutic candidates and is still being studied and investigated. This could delay regulatory approval, if any, for the relevant TCR therapeutic candidates. To the extent that any mis-pairing of TCR chains is identified, either in our or our competitors' clinical trials, additional investment may be required in order to modify relevant TCR therapeutic candidates and to further assess and validate the risk of such mis-pairing to patients. There is also no guarantee that following modification of the relevant TCR therapeutic candidate, such modified TCR therapeutic candidate will remain suitable for patient treatment, that it will eliminate the risk of mis-pairing of TCR chains or that regulatory approval will be obtained at all or on a timely basis in relation to such modified TCR therapeutic candidates. The occurrence of such events could significantly harm our business, prospects, financial condition and results of operations.

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We may not be able to identify and validate additional target peptides or isolate and develop affinity-enhanced TCRs that are suitable for validation and further development.

              The success of our TCR therapeutic candidates depends on both the identification of target peptides presented on cancer cells, which can be bound by TCRs, and isolation and affinity enhancement of TCRs, which can be used to treat patients if regulatory approval is obtained. There is an inherent risk that the number of target peptides that can be identified and/or our ability to develop and isolate suitable TCRs for affinity enhancement could be significantly lower than projected or that no additional TCR therapeutic candidates suitable for further development can be identified. Any failure to identify and validate further target peptides will reduce the number of potential TCR therapeutic candidates that we can successfully develop, which in turn will reduce the commercial opportunities available to us and increase our reliance on our NY-ESO TCR therapeutic candidate.

              In addition, there is no guarantee that our attempts to develop further TCR therapeutic candidates will result in candidates for which the safety and efficacy profiles enable progression to and through preclinical testing. Failure to identify further candidates for progression into preclinical testing and clinical programs will significantly impact our commercial returns, increase our reliance on the success of our existing NY-ESO and MAGE A-10 TCR therapeutic candidate programs and may significantly harm our business, prospects, financial condition and results of operations. If resources become limited or if we fail to identify suitable target peptides, naturally occurring TCRs or affinity-enhanced TCRs, our ability to submit INDs for further TCR therapeutic candidates may be delayed or never realized, which would have a materially adverse effect on our business.

We may encounter substantial delays in our clinical trials or may not be able to conduct our trials on the timelines we expect.

              Conduct of clinical trials is dependent on finding clinical sites prepared to carry out the relevant clinical trials, recruitment of patients both in terms of number and type of patients and general performance of the relevant clinical site. It is difficult to predict how quickly we will be able to recruit suitable patients, find suitable sites, begin clinical programs and administer our TCR therapeutic candidates.

              In addition, our clinical trials will compete with other clinical trials for TCR therapeutic candidates that are in the same therapeutic areas as our TCR therapeutic candidates, which will reduce the number and types of patients available to us, because some patients who might have opted to enroll in our trials may instead opt to enroll in a trial being conducted by one of our competitors. Because the number of qualified clinical investigators is limited, we currently, and expect to continue to, conduct some of our clinical trials at the same clinical trial sites that some of our competitors use, which will reduce the number of patients who are available for our clinical trials at such clinical trial sites. Moreover, because our TCR therapeutic candidates represent a departure from more commonly used methods for cancer treatment, potential patients and their physicians may opt to use conventional therapies, such as chemotherapy and hematopoietic cell transplantation, rather than enrollment in any of our current or future clinical trials.

              Even if we are able to enroll a sufficient number of patients in our clinical trials, delays in patient enrollment may result in increased costs or may affect the timing or outcome of the planned clinical trials, which could prevent completion of these trials and adversely affect our ability to advance the development of our TCR therapeutic candidates.

We may not be able to develop or obtain approval for the analytical assays and companion diagnostics required for commercialization of our TCR therapeutic candidates.

              Administration of our TCR therapeutic candidates requires the use of an immuno-chemistry screening assay in which patients are screened for the presence of the cancer peptide targeted by our

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TCR therapeutic candidates. This assay requires the identification of suitable antibodies which can be used to identify the presence of the relevant target cancer peptide.

              If safe and effective use of a biologic product depends on an in vitro diagnostic, such as a test to detect patients with HLA type A2, then the FDA generally requires approval or clearance of the diagnostic, known as a companion diagnostic, concurrently with approval of the therapeutic product. To date, the FDA has generally required in vitro companion diagnostics intended to select the patients who will respond to cancer treatment to obtain a pre-market approval, or PMA, which can take up to several years, for that diagnostic simultaneously with approval of the biologic product.

              We expect that, for our NY-ESO TCR therapeutic candidate, the FDA and similar regulatory authorities outside of the United States will require the development and regulatory approval of a companion diagnostic assay as a condition to approval. We also expect that the FDA may require PMA supplemental approvals for use of that same companion diagnostic as a condition of approval of additional TCR therapeutic candidates. We do not have experience or capabilities in developing or commercializing these companion diagnostics and plan to rely in large part on third parties to perform these functions. Companion diagnostic assays are subject to regulation by the FDA and similar regulatory authorities outside of the United States as medical devices and require separate regulatory approval prior to the use of such diagnostic assays with our TCR therapeutic candidates.

              If we, or any third parties that we engage to assist us, are unable to successfully develop companion diagnostic assays for use with our TCR therapeutic candidates, or are unable to obtain regulatory approval or experience delays in either development or obtaining regulatory approval, we may be unable to identify patients with the specific profile targeted by our TCR therapeutic candidates for enrollment in our clinical trials. Accordingly, further investment may be required to further develop or obtain the required regulatory approval for the relevant companion diagnostic assay, which would delay or substantially impact our ability to conduct further clinical trials or obtain regulatory approval.

Manufacturing and administering our TCR therapeutic candidates is complex and we may encounter difficulties in production, particularly with respect to process development or scaling up of our manufacturing capabilities. If we encounter such difficulties, our ability to provide supply of our TCR therapeutic candidates for clinical trials or for commercial purposes could be delayed or stopped.

              The process of manufacturing and administering our TCR therapeutic candidates is complex and highly regulated. The manufacture of our TCR therapeutic candidates involves complex processes, including manufacture of a lentiviral delivery vector containing the gene for our affinity-enhanced engineered TCR. Administration of our TCR therapeutic candidates includes harvesting white blood cells from the patient, isolating certain T cells from the white blood cells, combining patient T cells with our lentiviral delivery vector through a process known as transduction, expanding the transduced T cells to obtain the desired dose, and ultimately infusing the modified T cells back into the patient's body. As a result of the complexities, our manufacturing and supply costs are likely to be higher than those at more traditional manufacturing processes and the manufacturing process is less reliable and more difficult to reproduce. Our manufacturing process is and will be susceptible to product loss or failure due to logistical issues, including manufacturing issues associated with the differences in patients' white blood cells, interruptions in the manufacturing process, contamination, equipment or reagent failure, supplier error and variability in TCR therapeutic candidate and patient characteristics. Even minor deviations from normal manufacturing processes could result in reduced production yields, product defects, and other supply disruptions.

              If for any reason we lose a patient's white blood cells or such material gets contaminated or later processing steps fail at any point, the manufacturing process of the TCR therapeutic candidate for that patient will need to be completely restarted and the resulting delay may adversely affect that patient's outcome. If microbial, viral or other contaminations are discovered in our TCR therapeutic

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candidates or in the manufacturing facilities in which our TCR therapeutic candidates are made or administered, such manufacturing facilities may need to be closed for an extended period of time to investigate and remedy the contamination.

              As our TCR therapeutic candidates progress through preclinical programs and clinical trials towards approval and commercialization, it is expected that various aspects of the manufacturing and administration process will be altered in an effort to optimize processes and results. We have already identified some improvements to our manufacturing and administration processes, but these changes may not achieve the intended objectives, and could cause our TCR therapeutic candidates to perform differently and affect the results of planned clinical trials or other future clinical trials. In addition, such changes may require amendments to be made to regulatory applications which may further delay the timeframes under which modified manufacturing processes can be used for any TCR therapeutic candidate. For example, we are planning to make changes to the manufacturing process for cell products and vector material used in our NY-ESO TCR therapeutic candidate for which we are likely to need to conduct small clinical trials to gather safety data for each of the different indications for which larger clinical trials are planned. We intend to add an additional cohort of patients receiving our NY-ESO TCR therapeutic candidate manufactured with the new process to our ongoing Phase 1/2 clinical trials in synovial sarcoma to gather such safety data. If our NY-ESO TCR therapeutic candidate manufactured under the new process has a worse safety or efficacy profile than the prior investigational product, we may need to re-evaluate the use of that manufacturing process, which could significantly delay or even terminate the progress of our clinical trials.

              Developing a commercially viable process is a difficult and uncertain task, and there are risks associated with scaling to the level required for advanced clinical trials or commercialization, including, among others, increased costs, potential problems with process scale-out, process reproducibility, stability issues, lot consistency, and timely availability of reagents or raw materials. We may ultimately be unable to reduce the expenses associated with our TCR therapeutic candidates to levels that will allow us to achieve a profitable return on investment.

              We are in the process of developing and transferring new processes to facilitate such manufacture into third-party contract suppliers. Such process scale-up and transfer will require a demonstration of comparability between the product used in clinical trials and the potential commercial product manufactured by the new process at the new facility. If we are unable to demonstrate that our commercial scale product is comparable to the product used in clinical trials, we may not receive regulatory approval for that product without additional clinical trials. We cannot guarantee that we will be able to make the required modifications within currently anticipated timeframes or that such modifications, when made, will obtain regulatory approval or that the new processes or modified processes will successfully be transferred to the third party contract suppliers within currently anticipated timeframes. Any delay or failure in obtaining approval will impact our ability to commercialize and obtain marketing approval for our TCR therapeutic candidates. Such failure may also impact our collaboration with GSK and result in GSK not exercising options or not developing any of our additional TCR therapeutic candidates. Even if we are successful, our manufacturing capabilities could be affected by increased costs, unexpected delays, equipment failures, labor shortages, natural disasters, power failures and numerous other factors that could prevent us from realizing the intended benefits of our manufacturing strategy, which in turn could have a material adverse effect on our business. We have insurance to cover certain business interruption events, particularly research and development expenditure (capped at approximately £10 million) and committed costs (capped at £250,000). However, because our level of insurance is capped, it may be insufficient to fully compensate us if any of these events were to occur in the future.

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Our manufacturing process needs to comply with FDA regulations and foreign regulations relating to the quality and reliability of such processes. Any failure to comply with relevant regulations could result in delays in or termination of our clinical programs and suspension or withdrawal of any regulatory approvals.

              In order to commercially produce our products, we will need to comply with the FDA's cGMP regulations and guidelines. We may encounter difficulties in achieving quality control and quality assurance and may experience shortages in qualified personnel. We are subject to inspections by the FDA and comparable agencies in other jurisdictions to confirm compliance with applicable regulatory requirements. Any failure to follow cGMP or other regulatory requirements or delay, interruption or other issues that arise in the manufacture, fill-finish, packaging, or storage of our TCR therapeutic candidates as a result of a failure of our facilities or the facilities or operations of third parties to comply with regulatory requirements or pass any regulatory authority inspection could significantly impair our ability to develop and commercialize our TCR therapeutic candidates, including leading to significant delays in the availability of our TCR therapeutic candidates for our clinical trials or the termination of or suspension of a clinical trial, or the delay or prevention of a filing or approval of marketing applications for our TCR therapeutic candidates. Significant non-compliance could also result in the imposition of sanctions, including warning or untitled letters, fines, injunctions, civil penalties, failure of regulatory authorities to grant marketing approvals for our TCR therapeutic candidates, delays, suspension or withdrawal of approvals, license revocation, seizures or recalls of products, operating restrictions and criminal prosecutions, any of which could damage our reputation and our business.

The outcome of clinical trials is uncertain and our clinical trials may fail to demonstrate adequately the safety and efficacy of any of our TCR therapeutic candidates which would prevent or delay regulatory approval and commercialization.

              There is a risk in any clinical trial that side effects from our TCR therapeutic candidates will require a hold on, or termination of, our clinical programs or further adjustments to our clinical programs in order to progress our TCR therapeutic candidate. Our TCR therapeutic candidates are novel and unproven and regulators will therefore require evidence that the TCR therapeutic candidates are safe before permitting clinical trials to commence and evidence that the TCR therapeutic candidates are safe and effective before granting any regulatory approval. In particular, because our TCR therapeutic candidates are subject to regulation as biological products, we will need to demonstrate that they are safe, pure and potent for use in each target indication. The TCR therapeutic candidate must demonstrate an acceptable risk versus benefit profile in its intended patient population and for its intended use. The risk/benefit profile required for product licensure will vary depending on these factors and may include not only the ability to show tumor shrinkage, but also adequate duration of response, a delay in the progression of the disease and/or an improvement in survival. For example, response rates from the use of our TCR therapeutic candidates will not be sufficient to obtain regulatory approval unless we can also show an adequate duration of response.

              Clinical testing is expensive and can take many years to complete, and its outcome is inherently uncertain. Failure can occur at any time during the clinical trial process. Success in preclinical programs and early clinical trials does not ensure that later clinical trials will be successful. Moreover, the results of preclinical programs and early clinical trials of our TCR therapeutic candidates may not be predictive of the results of later-stage clinical trials. To date, we have only obtained interim results from Phase 1/2 clinical trials that are uncontrolled, involve small sample sizes and are of shorter duration than would be required for regulatory approval. There may be other reasons why our early clinical trials are not predictive of later clinical trials. In addition, the results of trials in one set of patients or line of treatment may not be predictive of those obtained in another and protocols may need to be revised based on unexpected early results. For example, in our ovarian cancer trial with our NY-ESO TCR therapeutic candidate, the first patient treated experienced a grade 3 Cytokine-Release

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Syndrome at day seven post-infusion, concomitant with a significant proliferation of the engineered T cells that constituted about 100% of the peripheral blood at day 14. This level of Cytokine-Release Syndrome had not been seen in previous results from trials using our NY-ESO TCR therapeutic candidate. The patient's tumor markers were also falling during this time. To manage the Cytokine-Release Syndrome, the patient was treated with high dose steroids that abrogated the engineered T-cell function. The protocol was then modified to allow for use of the anti-IL6R antibody, tocilizumab, for treatment of Cytokine-Release Syndrome in future patients, which has been shown to control Cytokine-Release Syndrome without abrogating the anti-tumor response. We expect there may be greater variability in results for our TCR therapeutic candidates which are administered on a patient-by-patient basis than for "off-the-shelf" products, like many other biologics. There is typically an extremely high rate of attrition from the failure of TCR therapeutic candidates proceeding through clinical trials. TCR therapeutic candidates in later stages of clinical trials may fail to show the desired safety and efficacy profile despite having progressed through preclinical programs and initial clinical trials. A number of companies in the biopharmaceutical industry have suffered significant setbacks in advanced clinical trials due to lack of efficacy or unacceptable safety issues, notwithstanding promising results in earlier trials. Most biologic candidates that begin clinical trials are never approved by regulatory authorities for commercialization. We cannot therefore guarantee that we will be successful in obtaining the required efficacy and safety profile from the performance of any of our clinical programs.

              In addition, even if such trials are successfully completed, we cannot guarantee that the FDA or foreign regulatory authorities will interpret the results as we do. Accordingly, more trials may be required before we can submit our TCR therapeutic candidate for regulatory approval. To the extent that the results of the trials are not satisfactory to the FDA or foreign regulatory authorities for support of a marketing application, we may be required to expend significant resources, which may not be available to us, to conduct additional trials in support of potential approval of our TCR therapeutic candidates. We cannot predict whether any of our TCR therapeutic candidates will satisfy regulatory requirements at all or for indications in which such TCR therapeutic candidates are currently being evaluated as part of any clinical programs.

We have limited experience conducting clinical trials which may cause a delay in any clinical program and in the obtaining of regulatory approvals.

              Although we have recruited a team that has significant experience with clinical trials, as a company we have limited experience in conducting clinical trials and no experience in conducting clinical trials through to regulatory approval of any TCR therapeutic candidate. In part because of this lack of experience, we cannot be certain that planned clinical trials will begin or be completed on time, if at all. Large-scale trials would require significant additional financial and management resources, and reliance on third-party clinical investigators, contract research organizations, or CROs, or consultants. Relying on third-party clinical investigators or CROs may force us to encounter delays that are outside of our control.

Our TCR therapeutic candidates may have undesirable side effects or have other properties that could halt their clinical development, prevent their regulatory approval, limit their commercial potential or otherwise result in significant negative consequences.

              Where any TCR therapeutic candidate has undesirable side effects, regulatory approval for such therapeutic may be delayed or suspended, or alternatively may be restricted to particular disease indications or states that are more limited than desirable. This could result in the failure of our products reaching the market or a reduction in the patient population for which any TCR therapeutic candidate can be used. Events that have been reported in more than 15% of patients and considered at least possibly related to our NY-ESO TCR therapeutic candidate include diarrhea, rash, fever, fatigue, disturbed liver function tests, nausea and anemia. Our NY-ESO TCR therapeutic candidate itself has

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been well tolerated with relatively few related adverse events above grade 3. Several events have been classified as serious adverse events and include neutropenia, pyrexia, Cytokine-Release Syndrome, Graft Versus Host Disease and dehydration. Graft Versus Host Disease, which impacts the gastrointestinal tract, has only been reported in our myeloma transplant study involving auto-SCT. We have also seen a suspected unexpected serious adverse reaction of grade 4 SVT in one patient.

              Any unacceptable toxicities arising in ongoing clinical programs could result in suspension or termination of those clinical programs. Any suspension or termination will affect other TCR therapeutic candidates and thereby impact our ability to recognize any product revenues. Any side effects may also result in the need to perform additional trials, which will delay regulatory approval for such TCR therapeutic candidate, if at all, and require additional resources and financial investment to bring the relevant TCR therapeutic candidate to market.

              In addition, the impact of TCR therapeutic candidates may vary from patient to patient and this may affect the number of patients who can be successfully treated with our TCR therapeutic candidates. Depending on the nature of the indication, certain patients may need to be excluded from treatment, which could also impact our ability to recruit patients to utilize such therapies or to recruit patients to conduct clinical trials in general for our TCR therapeutic candidates.

Clinical trials are expensive, time-consuming and difficult to implement.

              Clinical trials, depending on the stage, can be costly as well as difficult to implement and define, particularly with technologies that are not tried and tested, such as our TCR therapeutic candidates. These factors can lead to a longer clinical development timeline and regulatory approval process, including a requirement to conduct further or more complex clinical trials in order to obtain regulatory approval. Regulatory authorities may disagree with the design of any clinical program, and designing an acceptable program could lead to increased timeframes for obtaining of approvals, if any. In addition, progression of clinical trials depends the on ability to recruit suitable patients to those trials and delay in recruiting will impact the timeframes of such clinical trials and as a result the timeframes for obtaining regulatory approval, if any, for the relevant TCR therapeutic candidates.

              In particular, eligible patients must be screened for the target peptide and HLA type, which may reduce the number of patients who can be recruited for any clinical program. The ability to administer our TCR therapeutic candidates to patients in accordance with set protocols for the clinical trials and the results obtained depends on patient participation for the duration of the clinical trial, which many of these patients are unable to do because of their late-stage cancer and low or limited life expectancy.

              Although the initial results in our clinical trials to date may suggest a promising tolerability profile, these results may not be indicative of results obtained in later and larger clinical trials. Long-term follow-up of patients from earlier trials may also result in detection of additional side effects or identification of other safety issues. There is no guarantee of success in any clinical trial and there is a very high attrition rate for pharmaceutical or biological compounds entering clinical trials. Any side effects or negative safety issues identified at any stage of clinical development will require additional investigation and assessment which can result in additional costs and resource requirements that could delay or potentially terminate our clinical trials.

We may face difficulty in enrolling patients in our clinical trials.

              We may find it difficult to enroll patients in our clinical trials. For example, in our Phase 1/2 melanoma trial with our NY-ESO TCR therapeutic candidate, there was a delay in enrollment as a result of competition from other emerging therapies. Identifying and qualifying patients, including testing of patients for appropriate target peptides or HLA type, to participate in clinical trials of our TCR therapeutic candidates are critical to our success. The timing of our clinical trials depends on the

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speed at which we can recruit patients to participate in testing our TCR therapeutic candidates. If patients are unwilling to participate in our trials because of negative publicity from adverse events or for other reasons, including competitive clinical trials for similar patient populations, the timeline for recruiting patients, conducting trials and obtaining regulatory approval of potential products may be delayed or prevented. These delays could result in increased costs, delays in advancing our product development, delays in testing the effectiveness of our technology or termination of the clinical trials altogether. We may not be able to identify, recruit and enroll a sufficient number of patients, or those with required or desired characteristics to achieve sufficient diversity in a given trial in order to complete our clinical trials in a timely manner. Patient enrollment is affected by factors including:

•

eligibility criteria for the trial in question, in particular, presenting the correct HLA type and target antigen;



•

severity of the disease under investigation;



•

design of the trial protocol;



•

size of the patient population;



•

perceived risks and benefits of the TCR therapeutic candidate under trial;



•

novelty of the TCR therapeutic candidate and acceptance by oncologists;



•

proximity and availability of clinical trial sites for prospective patients;



•

availability of competing therapies and clinical trials;



•

efforts to facilitate timely enrollment in clinical trials;



•

patient referral practices of physicians; and



•

ability to monitor patients adequately during and after treatment.

              If we have difficulty enrolling a sufficient number of patients to conduct our clinical trials as planned, we may need to delay, limit or terminate ongoing or planned clinical trials, any of which would have an adverse effect on our business.

Our TCR therapeutic candidates for which we intend to seek approval as biologic products may face competition sooner than anticipated.

              The enactment of the Biologics Price Competition and Innovation Act of 2009, or BPCIA, created an abbreviated pathway for the approval of biosimilar and interchangeable biological products. The abbreviated regulatory pathway establishes legal authority for the FDA to review and approve biosimilar biologics, including the possible designation of a biosimilar as "interchangeable" based on its similarity to an existing reference product. Under the BPCIA, an application for a biosimilar product cannot be approved by the FDA until 12 years after the original branded product is approved under a BLA. On March 6, 2015, the FDA approved the first biosimilar product under the BPCIA. However, the law is complex and is still being interpreted and implemented by the FDA and as a result, its ultimate impact, implementation and meaning are subject to uncertainty. While it is uncertain when such processes intended to implement BPCIA may be fully adopted by the FDA, any such processes could have a material adverse effect on the future commercial prospects for our biological products.

              We believe that if our NY-ESO TCR therapeutic candidate is approved as a biological product under a BLA it should qualify for the 12-year period of exclusivity. However, there is a risk that the FDA will not consider our NY-ESO TCR therapeutic candidate or any additional TCR therapeutic candidates to be reference products for competing products, potentially creating the opportunity for generic competition sooner than anticipated. Additionally, this period of regulatory exclusivity does not apply to companies pursuing regulatory approval via their own traditional BLA, rather than via the

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abbreviated pathway. Moreover, the extent to which a biosimilar, once approved, will be substituted for any one of our reference products in a way that is similar to traditional generic substitution for non-biological products is not yet clear, and will depend on a number of marketplace and regulatory factors that are still developing.

              Foreign countries also have abbreviated regulatory pathways for biosimilars and hence even where the FDA does not approve a biosimilar biologic, a biosimilar could be approved using an abbreviated regulatory pathway in other markets where our TCR therapeutic candidates are approved and marketed.

Risks Related to Government Regulation

The FDA regulatory approval process is lengthy and time-consuming, and we may experience significant delays in the clinical development and regulatory approval of our TCR therapeutic candidates.

              We have not previously submitted a BLA to the FDA, or similar approval submissions to comparable foreign authorities. A BLA must include extensive preclinical and clinical data and supporting information to establish the TCR therapeutic candidate's safety and effectiveness for each desired indication. The BLA must also include significant information regarding the chemistry, manufacturing and controls for the product. We expect the novel nature of our TCR therapeutic candidates to create additional challenges in obtaining regulatory approval, if at all. For example, the FDA has limited experience with commercial development of T-cell therapies for cancer. Accordingly, the regulatory approval pathway for our TCR therapeutic candidates may be uncertain, complex, expensive and lengthy, and approval may not be obtained.

              We could also encounter delays if physicians encounter unresolved ethical issues associated with enrolling patients in clinical trials of our TCR therapeutic candidates in lieu of prescribing existing treatments that have established safety and efficacy profiles. Further, a clinical trial may be suspended or terminated by us, the Institutional Review Boards, or IRBs, for the institutions in which such trials are being conducted, the Data Monitoring Committee for such trial, or by the FDA or other regulatory authorities due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site by the FDA or other regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a TCR therapeutic candidate, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial. If we experience termination of, or delays in the completion of, any clinical trial of our TCR therapeutic candidates, the commercial prospects for our TCR therapeutic candidates will be harmed, and our ability to generate product revenue will be delayed. In addition, any delays in completing our clinical trials will increase our costs, slow our product development and approval process and jeopardize our ability to commence product sales and generate revenue.

              GSK may also experience similar difficulties in conducting future clinical trials of licensed TCR therapeutic candidates. Many of the factors that cause, or lead to, a delay in the commencement or completion of clinical trials may ultimately lead to the denial of regulatory approval of our TCR therapeutic candidates.

The FDA regulatory process can be difficult to predict, in particular whether for example accelerated approval processes are available or further unanticipated clinical trials are required will depend on the data obtained in our ongoing clinical trials.

              The regulatory approval process and the amount of time it takes us to obtain regulatory approvals for our TCR therapeutic candidates will depend on the data that are obtained in our ongoing clinical trials and in one or more future registrational or pivotal clinical trials. We may attempt to seek approval on a per indication basis for our TCR therapeutic candidates on the basis of a single pivotal

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trial. While the FDA requires in most cases two adequate and well-controlled pivotal clinical trials to demonstrate the efficacy of a product candidate, a single pivotal trial with other confirmatory evidence may be sufficient in rare instances where the trial is a large multicenter trial demonstrating internal consistency and a statistically very persuasive finding of a clinically meaningful effect on mortality, irreversible morbidity or prevention of a disease with a potentially serious outcome and confirmation of the result in a second trial would be practically or ethically impossible. Depending on the data we obtain, the FDA or other regulatory authorities may require additional clinical trials to be carried out or further patients to be treated prior to the granting of any regulatory approval for marketing of our TCR therapeutic candidates. It is difficult for us to predict with such a novel technology exactly what will be required by the regulatory authorities in order to take our TCR therapeutic candidates to market or the timeframes under which the relevant regulatory approvals can be obtained.

              In addition, depending on the data that are obtained by us in our current and future clinical trials, we may seek breakthrough therapy or fast track designation or accelerated approval from the FDA for our TCR therapeutic candidates and equivalent accelerated approval procedures in other countries. However, given the novel nature of our TCR therapeutic candidates, it is difficult for us to predict or guarantee whether the FDA or other regulatory authorities will approve such requests or what further clinical or other data may be required to support an application for such accelerated approval procedures.

              The process of obtaining marketing approvals, both in the United States and abroad, is expensive, may take many years if additional clinical trials are required, if approval is obtained at all, and can vary substantially based upon a variety of factors, including the type, complexity and novelty of the TCR therapeutic candidates involved. Changes in marketing approval policies during the development period, changes in or the enactment of additional statutes or regulations, or changes in regulatory review for each submitted product application, may cause delays in the approval or rejection of an application. The FDA and foreign regulatory authorities also have substantial discretion in the drug and biologics approval process. The number and types of preclinical programs and clinical trials that will be required for regulatory approval varies depending on the TCR therapeutic candidate, the disease or condition that the TCR therapeutic candidate is designed to address, and the regulations applicable to any particular TCR therapeutic candidate. Approval policies, regulations or the type and amount of clinical data necessary to gain approval may change during the course of a TCR therapeutic candidate's clinical development and may vary among jurisdictions, and there may be varying interpretations of data obtained from preclinical programs or clinical trials, either of which may cause delays or limitations in the approval or the decision not to approve an application. In addition, approval of our TCR therapeutic candidates could be delayed or refused for many reasons, including the following:

•

the FDA or comparable foreign regulatory authorities may disagree with the design or implementation of our clinical trials;



•

we may be unable to demonstrate to the satisfaction of the FDA or comparable foreign regulatory authorities that our TCR therapeutic candidates are safe and effective for any of their proposed indications;



•

the results of clinical trials may not meet the level of statistical significance required by the FDA or comparable foreign regulatory authorities for approval;



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we may be unable to demonstrate that our TCR therapeutic candidates' clinical and other benefits outweigh their safety risks;



•

the FDA or comparable foreign regulatory authorities may disagree with our interpretation of data from preclinical programs or clinical trials;

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•

the data collected from clinical trials of our TCR therapeutic candidates may not be sufficient to the satisfaction of the FDA or comparable foreign regulatory authorities to support the submission of a BLA or other comparable submission in foreign jurisdictions or to obtain regulatory approval in the United States or elsewhere;



•

our manufacturing processes or facilities or those of the third-party manufacturers with which we may not be adequate to support approval of our TCR therapeutic candidates; and



•

the approval policies or regulations of the FDA or comparable foreign regulatory authorities may significantly change in a manner rendering our clinical data insufficient for approval.

              It is possible that none of our TCR therapeutic candidates will ever obtain the appropriate regulatory approvals necessary to commercialize the TCR therapeutics. Any delay in obtaining, or failure to obtain, required approvals would materially adversely affect our ability to generate revenue from the particular TCR therapeutic candidate, which would result in significant harm to our business.

Obtaining and maintaining regulatory approval of our TCR therapeutic candidates in one jurisdiction does not mean that we will be successful in obtaining regulatory approval of our TCR therapeutic candidates in other jurisdictions.

              Obtaining and maintaining regulatory approval of our TCR therapeutic candidates in one jurisdiction does not guarantee that we will be able to obtain or maintain regulatory approval in any other jurisdiction, while a failure or delay in obtaining regulatory approval in one jurisdiction may have a negative effect on the regulatory approval process in others. For example, even if the FDA grants marketing approval of a TCR therapeutic candidate, comparable regulatory authorities in foreign jurisdictions must also approve the manufacturing, marketing and promotion of the TCR therapeutic candidate in those countries. Approval procedures vary among jurisdictions and can involve requirements and administrative review periods different from, and greater than, those in the United States, including additional preclinical programs or clinical trials as clinical trials conducted in one jurisdiction may not be accepted by regulatory authorities in other jurisdictions. In many jurisdictions outside the United States, a TCR therapeutic candidate must be approved for reimbursement before it can be approved for sale in that jurisdiction. In some cases, the price that we intend to charge for our TCR therapeutic candidates is also subject to approval.

              We may also submit marketing applications in other countries. Regulatory authorities in jurisdictions outside of the United States have requirements for approval of TCR therapeutic candidates with which we must comply prior to marketing in those jurisdictions. Obtaining foreign regulatory approvals and compliance with foreign regulatory requirements could result in significant delays, difficulties and costs for us and could delay or prevent the introduction of our TCR therapeutic candidates in certain countries. If we fail to comply with the regulatory requirements in international markets and/or receive applicable marketing approvals, our target market will be reduced and our ability to realize the full market potential of our TCR therapeutic candidates will be harmed.

We plan to seek breakthrough therapy or fast track designations and may pursue accelerated approval for some or all of our current TCR therapeutic candidates, but we may be unable to obtain such designations or, obtain or maintain the benefits associated with such designations.

              We may seek breakthrough therapy or fast track designations for our TCR therapeutic candidates in the United States or equivalent regulations elsewhere in the world. In 2012, the FDA established a breakthrough therapy designation which is intended to expedite the development and review of products that treat serious or life-threatening diseases when "preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development." The designation of a TCR therapeutic candidate as a breakthrough therapy provides

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potential benefits that include more frequent meetings with the FDA to discuss the development plan for the TCR therapeutic candidate and ensure collection of appropriate data needed to support approval; more frequent written correspondence from the FDA about things such as the design of the proposed clinical trials and use of biomarkers; intensive guidance on an efficient drug development program, beginning as early as Phase 1; organizational commitment involving senior managers; and eligibility for rolling review and priority review.

              Breakthrough therapy designation does not change the standards for product approval. We intend to seek breakthrough therapy designation for some or all of our TCR therapeutic candidates, but there can be no assurance that we will receive breakthrough therapy designation. Additionally, other treatments from competing companies may obtain the designations and impact our ability to develop and commercialize our TCR therapeutic candidates, which may adversely impact our business, financial condition or results of operation.

              We may also seek fast track designation. If a drug or biologic candidate is intended for the treatment of a serious or life-threatening condition or disease and the drug demonstrates the potential to address unmet medical needs for the condition, the sponsor may apply for fast track designation. Under the fast track program, the sponsor of a new drug or biologic candidate may request that the FDA designate the candidate for a specific indication as a fast track drug or biologic concurrent with, or after, the submission of the IND for the candidate. The FDA must determine if the drug or biologic candidate qualifies for fast track designation within 60 days of receipt of the sponsor's request. Even if we do apply for and receive fast track designation, we may not experience a faster development, review or approval process compared to conventional FDA procedures. The FDA may withdraw fast track designation if it believes that the designation is no longer supported by data from our clinical development program.

              We may also seek accelerated approval for products that have obtained fast track designation. Under the FDA's fast track and accelerated approval programs, the FDA may approve a drug or biologic for a serious or life-threatening illness that provides meaningful therapeutic benefit to patients over existing treatments based upon a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity, or prevalence of the condition and the availability or lack of alternative treatments. For drugs granted accelerated approval, post-marketing confirmatory trials have been required to describe the anticipated effect on irreversible morbidity or mortality or other clinical benefit. These confirmatory trials must be completed with due diligence. Moreover, the FDA may withdraw approval of our TCR therapeutic candidate or indication approved under the accelerated approval pathway if, for example,

•

the trial or trials required to verify the predicted clinical benefit of our TCR therapeutic candidate fail to verify such benefit or do not demonstrate sufficient clinical benefit to justify the risks associated with the drug;



•

other evidence demonstrates that our TCR therapeutic candidate is not shown to be safe or effective under the conditions of use;



•

we fail to conduct any required post approval trial of our TCR therapeutic candidate with due diligence; or



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we disseminate false or misleading promotional materials relating to the relevant TCR therapeutic candidate.

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Even if we receive regulatory approval of our TCR therapeutic candidates, we will be subject to ongoing regulatory obligations and continued regulatory review, which may result in significant additional expense as well as significant penalties if we fail to comply with regulatory requirements or experience unanticipated problems with our TCR therapeutic candidates.

              Any regulatory approvals that we receive for our TCR therapeutic candidates will require surveillance to monitor the safety and efficacy of the TCR therapeutic candidate. The FDA may also require a risk evaluation and mitigation strategy in order to approve our TCR therapeutic candidates, which could entail requirements for a medication guide, physician communication plans or additional elements to ensure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. In addition, if the FDA or a comparable foreign regulatory authority approves our TCR therapeutic candidates, the manufacturing processes, labeling, packaging, distribution, adverse event reporting, storage, advertising, promotion, import, export and recordkeeping for our TCR therapeutic candidates will be subject to extensive and ongoing regulatory requirements. These requirements include submissions of safety and other post-marketing information and reports, registration and listing, as well as continued compliance with cGMPs and current good clinical practices, or cGCPs, for any clinical trials that we conduct post-approval. We and our contract manufacturers will be subject to periodic unannounced inspections by the FDA to monitor and ensure compliance with cGMPs. We must also comply with requirements concerning advertising and promotion for any TCR therapeutic candidates for which we obtain marketing approval. Promotional communications with respect to prescription drugs, including biologics, are subject to a variety of legal and regulatory restrictions and must be consistent with the information in the product's approved labeling. Thus, we will not be able to promote any TCR therapeutic candidates we develop for indications or uses for which they are not approved. Later discovery of previously unknown problems with our TCR therapeutic candidates, including adverse events of unanticipated severity or frequency, or with our third-party manufacturers or manufacturing processes, or failure to comply with regulatory requirements, may result in, among other things:

•

restrictions on our ability to conduct clinical trials, including full or partial clinical holds on ongoing or planned trials;



•

restrictions on such products' manufacturing processes;



•

restrictions on the marketing of a product;



•

restrictions on product distribution;



•

requirements to conduct post-marketing clinical trials;



•

untitled or warning letters;



•

withdrawal of the products from the market;



•

refusal to approve pending applications or supplements to approved applications that we submit;



•

recall of products;



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fines, restitution or disgorgement of profits or revenue;



•

suspension or withdrawal of regulatory approvals;



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refusal to permit the import or export of our products;



•

product seizure;



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injunctions;



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imposition of civil penalties; or

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•

criminal prosecution.

              The FDA's and other regulatory authorities' policies may change and additional government regulations may be enacted that could prevent, limit or delay regulatory approval of our TCR therapeutic candidates. We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative action, either in the United States or abroad. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we may lose any marketing approval that we may have obtained and we may not achieve or sustain profitability.

              In addition, if following a pivotal clinical trial we were able to obtain accelerated approval of our NY-ESO TCR therapeutic candidate, the FDA will require us to conduct a confirmatory trial or trials to verify the predicted clinical benefit and additional safety studies. The results from the confirmatory trial or trials may not support the clinical benefit, which would result in the approval being withdrawn.

We may seek a conditional marketing authorization in Europe for some or all of our current TCR therapeutic candidates, but we may not be able to obtain or maintain such designation.

              As part of its marketing authorization process, the European Medicines Agency, or EMA, may grant marketing authorizations for certain categories of medicinal products on the basis of less complete data than is normally required, when doing so may meet unmet medical needs of patients and serve the interest of public health. In such cases, it is possible for the Committee for Medicinal Products for Human Use, or CHMP, to recommend the granting of a marketing authorization, subject to certain specific obligations to be reviewed annually, which is referred to as a conditional marketing authorization. This may apply to medicinal products for human use that fall under the jurisdiction of the EMA, including those that aim at the treatment, the prevention, or the medical diagnosis of seriously debilitating diseases or life-threatening diseases and those designated as orphan medicinal products.

              A conditional marketing authorization may be granted when the CHMP finds that, although comprehensive clinical data referring to the safety and efficacy of the medicinal product have not been supplied, all the following requirements are met:

•

the risk-benefit balance of the medicinal product is positive;



•

it is likely that the applicant will be in a position to provide the comprehensive clinical data;



•

unmet medical needs will be fulfilled; and



•

the benefit to public health of the immediate availability on the market of the medicinal product concerned outweighs the risk inherent in the fact that additional data are still required.

              The granting of a conditional marketing authorization is restricted to situations in which only the clinical part of the application is not yet fully complete. Incomplete preclinical or quality data may only be accepted if duly justified and only in the case of a product intended to be used in emergency situations in response to public-health threats. Conditional marketing authorizations are valid for one year, on a renewable basis. The holder will be required to complete ongoing trials or to conduct new trials with a view to confirming that the benefit-risk balance is positive. In addition, specific obligations may be imposed in relation to the collection of pharmacovigilance data.

              Granting a conditional marketing authorization allows medicines to reach patients with unmet medical needs earlier than might otherwise be the case and will ensure that additional data on a product are generated, submitted, assessed and acted upon. Although we may seek a conditional marketing authorization for one or more of our TCR therapeutic candidates by the EMA, the EMA or

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CHMP may ultimately not agree that the requirements for such conditional marketing authorization have been satisfied and hence delay the commercialization of our TCR therapeutic candidates.

We may not be able to obtain or maintain orphan drug exclusivity for our TCR therapeutic candidates.

              Regulatory authorities in some jurisdictions, including the United States and Europe, may designate drugs or biologics for relatively small patient populations as orphan drugs. Under the Orphan Drug Act, the FDA may designate a product as an orphan drug if it is a drug or biologic intended to treat a rare disease or condition, which is generally defined as a patient population of fewer than 200,000 individuals in the United States.

              Generally, if a product with an orphan drug designation subsequently receives the first marketing approval for the indication for which it has such designation, the product is entitled to a period of marketing exclusivity, which precludes the EMA or the FDA from approving another marketing application for the same drug for that time period. The applicable period is seven years in the United States and 10 years in Europe. The European exclusivity period can be reduced to six years if a drug no longer meets the criteria for orphan drug designation or if the drug is sufficiently profitable so that market exclusivity is no longer justified. Orphan drug exclusivity may be lost if the FDA or EMA determines that the request for designation was materially defective or if the manufacturer is unable to assure sufficient quantity of the drug to meet the needs of patients with the rare disease or condition.

              Some of our TCR therapeutic candidates may be eligible for orphan drug designation. In the United States, under the Orphan Drug Act, the FDA may grant orphan designation to a drug intended to treat a rare disease or condition. Such diseases and conditions are those that affect fewer than 200,000 individuals in the United States or, if they affect more than 200,000 individuals in the United States, there is no reasonable expectation that the cost of developing and making a drug product available in the United States for these types of diseases or conditions will be recovered from sales of the product. If the FDA grants orphan drug designation, the identity of the therapeutic agent and its potential orphan use are disclosed publicly by that agency. Orphan drug designation does not convey any advantage in or shorten the duration of the regulatory review and approval process, but it can lead to financial incentives, such as opportunities for grant funding toward clinical trial costs, tax advantages in-lieu of R&D tax credits and user-fee waivers. If a product that has orphan drug designation subsequently receives the first FDA approval for the disease or condition for which it has such designation, the product is entitled to orphan drug marketing exclusivity for a period of seven years. Orphan drug marketing exclusivity generally prevents the FDA from approving another application, including a full BLA, to market the same drug for the same indication for seven years, except in limited circumstances, including if the FDA concludes that the later drug is clinically superior to the approved drug. A drug is clinically superior if it is safer, more effective or makes a major contribution to patient care. Orphan drug marketing exclusivity rights in the United States may be lost if the FDA later determines that the request for designation was materially defective or if the manufacturer is unable to assure sufficient quantity of the drug to meet the needs of patients with the rare disease or condition. There can be no assurance that any TCR therapeutic candidate will be eligible for orphan drug designation in the United States or in other jurisdictions or that it will obtain orphan drug marketing exclusivity upon approval. Inability to obtain orphan drug designation for a specific TCR therapeutic candidate in the future would prevent us from taking advantage of the financial benefits associated with orphan drug designation and would preclude us from obtain marketing exclusivity upon approval, if any. Even if we obtain orphan drug exclusivity for a product, that exclusivity may not effectively protect the product from competition because different drugs can be approved for the same condition. Even after an orphan drug is approved, the FDA can subsequently approve another drug for the same condition if the FDA concludes that the later drug is clinically superior in that it is shown to be safer, more effective or makes a major contribution to patient care.

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Any failure by us to comply with existing regulations could harm our reputation and operating results.

              The production of our TCR therapeutic candidates is highly regulated and subject to constant inspection. The regulatory environment may also change from time to time. Any failure to comply with regulatory requirements, whether in the United States or in other countries in which our TCR therapeutic candidates are supplied, may result in investigation by regulatory authorities, suspension of regulatory authorizations and, as a result, suspension of clinical programs or ability to supply any of our TCR therapeutic candidates and potentially significant fines or other penalties being imposed in relation to any breach. Any failure may also harm our reputation and impact our ability going forward to obtain regulatory approvals for other TCR therapeutic candidates or require us to undertake additional organizational changes to minimize the risk of further breach.

Our research and development activities utilize hazardous, radioactive and biological materials. Should such materials cause injury or be used other than in accordance with applicable laws and regulations, we may be liable for damages.

              We use radioactive, hazardous and biological reagents and materials in our research and development at our U.K. site. We have obtained the appropriate certification required for the use of these reagents but our use is subject to compliance with applicable laws and there is a risk that should any third party or employee suffer injury or damage from radioactive, hazardous or biological reagents that we may incur liability or obligations to compensate such third parties or employees. We have employers liability insurance capped at £10.0 million per occurrence and public liability insurance capped at £3.0 million per occurrence, however, these amounts may be insufficient to compensate us if these events actually occur in the future.

We are subject to the U.K. Bribery Act, the U.S. Foreign Corrupt Practices Act and other anti-corruption laws, as well as export control laws, customs laws, sanctions laws and other laws governing our operations. If we fail to comply with these laws, we could be subject to civil or criminal penalties, other remedial measures, and legal expenses, which could adversely affect our business, results of operations and financial condition.

              Our operations are subject to anti-corruption laws, including the U.K. Bribery Act 2010, or Bribery Act, the U.S. Foreign Corrupt Practices Act, or FCPA, and other anti-corruption laws that apply in countries where we do business. The Bribery Act, the FCPA and these other laws generally prohibit us and our employees and intermediaries from bribing, being bribed or making other prohibited payments to government officials or other persons to obtain or retain business or gain some other business advantage. Under the Bribery Act, we may also be liable for failing to prevent a person associated with us from committing a bribery offense. We and our commercial partners operate in a number of jurisdictions that pose a high risk of potential Bribery Act or FCPA violations, and we participate in collaborations and relationships with third parties whose actions, if non-compliant, could potentially subject us to liability under the Bribery Act, FCPA or local anti-corruption laws. In addition, we cannot predict the nature, scope or effect of future regulatory requirements to which our international operations might be subject or the manner in which existing laws might be administered or interpreted.

              We are also subject to other laws and regulations governing our international operations, including regulations administered by the governments of the United Kingdom and the United States, and authorities in the European Union, including applicable export control regulations, economic sanctions on countries and persons, anti-money laundering laws, customs requirements and currency exchange regulations, collectively referred to as the Trade Control laws.

              However, there is no assurance that we will be completely effective in ensuring our compliance with all applicable anti-corruption laws, including the Bribery Act, the FCPA or other legal requirements, including Trade Control laws. If we are not in compliance with the Bribery Act, the

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FCPA and other anti-corruption laws or Trade Control laws, we may be subject to criminal and civil penalties, disgorgement and other sanctions and remedial measures, and legal expenses, which could have an adverse impact on our business, financial condition, results of operations and liquidity. Likewise, any investigation of any potential violations of the Bribery Act, the FCPA, other anti-corruption laws or Trade Control laws by U.K., U.S. or other authorities could also have an adverse impact on our reputation, our business, results of operations and financial condition.

If we are found in violation of federal or state "fraud and abuse" or other health care laws, we may be required to pay a penalty and/or be suspended from participation in federal or state health care programs, which may adversely affect our business, financial condition and results of operations.

              After we obtain marketing approval for our products in the United States, if any, we will be subject to various federal and state health care "fraud and abuse" and other health care laws. Healthcare providers, physicians and third-party payors play a primary role in the recommendation and use of pharmaceutical products that are granted marketing approval. Accordingly, arrangements with third-party payors, existing or potential customers and referral sources are subject to broadly applicable fraud and abuse and other healthcare laws and regulations, and these laws and regulations may constrain the business or financial arrangements and relationships through which manufacturers market, sell and distribute the products for which they obtain marketing approval.

              Such restrictions under applicable federal and state healthcare laws and regulations include the following:

•

the federal Anti-Kickback Statute, which prohibits, among other things, persons from knowingly and willfully soliciting, receiving, offering or paying remuneration, directly or indirectly, in cash or kind, in exchange for, or to induce, either the referral of an individual for, or the purchase, order or recommendation of, any good or service for which payment may be made under federal healthcare programs such as the Medicare and Medicaid programs. This statute has been interpreted to apply to arrangements between pharmaceutical manufacturers, on the one hand, and prescribers, purchasers and formulary managers on the other. Cases have been brought under false claims laws alleging that off-label promotion of pharmaceutical products or the provision of kickbacks has resulted in the submission of false claims to governmental health care programs. The Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act, collectively, the Healthcare Reform Act, amended the intent requirement of the federal Anti-Kickback Statute. A person or entity no longer needs to have actual knowledge of this statute or specific intent to violate it. Under federal government regulations, some arrangements, known as safe harbors, are deemed not to violate the federal Anti-Kickback Statute and analogous state law requirements;



•

the federal False Claims Act or FCA, which prohibits, among other things, individuals or entities from knowingly presenting, or causing to be presented, claims for payment from Medicare, Medicaid or other third-party payors that are false or fraudulent. Federal Anti-Kickback Statute violations and certain marketing practices, including off-label promotion, also may implicate the FCA. In addition, private individuals have the ability to bring actions on behalf of the government under the federal False Claims Act and under the false claims laws of several states;



•

federal criminal laws that prohibit executing a scheme to defraud any healthcare benefit program or making false statements relating to healthcare matters;



•

the federal Physician Payment Sunshine Act, which requires certain manufacturers of drugs, devices, biologics and medical supplies to report annually to the Centers for Medicare & Medicaid Services, or CMS, information related to payments and other transfers of value to physicians, other healthcare providers and teaching hospitals, and ownership and investment interests held by physicians and other healthcare providers and their immediate family members. The CMS publishes the reported data in a searchable form on an annual basis;

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•

The Health Insurance Portability and Accountability Act of 1996 (HIPAA) imposes criminal and civil liability for executing a scheme to defraud any healthcare benefit program or making false statements relating to healthcare matters;



•

HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act, which governs the conduct of certain electronic healthcare transactions and protects the security and privacy of protected health information; and



•

state and foreign law equivalents of each of the above federal laws, such as anti-kickback and false claims laws which may apply to: items or services reimbursed by any third-party payor, including commercial insurers; state laws that require pharmaceutical companies to comply with the pharmaceutical industry's voluntary compliance guidelines and the relevant compliance guidance issued by the federal government or otherwise restrict payments that may be made to healthcare providers and other potential referral sources; state laws that require drug manufacturers to report information related to payments and other transfers of value to physicians and other healthcare providers or marketing expenditures; and state laws governing the privacy and security of health information in certain circumstances, many of which differ from each other in significant ways and may not have the same effect, thus complicating compliance efforts. California and a few other states have passed laws that require pharmaceutical companies to comply with the April 2003 Office of Inspector General Compliance Program Guidance for Pharmaceutical Manufacturers and/or the Pharmaceutical Research and Manufacturers of America Code on Interactions with Healthcare Professionals. In addition, several states impose other marketing restrictions or require pharmaceutical companies to make marketing or price disclosures to the state. There are ambiguities as to what is required to comply with these state requirements and if we fail to comply with an applicable state law requirement we could be subject to penalties.

              Neither the government nor the courts have provided definitive guidance on the application of fraud and abuse laws to our business. Law enforcement authorities are increasingly focused on enforcing these laws. Although we seek to structure our business arrangements in compliance with all applicable requirements, these laws are broadly written, and it is often difficult to determine precisely how the law will be applied in specific circumstances. Accordingly, and it is possible that, once we begin marketing our product(s) some of our practices may be challenged under these laws. While we intend to structure our business arrangements to comply with these laws, it is possible that the government could allege violations of, or convict us of violating, these laws. Violation of any of the laws described above or any other governmental laws and regulations may result in penalties, including civil and criminal penalties, damages, fines, the curtailment or restructuring of operations, the exclusion from participation in federal and state healthcare programs and imprisonment. Furthermore, efforts to ensure that business activities and business arrangements comply with applicable healthcare laws and regulations can be costly for manufacturers of branded prescription products. Additionally, if we are found in violation of one or more of these laws our business, results of operations and financial condition may be adversely affected.

Our current cash projections include reliance on the ability to obtain certain tax credits and the operation of certain tax regimes with in the United Kingdom. Should these cease to be available, this could impact our ongoing requirement for investment and the timeframes within which additional investment is required.

              As a company that carries out extensive research and development activities, we benefit from the U.K. research and development tax credit regime for small and medium sized companies, whereby our principal research subsidiary company, Adaptimmune Limited, is able to surrender the trading losses that arise from its research and development activities for a payable tax credit of up to 33.4% of eligible research and development expenditures. Qualifying expenditures largely comprise employment costs for research staff, consumables and certain internal overhead costs incurred as part of research

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projects. Subcontracted research expenditures are eligible for a cash rebate of up to 21.7%. The majority of our pipeline research, clinical trials management and manufacturing development activities, all of which are being carried out by Adaptimmune Limited, are eligible for inclusion within these tax credit cash rebate claims.

              We may not be able to claim such research and development tax credits on research and development expenditures in relation to the GSK collaboration and licensing agreement because they may be considered as subsidized expenditures. We may not be able to continue to claim research and development tax credits in the future as we become a public company because we may no longer qualify as a small or medium sized company.

              We may also benefit in the future from the United Kingdom's "patent box" regime, which would allow certain profits attributable to revenues from patented products to be taxed at a rate that over time will be reduced to 10%. As we have many different patents covering our products, future upfront fees, milestone fees, product revenues, and royalties could be taxed at this favorably low tax rate. When taken in combination with the enhanced relief available on our research and development expenditures, we expect a long-term lower rate of corporation tax to apply to us. If, however, there are unexpected adverse changes to the United Kingdom research and development tax credit regime or the "patent box" regime, or we are unable to qualify for such advantageous tax legislation, our business, results of operations and financial condition may be adversely affected.

Risks Related to the Commercialization of Our TCR Therapeutic Candidates

The market opportunities for our TCR therapeutic candidates may be limited to those patients who have failed prior treatments.

              Initial approval of new cancer therapies may be limited to what is referred to as third-line use. Third-line treatment is the third type of treatment following initial, or first-line, treatment and second-line treatment, which is given when first-line treatment does not work or ceases working. However, cancer therapies may be used from the point at which cancer is detected in its early stages (first line) onward. Whenever the first-line therapy fails or the process is unsuccessful, second-line therapy may be administered, such as additional rounds of chemotherapy, radiation and antibody drugs or a combination of these treatments. If second-line therapies fail, patients are generally given the opportunity to receive third-line therapies, which tend to be more novel therapies. Our current clinical trials generally require that patients have received chemotherapy prior to enrollment. Depending upon the outcome of our current trials. we may conduct future clinical trials using our TCR therapeutic candidates for first-line therapy, but there can be no guarantee that clinical trials will be approved or that if approved such trials will lead to regulatory approval. If our TCR therapeutic candidates only receive third-line or second-line approval, the patient population to which we can supply our TCR therapeutic candidates will be significantly reduced, which may limit our commercial opportunities.

              Our estimates of the patient population that may be treated by our TCR therapeutic candidates is based on published information. This information may not be accurate in relation to our TCR therapeutic candidates and our estimates of potential patient populations could therefore be much higher than those that are actually available or possible for commercialization.

              In addition, these estimates are based on assumptions about the number of eligible patients which have the peptide and HLA type targeted by our TCR therapeutic candidates. Different patient populations will present different peptides according to their specific HLA type. HLA types vary across the patient population and, due to this variability, any therapy will initially only be suitable for treatment of patients expressing the particular HLA type presenting the relevant peptide. For example, approximately 50% of the U.S. Caucasian population expresses HLA A2, which contains the peptide used in our NY-ESO TCR therapeutic candidate program. Our current TCR therapeutic candidates have been developed for patients with HLA A2 which may reduce the size of the patient population

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that can be treated unless we develop and receive regulatory approval for TCR therapeutic candidates approved for additional HLA peptides.

We currently have no marketing and sales organization and have no experience in marketing products. If we are unable to establish marketing and sales capabilities or enter into agreements with third parties to market and sell our TCR therapeutic candidates, we may not be able to generate product revenue.

              As an organization, we have never marketed or supplied commercial pharmaceutical or biologic products or therapies. We do not currently have a dedicated sales force and will need to grow and develop the sales function and associated support network if we are to supply TCR therapeutic candidates on a commercial basis. As our TCR therapeutic candidates proceed through clinical programs, we intend to develop an in-house marketing organization and sales force, which will require significant capital expenditures, management resources, and time. We will have to compete with other pharmaceutical and biotechnology companies to recruit, hire, train, and retain marketing and sales personnel. This process may result in additional delays in bringing our TCR product candidate to market or in certain cases require us to enter into alliances with third parties in order to do so. However, there can be no assurance that we will be able to establish or maintain such collaborative arrangements, or even if we are able to do so, that they will result in effective sales forces. Any revenue we receive will depend upon the efforts of such third parties, which may not be successful. We may have little or no control over the marketing and sales efforts of such third parties, and our revenue from TCR therapeutic candidate sales may be lower than if we had commercialized our TCR therapeutic candidates ourselves. We also face significant competition in our search for third parties to assist us with the sales and marketing efforts of our TCR therapeutic candidates. Such competition may also result in delay or inability to supply TCR therapeutic candidates to particular countries or territories in the world which in turn will restrict the revenue that can be obtained from any TCR therapeutic candidate. Any inability on our part to develop in-house sales and commercial distribution capabilities or to establish and maintain relationships with third-party collaborators that can successfully commercialize any TCR therapeutic candidate in the United States or elsewhere will have a materially adverse effect on our business and results of operations.

If product liability lawsuits are brought against us, we may incur substantial liabilities and may be required to limit commercialization of our TCR therapeutic candidates.

              We face an inherent risk of product liability as a result of the clinical testing of our TCR therapeutic candidates and will face an even greater risk upon any commercialization. For example, we may be sued if any of our TCR therapeutic candidates causes or is perceived to cause injury or is found to be otherwise unsuitable during clinical testing, manufacturing, marketing or sale. Any such product liability claims may include allegations of defects in manufacturing, defects in design, a failure to warn of dangers inherent in the product, negligence, strict liability or a breach of warranties. Claims could also be asserted under state consumer protection acts. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit commercialization of our TCR therapeutic candidate. Even a successful defense would require significant financial and management resources and, regardless of the merits or eventual outcome, liability claims may result in:

•

decreased demand for our TCR therapeutic candidates;



•

injury to our reputation;



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withdrawal of clinical trial participants;



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initiation of investigations by regulators;



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costs to defend the related litigation;

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•

a diversion of management's time and our resources;



•

substantial monetary awards to trial participants or patients;



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product recalls, withdrawals or labeling, marketing or promotional restrictions;



•

loss of revenue;



•

exhaustion of any available insurance and our capital resources;



•

the inability to commercialize TCR therapeutic candidate; and



•

a decline in our share price.

              Our inability to obtain sufficient product liability insurance at an acceptable price to protect against potential product liability claims could also prevent or inhibit the commercialization of our TCR therapeutic candidates. We currently hold £15.0 million in clinical trial insurance coverage in the aggregate per year, with a per incident limit of £3.0 million. We also hold products and services liability insurance capped at £3.0 million in the aggregate and public liability insurance capped at £3.0 million per occurrence. These levels may not be adequate to cover all liabilities that we may incur. We may also need to increase our insurance coverage as we expand the scope of our clinical trials and commercialize any of our product TCR therapeutic candidates. In addition, insurance coverage is increasingly expensive. We may not be able to maintain insurance coverage at a reasonable cost or in an amount adequate to satisfy any liability that may arise.

Even if we obtain regulatory approval of our TCR therapeutic candidates, they may not gain market acceptance among physicians, patients, hospitals, cancer treatment centers and others in the medical community.

              The use of engineered T cells as a potential cancer treatment is a recent development and may not become broadly accepted by physicians, patients, hospitals, cancer treatment centers and others in the medical community. Additional factors will influence whether our TCR therapeutic candidates are accepted in the market, including:

•

the clinical indications for which our TCR therapeutic candidates are approved;



•

physicians, hospitals, cancer treatment centers and patients considering our TCR therapeutic candidates as a safe and effective treatment;



•

the potential and perceived advantages of our TCR therapeutic candidates over alternative treatments;



•

the prevalence and severity of any side effects;



•

product labeling or prescribing information requirements of the FDA or other regulatory authorities;



•

limitations or warnings contained in the labeling approved by the FDA;



•

the timing of market introduction of our TCR therapeutic candidates as well as competitive products;



•

the cost of treatment in relation to alternative treatments;



•

the availability of coverage, adequate reimbursement and pricing by third-party payors and government authorities;



•

the willingness of patients to pay for our TCR therapeutic candidate on an out-of-pocket basis in the absence of coverage by third-party payors and government authorities;

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•

relative convenience and ease of administration as compared to alternative treatments and competitive therapies; and



•

the effectiveness of our sales and marketing efforts.

              In addition, although we are not utilizing embryonic stem cells or replication competent vectors, adverse publicity due to the ethical and social controversies surrounding the therapeutic use of such technologies, and reported side effects from any clinical trials using these technologies or the failure of such trials to demonstrate that these therapies are safe and effective may limit market acceptance of our TCR therapeutic candidates. If our TCR therapeutic candidates are approved but fail to achieve market acceptance among physicians, patients, hospitals, cancer treatment centers or others in the medical community, we will not be able to generate significant revenue.

              Even if our TCR therapeutic candidates achieve market acceptance, we may not be able to maintain that market acceptance over time if new products or technologies are introduced that are more favorably received than our TCR therapeutic candidates, are more cost effective or render our TCR therapeutic candidates obsolete.

Coverage and reimbursement may be limited or unavailable in certain market segments for our TCR therapeutic candidates, which could make it difficult for us to sell our TCR therapeutic candidates profitably.

              Successful sales of our TCR therapeutic candidates, if approved, depend on the availability of coverage and adequate reimbursement from third-party payors. In addition, because our TCR therapeutic candidates represent new approaches to the treatment of cancer, we cannot accurately estimate the potential revenue from our TCR therapeutic candidates.

              Patients who are provided medical treatment for their conditions generally rely on third-party payors to reimburse all or part of the costs associated with their treatment. Obtaining coverage and adequate reimbursement from governmental healthcare programs, such as Medicare and Medicaid, and commercial payors is critical to new product acceptance.

              Government authorities and third-party payors, such as private health insurers and health maintenance organizations, decide which drugs and treatments they will cover and the amount of reimbursement. Reimbursement by a third-party payor may depend upon a number of factors, including, but not limited to, the third-party payor's determination that use of a product is:

•

a covered benefit under its health plan;



•

safe, effective and medically necessary;



•

appropriate for the specific patient;



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cost-effective; and



•

neither experimental nor investigational.

              Obtaining coverage and reimbursement approval of a TCR therapeutic candidate from a government or other third-party payor is a time-consuming and costly process will likely could require us to provide to the payor supporting scientific, clinical and cost-effectiveness data for the use of our products. Even if we obtain coverage for a given TCR therapeutic candidate, the resulting reimbursement payment rates might not be adequate for us to achieve or sustain profitability or may require co-payments that patients find unacceptably high. Patients are unlikely to use our TCR therapeutic candidates unless coverage is provided and reimbursement is adequate to cover a significant portion of the cost of our TCR therapeutic candidates.

              In the United States, no uniform policy of coverage and reimbursement for products exists among third-party payors. Therefore, coverage and reimbursement for products can differ significantly

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from payor to payor. As a result, the coverage determination process is often a time-consuming and costly process that will require us to provide scientific and clinical support for the use of our TCR therapeutic candidates to each payor separately, with no assurance that coverage and adequate reimbursement will be obtained.

              We intend to seek approval to market our TCR therapeutic candidates in both the United States and in selected jurisdictions. If we obtain approval in one or more foreign jurisdictions for our TCR therapeutic candidates, we will be subject to rules and regulations in those jurisdictions. In some foreign countries, particularly those in the EU, the pricing of biologics is subject to governmental control. In these countries, pricing negotiations with governmental authorities can take considerable time after obtaining marketing approval of a TCR therapeutic candidate. In addition, market acceptance and sales of our TCR therapeutic candidates will depend significantly on the availability of coverage and adequate reimbursement from third-party payors for our TCR therapeutic candidates and may be affected by existing and future health care reform measures.

              Third-party payors, whether domestic or foreign, or governmental or commercial, are developing increasingly sophisticated methods of controlling healthcare costs. In both the United States and certain foreign jurisdictions, there have been a number of legislative and regulatory changes to the health care system that could impact our ability to sell our products profitably. In particular, the recently enacted U.S. Healthcare Reform Act and its implementing regulations, among other things, revised the methodology by which rebates owed by manufacturers to the state and federal government for covered outpatient drugs and certain biologics, including our TCR therapeutic candidates, under the Medicaid Drug Rebate Program are calculated, increased the minimum Medicaid rebates owed by most manufacturers under the Medicaid Drug Rebate Program, extended the Medicaid Drug Rebate program to utilization of prescriptions of individuals enrolled in Medicaid managed care organizations, subjected manufacturers to new annual fees and taxes for certain branded prescription drugs, and provided incentives to programs that increase the federal government's comparative effectiveness research.

              Other legislative changes have been proposed and adopted in the United States since the Healthcare Reform Act was enacted. In August 2011, the Budget Control Act of 2011, among other things, created measures for spending reductions by Congress. A Joint Select Committee on Deficit Reduction, tasked with recommending a targeted deficit reduction of at least $1.2 trillion for the years 2013 through 2021, was unable to reach required goals, thereby triggering the legislation's automatic reduction to several government programs. This includes aggregate reductions of Medicare payments to providers up to two percent per fiscal year, which went into effect on April 1, 2013 and will remain in effect until 2024, unless additional congressional action is taken. In January 2013, President Obama signed into law the American Taxpayer Relief Act of 2012, or the ATRA, which, among other things, reduced Medicare payments to several providers, including hospitals, imaging centers and cancer treatment centers, and increased the statute of limitations period for the government to recover overpayments to providers from three to five years.

              There have been, and likely will continue to be, legislative and regulatory proposals at the foreign, federal and state levels directed at broadening the availability of healthcare and containing or lowering the cost of healthcare. We cannot predict the initiatives that may be adopted in the future. The continuing efforts of the government, insurance companies, managed care organizations and other payors of healthcare services to contain or reduce costs of healthcare and/or impose price controls may adversely affect:

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the demand for our TCR therapeutic candidates, if we obtain regulatory approval;



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our ability to set a price that we believe is fair for our TCR therapeutic candidates;



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our ability to generate revenue and achieve or maintain profitability;

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the level of taxes that we are required to pay; and



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the availability of capital.

              Any reduction in reimbursement from Medicare or other government programs may result in a similar reduction in payments from private payors, which may adversely affect our future profitability.

Risks Related to Our Reliance Upon Third Parties

We rely heavily on GSK for our NY-ESO TCR therapeutic candidate clinical program, which may also effect other TCR therapeutic candidates.

              Our ability to commercialize our NY-ESO TCR therapeutic candidate and our other TCR therapeutic candidates depends heavily on the ongoing collaboration with GSK and payments made by GSK to us upon achievement of specified milestones. GSK has the right to nominate four target programs in addition to the NY-ESO TCR therapeutic candidate program under the collaboration arrangements. We have no control over whether GSK will elect to progress additional targets under the collaboration arrangements and therefore trigger additional investment from GSK in our TCR therapeutic candidates. If GSK does not elect to do so, we may require additional capital or investment or need to enter into alternative strategic alliances. In addition, GSK has a right to terminate the collaboration and license agreement or any specific license under the collaboration and license agreement for any reason on provision of sixty days' notice. Termination may impact not only our requirement for additional investment or capital but also the timeframes within which current clinical programs can be performed and the development of a suitable commercial-scale manufacturing process for any of our TCR therapeutic candidates. In addition, GSK has an option to obtain an exclusive worldwide license to our NY-ESO TCR therapeutic candidate program, which is exercisable during specified time periods. If the option is exercised, GSK will assume full responsibility for our NY-ESO TCR therapeutic candidate program.

              The current development plan or any future development plan agreed upon between GSK and us may be unsuccessful or fail to result in candidate therapies that are feasible for further development or commercialization. There is therefore no guarantee that any payments due on commercialization of products under the agreement between GSK and us will be due or payable by GSK at any time or on the timeframes currently expected. In addition, milestone payments may not be paid where any development plan is terminated prior to completion for lack of feasibility or lack of identification of any suitable candidates that meet the required criteria for progression to the next stage of development.

              In addition, the development plan agreed upon with GSK and any future development plans will be subject to change as a result of risks inherent with the development of any pharmaceutical, biological or gene therapy product. Changes to the development plan may impact the timing and extent of milestone payments made by GSK to us.

              GSK has the ability to influence or control certain decisions relating to the development of therapies covered by our collaboration and license agreement with GSK. This ability could result in delays to the clinical programs covered by the collaboration or changes to the scope of those clinical programs, including the disease indications relevant to such clinical programs. Under the agreement, we are also prohibited from independently developing or commercializing therapies directed at the targets subject to outstanding options granted to GSK. In addition, GSK may have competing internal or commercial interests including its independent collaboration with Immunocore, any of which could impact our collaboration or the ability of GSK to take any clinical programs forward to the next stage following the exercise of their option. Novartis has publicly announced that it has opt-in rights over GSK's current and future oncology research and development pipeline. While specific details of those opt-in rights have not been made public, the existence of these opt-in rights could impact GSK's decision whether to exercise any option under our collaboration or the ability of GSK to take any

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clinical programs forward to the next stage, following the exercise of their option. The relationship with GSK could also result in disputes arising between us and GSK which could result in costly arbitration or litigation and could impact the ongoing clinical programs or progress of such clinical programs. All intellectual property rights arising from the performance of the collaboration and license agreement will be jointly owned apart from intellectual property rights that we solely create. Both GSK and we have freedom to use jointly owned intellectual property rights.

              Further development of our TCR therapeutic candidates is also dependent on the work currently planned to be carried out under the agreement with GSK and any delay in such work or termination by GSK of any development program or agreement, may result in substantial delays in the development of our TCR therapeutic candidates and ability to bring our TCR therapeutic candidates to market. Such termination or delays may also result in the need for further investment to replace revenue expected to be earned under the GSK collaboration and license agreement.

              The GSK collaboration programs relate to specific TCR therapeutic candidates directed to nominated targets. Should any of these programs not be successful or resulting clinical programs show a lack of efficacy or problems with safety, tolerability or durability of response, GSK may decide not to proceed further with such collaboration programs and our ability to obtain other partners for further development of such candidates or of new TCR therapeutic candidates could be significantly compromised.

We rely heavily on Thermo Fisher Scientific Inc., or ThermoFisher, and the technology that we license from them.

              The ability to use the ThermoFisher Dynabeads® CD3/CD28 technology to isolate, activate and expand T cells is important to our ongoing ability to offer TCR therapeutic candidates. In December 2012, we entered into a series of license and sub-license agreements with Life Technologies Corporation (now part of Thermo Fisher Scientific Inc.), or ThermoFisher. These agreements provide us with a field-based exclusive license under certain intellectual property rights owned or controlled by ThermoFisher in relation to the methods of use of the ThermoFisher Dynabeads® CD3/CD28 technology to isolate, activate and expand T-cells and enable transfection of the T-cells with any TCR genes to manufacture our TCR products and use and sell those TCR products to treat cancer, infectious disease and/or autoimmune disease. We also have a field-based exclusive sub-license under certain other patents which cover the method of use of the Dynabeads® CD3/CD28 and are controlled by ThermoFisher under a head-license from the University of Michigan, the United States Navy and the Dana-Farber Cancer Institute.

              We have a research supply agreement for the Dynabeads® CD3/CD28 CTS, which currently runs for a period of three years from June 2013. We are in process of negotiating a new supply agreement; however there is no certainty that a re-negotiation will be possible on commercially acceptable terms, which could impact the supply of TCR therapeutic candidates for clinical trials and require us to obtain additional regulatory approval. It is anticipated that under such new agreement, ThermoFisher will develop to our technical and regulatory specifications a Dynabeads® product that will be exclusively purchased by us and exclusively supplied by ThermoFisher in our field of use.

              ThermoFisher has the right to terminate for material breach or insolvency. If ThermoFisher terminates the exclusive license, sub-license and supply agreements or otherwise refuses to supply the Dynabeads® product, we will have to seek an alternative source of the beads or develop an alternative process methodology to enable supply of our TCR therapeutic candidates. An alternative source may be difficult to find or more expensive, which may delay timeframes either for clinical programs or ultimately commercial supply of our TCR therapeutic candidates. A requirement to identify an alternative source may also require a change in our regulatory application or additional regulatory

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testing to ensure that any alternative source is comparable and does not present any additional risk which could also result in our program experiencing delays and increased costs.

              The sub-license agreement, in addition to having the same relevant exclusivity scope and field-based restrictions and many of the terms are equivalent to those set out in the main license agreement with ThermoFisher also includes additional requirements that any manufacture of engineered TCR products for sale in the United States must occur in the United States and reserve rights for the United States government to use the technology in accordance with 35 U.S.C. § 200 et seq. and for the University of Michigan and Dana-Farber Cancer Institute to use the technology for non-commercial research purposes.

We rely on third parties to manufacture and supply our TCR therapeutic candidates, and we may have to rely on third parties to produce and process our TCR therapeutic candidates, if approved.

              We currently rely on outside contract manufacturing organizations ("CMOs") to manufacture, supply and process our TCR therapeutic candidates. If one or more of these CMOs become unable or unwilling to continue to manufacture our engineered TCR therapeutic candidates in the future, we may be forced to find an alternative third-party manufacturer, which we may not be able to do on commercially reasonable terms, if at all. Failure to identify a suitable alternative manufacturer could impact our business, financial condition or results of operations.

              We rely on a limited number of third-party manufacturers for clinical trial product supplies, and if we are unable to develop our own commercial manufacturing facility for any commercial product supplies, we will be exposed to the following risks:

•

We may be unable to contract with manufacturers on commercially acceptable terms or at all because the number of potential manufacturers is limited and the FDA, EMA and other comparable foreign regulators must approve any replacement manufacturer, which would require new testing and compliance inspections. In addition, a new manufacturer would have to be educated in, and develop substantially equivalent processes for, production of our TCR therapeutic candidates after receipt of any applicable regulatory approval.



•

Our third-party manufacturers might be unable to timely formulate and manufacture our TCR therapeutic candidates or produce the quantity and quality required to meet our clinical trial and commercial needs, if any.



•

Contract manufacturers may not be able to execute our manufacturing procedures appropriately.



•

Our future contract manufacturers may not perform as agreed or may not remain in the contract manufacturing business for the time required to supply our clinical trials or to successfully produce, store and distribute our TCR therapeutic candidates.



•

Manufacturers are subject to ongoing periodic unannounced inspection by the FDA, EMA, and other comparable foreign regulators and corresponding state agencies to ensure strict compliance with cGMP and other government regulations and corresponding foreign standards. Although we do not have day-to-day control over third-party manufacturers' compliance with these regulations and standards, we are responsible for ensuring compliance with such regulations and standards.



•

We may not own, or may have to share, the intellectual property rights to any improvements made by our third-party manufacturers in the manufacturing process for our TCR therapeutic candidates.



•

Our third-party manufacturers could breach or terminate their agreement with us.

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              Our contract manufacturers are also subject to the same risks we face in developing our own manufacturing capabilities, as described above. Each of these risks could delay our clinical trials, the approval, if any, of our TCR therapeutic candidates by the FDA or the commercialization of our TCR therapeutic candidates or result in higher costs or deprive us of potential product revenue. In addition, we will rely on third parties to perform release tests on our TCR therapeutic candidates prior to delivery to patients. If these tests are not appropriately performed and test data are not reliable, patients could be put at risk of serious harm. We do have insurance to cover certain costs and expenses related to business interruption capped at £3.0 million in the aggregate.

We have a shared development history with Immunocore, and as a result are reliant on resources and other support from Immunocore, which if not present could result in delays in our ability to progress new TCR therapeutic candidates to market.

              Our TCR technology was originally developed by Avidex, and was subsequently acquired by Medigene in 2006. We were formed as a new, separate company and licensed our TCR technology for T-cell therapy from Medigene in July 2008. Immunocore was subsequently formed as a new separate company and licensed its TCR technology for soluble TCRs from Medigene later in 2008 to develop soluble TCR proteins. Immunocore currently owns approximately 7.6% of the equity interests in Adaptimmune. All of our ordinary shareholders and their affiliates with the exception of Dr. Tayton-Martin also hold shares of Immunocore. These ordinary shareholders and their affiliates own 97.1% of the equity interests in Immunocore and Immunocore and its shareholders and their affiliates own 51.1% of the equity interests in Adaptimmune. Until March 2014, our Chief Executive Officer, or CEO, was also the CEO of Immunocore and he is currently on the board of Immunocore. In addition, two of our directors, Ian Laing and Jonathan Knowles also serve on the board of Immunocore and two of our greater than 5% shareholders, Nicholas Cross and George Robinson, are significant shareholders in, and are directors of, Immunocore. Our scientific co-founder, Bent Jakobsen, is also an employee of Immunocore.

              Both Adaptimmune and Immunocore focus on technologies that are based on TCR therapies. Each company focuses on distinct applications of, and utilizes different, TCRs. Immunocore uses soluble TCRs whereas Adaptimmune uses cellular TCR therapeutic candidates. Both soluble TCRs and Adaptimmune's TCR therapeutic candidates rely on the engineering of TCRs to create affinity-enhanced TCRs. In Adaptimmune's case, once the engineered affinity-enhanced TCR has been generated, the gene encoding that engineered TCR is transduced into patient T cells. With soluble TCRs, there is no transduction. For soluble TCRs, the engineered affinity-enhanced TCRs are combined with an antibody fragment, anti-CD3, and it is this combined TCR/anti-CD3 candidate that is then used to treat patients directly. The combined candidates are called ImmTACs. As a result, the end therapeutic candidates being developed by each company are different in terms of end structure, affinity, require different manufacturing and administration routes and are likely to have different properties in patients. For example, ImmTACs are not anticipated to persist beyond a few hours in a patient following administration, whereas Adaptimmune's TCR therapeutics have been shown to persist in patients for several months or more; ImmTACs are likely to require higher amounts of target peptide to be present and hence Adaptimmune's TCR therapeutics may address cancer cells with lower levels of antigen; ImmTACs rely on activating the patient's existing T cells through an anti-CD3-CD3 interaction, whereas Adaptimune's TCR therapeutic candidates activate T cells through direct binding to the target peptide and this results in a different mechanism of action being seen in in vitro tests.

              Notwithstanding the differences between Immunocore's and Adaptimmune's end products, there is a risk that both companies could potentially develop products or therapies that target the same peptide and are directly competitive and/or address the same indications and patient populations. For example, both companies could develop therapeutic candidates to the same peptide target and hence have a product addressing the same patient populations in the same way as any other competing technology. In addition, both Immunocore and Adaptimmune have entered into collaboration agreements with GSK, which could decide over time to devote greater time and resources to Immunocore at the expense of Adaptimmune.

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              We have a collaboration agreement with Immunocore regarding target identification and T-cell cloning which provides joint access to all currently identified peptide targets and use of Immunocore employees in conducting such identification. We are in the process of implementing our own T-cell cloning capabilities and plan to implement target identification, but will continue to identify targets jointly with Immunocore through our target collaboration agreement. However, there is a risk that Immunocore could refuse to provide such services on an ongoing basis or alternatively, be unable to provide such services. This may result in delay or termination of our planned research and development activities, which could have a material impact on our ability to develop or bring additional TCR therapeutic candidates to market. In addition, under the terms of the target collaboration agreement, Immunocore may terminate such agreement for any reason with six months notice and it is very unlikely that we could find a suitable replacement and would therefore have to develop these capabilities ourselves, which might take a long time and may delay our planned research and development activities.

              Under the terms of the target collaboration agreement, we also share a database of identified targets with Immunocore which has resulted from our joint target identification efforts. The contents of this target database are highly confidential and if disclosed to a third party, either as a result of a breach of the confidentiality terms between us and Immunocore or through a change of control in Immunocore, our business could be adversely impacted. If Immunocore is acquired, restructured or otherwise subject to a change of control or otherwise becomes insolvent or lacks liquidity, we could become associated with a third party and the working relationship between the two companies could be compromised. In any of these circumstances, Immunocore may cease cooperating with us or refuse or be unable to provide planned resources which could have a material adverse effect on our business.

              In addition, many of the patents relating to our underlying core technology in TCR engineering, are co-owned by us and Immunocore pursuant to an assignment and license agreement. Under this agreement, each of Immunocore and Adaptimmune utilize the jointly owned patents and know-how, with Adaptimmune focused on the treatment of patients with engineered TCR therapeutic candidates and Immunocore focused on the treatment of patients with soluble TCRs. Under the agreement, each of Immunocore and Adaptimmune grants the other an exclusive, royalty-free, irrevocable license, with the right to sub-license, to certain jointly owned patents and know-how. However, there is the potential that Immunocore could develop a soluble TCR product targeting the same cancer target that one of our TCR therapeutic candidates is targeting, and therefore compete directly with us.

              We occupy our corporate headquarters in the United Kingdom, where we conduct most of our operations, including our in-house research and laboratory facilities, under subleases from Immunocore. These subleases contain rolling mutual break option provisions that could be effective from June 1, 2017 onwards, on service of six months' prior notice. We have a transitional services agreement with Immunocore under which Dr. Bent Jakobsen, a scientific co-founder of both Adaptimmune and Immunocore, will continue to devote time to each company. If our relationship with Immunocore deteriorated, whether as a result of a change at that company or due to external events affecting Immunocore, our relationship with our landlord and our access to Dr. Bent Jakobsen could be adversely affected which could harm our business.

We rely on third parties to conduct our clinical trials. If these third parties do not successfully carry out their contractual duties or meet expected deadlines, we may not be able to obtain regulatory approval of or commercialize our TCR therapeutic candidates.

              We depend upon independent investigators and collaborators, such as universities, medical institutions, CROs and strategic partners to conduct our preclinical programs and clinical trials under agreements with us. We expect to have to negotiate budgets and contracts with CROs and trial sites, which may result in delays to our development timelines and increased costs. We rely heavily on these third parties over the course of our clinical trials, and we do not have day-to-day control of their

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activities. Nevertheless, we are responsible for ensuring that each of our trials is conducted in accordance with applicable protocols and legal, regulatory and scientific standards, and our reliance on third parties does not relieve us of our regulatory responsibilities. We and these third parties are required to comply with cGCPs, which are regulations and guidelines enforced by the FDA and comparable foreign regulatory authorities for TCR therapeutic candidates in clinical development. Regulatory authorities enforce these cGCPs through periodic inspections of trial sponsors, principal investigators and trial sites. If we or any of these third parties fail to comply with applicable cGCP regulations and guidelines, the clinical data generated in our clinical trials may be deemed unreliable and the FDA or comparable foreign regulatory authorities may require us to perform additional clinical trials before approving our marketing applications. We cannot provide assurances that, upon inspection, such regulatory authorities will determine that any of our clinical trials comply with the cGCP regulations. In addition, our clinical trials must be conducted with biologic product produced under cGMPs and will require a large number of subjects. Our failure or any failure by these third parties to comply with these regulations or to support BLA for approval of our NY-ESO TCR therapeutic candidate for the treatment of a sufficient number of patients may require us to repeat clinical trials, which would delay the regulatory approval process. Moreover, our business may be implicated if any of these third parties violates federal or state fraud and abuse or false claims laws and regulations or healthcare privacy and security laws.

              Any third parties conducting our clinical trials are not and will not be our employees and, except for remedies available to us under our agreements with such third parties, we cannot control whether or not they devote sufficient time and resources to our ongoing clinical trials and preclinical programs. These third parties may also have relationships with other commercial entities, including our competitors, for whom they may also be conducting clinical trials or other drug or biologic development activities, which could affect their performance on our behalf. If these third parties do not successfully carry out their contractual duties or obligations or meet expected deadlines, if they need to be replaced or if the quality or accuracy of the clinical data they obtain is compromised due to the failure to adhere to our clinical protocols or regulatory requirements or for other reasons, our clinical trials may be extended, delayed or terminated and we may not be able to complete development of, obtain regulatory approval of, or successfully commercialize our TCR therapeutic candidates. As a result, our financial results and the commercial prospects for our TCR therapeutic candidates would be harmed, our costs could increase and our ability to generate revenue could be delayed.

              Switching or adding third parties to conduct our clinical trials involves substantial cost and requires extensive management time and focus. In addition, there is a natural transition period when a new third party commences work. As a result, delays may occur, which can materially impact our ability to meet our timelines for bringing our TCR therapeutic candidates to market, if at all.

We rely on third parties to obtain reagents and raw materials.

              The manufacture of our TCR therapeutic candidates requires access to a number of reagents and other raw materials from third parties. Such third parties may refuse to supply such reagents or other raw materials or alternatively refuse to supply on commercially reasonable terms. There may also be capacity issues at such third-party suppliers that impact our ability to increase production of our TCR therapeutic candidates.

              Some of the materials used in the manufacture and processing of our TCR therapeutic candidates may only be supplied by one or a few vendors, which means that, should those vendors be unable to supply, for whatever reason, our ability to manufacture TCR therapeutic candidates and progress TCR therapeutic candidates through clinical trials could be severely impacted and result in additional delays. Such failure to supply could also impact other supply relationships with other third parties and potentially result in additional payments made in relation to such delays.

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Risks Related to Our Intellectual Property

Our TCR therapeutic candidates could be at risk of biosimilar development.

              Expedited routes or abbreviated procedures for obtaining regulatory approval for products aiming to target the same cancer peptide as our TCR therapeutic candidates may be available to third parties, which we cannot control or prevent. For example, third parties could develop affinity-enhanced TCRs binding to the same targets and regulatory authorities may accept that they are interchangeable with our corresponding TCR therapeutic candidates and, as a result, grant regulatory approval for such competing products. Entry into the market of such competing products may impact the price of our TCR therapeutic candidates and the extent of commercialization possible in relation to such TCR therapeutic candidates.

We may be forced to litigate to enforce or defend our intellectual property rights, and/or the intellectual property rights of our licensors.

              We may be forced to litigate to enforce or defend our intellectual property rights against infringement and unauthorized use by competitors, and to protect our trade secrets. In so doing, we may place our intellectual property at risk of being invalidated, held unenforceable, narrowed in scope or otherwise limited. Further, an adverse result in any litigation or defense proceedings may increase the risk of non-issuance of pending applications. In addition, if any licensor fails to enforce or defend its intellectual property rights, this may adversely affect our ability to develop and commercialize our TCR therapeutic candidates and to prevent competitors from making, using, and selling competing products. Any such litigation could be very costly and could distract our management from focusing on operating our business. The existence and/or outcome of any such litigation could harm our business, results of operations and financial condition.

              Furthermore, because of the substantial amount of discovery required in connection with intellectual property litigation, there is a risk that some of our confidential and proprietary information could be compromised by disclosure during this type of litigation. In addition, there could be public announcements of the results of hearings, motions or other interim proceedings or developments. If securities analysts or investors perceive these results to be negative, it could have a substantial adverse effect on the price of our ordinary shares.

We may not be able to protect our proprietary technology in the marketplace or the cost of doing so may be prohibitive or excessive.

              Our success will depend, in part, on our ability to obtain patents, protect our trade secrets and operate without infringing on the proprietary rights of others. We rely upon a combination of patents, trade secret protection (i.e., know-how), and confidentiality agreements to protect the intellectual property of our TCR therapeutic candidates. The scope and validity of patents in the pharmaceutical field involve complex legal and scientific questions and can be uncertain. Where appropriate, we seek patent protection for certain aspects of our TCR therapeutic candidates and technology. Filing, prosecuting and defending patents throughout the world would be prohibitively expensive, so our policy is to patent technology in jurisdictions with significant commercial opportunities. However, patent protection may not be available for some of the TCR therapeutic candidates or technology we are developing. If we must spend significant time and money protecting or enforcing our patents, designing around patents held by others or licensing, potentially for large fees, patents or other proprietary rights held by others, our business results of operations and financial condition may be harmed. We may not develop additional proprietary products that are patentable.

              Many companies have encountered significant problems in protecting and enforcing intellectual property rights in foreign jurisdictions. The legal systems of certain countries, particularly certain developing countries, do not favor the enforcement of patents and other intellectual property rights, particularly those relating to pharmaceuticals, which could make it difficult for us to stop the infringement of our patents or marketing of competing products in violation of our proprietary rights

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generally. Proceedings to enforce our patent rights in foreign jurisdictions could result in substantial cost and divert our efforts and attention from other aspects of our business.

              In addition, patents have a limited lifespan. In most countries, including the United States, the standard expiration of a patent is 20 years from the effective filing date. Various extensions of patent term may be available in particular countries, however in all circumstances the life of a patent, and the protection it affords, has a limited term. If we encounter delays in obtaining regulatory approvals, the period of time during which we could market a product under patent protection could be reduced. We expect to seek extensions of patent terms where these are available in any countries where we are prosecuting patents. Such possible extensions include those permitted under the Drug Price Competition and Patent Term Restoration Act of 1984 in the United States, which permits a patent term extension of up to five years to cover an FDA-approved product. The actual length of the extension will depend on the amount of patent term lost while the product was in clinical trials. However, the applicable authorities, including the FDA in the United States, and any equivalent regulatory authority in other countries, may not agree with our assessment of whether such extensions are available, and may refuse to grant extensions to our patents, or may grant more limited extensions than we request. If this occurs, our competitors may be able to take advantage of our investment in development and clinical trials by referencing our clinical and non-clinical data, and then may be able to launch their product earlier than might otherwise be the case.

              Any loss of, or failure to obtain, patent protection could have a material adverse impact on our business. We may be unable to prevent competitors from entering the market with products that are similar to or the same as our TCR therapeutic candidates.

              Further given that our technology relates to the field of genetic engineering, political pressure or ethical decisions may result in a change to the scope of patent claims for which we may be eligible. Different patent offices throughout the world may adopt different procedures and guidelines in relation to what is and is not patentable and as a result different protection could be obtained in different areas of the world which may impact our ability to maximize commercialization of our technology.

              We may also incur increased expenses and cost in relation to the filing and prosecution of patent applications where third parties choose to challenge the scope or oppose the grant of any patent application or, following grant, seek to limit or invalidate any patent. On April 13, 2015, we received notification of a third party observation filed against one of the patent applications (PCT/GB2013/053320) jointly owned with Immunocore Limited and covering one aspect of our underlying processes. The third party observation cites a reference which the third party considers to be novelty destroying in relation to claims 1-14 of our patent application. We are currently evaluating this notification. Any increased prosecution or defense required in relation to such patents and patent applications, whether relating to this third party observation or any other third party challenge or opposition, entails increased cost and resource commitment to the business and may result in patents and patent applications being abandoned, invalidated or narrowed in scope.

We may be unable to adequately prevent disclosure of trade secrets and other proprietary information.

              We rely on trade secrets to protect our proprietary know-how and technological advances, especially where we do not believe patent protection is appropriate or obtainable. However, trade secrets are difficult to protect. We rely, in part, on confidentiality agreements with our employees, consultants, outside scientific collaborators, sponsored researchers and other advisors to protect our trade secrets and other proprietary information. These agreements may not effectively prevent disclosure of confidential information and may not provide an adequate remedy in the event of unauthorized disclosure of confidential information. In addition, others may independently discover our trade secrets and proprietary information. Costly and time-consuming litigation could be necessary to enforce and determine the scope of our proprietary rights. Failure to obtain or maintain trade secret protection, or failure to adequately protect our intellectual property, could enable competitors to develop generic products or use our proprietary information to develop other products that compete

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with our TCR therapeutic candidates or have additional, material adverse effects upon our business, results of operations and financial condition.

              In addition, we provide samples to third parties under material transfer agreements, including to research institutions or other organizations that we cannot control. There is a risk that such third parties could disclose details of those samples or carry out further research in relation to provided samples which results in intellectual property rights that block our future freedom to operate, and to which we may not be able to obtain a license on commercially acceptable terms or at all. In addition, provision of samples and our confidential information to such parties could facilitate or assist such parties in development of competing products.

If third parties claim that our activities or products infringe upon their intellectual property, our operations could be adversely affected.

              There is a substantial amount of litigation, both within and outside the United States, involving patents and other intellectual property rights in the pharmaceutical industry. We may, from time to time, be notified of claims that we are infringing upon patents, trademarks, copyrights, or other intellectual property rights owned by third parties, and we cannot provide assurances that other companies will not, in the future, pursue such infringement claims against us or any third-party proprietary technologies we have licensed. If we were found to infringe upon a patent or other intellectual property right, or if we failed to obtain or renew a license under a patent or other intellectual property right from a third party, or if a third party that we were licensing technologies from was found to infringe upon a patent or other intellectual property rights of another third party, we may be required to pay damages, including triple damages if the infringement is found to be willful, suspend the manufacture of certain TCR therapeutic candidates or reengineer or rebrand our TCR therapeutic candidates, if feasible, or we may be unable to enter certain new product markets. Any such claims could also be expensive and time-consuming to defend and divert management's attention and resources. Our competitive position could suffer as a result. In addition, if we have declined to enter into a valid non-disclosure or assignment agreement for any reason, we may not own an invention or intellectual property rights and may not be adequately protected. Although we have reviewed certain third-party patents and patent filings that we believe may be relevant to our TCR therapeutic candidates, we have not conducted a full freedom-to-operate search or analysis for such TCR therapeutic candidates, and we may not be aware of patents or pending or future patent applications that, if issued, would block us from commercializing our TCR therapeutic candidates. Thus, we cannot guarantee that we can successfully commercialize TCR therapeutic candidates in a way that will not infringe any third party's intellectual property.

Licenses may be required from third parties in relation to any TCR therapeutic candidates offered by us.

              We may identify third-party intellectual property rights that are required to enable the further development, commercialization, manufacture or development of our TCR therapeutic candidates. Licenses to such intellectual property rights may or may not be available on commercial terms that are acceptable to us. As a result we may incur additional license fees for such intellectual property rights, or the cost and expenses to identify an alternative route for commercialization, that does not require the relevant third-party intellectual property rights, or the cost and diversion of resources required to challenge any such third party intellectual property rights.

              We have identified two U.S. patents that have very broad claims relating to TCRs, and we have requested re-examination of one of these U.S. patents to demonstrate the invalidity of these claims. In that re-examination, in a January 29, 2015 Office Action, the USPTO adopted our position and rejected all claims under re-examination as anticipated or obvious, and in a related pending patent application of The Board of Trustees of the University of Illinois, in an August 18, 2014 Office Action, the USPTO also adopted our position and rejected the claims based on our arguments and evidence of our re-examination request. There is a risk that this decision could be appealed successfully which

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would prevent us from narrowing the scope of the relevant patent and as a result a license may be required.

              We have identified third party European patent applications which relate to high affinity soluble TCR proteins and methods. We have filed third-party observations in relation to one of these third party European patent application. The claims as drafted are broad and as a result could cover soluble TCRs having a specific level of binding and carrying one or more mutations in a complementarity determining region, or CDR, irrespective of the method by which the TCRs are produced. Should these patent application proceed to grant in Europe with claims of such broad scope, we will need to consider filing Opposition proceedings against the grant of the European patents at the European Patent Office and/or filing for revocation of the national patents derived from the European patents before relevant national patent offices and/or courts.

              We have also identified a family of third party patents under which we may require a license in relation to a structural component of our lentiviral vector (cPPT) prior to any commercialization of TCR therapeutic candidates. We believe such licenses are available and we are in discussions to procure a license or freedom to operate under the relevant patent rights.

              We may also require licenses under third-party patents covering certain peptide sequences or the use of those peptides. Such licenses will require payment of sums by us and we cannot guarantee that the terms of such licenses will be available on commercially acceptable terms or at all, which could limit the peptides which can be used by us and the efficacy of the final affinity-enhanced TCRs that we are able to offer.

              Further or other third-party patents and patent applications may be identified from time to time that require prospective action by us to prevent the grant of broad claims. Such prospective action requires time and expense and also impacts on the resources generally available to us.

Where we license certain technology from a third party, the prosecution, maintenance and defense of the patent rights licensed from such third party may be controlled by the third party which may impact the scope of patent protection which will be obtained or enforced.

              Where we license patent rights or technology from a third-party, control of such third-party patent rights may vest in the licensor, particularly where the license is non-exclusive or field restricted. This may mean that we are not able to control or affect the scope of the claims of any relevant third-party patent or have control over any enforcement of such a patent. Where a licensor brings an enforcement action, this could negatively impact our business or result in additional restrictions being imposed on the license we have and the scope of such license, or result in invalidation or limitation of the scope of the licensed patent. In addition, should we wish to enforce the relevant patent rights against a third person, we may be reliant on consent from the relevant licensor or the cooperation of the licensor. The licensor may refuse to bring such action and leave us unable to restrict competitor entry into the market.

Issued patents protecting our TCR therapeutic candidates could be found invalid or unenforceable if challenged in court or at the USPTO.

              If we or one of our licensing partners initiate legal proceedings against a third party to enforce a patent protecting one of our TCR therapeutic candidates, the defendant could counterclaim that the patent protecting our TCR therapeutic candidate, as applicable, is invalid and/or unenforceable. In patent litigation in the United States, defendant counterclaims alleging invalidity and/or unenforceability are commonplace, and there are numerous grounds upon which a third party can assert invalidity or unenforceability of a patent. Third parties may also raise similar claims before administrative bodies in the United States or abroad, even outside the context of litigation. Such mechanisms include re-examination, post grant review, and equivalent proceedings in foreign jurisdictions (e.g., opposition proceedings). Such proceedings could result in revocation or amendment to our patents in such a way that they no longer cover our TCR therapeutic candidates. The outcome

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following legal assertions of invalidity and unenforceability is unpredictable. With respect to the validity question, for example, we cannot be certain that there is no invalidating prior art, of which we, our patent counsel and the patent examiner were unaware during prosecution. If a defendant were to prevail on a legal assertion of invalidity and/or unenforceability, we would lose at least part, and perhaps all, of the patent protection for our TCR therapeutic candidates. Such a loss of patent protection could have a material adverse impact our business, financial condition and results of operations.

Changes in U.S. patent law could diminish the value of patents in general, thereby impairing our ability to protect our products.

              As is the case with other biopharmaceutical companies, our success is heavily dependent on intellectual property, particularly patents. Obtaining and enforcing patents in the biopharmaceutical industry involve both technological and legal complexity, and is therefore costly, time-consuming and inherently uncertain. In addition, the United States has recently enacted and is currently implementing wide-ranging patent reform legislation. Recent U.S. Supreme Court rulings have narrowed the scope of patent protection available in certain circumstances and weakened the rights of patent owners in certain situations. In addition to increasing uncertainty with regard to our ability to obtain patents in the future, this combination of events has created uncertainty with respect to the value of patents, once obtained. Depending on decisions by the U.S. Congress, the federal courts, and the USPTO, the laws and regulations governing patents could change in unpredictable ways that would weaken our ability to obtain new patents or to enforce our existing patents and patents that we might obtain in the future. For example, in the recent case, Assoc. for Molecular Pathology v. Myriad Genetics, Inc., the U.S. Supreme Court held that certain claims to DNA molecules are not patentable. While we do not believe that any of the patents owned or licensed by us will be found invalid based on this decision, we cannot predict how future decisions by the courts, the U.S. Congress or the USPTO may impact the value of our patents.

Our ability to protect our intellectual property rights in territories outside of the United States may vary and thus affect our ability to obtain revenue from our TCR therapeutic candidates.

              Filing, prosecuting and defending patents on our TCR therapeutic candidates in all countries throughout the world would be prohibitively expensive, and the extent of intellectual property rights may be less extensive than those which can be obtained in the United States. Consequently, we may not be able to prevent third parties from practicing our inventions in all countries outside the United States, or from selling or importing products made using our inventions in and into the United States or other jurisdictions. Competitors may use our technologies in jurisdictions where we have not obtained patent protection to develop their own products and further, may export otherwise infringing products to territories where we have patent protection, but enforcement is not as strong as that in the United States. These products may compete with our products and our patents or other intellectual property rights may not be effective or sufficient to prevent them from competing.

              Many companies have encountered significant problems in protecting and defending intellectual property rights in foreign jurisdictions. The legal systems of certain countries, particularly certain developing countries, do not favor the enforcement of patents, trade secrets and other intellectual property protection, particularly those relating to biopharmaceutical products, which could make it difficult for us to stop the infringement of our patents or marketing of competing products in violation of our proprietary rights generally. Proceedings to enforce our patent rights in foreign jurisdictions could result in substantial costs and divert our efforts and attention from other aspects of our business, could put our patents at risk of being invalidated or interpreted narrowly and our patent applications at risk of not issuing and could provoke third parties to assert claims against us. We may not prevail in any lawsuits that we initiate and the damages or other remedies awarded, if any, may not be commercially meaningful. Accordingly, our efforts to enforce our intellectual property rights around the

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world may be inadequate to obtain a significant commercial advantage from the intellectual property that we develop or license.

Risks Related to Employee Matters and Managing Growth

We depend upon our key personnel and our ability to attract and retain employees.

              We are heavily dependent on the ongoing employment and involvement of certain key employees in particular, James Noble, our Chief Executive Officer, Dr. Helen Tayton-Martin, our Chief Operating Officer, and Dr. Gwendolyn Binder-Scholl, who heads our clinical and regulatory development efforts in the United States. We are investigating options for key-man insurance to protect against any unforeseen events affecting such individuals, however our ongoing business is highly dependent on our ability to retain the services of these key personnel. In addition, James Noble and Dr. Helen Tayton-Martin, are in a personal relationship. They are our co-founders, two of our most senior executive officers and are a vital part of our business. If the personal relationship ended or they could otherwise not amicably work with each other, one of them may decide to leave us which would materially harm our business.

              In addition, we anticipate a requirement to expand the personnel available to us very rapidly in order to achieve our planned business activities and aims. Such expansion is dependent on our ability to recruit experienced and suitably trained employees or consultants, and to retain such employees on a long term basis. Our ability to take our existing pipeline of TCR therapeutics and to meet the demands of the GSK collaboration may be compromised or delayed where we are unable to recruit sufficient personnel on a timely basis.

              To induce employees to remain at our company, in addition to salary and cash incentives, we have provided share options that vest over time, with higher awards of share options being made to senior employees. The value to employees of share options that vest over time may be significantly affected by movements in our share price that are beyond our control, and may at any time be insufficient to counteract more lucrative offers from other companies. Despite our efforts to retain valuable employees, members of our management, scientific and development teams may terminate their employment with us on short notice. Although we have employment agreements with all of our employees, in the United Kingdom, these employment agreements provide for mutual six months' notice periods in the case of Mr. Noble and Dr. Tayton-Martin; mutual three months' notice periods in the case of senior managers and mutual one month notice periods for all other employees. In the United States, these employment agreements provide for at-will employment except that our employment agreement with Dr. Binder-Scholl provides for a mutual one month notice period, and our employment agreements with Dr. Rafael Amado, our Chief Medical Officer, and Adrian Rawcliffe, our Chief Financial Officer, provide that Dr. Amado and Mr. Rawcliffe must provide 60 days' written notice for termination without cause. This means that any of our employees in the United States, except for Dr. Binder-Scholl, Dr. Amado and Mr. Rawcliffe, could leave our employment at any time, with or without notice. Our success also depends on our ability to continue to attract, retain and motivate highly skilled junior, mid-level and senior managers as well as junior, mid-level and senior scientific and medical personnel.

We will need to grow the size and capabilities of our organization, and we may experience difficulties in managing this growth.

              As of April 27, 2015, we had 106 full-time equivalent employees. As our development and commercialization plans and strategies develop, and as we transition into operating as a public company, we must add a significant number of additional managerial, operational, sales, marketing, financial, and other personnel. Future growth will impose significant added responsibilities on members of management, including:

•

identifying, recruiting, integrating, maintaining, and motivating additional employees;

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•

managing our internal development efforts effectively, including the clinical and FDA review process for our TCR therapeutic candidates, while complying with our contractual obligations to contractors and other third parties; and



•

improving our operational, financial and management controls, reporting systems, and procedures.

              Our future financial performance and our ability to commercialize our TCR therapeutic candidates will depend, in part, on our ability to effectively manage any future growth, and our management may also have to divert a disproportionate amount of its attention away from day-to-day activities in order to devote a substantial amount of time to managing these growth activities.

              We also rely on third parties to provide certain of our manufacturing and quality capabilities. See "—Risks Related to Our Reliance Upon Third Parties."

              If we are not able to effectively expand our organization by hiring new employees and expanding our groups of consultants and contractors, we may not be able to successfully implement the tasks necessary to further develop and commercialize our TCR therapeutic candidates and, accordingly, may not achieve our research, development, and commercialization goals.

We expect to face intense competition, often from companies with greater resources and experience than we have.

              Immunotherapy is an intensely competitive area with many of the large pharmaceutical companies having products and therapies already in clinical trials for cancer indications and autoimmune diseases. The larger resources of these companies may enable them to take therapies all the way through the regulatory process, while we will require additional investment or input from collaborators such as GSK to take our TCR therapeutic candidates through the regulatory process and commercialization. Smaller or early-stage companies may also prove to be significant competitors, particularly if such companies align with pharmaceutical partners and compete for patients. Results obtained by such competitors in clinical trials could also impact our ability to obtain regulatory approval or delay such approval in the event of a safety issue or other negative clinical result associated with similar T-cell or TCR therapeutic candidates.

              In particular, we face competition from chimeric antigen receptor T cell, or CAR-T, technologies from companies such as Novartis AG/University of Pennsylvania, Kite Pharma, Inc./Amgen Inc./National Cancer Institute, bluebird bio, Inc./Celgene Corporation/Baylor College of Medicine, Intrexon Corporation/Ziopharm Oncology, Inc./MD Anderson Cancer Center, Juno Therapeutics, Inc./Fred Hutchinson Cancer Research Center/Memorial Sloan Kettering Cancer Center, Cellectis SA/Pfizer Inc. and Bellicum Pharmaceuticals Inc. In the TCR space, we face competition from Juno Therapeutics, Inc., Kite Pharma, Inc., Medigene AG and Takara Bio, Inc. Kite Pharma has a murine derived TCR product in development targeting NY-ESO-1. Should Kite Pharma or any of our other competitors be successful in advancing a TCR product targeting NY-ESO-1 through development, our ability to develop and advance our NY-ESO TCR therapeutic candidate could be adversely affected. We may also face competition from other non-TCR and non-cell based treatments such as antibody and check point inhibitor therapies offered by companies such as Amgen Inc., AstraZeneca plc, Bristol-Myers Squibb Company, Incyte Corporation, Merck & Co., Inc., and Roche Holding Ltd. Even if we obtain regulatory approval for our TCR therapeutic candidates, we may not be the first to market, which could affect both demand for and price of our TCR therapeutic candidates.

              Although Immunocore is focused on soluble TCRs rather than engineered TCR therapeutic candidates, we could also face competition from Immunocore if it develops or acquires products directed at the same targets or indications as our TCR therapeutic product candidates.

              Moreover, many of our employees have come from a shared background within Immunocore and there is an awareness within Immunocore of certain of our confidential information on the technology platform controlled through confidentiality agreements in employee contracts. This

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knowledge could be used by Immunocore to facilitate its own developments or to target competitive products against our products placing it in a preferable position as compared to third party competitors.

Failure of our information technology systems could significantly disrupt the operation of our business.

              Our ability to execute our business plan and to comply with regulators' requirements with respect to data control and data integrity, depends, in part, on the continued and uninterrupted performance of our information technology systems and similar systems used by third-party providers that we rely on. These systems are vulnerable to damage from a variety of sources, including telecommunications or network failures, malicious human acts and natural disasters. Moreover, despite network security and back-up measures, some of our servers are potentially vulnerable to physical or electronic break-ins, computer viruses and similar disruptive problems. Despite the precautionary measures we have taken to prevent unanticipated problems that could affect our information systems, sustained or repeated system failures or problems arising during the upgrade of any of our information systems that interrupt our ability to generate and maintain data, and in particular to operate our proprietary technology platform, could adversely affect our ability to operate our business. In addition, where disruption to such systems occurs at third-party providers, we may have limited ability to find alternative providers in any required timeframes or at all, and such disruption could significantly affect our ability to proceed with clinical or analytical or development programs.

Business disruptions could seriously harm our future revenue and financial condition and increase our costs and expenses.

              Our operations and those of our third party suppliers and collaborators could be subject to earthquakes, power shortages, telecommunications failures, water shortages, floods, hurricanes or other extreme weather conditions, medical epidemics, labor disputes or other business interruptions. While the company has business interruption insurance policies in place which are capped at £3.0 million in the aggregate, any interruption could seriously harm our ability to timely proceed with any clinical programs or to supply TCR therapeutic candidates on a commercial basis or for use in clinical programs.

We are exposed to risks related to currency exchange rates.

              We conduct a significant portion of our operations outside the United Kingdom. Because our financial statements are presented in pounds sterling, changes in currency exchange rates have had and could have a significant effect on our operating results. In addition, our arrangements with GSK are denominated in pounds sterling. Exchange rate fluctuations between local currencies and the pound sterling create risk in several ways, including the following: weakening of the pound sterling may increase the pound sterling cost of overseas research and development expenses and other costs outside the United Kingdom; strengthening of the pound sterling may decrease the value of any future revenues denominated in other currencies; the exchange rates on non-sterling transactions and cash deposits can distort our financial results; and commercial pricing and profit margins are affected by currency fluctuations.

We may be classified as a passive foreign investment company in any taxable year and U.S. holders of our ordinary shares could be subject to adverse U.S. federal income tax consequences.

              The rules governing passive foreign investment companies, or PFICs, can have adverse effects for U.S. federal income tax purposes. The tests for determining PFIC status for a taxable year depend upon the relative values of certain categories of assets and the relative amounts of certain kinds of income. The determination of whether we are a PFIC depends on the particular facts and circumstances (such as the valuation of our assets, including goodwill and other intangible assets) and may also be affected by the application of the PFIC rules, which are subject to differing interpretations. The fair market value of our assets is expected to relate, in part, to (a) the market price of our

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ordinary shares and (b) the composition of our income and assets, which will be affected by how, and how quickly, we spend any cash that is raised in any financing transaction, including this offering.

              If we are a PFIC, U.S. holders of our ordinary shares would be subject to adverse U.S. federal income tax consequences, such as ineligibility for any preferred tax rates on capital gains or on actual or deemed dividends, interest charges on certain taxes treated as deferred, and additional reporting requirements under U.S. federal income tax laws and regulations. A U.S. holder of our ordinary shares may be able to mitigate some of the adverse U.S. federal income tax consequences described above with respect to owning the ordinary shares if we are classified as a PFIC, provided that such U.S. investor is eligible to make, and validly makes, a "mark-to-market" election. In certain circumstances a U.S. Holder can make a "qualified electing fund" election to mitigate some of the adverse tax consequences described with respect to an ownership interest in a PFIC by including in income its share of the PFIC's income on a current basis. However, we do not currently intend to prepare or provide the information that would enable a U.S. Holder to make a qualified electing fund election.

              Investors should consult their own tax advisors regarding all aspects of the application of the PFIC rules to our ordinary shares. For more information related to classification as a PFIC, see "Taxation—U.S. Federal Income Taxation—Passive Foreign Investment Company Considerations."

Risks Related to the ADSs and This Offering

We do not know whether an active, liquid and orderly trading market will develop for our ADSs or what the market price of our ADSs will be and as a result it may be difficult for you to sell your ADSs.

              This offering constitutes the initial public offering of our ADSs, and no public market for the ADSs currently exists. We have received approval to list the ADSs on Nasdaq, and we expect our ADSs to be quoted on Nasdaq, subject to completion of customary procedures in the United States. Any delay in the commencement of trading of the ADSs on Nasdaq would impair the liquidity of the market for the ADSs and make it more difficult for holders to sell the ADSs.

              If the ADSs are listed on Nasdaq and quoted on Nasdaq, there can be no assurance that an active trading market for the ADSs will develop or be sustained after this offering is completed. The initial offering price has been determined by negotiations among the lead underwriters and us. Among the factors considered in determining the initial offering price were our future prospects and the prospects of our industry in general, our revenue, net income and certain other financial and operating information in recent periods, and the market prices of securities and certain financial and operating information of companies engaged in activities similar to ours. However, there can be no assurance that following this offering the ADSs will trade at a price equal to or greater than the public offering price.

The price of our ADSs may be volatile, and you could lose all or part of your investment.

              The trading price of our ADSs following this offering is likely to be highly volatile and could be subject to wide fluctuations in response to various factors, some of which are beyond our control, including limited trading volume. In addition to the factors discussed in this "Risk Factors" section and elsewhere in this prospectus, these factors include:

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the commencement, enrollment or results of our planned clinical trials;



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the loss of any of our key scientific or management personnel;



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announcements of the failure to obtain regulatory approvals or receipt of a complete response letter from the FDA;



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announcements of undesirable restricted labeling indications or patient populations, or changes or delays in regulatory review processes;



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announcements of therapeutic innovations or new products by us or our competitors;

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•

adverse actions taken by regulatory agencies with respect to our clinical trials, manufacturing supply chain or sales and marketing activities;



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changes or developments in laws or regulations applicable to our TCR therapeutic candidates;



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any adverse changes to our relationship with licensors, manufacturers or suppliers;



•

the failure of our testing and clinical trials;



•

unanticipated safety concerns;



•

the failure to retain our existing, or obtain new, collaboration partners;



•

announcements concerning our competitors or the pharmaceutical industry in general;



•

the achievement of expected product sales and profitability;



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the failure to obtain reimbursements for our TCR therapeutic candidates or price reductions;



•

manufacture, supply or distribution shortages;



•

actual or anticipated fluctuations in our operating results;



•

our cash position;



•

changes in financial estimates or recommendations by securities analysts;



•

potential acquisitions;



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the trading volume of ADSs on Nasdaq;



•

sales of our ADSs or ordinary shares by us, our executive officers and directors or our shareholders in the future;



•

general economic and market conditions and overall fluctuations in the U.S. equity markets; and



•

changes in accounting principles.

              In addition, the stock market in general, and Nasdaq and biopharmaceutical companies in particular, have experienced extreme price and volume fluctuations that have often been unrelated or disproportionate to the operating performance of these companies. Broad market and industry factors may negatively affect the market price of our ADSs, regardless of our actual operating performance. Further, a decline in the financial markets and related factors beyond our control may cause the price of our ADSs to decline rapidly and unexpectedly. If the market price of our ADSs after this offering does not exceed the initial public offering price, you may not realize any return on your investment in us and may lose some or all of your investment.

Substantial future sales of our ordinary shares or ADSs in the public market, or the perception that these sales could occur, could cause the price of the ADSs to decline.

              Additional sales of our ordinary shares or ADSs in the public market after this offering, or the perception that these sales could occur, could cause the market price of the ADSs to decline. Upon completion of this offering, we will have 424,711,900 ordinary shares outstanding (or 434,836,900 ordinary shares if the underwriters exercise in full their option to purchase additional ADSs). All ADSs sold in this offering will be freely transferable without restriction or additional registration under the U.S. Securities Act of 1933, as amended, or the Securities Act unless purchased by our affiliates. The remaining ordinary shares will be available for sale upon the expiration of a lock-up period, which we expect will expire 180 days after the date of this prospectus. Any or all of these shares may be released prior to expiration of the lock-up period at the discretion of the lead underwriter for this offering. To the extent shares are released before the expiration of the lock-up period and these shares are sold into the market, the market price of our ADSs could decline.

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You may not have the same voting rights as the holders of our ordinary shares and may not receive voting materials in time to be able to exercise your right to vote.

              Except as described in this prospectus, holders of the ADSs will not be able to exercise voting rights attaching to the ordinary shares evidenced by the ADSs on an individual basis. Holders of the ADSs will appoint the depositary or its nominee as their representative to exercise the voting rights attaching to the ordinary shares represented by the ADSs. You may not receive voting materials in time to instruct the depositary to vote, and it is possible that you, or persons who hold their ADSs through brokers, dealers or other third parties, will not have the opportunity to exercise a right to vote.

You may not receive distributions on our ordinary shares represented by the ADSs or any value for them if it is illegal or impractical to make them available to holders of ADSs.

              The depositary for the ADSs has agreed to pay to you the cash dividends or other distributions it or the custodian receives on our ordinary shares or other deposited securities after deducting its fees and expenses. You will receive these distributions in proportion to the number of our ordinary shares your ADSs represent. However, in accordance with the limitations set forth in the deposit agreement, it may be unlawful or impractical to make a distribution available to holders of ADSs. We have no obligation to take any other action to permit distribution on the ADSs, ordinary shares, rights or anything else to holders of the ADSs. This means that you may not receive the distributions we make on our ordinary shares or any value from them if it is unlawful or impractical to make them available to you. These restrictions may have a material adverse effect on the value of your ADSs.

We do not intend to pay dividends on our ordinary shares so any returns will be limited to the value of our ADSs.

              We currently anticipate that we will retain future earnings for the development, operation and expansion of our business and do not anticipate declaring or paying any cash dividends for the foreseeable future. Any return to shareholders will therefore be limited to the appreciation of their ADSs.

We have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

              Our management will have broad discretion in the application of the net proceeds from this offering. Because of the number and variability of factors that will determine our use of the net proceeds, their ultimate use may vary substantially from their currently intended use. Our management might not apply our net proceeds in ways that ultimately increase the value of your investment. While we expect to use the net proceeds from this offering as set forth in "Use of Proceeds," we are not obligated to do so. The failure by our management to apply these funds effectively could harm our business. If we do not invest or apply the net proceeds in ways that enhance shareholder value, we may fail to achieve expected financial results, which could adversely affect our business, financial condition and results of operations, and cause the price of our ADSs to decline.

As a new investor, you will experience substantial dilution as a result of this offering.

              The public offering price per ADS will be substantially higher than the net tangible book value per ADS prior to the offering. Consequently, if you purchase ADSs in this offering at the initial public offering price of $17.00 per ADS, you will incur immediate dilution of $13.22 per ADS (or $12.84 per ADS if the underwriters exercise in full their option to purchase additional ADSs). For further information regarding the dilution resulting from this offering, please see the section entitled "Dilution" in this prospectus. In addition, you may experience further dilution to the extent that additional ordinary shares are issued upon the exercise of outstanding options. This dilution is due to our earlier investors paying substantially less than the initial public offering price when they purchased their ordinary shares.

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If securities or industry analysts do not publish research reports about our business, or if they issue an adverse opinion about our business, the price of our ADSs and trading volume could decline.

              The trading market for our ADSs will be influenced by the research and reports that industry or securities analysts publish about us or our business. We do not currently have and may never obtain research coverage by securities and industry analysts. If no or few analysts commence research coverage of us, or one or more of the analysts who cover us issues an adverse opinion about our company, the price of our ADSs would likely decline. If one or more of these analysts ceases research coverage of us or fails to regularly publish reports on us, we could lose visibility in the financial markets, which in turn could cause the price of our ADSs or trading volume to decline.

As a foreign private issuer, we are exempt from a number of rules under the U.S. securities laws and are permitted to file less information with the Securities and Exchange Commission than U.S. companies. This may limit the information available to holders of the ADSs.

              We are a "foreign private issuer," as defined in the Securities and Exchange Commission's, or SEC, rules and regulations and, consequently, we are not subject to all of the disclosure requirements applicable to companies organized within the United States. For example, we are exempt from certain rules under the Exchange Act, that regulate disclosure obligations and procedural requirements related to the solicitation of proxies, consents or authorizations applicable to a security registered under the Exchange Act. In addition, our officers and directors are exempt from the reporting and "short-swing" profit recovery provisions of Section 16 of the Exchange Act and related rules with respect to their purchases and sales of our securities. Moreover, we are not required to file periodic reports and financial statements with the SEC as frequently or as promptly as U.S. public companies. Accordingly, there may be less publicly available information concerning our company than there is for U.S. public companies.

              As a foreign private issuer, we will file an annual report on Form 20-F within four months of the close of each fiscal year ended June 30 and reports on Form 6-K relating to certain material events promptly after we publicly announce these events. However, because of the above exemptions for foreign private issuers, our shareholders will not be afforded the same protections or information generally available to investors holding shares in public companies organized in the United States.

As a foreign private issuer, we are not subject to certain Nasdaq corporate governance rules applicable to U.S. listed companies.

              We will rely on a provision in Nasdaq's corporate governance rules that allows us to follow English corporate law and the Companies Act 2006 with regard to certain aspects of corporate governance. This allows us to follow certain corporate governance practices that differ in significant respects from the corporate governance requirements applicable to U.S. companies listed on Nasdaq.

              For example, we are exempt from Nasdaq regulations that require a listed U.S. company to: have a majority of the board of directors consist of independent directors; require non-management directors to meet on a regular basis without management present; have a quorum for shareholder meetings of not less than 33¹/3% of the outstanding shares of the Company's voting stock; and promptly disclose any waivers of the code for directors or executive officers that should address certain specified items.

              In accordance with our Nasdaq listing, our Audit Committee is required to comply with the provisions of Section 301 of the Sarbanes-Oxley Act and Rule 10A-3 of the Exchange Act, both of which are also applicable to Nasdaq-listed U.S. companies. Because we are a foreign private issuer, however, our Audit Committee is not subject to additional Nasdaq requirements applicable to listed U.S. companies, including an affirmative determination that all members of the Audit Committee are "independent," using more stringent criteria than those applicable to us as a foreign private issuer. Furthermore, Nasdaq's corporate governance rules require listed U.S. companies to, among other

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things, seek shareholder approval for the implementation of certain equity compensation plans and issuances of ordinary shares, which we are not required to follow as a foreign private issuer.

We are an emerging growth company within the meaning of the Securities Act and will take advantage of certain reduced reporting requirements.

              We are an "emerging growth company," as defined in the Jumpstart Our Business Start-ups Act of 2012, or the JOBS Act, and have elected to take advantage of the following provisions of the JOBS Act: the exemption from the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act; a requirement of only two years of audited financial statements in addition to any required interim financial statements and correspondingly reduced disclosure in management's discussion and analysis of financial condition and results of operations; not providing all of the compensation disclosure that may be required of non-emerging growth public companies under the U.S. Dodd-Frank Wall Street Reform and Consumer Protection Act; not disclosing certain executive compensation-related items such as the correlation between executive compensation and performance and comparisons of the Chief Executive Officer's compensation to employee compensation; not complying with any requirement that may be adopted by the Public Company Accounting Oversight Board regarding mandatory audit firm rotation or a supplement to the auditor's report providing additional information about the audit and the financial statements (auditor discussion and analysis and an extended transition period to comply with new or revised accounting standards applicable to public companies). In addition, to the extent that we no longer qualify as a foreign private issuer, we have elected to take advantage of (1) reduced disclosure obligations regarding executive compensation in our periodic reports and proxy statements; and (2) exemptions from the requirements of holding a non-binding advisory vote on executive compensation including golden parachute compensation. As a result of these elections, our future financial statements may not be comparable to companies that comply with these obligations earlier and our investors may not have access to certain information they may deem important.

              Our independent registered public accounting firm will not be required to provide an attestation report on the effectiveness of our internal control over financial reporting as long as we qualify as an "emerging growth company," which may increase the risk that weaknesses or deficiencies in our internal control over financial reporting go undetected and may make it more difficult for investors and securities analysts to evaluate our company. We cannot predict if investors will find the ADSs less attractive because we may rely on these exemptions. If some investors find our ADSs less attractive, there may be a less active trading market for the ADSs, and the price of the ADSs may be more volatile and may decline.

If we fail to establish and maintain proper internal controls, our ability to produce accurate financial statements or comply with applicable regulations could be impaired.

              Section 404(a) of the Sarbanes-Oxley Act, requires that beginning with our second annual report following our initial public offering, management assess and report annually on the effectiveness of our internal controls over financial reporting and identify any material weaknesses in our internal controls over financial reporting. Although Section 404(b) of the Sarbanes-Oxley Act requires our independent registered public accounting firm to issue an annual report that addresses the effectiveness of our internal controls over financial reporting, we have opted to rely on the exemptions provided in the JOBS Act, and consequently will not be required to comply with SEC rules that implement Section 404(b) of the Sarbanes-Oxley Act until such time as we are no longer an emerging growth company.

              We expect our first Section 404(a) assessment will take place for our annual report for our fiscal year ending June 30, 2016. The presence of material weaknesses could result in financial statement errors which, in turn, could lead to errors in our financial reports, delays in our financial reporting, we could require us to restate our operating results or our auditors may be required to issue a qualified audit report. We might not identify one or more material weaknesses in our internal controls in connection with evaluating our compliance with Section 404(a) of the Sarbanes-Oxley Act. In order to maintain and improve the effectiveness of our disclosure controls and procedures and internal controls over financial reporting, we will need to expend significant resources and provide significant management oversight.

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Implementing any appropriate changes to our internal controls may require specific compliance training of our directors and employees, entail substantial costs in order to modify our existing accounting systems, take a significant period of time to complete and divert management's attention from other business concerns. These changes may not, however, be effective in maintaining the adequacy of our internal control.

              If either we are unable to conclude that we have effective internal controls over financial reporting or, at the appropriate time, our independent auditors are unwilling or unable to provide us with an unqualified report on the effectiveness of our internal controls over financial reporting as required by Section 404(b) of the Sarbanes-Oxley Act, investors may lose confidence in our operating results, the price of our ADSs could decline and we may be subject to litigation or regulatory enforcement actions. In addition, if we are unable to meet the requirements of Section 404 of the Sarbanes-Oxley Act, we may not be able to remain listed on the Nasdaq.

We will incur significant increased costs as a result of operating as a company whose ADSs are publicly traded in the United States, and our management will be required to devote substantial time to new compliance initiatives.

              As a company whose ADSs will be publicly traded in the United States, we will incur significant legal, accounting, insurance and other expenses that we did not previously incur. In addition, the Sarbanes-Oxley Act, the Dodd-Frank Wall Street Reform and Consumer Protection Act and related rules implemented by the SEC and Nasdaq have imposed various requirements on public companies including requiring establishment and maintenance of effective disclosure and financial controls. Our management and other personnel will need to devote a substantial amount of time to these compliance initiatives. Moreover, these rules and regulations will increase our legal and financial compliance costs and will make some activities more time-consuming and costly. For example, we expect these rules and regulations to make it more difficult and more expensive for us to obtain director and officer liability insurance, and we may be required to incur substantial costs to maintain the same or similar coverage. These laws and regulations, could also make it more difficult and expensive for us to attract and retain qualified persons to serve on our board of directors, our board committees or as our executive officers. Furthermore, if we are unable to satisfy our obligations as a public company, we could be subject to delisting of the ADSs from Nasdaq, fines, sanctions and other regulatory action and potentially civil litigation.

U.S. investors may have difficulty enforcing civil liabilities against us, our directors, members of senior management and the experts named in this prospectus.

              Some of our directors, members of senior management and the experts named in this prospectus are non-residents of the United States, and all or a substantial portion of the assets of such persons are located outside the United States. As a result, it may not be possible to serve process on such persons or us in the United States or to enforce judgments obtained in U.S. courts against them or us based on civil liability provisions of the securities laws of the United States. Mayer Brown International LLP, our English solicitors, advised us that there is doubt as to whether English courts would enforce certain civil liabilities under U.S. securities laws in original actions or judgments of U.S. courts based upon these civil liability provisions. In addition, awards of punitive damages in actions brought in the United States or elsewhere may be unenforceable in the United Kingdom. An award for monetary damages under the U.S. securities laws would be considered punitive if it does not seek to compensate the claimant for loss or damage suffered and is intended to punish the defendant. The enforceability of any judgment in the United Kingdom will depend on the particular facts of the case as well as the laws and treaties in effect at the time. The United States and the United Kingdom do not currently have a treaty providing for recognition and enforcement of judgments (other than arbitration awards) in civil and commercial matters.

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The rights of our shareholders may differ from the rights typically offered to shareholders of a U.S. corporation.

              We are incorporated under English law. The rights of holders of ordinary shares and, therefore, certain of the rights of holders of ordinary shares, are governed by English law, including the provisions of the Companies Act 2006, and, upon adoption, by our amended articles of association, or "New Articles of Association." These rights differ in certain respects from the rights of shareholders in typical U.S. corporations. See "Description of Share Capital and Articles of Association—Differences in Corporate Law" in this prospectus for a description of the principal differences between the provisions of the Companies Act 2006 applicable to us and, for example, the Delaware General Corporation Law relating to shareholders' rights and protections.

We may lose our foreign private issuer status which would then require us to comply with the Exchange Act's domestic reporting regime and cause us to incur significant legal, accounting and other expenses.

              We are a foreign private issuer and therefore we are not required to comply with all of the periodic disclosure and current reporting requirements of the Exchange Act applicable to U.S. domestic issuers. We may no longer be a foreign private issuer as early as December 31, 2015, which would require us to comply with all of the periodic disclosure and current reporting requirements of the Exchange Act applicable to U.S. domestic issuers as of July 1, 2016. In order to maintain our current status as a foreign private issuer, either (a) a majority of our ordinary shares must be either directly or indirectly owned of record by non-residents of the United States or (b)(i) a majority of our executive officers or directors may not be U.S. citizens or residents, (ii) more than 50% of our assets cannot be located in the United States and (iii) our business must be administered principally outside the United States. If we lost this status, we would be required to comply with the Exchange Act reporting and other requirements applicable to U.S. domestic issuers, which are more detailed and extensive than the requirements for foreign private issuers. We may also be required to make changes in our corporate governance practices in accordance with various SEC and Nasdaq rules. The regulatory and compliance costs to us under U.S. securities laws if we are required to comply with the reporting requirements applicable to a U.S. domestic issuer may be significantly higher than the costs we would incur as a foreign private issuer. As a result, we expect that a loss of foreign private issuer status would increase our legal and financial compliance costs and would make some activities highly time consuming and costly. We also expect that if we were required to comply with the rules and regulations applicable to U.S. domestic issuers, it would make it more difficult and expensive for us to obtain director and officer liability insurance, and we may be required to accept reduced coverage or incur substantially higher costs to obtain coverage. These rules and regulations could also make it more difficult for us to attract and retain qualified members of our board.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

              This prospectus contains estimates and forward-looking statements, principally in "Risk Factors," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and "Business." Some of the matters discussed concerning our operations and financial performance include estimates and forward-looking statements within the meaning of the Securities Act and the Exchange Act.

              These forward-looking statements are subject to known and unknown risks, uncertainties, assumptions and other factors that could cause our actual results of operations, financial condition, liquidity, performance, prospects, opportunities, achievements or industry results, as well as those of the markets we serve or intend to serve, to differ materially from those expressed in, or suggested by, these forward-looking statements. These forward-looking statements are based on assumptions regarding our present and future business strategies and the environment in which we expect to operate in the future. Important factors that could cause those differences include, but are not limited to:

•

our ability to advance our NY-ESO TCR therapeutic candidate to a point where GSK exercises the option to license the product;



•

our ability to successfully advance our MAGE A-10 therapeutic candidate through clinical development;



•

the success, cost and timing of our product development activities and clinical trials;



•

our ability to submit an IND and successfully advance our technology platform to improve the safety and effectiveness of our existing TCR therapeutic candidates;



•

the rate and degree of market acceptance of T-cell therapy generally and of our TCR therapeutic candidates;



•

government regulation and approval, including, but not limited to, the expected regulatory approval timelines for TCR therapeutic candidates;



•

patents, including, any legal challenges thereto;



•

adverse developments in our relationship with Immunocore;



•

the level of pricing and reimbursement for our TCR therapeutic candidates;



•

general economic and business conditions or conditions affecting demand for our TCR therapeutic candidates in the markets in which we operate, both in the United States and internationally;



•

volatility in equity markets in general and in the biopharmaceutical sector in particular;



•

fluctuations in the price of raw materials and utilities;



•

our relationships with suppliers and other third-party providers;



•

increased competition from other companies in the biotechnology and pharmaceutical industries;



•

claims for personal injury or death arising from the use of our TCR therapeutic candidates produced by us;



•

changes in our business strategy or development plans, and our expected level of capital expenses;



•

our ability to attract and retain qualified personnel;



•

regulatory, environmental, legislative and judicial developments;

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•

a change in our status as an emerging growth company under the JOBS Act or a foreign private issuer; and



•

additional factors that are not known to us at this time.

              Additional factors that could cause actual results, financial condition, liquidity, performance, prospects, opportunities, achievements or industry results to differ materially include, but are not limited to, those discussed under "Risk Factors" in this prospectus. Additional risks that we may currently deem immaterial or that are not presently known to us could also cause the forward-looking events discussed in this prospectus not to occur. The words "believe," "may," "will," "estimate," "continue," "anticipate," "intend," "expect" and similar words are intended to identify estimates and forward-looking statements. Estimates and forward-looking statements speak only at the date they were made, and we undertake no obligation to update or to review any estimate and/or forward-looking statement because of new information, future events or other factors. Estimates and forward-looking statements involve risks and uncertainties and are not guarantees of future performance. Our future results may differ materially from those expressed in these estimates and forward-looking statements. In light of the risks and uncertainties described above, the estimates and forward-looking statements discussed in this prospectus might not occur, and our future results and our performance may differ materially from those expressed in these forward-looking statements due to, inclusive of, but not limited to, the factors mentioned above. Because of these uncertainties, you should not make any investment decision based on these estimates and forward-looking statements.

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EXCHANGE RATES

              Fluctuations in the exchange rate between the pound sterling and the U.S. dollar will affect the U.S. dollar amounts received by owners of the ordinary shares on conversion of dividends, if any, paid in pounds sterling on the ordinary shares and will affect the U.S. dollar price of the ordinary shares on Nasdaq. The table below shows the period end, average, high and low exchange rates of U.S. dollars per pound sterling for the periods shown. Average rates are computed by using the noon buying rate of the Federal Reserve Bank of New York for the U.S. dollar on the last business day of each month during the relevant year indicated or each business day during the relevant month indicated. The rates set forth below are provided solely for your convenience and may differ from the actual rates used in the preparation of our consolidated financial statements included in this prospectus and other financial data appearing in this prospectus.

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USE OF PROCEEDS

              We estimate that we will receive total estimated net proceeds from this offering of approximately $175.7 million, based on the initial public offering price of $17.00 per ADS, or $202.3 million if the underwriters exercise their option to purchase additional ADSs in full, in each case after deducting estimated underwriting discounts and commissions and estimated expenses of the offering payable by us.

              As of December 31, 2014, we had approximately $101.5 million of cash and cash equivalents and $24.8 million of short-term deposits. We intend to use the net proceeds we receive from this offering together with our existing cash on hand, as follows:

•

$30 million to advance and accelerate the clinical development of our MAGE A-10 TCR therapeutic candidate through Phase 1/2 clinical trials;



•

$25 million to put in place a pilot manufacturing capability for our clinical trials and fund its operations until the middle of 2018, and to initiate a feasibility assessment for a commercially viable manufacturing platform for all of our TCR therapeutic candidates;



•

$140 million to advance additional TCR therapeutic candidates into preclinical testing, continue preclinical testing of our AFP TCR therapeutic candidate and progress such TCR therapeutic candidates through to clinical trials as quickly as possible; and



•

the remainder to fund working capital, including other general corporate purposes.

              The expected uses of the net proceeds we receive from this offering represent our intentions based upon our current plans and business conditions. The amounts and timing of our actual expenses may vary significantly depending on numerous factors including progression of our TCR therapeutic candidates through their respective preclinical and clinical programs and the data obtained. Accordingly, we will have broad discretion over the uses of the net proceeds from this offering, and investors will be relying on the judgment of our management regarding the application of the net proceeds.

              Based on our planned use of the net proceeds from this offering, our existing cash and cash equivalents on hand together with expected milestone payments to us under our GSK collaboration and license agreement, we estimate that such funds will be sufficient to enable us to advance and accelerate clinical development of existing preclinical candidates, put in place a pilot manufacturing capability for our clinical trials and fund its operations until the middle of 2018, and to initiate a feasibility assessment for a commercially viable manufacturing platform, advance additional TCR therapeutic candidates into preclinical testing, progress such TCR therapeutic candidates through clinical trials, and fund our operating expenses and capital expenditure requirements for the foreseeable future, including for at least the next 24 months. We have based this estimate on assumptions that may prove to be wrong, and we could use our available capital resources sooner than we currently expect in which case we would need to secure additional funding to further advance our MAGE A-10 TCR therapeutic candidate through clinical development and for future TCR therapeutic candidates we choose to develop. Pending these uses, we intend to invest the net proceeds from this offering in short or medium-term interest-bearing obligations, investment-grade instruments, certificates of deposit or direct or guaranteed obligations of the U.K. or U.S. governments.

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DIVIDENDS AND DIVIDEND POLICY

              Since our inception, we have not declared or paid any dividends on our ordinary shares. We intend to retain any earnings for use in our business and do not currently intend to pay dividends on our ordinary shares. The declaration and payment of any future dividends will be at the discretion of our board of directors and will depend upon our results of operations, cash requirements, financial condition, contractual restrictions, restrictions imposed by our indebtedness, any future debt agreements or applicable laws and other factors that our board of directors may deem relevant.

              See "Description of American Depositary Shares—Dividends and Distributions" in this prospectus for more information on dividend rights as a holder of ADSs.

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CORPORATE REORGANIZATION

              Adaptimmune Therapeutics Limited was formed in December 2014 as a private company with limited liability in England and Wales. It was incorporated with nominal assets and liabilities for the purpose of consummating the corporate reorganization described herein. Upon the formation of Adaptimmune Therapeutics Limited, Mr. Noble became the sole shareholder of Adaptimmune Therapeutics Limited, holding one ordinary share in the capital of Adaptimmune Therapeutics Limited.

              Adaptimmune Limited was formed as a new, separate company and licensed its TCR technology from Medigene AG in July 2008. Pursuant to the terms of the first stage of a corporate reorganization, on February 23, 2015, all shareholders of Adaptimmune Limited exchanged each of the Series A preferred shares and ordinary shares held by them for newly issued Series A preferred shares and ordinary shares of Adaptimmune Therapeutics Limited on a one-for-100 basis, and, as a result, Adaptimmune Limited became a wholly owned subsidiary of Adaptimmune Therapeutics Limited. On March 20, 2015, all holders of options over ordinary shares of Adaptimmune Limited exchanged each of their options for equivalent options over ordinary shares of Adaptimmune Therapeutics Limited. On April 1, 2015, Adaptimmune Therapeutics Limited re-registered as a public limited company with the name Adaptimmune Therapeutics plc.

              The following description summarizes all the stages of our corporate reorganization.

Exchange of Adaptimmune Limited shares for Adaptimmune Therapeutics Limited shares

              Prior to this offering, the share capital of Adaptimmune Limited was divided into Series A preferred shares and ordinary shares. On February 23, 2015, the Series A preferred shareholders of Adaptimmune Limited exchanged each Series A preferred share in Adaptimmune Limited for 100 newly issued Series A preferred shares of Adaptimmune Therapeutics Limited and the ordinary shareholders of Adaptimmune Limited exchanged each of their ordinary shares of Adaptimmune Limited for 100 newly issued ordinary shares of Adaptimmune Therapeutics Limited.

              As a result, Adaptimmune Therapeutics Limited became the sole shareholder of Adaptimmune Limited, and the former Series A preferred shareholders of Adaptimmune Limited became holders of an aggregate of 175,841,800 Series A preferred shares of Adaptimmune Therapeutics Limited, while the former ordinary shareholders of Adaptimmune Limited became holders of an aggregate of 181,370,100 ordinary shares of Adaptimmune Therapeutics Limited.

Exchange of Adaptimmune Limited share options for Adaptimmune Therapeutics Limited share options

              As of February 28, 2015, there were 206,427 outstanding options held by certain directors, officers, employees and consultants to purchase ordinary shares of Adaptimmune Limited. The holders of the outstanding 206,427 options to purchase ordinary shares in Adaptimmune Limited accepted an offer of equivalent options to purchase an aggregate of 20,642,700 ordinary shares in Adaptimmune Therapeutics Limited in exchange for the release of the original options. This exchange was completed on March 20, 2015.

Re-registration of Adaptimmune Therapeutics Limited as Adaptimmune Therapeutics plc

              Following Adaptimmune Limited having become a wholly-owned subsidiary of Adaptimmune Therapeutics Limited and the exchange of share options described above, Adaptimmune Therapeutics Limited re-registered as a public limited company on April 1, 2015. The number of ordinary shares and options held by holders was not affected by the re-registration.

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              We refer to the above-described reorganization pursuant to which Adaptimmune Therapeutics Limited acquired the entire issued share capital of Adaptimmune Limited in exchange for the issue of Series A preferred shares and ordinary shares by Adaptimmune Therapeutics Limited, the exchange of share options and the re-registration of Adaptimmune Therapeutics Limited as Adaptimmune Therapeutics plc together as our corporate reorganization.

              Certain resolutions were required to be passed by the shareholders of Adaptimmune Therapeutics plc prior to the completion of this offering, details of which are set out in "Description of Share Capital and Articles of Association." We have received all such required approvals from our shareholders.

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CAPITALIZATION

              The following table presents our total capitalization and cash and cash equivalents as of December 31, 2014:

•

on an actual basis; and



•

on a pro forma as adjusted basis to give further effect to (i) the sale by us of 11,250,000 ADSs in this offering at the initial public offering price of $17.00 per ADS, after deduction of the underwriting discounts and commissions and estimated offering expenses payable by us and assuming no exercise of the option by the underwriters to purchase additional ADSs, and (ii) the exchange of each Series A preferred share and ordinary share in the capital of Adaptimmune Limited for newly issued Series A preferred shares and ordinary shares of Adaptimmune Therapeutics Limited on a one-for-100 basis as part of our corporate reorganization; and (iii) the automatic conversion of all our outstanding Series A preferred shares into an aggregate of 175,841,800 ordinary shares immediately prior to the admission of our ADSs to trading on Nasdaq in connection with this offering.

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DILUTION

              If you invest in the ADSs, your interest will be diluted to the extent of the difference between the initial public offering price per ADS and our net tangible book value per ADS after this offering. Dilution results from the fact that the initial public offering price per ADS is substantially in excess of the net tangible book value per ordinary share. Our net tangible book value as of December 31, 2014 was approximately $91.9 million or $0.26 per ordinary share ($1.54 per ADS). Net tangible book value per share represents the amount of total tangible assets, minus the amount of total liabilities, divided by the total number of ordinary shares outstanding. Dilution is determined by subtracting net tangible book value per ADS from the initial public offering price per ADS set forth on the cover page of this prospectus and after deducting underwriting discounts and commissions and estimated offering expenses payable by us.

              Without taking into account any other changes in such net tangible book value after December 31, 2014, other than to give effect to our sale of ADSs offered in this offering at the initial public offering price of $17.00 per ADS after deduction of underwriting discounts and commissions and estimated offering expenses payable by us, our pro forma net tangible book value at December 31, 2014 would have been $0.63 per outstanding ordinary share ($3.78 per ADS), including ordinary shares underlying our outstanding ADSs. This represents an immediate increase in pro forma net tangible book value of $0.37 per ordinary share, or $2.24 per ADS, to existing shareholders and an immediate dilution in net tangible book value of $2.20 per ordinary share, or $13.22 per ADS, to purchasers of ADSs in this offering. The following table presents this dilution to new investors purchasing ADSs in the offering:

              The following table summarizes, on a pro forma basis as of December 31, 2014, the differences between the shareholders as of December 31, 2014 and the new investors with respect to the number of ordinary shares purchased from us, the total consideration paid to us and the average price per ordinary share paid at the initial public offering price of $17.00 per ADS before deducting underwriting discounts and commissions and estimated offering expenses payable by us. The total number of ADSs does not include 1,687,500 ADSs issuable pursuant to the exercise of the option granted to the underwriters.

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              The share information above:

•

excludes 29,826,662 of our ordinary shares, issuable upon exercise of outstanding options under equity incentive arrangements, as of March 31, 2015;



•

excludes 2,619,338 of our ordinary shares potentially issuable pursuant to future awards which may be granted after March 31, 2015 and before the completion of our initial public offering under our equity incentive plans (we do not intend to grant any such options);



•

excludes 1,270,000 of our ordinary shares potentially issuable pursuant to awards intended to be granted immediately after the completion of our initial public offering under the Adaptimmune Therapeutics plc 2015 Share Option Scheme at an exercise price per ordinary share equal to the initial public offering price of the ADSs in this offering divided by six (reflecting the ADS to ordinary share ratio);



•

excludes ordinary shares potentially issuable pursuant to other future awards under the Adaptimmune Therapeutics plc 2015 Share Option Scheme and the Adaptimmune Therapeutics plc 2015 Company Share Option Plan in an amount of up to 8% of our issued share capital immediately following this offering on a fully diluted basis;



•

gives effect to the exchange by holders of each of the Series A preferred shares and ordinary shares of Adaptimmune Limited for newly issued Series A preferred shares and ordinary shares of Adaptimmune Therapeutics Limited (now Adaptimmune Therapeutics plc) on a one-for-100 basis as part of our corporate reorganization; and



•

assumes no exercise by the underwriters of their option to purchase up to 1,687,500 additional ADSs.

              The discussion and tables above assume the conversion of all of our outstanding Series A preferred shares into an aggregate of 175,841,800 ordinary shares immediately prior to the admission of our ADSs to trading on Nasdaq.

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SELECTED CONSOLIDATED FINANCIAL INFORMATION

              The following table summarizes our consolidated financial data as of the dates and for the periods indicated. The consolidated financial data as of June 30, 2014 and 2013 and for the years ended June 30, 2014 and 2013 have been derived from our consolidated financial statements, which have been prepared in accordance with International Financial Reporting Standards, or IFRS, as issued by the International Accounting Standards Board, or IASB, and audited in accordance with the standards of the U.S. Public Company Accounting Oversight Board, and included elsewhere in this prospectus.

              The consolidated financial data as of and for the six months ended December 31, 2013 and 2014 have been derived from our unaudited interim consolidated financial statements included elsewhere in this prospectus. The unaudited interim consolidated financial statements have been prepared on the same basis as our audited consolidated financial statements and include all normal recurring adjustments that we consider necessary for a fair statement of our financial position and operating results as of the dates and for the periods presented.

              We maintain our books and records in, and our consolidated financial statements are prepared and presented in, pounds sterling, our presentation currency. Solely for the convenience of the reader, our consolidated financial statements as of and for the year ended June 30, 2014 and the six months ended December 31, 2014 have been translated into U.S. dollars at £1.00 = $1.5578 based on the certified foreign exchange rates published by the Federal Reserve Bank of New York on December 31, 2014. Such convenience translation should not be construed as a representation that the pound sterling amounts have been or could be converted into U.S. dollars at this or at any other rate of exchange, or at all.

              Our historical results are not necessarily indicative of the results that may be expected in the future. Our interim financial results for the periods presented are not necessarily indicative of results for a full year or for any subsequent interim period. The following summary consolidated financial data should be read in conjunction with "Management's Discussion and Analysis of Financial Condition and Results of Operations" and our consolidated financial statements included elsewhere in this prospectus.

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MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS

              The following discussion of our financial condition and results of operations should be read in conjunction with "Selected Consolidated Financial Information," and our consolidated financial statements included elsewhere in this prospectus. We present our consolidated financial statements in pounds sterling and in accordance with International Financial Reporting Standards, or IFRS, as issued by the International Accounting Standards Board, or IASB.

              The statements in this discussion regarding industry outlook, our expectations regarding our future performance, liquidity and capital resources and other non-historical statements are forward-looking statements. These forward-looking statements are subject to numerous risks and uncertainties, including, but not limited to, the risks and uncertainties described in "Risk Factors" and "Special Note Regarding Forward-Looking Statements" in this prospectus. Our actual results may differ materially from those contained in or implied by any forward-looking statements.

              Solely for the convenience of the reader, unless otherwise indicated, all pound sterling amounts as of and for the year ended June 30, 2014 and the six months ended December 31, 2014 have been translated into U.S. dollars at the rate at December 31, 2014, of £1.00 = $1.5578. These translations should not be considered representations that any such amounts have been, could have been or could be converted into U.S. dollars at that or any other exchange rate as of that or any other date.

Overview

              We are a clinical-stage biopharmaceutical company focused on novel cancer immunotherapy products based on our T-cell receptor platform. We have developed a comprehensive proprietary platform that enables us to identify cancer targets in the form of peptides, find and genetically engineer T-cell receptors, or TCRs, and produce TCR therapeutic candidates for administration to patients. We engineer TCRs to increase their affinity to cancer-specific peptides, including our lead target peptides, NY-ESO and MAGE A-10 in order to target and then destroy cancer cells in patients. Unlike current antibodies and therapies that are based on the use of chimeric antigen receptor T cells, or CAR-Ts, our TCR therapeutic candidates are able to target intracellular as well as extracellular cancer antigens. This capability significantly increases the breadth of targets, particularly as intracellular targets are known to be more closely associated with cancer, but are inaccessible with other autologous T-cell immunotherapy approaches. We believe this approach will lead to TCR therapeutic candidates that have the potential to significantly impact cancer treatment and clinical outcomes of patients with cancer.

              To date, we have financed our operations primarily through private placements of equity securities, including preferred shares, government grants, research and development tax credits and payments for collaborative research and development services. Through December 31, 2014, we have raised £20.2 million through the issuance of ordinary shares, and a further £62.5 million through the issuance of Series A preferred shares. In the year ended June 30, 2014, we received a cash upfront fee of £25 million under our collaboration and license agreement with GlaxoSmithKline, or GSK, of which we recognized £0.4 million as revenue. In the six months ended December 31, 2014, we received cash milestone payments from GSK of £2.5 million and achieved a further £2.0 million milestone that was paid in January 2015. The total revenue recognized under the GSK collaboration and license agreement in the six months ended December 31, 2014 was £2.4 million. Through December 31, 2014, we recognized £0.6 million of income in the form of government grants from the United Kingdom and European Union, and recognized £2.2 million in the form of research and development tax credits.

              We have generated losses since our inception in 2008, during which time we have devoted substantially all of our resources to our research and development efforts relating to our TCR therapeutic candidates, including engaging in activities to manufacture and supply our TCR therapeutic candidates for clinical trials in compliance with current good manufacturing practices, or cGMP,

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conducting clinical trials of our TCR therapeutic candidates, providing general and administrative support for these operations and protecting our intellectual property. We do not have any products approved for sale and have not generated any revenue from product supplies or royalties. Based on our current plans, we do not expect to generate product or royalty revenues unless and until we obtain marketing approval for, and commercialize, any of our TCR therapeutic candidates.

              For the years ended June 30, 2013 and 2014, we incurred net losses of £5.6 million and £7.5 million, respectively. For the six months ended December 31, 2013 and 2014, we incurred net losses of £3.1 million and £3.1 million, respectively. As of December 31, 2014, we had an accumulated deficit of £21.9 million. We expect to continue incurring significant losses as we continue with our research and development programs and to incur general and administrative costs associated with our operations. The extent of funding required to develop our product candidates is difficult to estimate given the novel nature of our TCR therapeutic candidates. Our profitability is dependent upon the successful development, approval, and commercialization of our TCR therapeutic candidates, successfully achieving GSK milestones and achieving a level of revenues adequate to support our cost structure. We may never achieve profitability, and unless and until we do, we will continue to need to raise additional cash. We intend to fund future operations through milestone payments under our collaboration and license agreement with GSK and additional equity financings.

              We do not expect to generate revenue from sales of our TCR therapeutic candidates unless and until we successfully complete development and obtain regulatory approval for one or more of our TCR therapeutic candidates, which we expect will take a number of years and is subject to significant uncertainty. We have no manufacturing facilities and all of our manufacturing activities are contracted out to third parties. Additionally, we currently utilize third-party contract research organizations, or CROs, to carry out our clinical development activities, and we do not yet have a sales organization. If we obtain regulatory approval for any of our TCR therapeutic candidates, we expect to incur significant commercialization expenses related to sales, marketing, manufacturing and distribution of our TCR therapeutic candidates.

Strategic Collaborations and Licensing Agreements

              We entered a strategic collaboration with GSK in May 2014 regarding the development, manufacture and commercialization of TCR therapeutic candidates. We expect to capitalize on GSK's drug development and regulatory expertise and commercial capabilities to bring our partnered therapeutic products to market. Under the collaboration and license agreement, we received an upfront payment of £25 million and are entitled to various milestone payments based on the achievement of specified development and commercialization milestones by either us or GSK. As previously announced, these milestone payments have a potential value of approximately $350 million over the next seven years. In the six months ended December 31, 2014, we received cash milestone payments from GSK of £2.5 million and achieved a further £2.0 million milestone that was paid in January 2015. The total revenue recognized under the GSK collaboration and license agreement in the six months ended December 31, 2014 was £2.4 million. Development milestones are payable on a collaboration program by collaboration program basis.

              Adaptimmune and Immunocore have a shared history, some overlap in our board membership and substantial overlap in our shareholder base. We have entered into several agreements regarding the shared use of certain services including licensing and research collaboration. Since inception, we have maintained separate financial statements and we believe our agreements are on an arm's length basis. Accordingly, we do not believe our relationship with Immunocore has had or will have a significant impact on our financial statements.

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Grants

              In February 2014, we were awarded a £2.2 million grant from the United Kingdom Technology Strategy Board, or TSB, to fund the U.K. clinical development of our adopted T-cell therapy for breast cancer, using our engineered TCR to a second cancer testis peptide. The TSB is a not-for-profit body funded by the United Kingdom national government. Under the terms of the grant, we retain all rights, results and intellectual property relating to the program. The TSB will pay us under this grant in quarterly installments based on costs incurred and we expect to utilize it over a three-year period that commenced in January 2014. For the year ended June 30, 2014 and for the six months ended December 31, 2014, we recognized income of £0.1 million and £0.2 million, respectively, from this grant.

              In 2012, we were awarded a £0.2 million grant as part of a collaboration program called ATTACK 2 (Adoptive engineered T-cell Targeting to Activate Cancer Killing). This program is funded by a European Union Framework Seven (FP7) sponsored by The Christie Trials Co-ordination Unit and is intended to cover two Phase 1/2 clinical trials at seven clinical sites in the United Kingdom, Netherlands, Italy and Sweden using our NY-ESO TCR therapeutic candidate. We expect to receive payments under this grant in quarterly installments based on costs incurred over a four-year period starting in the first quarter of 2015.

Important Financial and Operating Terms and Concepts

Revenue

              To date, we have not generated any revenue from the sales of our TCR therapeutic candidates. Our revenues have been solely derived from our collaboration and license agreement with GSK. The terms of this arrangement contain multiple milestones associated with: (i) co-development of our NY-ESO TCR therapeutic candidate, (ii) associated manufacturing optimization work and (iii) co-development of other TCR target programs. Fair value is attributable to these elements based on the value attributed to each by the partner. GSK is also obligated to pay us certain milestone fees, which are generally non-refundable and are payable upon satisfactory completion of specified research and development activities.

Other Income

              We generate grant income primarily through research and development grant programs offered by the U.K. and EU governments. We recognize grant income when there is reasonable likelihood that we will receive the grant and we have complied with the terms of the grant.

              We also have received income from Immunocore Limited ("Immunocore") under a transitional services agreement, which we will no longer receive under our revised transitional services agreement with Immunocore.

Research and Development Expenses

              Research and development expenses consist principally of:

•

salaries for research and development staff and related expenses, including management benefits;



•

costs for production of preclinical compounds and drug substances by contract manufacturers;



•

fees and other costs paid to contract research organizations in connection with additional preclinical testing and the performance of clinical trials;



•

costs of related facilities, materials and equipment;

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•

costs associated with obtaining and maintaining patents and other intellectual property;



•

amortization and depreciation of tangible and intangible fixed assets used to develop our TCR therapeutic candidates; and



•

share-based compensation expenses.

              In the fiscal years ended June 30, 2013 and 2014, we spent £5.4 million and £7.4 million, respectively, on research and development. In the six months ended December 31, 2013 and 2014, we spent £2.7 million and £5.7 milllion, respectively, on research and development. We expect that our total research and development expenses in 2015 will be significantly higher than in fiscal years 2013 and 2014 as we continue to invest in our technology platform, current clinical trials, and manufacturing optimization activities, as well as develop our pipeline of TCR therapeutic candidates.

              During the fiscal years ended June 30, 2015 and 2016, we plan to increase the number of clinical trials we are running, both in new indications (including our MAGE-A10 TCR therapeutic candidate) and as part of the GSK collaboration for our NY-ESO TCR therapeutic candidate. In order to commence these trials, we must incur in advance the costs of preclinical testing, vector production and other substances. The process optimization activities planned under the GSK collaboration will also require a large increase in the research and development expenses, which we expect will be funded by receipt of milestone payments from GSK. We expect to increase the number of staff employed in our research and development departments in order to invest in our future pipeline of TCR therapeutic candidates, develop our platform and manage clinical trials. This will significantly increase the related salaries and share-based compensation expenses, as well as require higher expenditures on facilities, materials and equipment.

              We expense research and development costs as incurred. We recognize costs for certain development activities based on an evaluation of the progress to completion of specific tasks using information and data provided to us by our vendors and our clinical sites.

              Our research and development expenses may vary substantially from period to period based on the timing of our research and development activities, which depends upon the timing of initiation of clinical trials and the rate of enrollment of patients in clinical trials. We expect research and development expenses to increase as we advance the development of our preclinical TCR therapeutic candidates. The successful development of our TCR therapeutic candidates is highly uncertain. At this time, we cannot reasonably estimate the nature, timing and estimated costs of the efforts that will be necessary to complete the development of, or the period, if any, in which material net cash inflows may commence from, any of our TCR therapeutic candidates.

              We may never succeed in achieving regulatory approval for any of our TCR therapeutic candidates. The duration, costs, and timing of clinical trials and development of our TCR therapeutic candidates will depend on a variety of factors, including:

•

the scope, rate of progress, and expense of our ongoing as well as any additional clinical trials and other research and development activities;



•

uncertainties in clinical trial enrollment rate;



•

future clinical trial results;



•

significant and changing government regulation; and



•

the timing and receipt of any regulatory approvals.

              A change in the outcome of any of these variables may significantly change the costs and timing associated with the development of that TCR therapeutic candidate. For example, if the FDA, or another regulatory authority, requires us to conduct clinical trials beyond those that we currently anticipate will be required for regulatory approval, or if we experience significant delays in enrollment

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in any of our clinical trials, we could be required to expend significant additional financial resources and time on the completion of clinical development.

General and Administrative Expenses

              Our general and administrative expenses consist principally of:

•

salaries for employees other than research and development staff, including benefits;



•

business development expenses, including travel expenses;



•

professional fees for auditors and other consulting expenses not related to research and development activities;



•

professional fees for lawyers not related to the protection and maintenance of our intellectual property;



•

cost of facilities, communication, and office expenses;



•

information technology expenses;



•

amortization and depreciation of tangible and intangible fixed assets not related to research and development activities; and



•

share-based compensation expenses.

              We expect that our general and administrative expenses will increase after this offering, primarily due to the costs of operating as a public company, such as additional legal, accounting, and corporate governance expenses, including expenses related to compliance with the Sarbanes-Oxley Act, directors' and officers' insurance premiums, and investor relations. In addition, we were initially formed without our own administrative infrastructure and therefore relied on Immunocore, a company with whom we have a shared history, to provide certain administrative services to us under a facilities and services agreement. Over the past year and going forward, we have begun to put in place our own administrative infrastructure and therefore rely on Immunocore to a lesser extent than in prior years to provide administrative services to us. We also have a number of other agreements with Immunocore but we have always maintained separate financial statements and audit procedures. See "Related Party Transactions—Agreements with Immunocore Limited."

Finance Income and Costs

              Finance income includes interest earned on our instant-access cash reserves as well as foreign exchange gains on cash held in U.S. dollars. Finance costs consist primarily of interest charged on any bank overdrafts.

              For the six months ended December 31, 2014, we reported a foreign exchange gain of £1.4 million within other income.

Taxation

              We are subject to corporate taxation in the United Kingdom. Our subsidiary Adaptimmune LLC is subject to corporate taxation in the United States. Our tax recognized represents the sum of the tax currently payable or recoverable. No deferred tax assets are recognized on our losses carried forward because there is currently no indication that we shall make sufficient profits to utilize these tax losses.

              As a company that carries out extensive research and development activities, we benefit from the U.K. research and development tax credit regime for small and medium sized companies, whereby our principal research subsidiary company, Adaptimmune Limited, is able to surrender the trading losses that arise from its research and development activities for a payable tax credit of up to 33.4% of eligible research and development expenditures. Qualifying expenditures largely comprise employment costs for research staff, consumables and certain internal overhead costs incurred as part of research

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projects. Subcontracted research expenditures are eligible for a cash rebate of up to 21.7%. A large proportion of costs in relation to our pipeline research, clinical trials management and manufacturing development activities, all of which are being carried out by Adaptimmune Limited, are eligible for inclusion within these tax credit cash rebate claims.

              We may not be able to claim such research and development tax credits on research and development expenditures in relation to the GSK collaboration and licensing agreement because they may be considered as subsidized expenditures. We may not be able to continue to claim research and development tax credits in the future as we become a public company because we may no longer qualify as a small or medium sized company.

              Unsurrendered tax losses can be carried forward to be offset against future taxable profits. After accounting for tax credits receivable, there are accumulated tax losses for carry forward in the UK amounting to £14 million at June 30, 2014. No deferred tax asset is recognized in respect of accumulated tax losses on the basis that suitable future trading profits are not sufficiently certain.

              We may also benefit in the future from the United Kingdom's "patent box" regime, which would allow certain profits attributable to revenues from patented products to be taxed at a rate that over time will be reduced to 10%. As we have many different patents covering our products, future upfront fees, milestone fees, product revenues, and royalties could be taxed at this favorably low tax rate. When taken in combination with the enhanced relief available on our research and development expenditures, we expect a long-term lower rate of corporation tax to apply to us. As such, we consider that the United Kingdom is a favorable location for us to continue to conduct our business for the long term.

              Value Added Tax ("VAT") is charged on all qualifying goods and services by VAT-registered businesses. An amount of 20% of the value of the goods or services is added to all sales invoices and is payable to the UK tax authorities. Similarly, VAT paid on purchase invoices is reclaimable from the UK tax authorities.

Results of Operations

Comparison of the Six Months Ended December 31, 2014 and 2013

              The following table summarizes the results of our operations for the six months ended December 31, 2014 and 2013, together with the changes to those items.

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Revenue

              Revenue increased from £0 for the six months ended December 31, 2013 to £2.4 million for the six months ended December 31, 2014 due to recognition of revenue under the collaboration and licensing agreement with GSK, which was entered into on May 30, 2014. We expect our revenue in the year ending June 30, 2015 to be significantly higher than the same period in 2014 because we expect to achieve additional milestones under the GSK collaboration and license agreement and to recognize related receivables from milestone payments in 2015.

Research and Development Expenses

              During the six months ended December 31, 2014, our research and development expenses were £5.7 million, an increase of 109% from the six months ended December 31, 2013. Our research and development expenses are highly dependent on the phases of our research projects and therefore fluctuate from year to year. We expect our total research and development expenses in the six months ending December 31, 2015 to be higher than our expenses in the same periods in 2013 and 2014 due to the ongoing advancement of our preclinical programs and clinical trials.

              The increase in our research and development expenses in the six months ended December 31, 2014 from the same period in 2013 was primarily due to an increase in two key drivers of our expenses:

•

The increase in the number of employees engaged in research and development from an average of 23 to 42. These costs include salaries, facilities, materials, equipment, depreciation of tangible fixed assets, and expenses for share-based compensation; and



•

An increase in subcontracted expenditures, including clinical trial expenses, CRO costs, and manufacturing expenses drive by increased recruitment in our clinical trials.

              We have not historically tracked the internal costs of each research and development project since employees may be engaged in multiple projects at a time. In the six months ended December 31, 2014, we employed an average of 13 employees working in our clinical and development teams, primarily responsible for development of our TCR therapeutic candidates targeting NY-ESO and MAGE-A10. The remainder of our scientific employees are engaged in developing our future pipeline.

              Our subcontracted costs for the six months ended December 31, 2014 were £2.6 million, of which £2.1 million related to our TCR therapeutic candidate targeting NY-ESO.

General and Administrative Expenses

              General and administrative expenses increased by 165% to £2.1 million for the six months ended December 31, 2014 from £0.8 million in the same period in 2013. This increase was primarily due to the addition of key management and other professionals, and related costs to support our growth, including facilities costs, IT costs and consultancy. In particular, our corporate headcount increased from an average of three to 10, increasing the costs of salaries, travel and expenses for share-based compensation.

Finance Income and Finance Expense

              Finance income was £1.5 million for the six months ended December 31, 2014, compared to an expense for the same period in 2013. Finance income consisted primarily of £1.4 million arising from exchange gains on cash and deposits held in U.S. dollars.

Taxation

              The research and development tax credit increased by 36% to £0.5 million for the six months ended December 31, 2014 from £0.4 million in the same period in 2013. The increase was driven by the increase in our research and development expenditures. The proportion of those expenditures that is

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eligible for research and development tax credits decreased during that period due to the income received under the GSK collaboration and license agreement and therefore the increase in the tax credit is less than the increase in the research and development expenditure.

Comparison of Years Ended June 30, 2014 and 2013

              The following table summarizes the results of our operations for the years ended June 30, 2014 and 2013, together with the changes to those items.

Revenue

              Revenue increased from £0.0 for the year ended June 30, 2013 to £0.4 million for the year ended June 30, 2014 due to recognition of revenue under the collaboration and licensing agreement with GSK, which was entered into on May 30, 2014. We expect our revenue in the year to June 30, 2015 to be significantly higher than the same period in 2014 due to recognition of revenue in connection with work performed under the GSK agreement.

Research and Development Expenses

              Research and development expenses increased by 37% to £7.4 million for the year ended June 30, 2014 from £5.4 million in the same period in 2013. Our research and development expenses are highly dependent on the phases of our research projects and therefore fluctuate from year to year. We expect our total research and development expenses in the year ended June 30, 2015 to be higher than our expenses in our fiscal years ended June, 2013 and 2014 due to the ongoing advancement of our preclinical programs and clinical trials.

              The increase in our research and development expenses in the year ended June 30, 2014 from the same period in 2013 was primarily due to an increase in two key drivers of our expenses:

•

The increase in the number of employees engaged in research and development from an average of 17 to 27. These costs include salaries, facilities, materials, equipment, depreciation of tangible fixed assets, and expenses for share-based compensation; and



•

An increase in subcontracted expenditures, including clinical trial expenses, CRO costs, and manufacturing expenses drive by increased recruitment in our clinical trials.

              We have not historically tracked the internal costs of each research and development project since employees may be engaged in multiple projects at a time. In the year ended June 30, 2014, we employed an average of 11 employees working in our clinical and development teams, primarily

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responsible for development of our TCR therapeutic candidates targeting NY-ESO and MAGE-A10. The remainder of our scientific employees are engaged in developing our future pipeline.

              Our subcontracted costs for the year ended June 30, 2014 were £3.2 million, which were substantially all related to our TCR therapeutic candidate targeting NY-ESO.

General and Administrative Expenses

              General and administrative expenses increased by 101% to £1.6 million for the year ended June 30, 2014 from £0.8 million in the same period in 2013. This was primarily due to the addition of key management and other professionals, and related costs to support our growth.

Finance Income and Finance Expense

              Finance income and finance expense were both less than £0.1 million for the years ended June 30, 2014 and 2013. Finance income consisted of bank interest on cash balances and short-term deposits. Finance expense consisted of bank interest on overdraft arrangements.

Taxation

              The research and development tax credit increased by 70% to £1.0 million for the year ended June 30, 2014 from £0.6 million in the same period in 2013. The increase was driven by the increase in our research and development expenditures; the increase in the proportion of those expenditures that is eligible for research and development tax credits; and an increase in the rate of tax credits from 11.0% to 14.5% that became effective on April 1, 2014.

Liquidity and Capital Resources

Sources of Funds

              Since our inception, we have incurred significant net losses and negative cash flows from operations, with the exception of the year ended June 30, 2014, when we incurred a net loss but generated positive cash flows from operations. We incurred net losses of £7.5 million and £5.6 million in the years ended June 30, 2014 and 2013, respectively, and net losses of £3.1 million and £3.1 million in the six months ended December 31, 2014 and 2013, respectively. We generated £21.9 million of cash from operating activities in the year ended June 30, 2014 and used £5.1 million of cash for operating activities for the year ended June 30, 2013. We used £9.7 million and £3.5 million cash for operating activities in the six months ended December 31, 2014 and 2013, respectively. As of June 30, 2014 and December 31, 2014, we had accumulated deficits of £18.9 million and £21.9 million, respectively.

              As of June 30, 2014 and December 31, 2014, we had cash and cash equivalents of £30.1 million and £65.2 million, respectively. To date, we have financed our operations primarily through private placements of equity securities, government grants, research and development tax credits, and payments for collaborative research and development services. Through December 31, 2014, we have raised £20.2 million through the issuance of ordinary shares, and a further £62.5 million through the issue of Series A preferred shares. In the year ended June 30, 2014, we received a cash up-front fee of £25 million under our collaboration and license agreement with GSK, of which £0.4 million was recognized as revenue. In the six months ended December 31, 2014, we received cash payments of £2.5 million upon the achievement of a milestone under the GSK collaboration and license agreement and achieved a further milestone resulting in £2.0 million that was paid in January 2015. The total revenue recognized under the GSK collaboration in the six months ended December 31, 2014 was £2.4 million. Through December 31, 2014, we recognized £0.6 million of income in the form of government grants from the United Kingdom and the European Union, and we have recognized £2.2 million in the form of research and development tax credits.

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              We believe that our cash and cash equivalents as of December 31, 2014 of £65.2 million coupled with the £15.9 million of short-term investments will be sufficient to fund our operations, including currently anticipated research and development activities and planned capital spending, for the foreseeable future, including for at least the next 24 months from the effective date of this offering.

              If we obtain regulatory approval to advance any of our TCR therapeutic candidates into pivotal clinical trials or to commercialization, we will incur significant research and development expenses, and also commercialization expenses related to product sales, marketing, manufacturing and distribution. Accordingly, we will seek to fund our operations through milestone payments under our agreement with GSK and additional equity financings.

Cash Flows

              The following table summarizes the results of our cash flows for the six months ended December 31, 2014 and 2013 and the years ended June 30, 2014 and 2013.

Operating Activities

              Net cash used in operating activities was £3.5 million for the six months ended December 31, 2013. The loss before taxation for the period to December 31, 2013 was £3.5 million, which included noncash items of £0.2 million. The noncash items consisted primarily of equity-settled share-based compensation expense. We also had a net cash outfow of £0.8 million from changes in operating assets and liabilities during the period. The significant items in the changes in operating assets and liabilities were timing differences on payments over the period end. In this period, we also received a £0.6 million research and development tax credit relating to research and development activities performed in the previous year.

              Net cash used in operating activities was £9.7 million for the six months ended December 31, 2014. The loss before taxation for this period was £3.6 million, which included noncash net deductions of £1.0 million. The noncash items consisted primarily of the foreign exchange gain on cash and deposits of £1.4 million, offset by depreciation expense on plant and equipment £0.2 million and equity-settled share-based compensation expense £0.2 million. We also had a net cash outflow of £5.0 million from changes in operating assets and liabilities during the period. The most significant item in the changes in operating assets and liabilities was the payment of the £5 million Value Added Tax liability that arose on the £25.0 million upfront fee receivable from GSK in June 2014. The changes in operating assets and liabilities also included an increase £2.4 million of milestone payment due from GSK that was outstanding at the period end and subsequently paid in January 2015. This is offset by increases in liabilities as a result of increased operational expenditure.

              Net cash used in operating activities was £5.1 million for the year ended June, 30, 2013. The loss before taxation for the year ended June 30, 2013 was £6.1 million, which included noncash items of £

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0.1 million. The noncash items consisted primarily of equity-settled share-based compensation expense. We also had a net cash inflow of £0.6 million from changes in operating assets and liabilities during the period. The significant items in the changes in operating assets and liabilities were an increase in trade payables and accruals by £0.7 million as a result of increased operating expenditures. In 2013, we also received a £0.3 million research and development tax credit relating to research and development activities performed in the previous year.

              Net cash from operating activities was £21.9 million for the year ended June 30, 2014. This was significantly influenced by receipt of a payment of £25 million from GSK upon initiation of the collaboration and licensing agreement. The loss before taxation for the year ended June 30, 2014 was £8.4 million, which included noncash items of £0.5 million. The noncash items consisted primarily of depreciation expense on plant and equipment £0.1 million, equity-settled share-based compensation expense £0.2 million, and foreign exchange translation differences of £0.1 million. We also had a net cash inflow of £29.2 million from changes in operating assets and liabilities during the period. The significant items in the changes in operating assets and liabilities were an increase in deferred income in relation to the GSK collaboration and licensing agreement by £24.6 million and an increase in the VAT liability by £5.0 million, primarily as a result of VAT payable on the initial fee received from GSK. In 2014, we received a £0.6 million research and development tax credit relating to research and development activities performed in the previous year.

Investing Activities

              Net cash used in investing activities was £0.7 million and £17.2 million for the six months ended December 31, 2013 and 2014, respectively. These amounts included purchases of property and equipment of £0.7 million and £1.2 million for the six months ended December 31, 2013 and 2014, respectively, related to the expansion of our laboratory facilities in the United Kingdom. The net cash used in investing activities in the six months ended December 31, 2014 also included the investment of £15.9 million in short-term cash deposits with maturities greater than three months but less than 12 months.

              Net cash used in investing activities was £0.1 million and £0.9 million for the years ended June 30, 2013 and 2014, respectively. These amounts related primarily to purchases of property and equipment of £0.1 million and £0.9 million for the years ended June 30, 2013 and 2014, respectively, related to the expansion of our laboratory facilities in the United Kingdom.

Financing Activities

              Net cash from financing activities was £5.2 million and £60.6 million for the six months ended December 31, 2013 and 2014, respectively. These amounts included proceeds from the issue of ordinary and preferred share capital of £5.2 million and £60.6 million for the six months ended December 31, 2013 and 2014, respectively.

              Net cash from financing activities was £2.4 million and £9.9 million for the years ended June 30, 2013 and 2014, respectively. These amounts consisted of proceeds from the issue of ordinary share capital.

Operating and Capital Expenditure Requirements

              We have not achieved profitability on a quarterly or annual basis since our inception, and we expect to incur net losses in the future. We expect that our operating expenses will increase as we continue to invest to grow our internal pipeline of TCR therapeutic candidates, hire additional employees, and increase research and development expenditures.

              Additionally, as a public company, we will incur significant audit, legal and other expenses that we did not incur as a private company. We believe that our existing capital resources, including funds

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raised through the Series A financing in September 2014, together with the net proceeds from this offering, will be sufficient to fund our operations, including currently anticipated research and development activities and planned capital spending, for the foreseeable future.

              Our future funding requirements will depend on many factors, including but not limited to:

•

the scope, rate of progress, and cost of our clinical trials, preclinical programs, and other related activities;



•

the extent of success in our early preclinical and clinical stage research programs, which will determine the amount of funding required to further the development of our TCR therapeutic candidates;



•

the progress that we make in developing new TCR therapeutic candidates based on our technology platform;



•

the cost of manufacturing clinical supplies and establishing commercial supplies of our TCR therapeutic candidates and any products that we may develop;



•

the costs involved in filing and prosecuting patent applications and enforcing and defending potential patent claims;



•

the outcome, timing, and cost of regulatory approvals of our other TCR therapeutic candidates;



•

the cost and timing of establishing sales, marketing, and distribution capabilities;



•

the timing of achievement of the milestones and related payments from GSK;



•

the extent to which we seek to retain development rights to our pipeline of new TCR therapeutic candidates; and



•

the costs of hiring additional skilled employees to support our continued growth.

Contractual Obligations and Commitments

              The following table summarizes our contractual commitments and obligations as of December 31, 2014.

Off-Balance Sheet Arrangements

              We did not have during the periods presented, and we do not currently have, any off-balance sheet arrangements, as defined in the rules and regulations of the SEC other than operating leases as described under "Contractual Obligations and Commitments" above.

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              We do not have any relationships with unconsolidated entities or financial partnerships, such as entities often referred to as structured finance or special purpose entities, which would have been established for the purpose of facilitating off-balance sheet arrangements or for any other contractually narrow or limited purpose.

Quantitative and Qualitative Disclosures about Market Risk

              Market risk arises from our exposure to fluctuation in interest rates and currency exchange rates. These risks are managed by maintaining an appropriate mix of cash deposits in various currencies, placed with a variety of financial institutions for varying periods according to expected liquidity requirements.

              We are exposed to market risks in the ordinary course of our business, which are principally limited to interest rate fluctuations and foreign currency exchange rate fluctuations. These risks are managed by maintaining an appropriate mix of cash deposits in various currencies, placed with a variety of financial institutions for varying periods according to expected liquidity requirements.

Interest Rate Risk

              As of December 31, 2014, we had cash and cash equivalents of £65.2 million and short-term deposits of £15.9 million. As of June 30, 2014, we had cash and cash equivalents of £30.1 million. Our exposure to interest rate sensitivity is impacted by changes in the underlying U.K. bank interest rates. Our surplus cash and cash equivalents are invested in interest-bearing savings and money market accounts from time to time. We have not entered into investments for trading or speculative purposes. Due to the conservative nature of our investment portfolio, which is predicated on capital preservation of investments with short-term maturities, we do not believe an immediate one percentage point change in interest rates would have a material effect on the fair market value of our portfolio, and therefore we do not expect our operating results or cash flows to be significantly affected by changes in market interest rates.

Currency Risk

              Our functional currency is pounds sterling (GBP), and commonly our transactions, including revenue, are denominated in that currency. However, we incur a significant proportion of expenses in other currencies and are exposed to the effects of exchange rates. We seek to minimize this exposure by passively maintaining other currency cash balances at levels appropriate to meet foreseeable expenses in these other currencies. We do not use forward exchange contracts to manage exchange rate exposure. A 1% increase in exchange rates would have reduced the carrying value of our net financial assets and liabilities in foreign currencies at June 30, 2014 by £0.02 million. A 1% increase in exchange rates would have reduced the carrying value of our net financial assets and liabilities in foreign currencies at December 31, 2014 by £0.4 million.

Commodity Price Risk

              We are exposed to commodity price risk as a result of our operations. However, given the size of our operations, the costs of managing exposure to commodity price risk exceed any potential benefits. We will revisit the appropriateness of this policy should our operations change in size or nature. We have no exposure to equity securities price risk as we hold no listed or other equity investments.

Jumpstart Our Business Startups Act of 2012

              The Jumpstart Our Business Startups Act of 2012, or JOBS Act, contains provisions that, among other things, reduce certain reporting requirements for an "emerging growth company." We

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qualify as an emerging growth company and as such, we are electing to take advantage of the following exemptions:

•

not providing an auditor attestation report on our system of internal controls over financial reporting;



•

not providing all of the compensation disclosure that may be required of non-emerging growth public companies under the U.S. Dodd-Frank Wall Street Reform and Consumer Protection Act;



•

only two years of audited financial statements in addition to any required interim financial statements and correspondingly reduced disclosure in management's discussion and analysis of financial condition and results of operations;



•

an extended transition period to comply with new or revised accounting standards;



•

to the extent that we no longer qualify as a foreign private issuer, (1) reduced disclosure obligations regarding executive compensation in our periodic reports and proxy statements; and (2) exemptions from the requirements of holding a non-binding advisory vote on executive compensation, including golden parachute compensation;



•

not disclosing certain executive compensation-related items such as the correlation between executive compensation and performance and comparisons of the Chief Executive Officer's compensation to employee compensation; and



•

not complying with any requirement that may be adopted by the Public Company Accounting Oversight Board regarding mandatory audit firm rotation or a supplement to the auditor's report providing additional information about the audit and the financial statements (auditor discussion and analysis).

              These exemptions will apply for a period of five years following the completion of our initial public offering or until we no longer meet the requirements of being an "emerging growth company," whichever is earlier. We would cease to be an emerging growth company if we have more than $1.0 billion in annual revenue, have more than $700 million in market value of our ordinary shares held by non-affiliates or issue more than $1.0 billion of non-convertible debt over a three-year period. Once we cease to be an emerging growth company, we will not be entitled to the exemptions provided under the JOBS Act.

Critical Judgments in Applying Our Accounting Policies

              In the application of our accounting policies, we are required to make judgments, estimates, and assumptions about the value of assets and liabilities for which there is no definitive third party reference. The estimates and associated assumptions are based on historical experience and other factors that are considered to be relevant. Actual results may differ from these estimates.

              Our estimates and assumptions are reviewed on an ongoing basis. Revisions to accounting estimates are recognized in the period in which the estimate is revised if the revision affects only that period or in the period of the revisions and future periods if the revision affects both current and future periods.

              The following are our critical judgments, except those involving estimation uncertainty, that we have made in the process of applying our accounting policies and that have the most significant effect on the amounts recognized in our consolidated financial statements included elsewhere in this prospectus.

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Revenue Recognition

              We recognize revenue in accordance with IAS 18. Revenue is recognized to the extent that it obtains the right to consideration in exchange for its performance and is measured at the fair value of the consideration received excluding Value-Added Tax (VAT).

              Our revenue to date has been derived solely from the supply of services under the GSK collaboration and licensing agreement and represents the value of contract deliverables. Payments under the agreement include advanced payments upon commencement of various work-streams or milestone payments.

              If a payment is for multiple deliverables, judgment is required to attribute the fair value to the various elements. We do not consider there to be observable third party price information for the fair value of our deliverables; the most reliable evidence available to us for fair value attribution is the value of our deliverables separately negotiated with GSK, which is an acceptable basis under IAS 18. The only instance where a payment has been for multiple deliverables is the upfront consideration we received from GSK, which was allocated between the license agreement, a contribution to development activities and a contribution to new targets. Revenue for all of these is recognized as services are provided.

              If a contract deliverable has only been partially completed at the balance sheet date, revenue is calculated by reference to the value of services performed as a proportion of the total services to be performed for each deliverable, or on a straight-line basis if the pattern of performance cannot be estimated. The amount of revenue recognized is limited to non-refundable amounts already received or reasonably certain to be received.

              If payments are received from a customer in advance of services provided, the amounts are recorded as deferred income and are included within liabilities.

              We consider payments reasonably certain to be received at the point that satisfactory criteria are agreed with GSK. We regularly review the proportion of total services to be performed for each deliverable or the period of time over which the revenue is deferred based on facts known at the time. The process involves review of monthly expenditures and inquiry with our personnel to monitor the performance of the GSK collaboration and license agreement. If circumstances arise that may change the original estimates of progress toward completion of a deliverable, then estimates are revised. These revisions may result in increases or decreases in estimated revenues and are reflected in income in the period in which the circumstances that give rise to the revision become known to management.

              Performance of contract deliverables may vary significantly over time from initial estimates, and, therefore, the amount of revenue recognized is subject to variations. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differs from the actual status and timing of services performed, we may report amounts that are too high or too low in any particular period. To date, there has been no material difference from our estimates to the amount of revenue that can be reliably recognized.

Research and Development Expenditures, including Clinical Trial Expenses

              Research and development expenditures include direct and indirect costs of these activities, including staff costs and materials, as well as external contracts. All such expenditures are expensed as incurred unless the capitalization criteria of IAS 38 have been satisfied, in which case the costs are capitalized as intangible assets. To date, we do not believe any expenditure meets the capitalization criteria because of the uncertainty of successfully completing pivotal clinical trials and obtaining regulatory approval.

              As part of the process of preparing our financial statements, we are required to estimate our accrued expenses. This process involves reviewing open contracts and purchase orders, communicating with our personnel to identify services that have been performed on our behalf, and estimating the level of service performed and the associated cost incurred for the service when we have not yet been

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invoiced or otherwise notified of the actual cost. The majority of our service providers invoice us monthly in arrears for services performed. We make estimates of our accrued expenses as of each balance sheet date in our financial statements based on facts and circumstances known to us at that time. We may confirm the accuracy of our estimates with the applicable service providers and make adjustments if necessary. Examples of estimated accrued research and development expenses include fees paid to: CROs in connection with clinical trials; operators of investigative sites in connection with clinical trials; vendors in connection with preclinical development activities; and vendors related to product manufacturing, development and distribution of clinical supplies.

              We base our expenses related to clinical trials on our estimates of the services received and efforts expended pursuant to contracts with multiple CROs that conduct and manage clinical trials on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the clinical expense. Payments under some of these contracts depend on factors such as the successful enrollment of subjects and the completion of clinical trial milestones. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the accrual or prepaid amount accordingly.

              Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, we may report amounts that are too high or too low in any particular period. To date, there has been no material difference between our estimates and the amount actually incurred.

Key Sources of Estimation Uncertainty

              The key assumptions concerning the future, and other key sources of estimation uncertainty at the balance sheet date, that have a significant risk of causing a material adjustment to the carrying amounts of assets and liabilities within the next year are discussed below.

Share-based Compensation

              We award options to certain of our employees, directors and consultants to purchase shares in our parent company. All of these arrangements are settled in equity at a predetermined price and generally vest over a period of three to four years. All share options have a life of 10 years before expiration. We measure share-based compensation at the grant date based on the fair value of the award and we recognize it as an expense over the required service period, which is generally equal to the vesting period. We determine the fair value of our share options using the Black-Scholes option-pricing model, with a corresponding increase in reserves.

              In accordance with IFRS 1 (First Time Adoption of IFRS), we apply IFRS 2 (Share-based Payment) to equity instruments that had not vested by July 1, 2012.

              Our share-based compensation expense was as follows:

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              In future periods we expect our share-based compensation expense to increase due in part to our existing unrecognized share-based compensation expenses and as we grant additional share-based awards to continue to attract and retain our employees.

Valuation of Share Options

              The Black-Scholes option pricing model requires the input of subjective assumptions, including assumptions about the expected life of share-based compensation awards and share price volatility. In addition, as a privately held company, one of the most subjective inputs into the Black-Scholes option pricing model is the estimated fair value of our ordinary shares. After considering the market approach, the income approach and the asset-based approach, we decided to utilize the market approach to determine the estimated fair value of our ordinary shares based on our view that this approach is most appropriate for a clinical stage biopharmaceutical company at this point in our business. We have considered the American Institute of Certified Public Accountants' Practice Aid: "Valuation of Privately-Held Company Equity Securities Issued as Compensation" in addition to input from management, the likelihood of completing an initial public offering and recent transactions with investors. We also considered the reports of an independent third party valuation firm.

              As a privately-held company, our share price does not have sufficient historical volatility for us to adequately assess the fair value of the share option grants, therefore we have considered the historical volatility of other comparable publicly traded companies. Based on our analysis, we concluded that a volatility of 60% was appropriate for our valuation of our share options. We intend to continue to consistently apply this methodology using the same comparable companies until a sufficient amount of historical information regarding the volatility of our own share price as a public company becomes available.

              We use a five-year expected life in valuing our share options beginning with the option grant date. The expected life we use in the calculation of share-based compensation is the time from the grant date to the expected exercise date. The life of the options depends on the option expiration date, volatility of the underlying shares and vesting features.

              IFRS 2 requires the use of the risk-free interest rate of the country in which the entity's shares are principally traded with a remaining term equal to the expected life of the option. We have applied the appropriate risk-free rate, using the Bank of England's estimates of gilt yield curve as at the respective share option grant dates.

Valuation of Share Price

              The Black-Scholes model requires an assumption of the underlying share price at the date that options are granted, which may be different from the option exercise price.

              We raised £4.3 million of equity from certain of our existing investors and Immunocore Limited on March 31, 2014 at a price of £0.14 per ordinary share. These purchasers were aware of the possibility of a partnership with a large pharmaceutical company as well as other potential funding sources. At the time, there were no plans for an initial public offering and the majority of shareholders did not subscribe to this offering. We subsequently issued share options on March 31, April 14, April 15, April 17 and April 30, 2014. These share options were awarded based on the underlying share price of £0.14 per ordinary share, the same price of the shares purchased by investors on March 31, 2014. On June 2, 2014, we announced our collaboration and license agreement with GSK. As part of the valuation analysis, our Board of Directors determined that there were no significant internal or external value generating events between March 31 and April 30, 2014 that would have materially altered the underlying share price.

              The exercise price of the options we granted in March 2014 of £0.112 per ordinary share has been agreed with HM Revenue & Customs' Shares and Assets Valuation as being the market value of the underlying shares at the date of grant for the purposes of the U.K. tax advantage enterprise management incentives we took advantage of for our fiscal year ended June 30, 2014.

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              On September 23, 2014, we issued 175,841,800 Series A preferred shares at a price of £0.3557 per share to new investors. These shares are convertible to ordinary shares at a rate of one-for-one upon a qualified IPO if it occurs within twelve months of issuance of the Series A preferred shares. On December 19 and December 31, 2014, we issued share options based on an underlying share price of £0.3557 per share. Following the issuance of these options, we received and considered a valuation prepared by an independent third-party valuation firm using the Market Approach for enterprise valuation, which incorporated the Probability Weighted Expected Return Method, or PWERM, and determined that £0.39 per share was the appropriate price to be used in the Black-Scholes Option Pricing Model, or OPM.

              In March 2015, the Company significantly enhanced its board and management team through the appointment of a new Chief Financial Officer, a Chief Medical Officer and a new non-executive director, all with significant industry experience. The Company commissioned and received on March 9, 2015, a contemporaneous independent valuation analysis of its ordinary shares as at March 2, 2015. That valuation analysis used a market approach and applied a combination of the OPM, and the PWERM to derive the fair value of the Company's ordinary shares. In that valuation, the Company considered the probability of an IPO scenario compared to a staying private scenario and the likely market value of the Company in each scenario. It also factored in both the illiquidity of the current shares and the time value of money to a potential liquidity event. In addition the valuation in the staying private scenario accounted for the incremental valuation of the preferred shares. Based on that result, as well as consideration of other qualitative factors, the Company's Board of Directors determined that the fair value of the Company's ordinary shares was £0.50 per share throughout March 2015. The Company granted options over 9,183,962 ordinary shares in March 2015 which vest over a four-year period.

              The following table summarizes by grant date the number of ordinary shares subject to options granted from July 1, 2014 through March 31, 2015, the per share exercise price of the award, the fair value of our ordinary shares on each grant date, and the per share estimated fair values of the awards:

Deferred Tax and Current Tax Credits

              Tax on the profit or loss for the year comprises current and deferred tax. Tax is recognized in the income statement, except to the extent that it relates to items recognized directly in equity, in which case it is recognized in equity.

              Current tax is the expected tax payable on the taxable income or loss for the year, using tax rates enacted or substantively enacted at the balance sheet date, and any adjustment to tax payable in respect of previous years.

              Tax credits are accrued for the year based on calculations that conform to the U.K. research and development tax credit regime applicable to small and medium sized companies.

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              We may not be able to claim such research and development tax credits on research and development expenditures in relation to the GSK collaboration and licensing agreement because they may be considered as subsidized expenditures. We may not be able to continue to claim research and development tax credits in the future as we become a public company because we may no longer qualify as a small or medium sized company.

              Deferred tax is provided on temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for taxation purposes. The amount of deferred tax provided is based on the expected manner of realization or settlement of the carrying amount of assets and liabilities, using tax rates enacted or substantively enacted at the balance sheet date.

              A deferred tax asset is recognized only to the extent that it is probable that future taxable profits will be available against which the asset can be utilized. No deferred tax assets are recognized on our losses carried forward because there is currently no indication that we shall make sufficient profits to utilize these tax losses.

New IFRS and Interpretations

              There are no IFRS as issued by the IASB or interpretations issued by the IFRS interpretations committee that are effective for the first time for the fiscal year beginning on or after June 30, 2013 that would be expected to have a material impact on our financial position, except as described below.

              IFRS 15 establishes the principles that an entity must apply to report useful information about the nature, amount, timing, and uncertainty of revenue and cash flows arising from a contract. IFRS 15 requires that an entity recognize revenue in an amount that reflects the consideration to which the entity expects to be entitled in exchange for goods or services. The standard is effective for an entity's first annual IFRS financial statements for a period beginning on or after January 1, 2017. We are currently in the process of assessing the impact of this standard.

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BUSINESS

Overview

              We are a clinical-stage biopharmaceutical company focused on novel cancer immunotherapy products based on our T-cell receptor platform. We have developed a comprehensive proprietary platform that enables us to identify cancer targets in the form of peptides, which are short sequences of amino acids, find and genetically engineer T-cell receptors, or TCRs, and produce TCR therapeutic candidates for administration to patients. We engineer TCRs to increase their affinity to cancer-specific peptides, including our lead target peptides, NY-ESO-1 and MAGE A-10, in order to target and then destroy cancer cells in patients. Unlike current antibodies and therapies that are based on the use of chimeric antigen receptor T cells, or CAR-Ts, our TCR therapeutic candidates are able to target intracellular as well as extracellular cancer antigens. This capability significantly increases the breadth of targets, particularly as intracellular targets are known to be more closely associated with cancer, but are inaccessible with other autologous T-cell immunotherapy approaches. We believe this approach will lead to TCR therapeutic candidates that have the potential to significantly impact cancer treatment and clinical outcomes of patients with cancer.

              Our lead program is an affinity-enhanced TCR therapeutic targeting the NY-ESO-1, or NY-ESO, cancer antigen. We are conducting Phase 1/2 clinical trials for our NY-ESO TCR therapeutic candidate in patients with solid tumors and hematological malignancies including synovial sarcoma, multiple myeloma, melanoma, ovarian cancer and esophageal cancer. As of February 28, 2015, we had administered our NY-ESO TCR therapeutic candidate to 44 patients across several cancer indications. In both synovial sarcoma and multiple myeloma, we have seen responses and preliminary evidence of tumor reduction in patients with highly refractory cancers. In our synovial sarcoma trial, as of February 28, 2015, 10 patients had received our NY-ESO TCR therapeutic candidate and of these, six patients had responded, with one complete response (before relapse at nine months) and five partial responses. Of the patients with a partial response, the first three patients subsequently underwent resection for residual disease and one of those three patients has remained without evidence of any disease as of February 2, 2015. Results from the multiple myeloma trial following autologous stem cell transplant, or auto-SCT, showed a 59% complete or near complete response rate at 100 days post-administration in 22 patients with active disease at the time of transplant. The NY-ESO engineered T cells have persisted in the myeloma trial for six months in all but one patient and, in a subset of patients, for two years following administration. In addition, based on our clinical data to date, we believe our NY-ESO TCR therapeutic candidate has a promising tolerability profile.

              We expect to report further data on these trials, as well as additional trials, in 2015 and 2016. If we continue to receive further encouraging clinical data, we plan to accelerate the clinical program for our NY-ESO TCR therapeutic candidate, which we are developing in partnership with GlaxoSmithKline, or GSK. We believe our NY-ESO TCR therapeutic candidate may be eligible for expedited regulatory approval pathways, including fast track, breakthrough therapy and accelerated approval.

              We have a number of programs outside of the GSK collaboration. Specifically, we plan to submit an Investigational New Drug Application, or IND, for our TCR therapeutic candidate directed at MAGE A-10, initially focused on breast or lung cancer, in 2015. In addition to this program, we expect to leverage our TCR technology platform to continue to build our pipeline of proprietary TCR therapeutic candidates, including our TCR therapeutic candidate directed to Alpha Fetoprotein, or AFP, which has started preclinical testing. We have identified over 30 intracellular target peptides that are preferentially expressed in cancer cells and have ongoing unpartnered research programs on eight of these. We believe these eight unpartnered research programs are relevant to a wide range of cancer indications.

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              Our expertise and leadership in the field of TCRs is underscored by the large pipeline of TCRs we have identified and validated and by the promising early data with our NY-ESO TCR therapeutic candidate in both solid tumors and hematological malignancies. The following table summarizes our most advanced TCR therapeutic candidates:

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(1)

GSK retains an exclusive option to license NY-ESO TCR for all indications.

              We retain full ownership of our current preclinical pipeline of engineered TCR therapeutic candidates, including our MAGE A-10 TCR therapeutic candidate together with TCR therapeutic candidates in eight additional unpartnered research programs.

              Cancer is a leading cause of death worldwide and is characterized by the uncontrolled growth of abnormal cells whose ability to evade the immune system's surveillance is a key factor in their proliferation and persistence. Despite advances made in the treatments available to cancer patients, there continues to be a high unmet need for additional products and treatments, especially for patients with recurrent tumors or cancer types that are resistant to current therapeutic alternatives. Immunotherapy is a form of cancer treatment that uses a patient's own immune system to combat cancer and is one of the most actively pursued areas of research by biotechnology and pharmaceutical companies today. Interest in immunotherapy is largely driven by recent compelling efficacy data in cancers with historically bleak outcomes and by the potential to achieve a cure or functional cure for some patients. We believe that immunotherapy has the potential to become the primary cancer treatment for recurrent tumors or cancer types that are resistant to current therapeutic alternatives.

              While the field of immunotherapy in cancer has now achieved proof of concept and yielded significant durable responses in multiple tumor types, there remain major tumor types (e.g., colon, breast and prostate) as well as patient groups within responsive tumors (e.g., subsets of patients with melanoma and lung, renal and ovarian cancers) that do not respond to current immunotherapy approaches. One theory to explain this non-responsiveness is that certain tumors require direct immune stimulation. The CAR-T technologies seek to deliver activated T cells towards malignancies to initiate an immune response. The primary challenges in the field have been to achieve an acceptable efficacy and safety profile, or therapeutic index, to successfully target solid tumors. As such, the major successes in CAR-T technologies have primarily been in hematological malignancies. Our research efforts are

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focused entirely on targeting tumors in ways that may result in an improved therapeutic index and have potential applications in solid tumors as well as hematological malignancies. We believe our TCR technology, in contrast to that of CAR-T, allows for more specificity in targeting tumors versus healthy tissue through the ability to target intracellular peptides. In addition, we have invested heavily in an extensive preclinical safety testing program that is designed to minimize any off-target cross-reactivity of our TCR therapeutic candidates.

              The immune system plays an important role in targeting and destroying cancer cells. Specifically, T cells, which are a type of white blood cell, and their receptors create a natural system that is designed to scan the body for diseased cells. In general, cells process proteins internally and then convert these proteins into peptide fragments which are then presented on the cell surface by a protein complex called the Human Leukocyte Antigen, or HLA. TCRs naturally scan these peptide fragments to search for abnormalities. Binding of naturally occurring TCRs to cancer targets, however, tends to be very poor because cancer proteins appear very similar to naturally occurring proteins on healthy cells and TCRs that recognize what the body sees as "self-proteins" are eliminated during early human development.

              We engineer naturally occurring TCRs and enhance their ability to target and bind to cancer peptides thereby enabling a highly targeted immunotherapy. Our proprietary technology platform includes the identification of target peptides, successful engineering of affinity-enhanced TCRs, preclinical safety testing and optimized manufacturing processes suitable for producing engineered TCR therapeutic candidates for use in clinical trials and commercialization. Engineering TCRs requires balancing the need for higher affinity to the target peptide with the risk of cross-reactivity, which increases at higher affinities. We believe this is one of our core competitive advantages given our proven ability to overcome the challenging nature of this process and develop affinity-enhanced TCRs.

              Once we identify a specific cancer target, we create an engineered affinity-enhanced TCR, which then undergoes extensive preclinical safety testing before administration to patients. The process for treating a patient with an engineered TCR therapeutic candidate involves extracting the patient's T cells and then combining the extracted cells with our delivery system containing the gene for our affinity-enhanced TCR, through a process known as transduction. Our delivery system uses a type of virus known as lentivirus to transduce the patient's T cells and is referred to as a lentiviral vector. The transduced T cells are then expanded and infused into the patient. When these T cells encounter an HLA-peptide complex, they multiply and initiate the destruction of the targeted cancer cells.

              Our NY-ESO TCR therapeutic candidate represents the culmination of years of engineering and preclinical research, and, to date we have produced encouraging clinical data in synovial sarcoma and multiple myeloma. We have also utilized our proprietary TCR technology platform to develop a pipeline of TCR therapeutic candidates that we believe may be effective in a variety of cancer types that are unresponsive to currently available and experimental therapies.

              Under our collaboration and license agreement with GSK, GSK funds the development of, and has an option to obtain an exclusive license to, our NY-ESO TCR therapeutic candidate. In addition, GSK has the right to nominate four additional target peptides. The first of these additional targets will be selected from a pool of three target peptides, with the pool having already been jointly chosen by GSK and us. Following completion of initial research on these three target peptides, GSK is entitled to nominate one TCR therapeutic candidate, and we will retain all rights to the other two TCR therapeutic candidates. In addition, three other target peptides may be selected by GSK in the future. These target peptides are outside of our eight unpartnered research programs and any other programs relating to target peptides where Adaptimmune initiates development of a TCR therapeutic candidate. We retain full ownership of our current preclinical pipeline of engineered TCR therapeutic candidates, including the MAGE A-10 TCR therapeutic candidate together with TCR therapeutic candidates in eight additional unpartnered research programs.

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              We have a strong portfolio of patents covering the engineering of TCRs and composition of matter of our lead therapeutic candidates, our proprietary TCR technology platform and certain aspects of our manufacturing processes. Our technology platform and clinical programs have enabled us to raise over $103 million in equity from mutual funds, healthcare-dedicated funds and others. This financing has allowed us to enhance and expand our clinical and preclinical programs as well as build our team with additional scientists. This support from equity investors is complemented by our strategic collaboration with GSK.

Our Strengths

•

Our lead program has provided preliminary evidence of clinical responses in hematological malignancies and solid tumors that have historically been hard to treat.    We are conducting ongoing clinical trials for our NY-ESO TCR therapeutic candidate. As of February 28, 2015, we had seen one complete response and five partial responses out of 10 patients in our synovial sarcoma trial and a 59% complete and near complete response rate in 25 patients in our multiple myeloma trial in conjunction with auto-SCT, assessed at 100 days. In addition, based on our clinical data to date, we believe our NY-ESO TCR therapeutic candidate has a promising tolerability profile.



•

We have developed a comprehensive proprietary technology platform centered on the development of TCR therapeutic candidates and associated process and manufacturing capabilities.    Our proprietary technology platform covers identification of target peptides, successful identification and engineering of affinity-enhanced TCRs, preclinical safety testing and optimized manufacturing processes suitable for producing engineered TCR therapeutic candidates for use in clinical trials and commercialization. We believe our technology platform, which has been developed over a decade, will enable development of additional TCR therapeutic candidates targeting cancers that have previously been difficult to treat.



•

We have identified a large and growing pool of cancer targets for which we can develop additional TCR therapeutic candidates.    We have identified over 30 intracellular target peptides that are preferentially expressed in cancer cells and have ongoing unpartnered research programs on eight of these. Because our technology relies upon the body's natural system of processing intracellular proteins and most cancer peptides are located intracellularly, the number of peptides that we can target with our engineered TCR therapeutic candidates is potentially large. Our approach contrasts with CAR-T technologies which use antibody binding recognition systems to artificially activate T cells and can only bind to whole surface proteins expressed on the targeted cell. While our TCR therapeutic candidates are initially suitable for patients with HLA A2, we believe our platform will be applicable to multiple HLA types, enabling broad coverage of the HLA types that make up the majority of the patient population.



•

We have a strong and growing intellectual property portfolio to protect our products and proprietary platform.    We have a strong intellectual property portfolio covering the target identification, affinity enhancement and comprehensive preclinical testing processes as well as composition of matter claims over our engineered TCR therapeutic candidates.



•

Our strategic alliance with GSK provides additional support in product development and regulatory experience.    We believe our strategic partner, GSK, provides experience in manufacturing, biologic development and regulatory planning and quality systems. Further, we expect to use knowledge gained from our NY-ESO TCR therapeutic candidate program

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to improve the development pathways for our unpartnered TCR therapeutic candidate programs.

•

We have a highly knowledgeable and experienced management team with extensive industry experience and expertise in the United States and in Europe.    Our senior management, which has substantial experience in the biopharmaceutical industry, includes our CEO, James Noble, who has 24 years of experience serving on the boards of public and private companies in the biotechnology sector from Europe and the United States, including seven years as our founding CEO and a further six years as the founding CEO of Avidex Ltd, our predecessor company. Our Chief Operating Officer, Dr. Helen Tayton-Martin, has 23 years of experience in the pharmaceutical, biotechnology and consulting industries in disciplines including preclinical and clinical development, outsourcing, strategic planning, due diligence and business development. Dr. Gwendolyn Binder-Scholl, who heads our clinical and regulatory development efforts in the United States, has 14 years of industry and academic experience in cellular and gene therapy translational research and drug development.

Our Business Strategy

              Our strategic objective is to build a global oncology business with an extensive portfolio of engineered TCR therapeutic candidates that have the potential to significantly impact the clinical outcomes of patients with cancer. In order to achieve our objective, we are focused on the following strategies:

              Rapidly advance our NY-ESO TCR therapeutic candidate into registrational trials. We are collaborating with GSK to advance our NY-ESO TCR therapeutic candidate and expand and accelerate our clinical trials into additional sites, both in the United States and in Europe. We believe data from these trials, if positive, may enable us to go directly into one or more registrational or pivotal clinical trials. We are currently conducting five Phase 1/2 clinical trials in multiple cancer types including synovial sarcoma, multiple myeloma, melanoma, ovarian cancer and esophageal cancer and expect to commence an additional clinical trial for non-small cell lung cancer in 2015.

              Advance our MAGE A-10 and other therapeutic candidates through clinical development. We retain full development and commercialization rights to our MAGE A-10 therapeutic candidate and intend to submit an IND for this product candidate in 2015. We believe that our MAGE A-10 TCR therapeutic candidate has the potential to be effective in many solid tumors, including breast or lung cancer. Currently, we do not intend to partner our MAGE A-10 TCR therapeutic candidate or our other preclinical TCR therapeutic candidates.

              Advance further TCR therapeutic candidates from our unpartnered portfolio to the product development stage. We currently have eight active unpartnered research programs on potential TCR therapeutic candidates. We intend to advance these research programs into preclinical and clinical development as soon as practicable.

              Leverage our TCR technology platform by continuing to identify cancer targets that are not accessible by current antibody and CAR-T approaches. We intend to continue to generate our TCR therapeutic candidates from our fully integrated technology platform, which enables the systematic identification and validation of suitable target peptides, T-cell cloning, engineering of TCRs and comprehensive preclinical testing processes.

              Continue to improve potency and durability of response to our TCR therapeutic candidates. We intend to continue further developing our TCR therapeutic candidates by improving potency and durability and also exploring the addition of other components in our lentiviral vector, which would be expressed in the TCR therapeutic candidate alongside the engineered TCR.

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              Optimize and expand our process development and manufacturing capabilities to maintain our leadership position in the TCR space. We plan to optimize the manufacture, supply, associated analytical expertise and quality systems for our TCR therapeutic candidates to ensure that our manufacturing capability is sufficient for later stage clinical trials and commercial supply.

              Leverage our existing strategic alliance with GSK. We expect to capitalize on GSK's drug development and regulatory expertise and commercial capabilities to bring our partnered therapeutic products to market. We expect to apply knowledge gained from our NY-ESO TCR therapeutic candidate collaboration program with GSK to the development and commercialization of other TCR therapeutic candidates in our pipeline.

              Expand our intellectual property portfolio. We intend to continue building on our technology platform, comprised of intellectual property, proprietary methods and know-how in the field of TCRs. These assets form the foundation for our ability to not only strengthen our product pipeline, but also to successfully defend and expand our position as a leader in the field of TCRs.

Background on TCRs

              There are two modes of action by which the body's natural immune system targets diseased cells. The first uses an antibody recognition system, which targets whole proteins on the cell surface. The other is through TCRs that target the HLA peptide complex. The HLA peptide complex derives from intracellular target proteins that are broken down into short peptide fragments, which are captured by the HLA for presentation on the cell surface. TCRs target and bind to a specific HLA peptide complex, as shown in the illustration below, resulting in the destruction of those targeted cells. The target peptides that are presented by the HLA peptide complex include the whole array of proteins expressed by a cell, not just transmembrane or cell-surface proteins. The majority of cancer targets are located inside the cell.

              For our initial NY-ESO TCR therapeutic candidate, we are targeting HLA A2, which is found in approximately 50% of the U.S. Caucasian population and is one of the most common HLA types globally. Among patients with a specific HLA type, the same peptide is presented consistently, which means that any engineered TCR therapeutic candidate targeting that peptide will be able to target the same peptide presented in nearly all patients of that HLA type. We are also working on programs for TCR therapeutic candidates that target the other most common HLA types.

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Limitations of Natural Affinity TCRs and the Importance of Engineering

              Binding of naturally occurring TCRs to any presented cancer peptides can be very poor for three reasons:

•

Very few TCRs are capable of recognizing cancer-specific target peptides because cancer proteins (and the target peptides presented on HLA from cancer cells) appear very similar to naturally occurring proteins and any related high-affinity TCRs are eliminated early in human development.



•

Cancer cells reduce the HLA presentation such that the TCR can no longer naturally recognize the target as a cancer cell.



•

The body has no capacity to enhance the affinity of a TCR to the cancer HLA peptide complex, unlike antibodies where affinity maturation occurs in response to exposure to the disease protein.

This means that the natural immune system is unable to recognize and respond to most cancer cells and, even if it does respond, the response is typically very poor.

Our Engineered TCR Therapeutic Candidates

              Our engineered TCR therapeutic candidates start with naturally occurring TCRs, which we then enhance in order to increase their ability to recognize and bind to cancer target peptides presented by the HLA peptide complex. We believe this has the potential to result in a targeted and effective treatment.

              The TCRs consist of two associated protein chains: the alpha (a) and beta (b) chains. Each of the chains has two regions: a variable region and a constant region. The constant region sits next to the T-cell membrane and the variable region of the two chains binds to the target peptides. The variable region of each TCR chain has three hyper-variable complementarity determining regions, or CDRs. Our technology modifies these CDRs in order to enhance affinity to the cancer cell's HLA peptide complex.

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              By genetically engineering the TCR sequence, we produce an enhanced TCR with increased affinity for the cancer target peptides. This process improves the ability of the engineered T cell to recognize cancer targets that are present at very low levels and subsequently activate the immune system. It is not known a priori what affinity will be required for each TCR to be effective. We therefore produce libraries of affinity-enhanced TCRs from which we select a panel, which we test for potency and potential for cross-reactivity, or binding to non-cancerous cells. The effect of enhancing TCR affinity can be shown in the chart below:

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              We then select the TCR that we believe will allow us to develop the most effective TCR therapeutic candidate, which we test for ability to destroy cancer cells (potency) and ability to leave non-cancerous cells intact (minimal cross-reactivity).

              The two circles above show results from tests designed to see whether a T cell is activated in the presence of a cancer cell. Activation is shown in this test by the presence of dark spots. The circle on the left shows that a natural affinity T-cell receptor does not recognize the cancer cells and is therefore not activated. The circle on the right shows that a higher affinity T-cell receptor does recognize the same cancer cells and is therefore activated to destroy them.

Differences between TCRs and CAR-Ts

              Current alternative T-cell therapies in development utilize CAR-T technologies to modify T cells for therapeutic effect. T cells do not naturally express anything that would normally recognize a whole protein. CAR-Ts attach an antibody fragment to a T cell to recognize a whole surface protein expressed on the target cell, a recognition system that does not occur naturally. Therefore, this antibody fragment must be artificially linked to a number of signaling domain proteins within the T cell designed to activate the T cell once the antibody recognition fragment binds to a protein on the target cell. Although not HLA-restricted in the same way as our TCR therapies, use of CAR-Ts is limited by the relatively small number of identified cancer targets expressed on the cell surface and which can be bound by the CAR-T technology.

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              The following illustration shows the different targets being addressed by typical CAR-T cells and our engineered TCR therapeutic candidates.

              The main differences between our TCR therapeutic candidates and CAR-T therapies are as follows:

              Nature of Recognition System.    Our engineered TCRs enhance the affinity of the natural TCR system using the cell's own internal signaling machinery, which means that there is no need to change the T cell in other ways. In contrast, the CAR-T technology adds an antibody recognition system to a T cell, creating a construct that is not seen in nature. CAR-T technology, therefore, has to alter the intracellular machinery in order to activate the T cell.

              Greater Number of Targets.    TCRs recognize peptide fragments from proteins present within the cell and expressed on the cell's surface, whereas CAR-Ts can only recognize whole proteins expressed on the cell's surface. TCRs are capable of targeting a greater number of proteins and may be able to more selectively target cancer cells and target a broader array of tumor types.

              Expression on Healthy Tissue.    To date, the identified targets of CAR-T technologies are not only more limited in number, but also expressed on healthy tissue. Our TCR therapies are selected against targets which are either not generally expressed on healthy tissue or expressed only in certain patient sub-populations or at minimal levels.

              HLA Restriction.    TCRs recognize proteins that are presented to the immune system as a peptide bound to an HLA type, and are therefore limited to a certain HLA type. HLA types vary across the human population, but we are targeting HLA A2, which is found in approximately 50% of the U.S. Caucasian population and is one of the most common HLA types globally. Unlike TCRs, CAR-Ts are capable of recognizing the target protein on the cell surface regardless of HLA type.

              By choosing the target peptides that our engineered TCR therapeutic candidates recognize, our therapeutics can potentially be directed to cancers that are currently untreatable or have poor clinical outcomes. Our engineered TCR therapeutic candidates recognize specific cancer targets that may be present on several different tumor types, including solid tumors. The expression of these cancer targets

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may also be associated with higher-grade and/or late-stage tumors, which are generally associated with a poor prognosis.

Our Technology Platform

              Our current engineered TCR therapeutic candidates are dependent on our integrated and proprietary technology platform that has been developed over more than 10 years.

Target Peptide Identification

              We have identified and validated over 30 intracellular target cancer peptides. Our proprietary identification system provides target peptides suitable for commencing a TCR therapeutic candidate program. We believe our eight target peptides that have been prioritized for engineered TCR therapeutic candidate development all have very low levels of cross-reactivity to non-cancerous cells and therefore are well suited for development.

              Validation and identification of potential targets requires (a) analysis of presentation of the relevant target peptides in cancer cells; (b) analysis of presentation of the relevant target peptide in healthy tissue for prediction of cross-reactivity; and (c) validation of presentation on the cancer cell surface.

Identification and Generation of an Engineered TCR Therapeutic Candidate

              Once the target peptide has been identified and validated, we can generate an engineered TCR therapeutic candidate through isolation of the natural TCRs followed by genetic engineering. Our internal process is reliant on the following factors:

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Our ability to identify and quickly develop engineered TCR therapeutic candidates through a proprietary process enabling rapid identification and cloning of TCRs and hence progression to engineered TCRs capable of binding to any selected target peptide.



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Our ability to make stable, soluble TCRs to enable measurement and analysis of engineered TCR proteins and resulting identification of engineered TCRs required for target peptide binding. This requires the use of our proprietary di-sulfide bond methodology.



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Our ability to utilize a proprietary phage display system for TCRs. Phage display is a technique widely used in antibody research to enhance affinity of monoclonal antibodies for therapy. In our experience, antibody phage display systems do not work with TCRs. We have therefore developed and use a proprietary phage display approach that enables isolation of engineered TCRs and, as a result, we are able to select engineered TCRs from a large, diversified library.

Preclinical Testing

              We have developed a proprietary preclinical screening program that seeks to minimize any potential off-target binding or cross-reactivity and thereby aims to improve the safety profile of our products. All engineered TCR therapeutic candidates will be subjected to this rigorous preclinical screening program. We developed and optimized this program as a result of off-target cross-reactivity in one of our previous TCR therapeutic candidates, MAGE-A3, in which cross-reactivity is believed to have caused two deaths in clinical programs. The preclinical screening program seeks to identify the amino acids to which the engineered TCR therapeutic candidate will bind within any target peptide, thereby identifying those amino acids that are important for TCR recognition of any target peptide. That information can then be deployed to identify other off-target sequences within the human body that could also be bound.

              Our preclinical screening program identifies potential cross-reactivity including binding to peptides presented on other HLA types (allo-reactivity), platelet activation and reactivity in different cell systems (e.g., cardiomyocytes, hepatocytes, endothelial cells, astrocytes and neurons). Our

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preclinical screening program is split into three main stages: molecular analysis, human cell testing and potency/efficacy testing.

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Molecular analysis uses a variety of techniques to systematically identify peptides within the human body that are similar to the target peptide and which therefore might be bound by the affinity-enhanced engineered TCR. The testing is intended to identify any potential cross-reactivity. The amino acids within the affinity-enhanced TCR, which are important for binding to a peptide, are identified by substitution of the relevant amino acids. Based on identification of those binding amino acids, variations of the target peptide which are also capable of being bound by the engineered TCR are then identified. Theoretical cross-reactivity against peptides within the human body which have any of the amino acid sequences capable of being bound by the affinity-enhanced engineered TCR can then be identified and investigated to see if such peptides are actually presented on cells and whether they can be bound by the affinity-enhanced engineered TCR.



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Human cell testing is used to assess whether the affinity-enhanced engineered TCR binds to samples of normal cells and whole blood samples.



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Potency/efficacy testing is used to assess the potency and efficacy of the affinity-enhanced engineered TCR.

Delivery of TCR Therapeutic Candidates to Patients

              Patients eligible for clinical trials with our engineered TCR therapeutic candidates have a portion of their white blood cells collected using a process called leukapheresis, a procedure in which a patient's blood is extracted and the white blood cells are separated from the remaining fractions. The extracted white blood cells are transferred to a U.S. central manufacturing facility operated by a contract development and manufacturing organization (currently Progenitor Cell Therapy LLC) for manufacturing of the TCR therapeutic candidate that we administer to the patient. CD4 and CD8 T cells are isolated from the white blood cells and mixed with our lentiviral vector to transduce the T cells with the genes encoding the affinity-enhanced TCRs and also with the artificial peptide presenting cell microbeads (antibody-bound magnetic Dynabeads® CD3/CD28) to expand the T cells. The transduced T cells are then expanded for nine to 12 days, and concentrated and frozen to permit release testing. Cell product can be stored long term until the patient is ready to receive the infusion, although typically patients receive the cell product within 21 to 28 days after their leukapheresis.

              We use a lentiviral vector to transfer the modified genes for the affinity-enhanced TCR into patient T cells. The lentiviral vector is referred to as a self-inactivating vector derived from HIV-1 and was chosen because it has an enhanced biosafety profile and produces stable modified cells. The vector includes the transgene required for production of engineered TCRs and also three packaging plasmids. We continue to make a number of enhancements to the vector and cell processing as we further develop our TCR therapeutic candidates.

              All of our current engineered TCR therapeutic candidates in clinical trials utilize an initial lympho-depletion chemotherapy conditioning step to activate proliferation and enhance the effectiveness of our TCR therapeutic candidate.

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              The diagram below illustrates the process by which our TCR therapeutic candidates are prepared and administered to patients.

Next Generation Technology Platform Development

Manufacturing

              In parallel with our ongoing clinical programs and underlying target peptide identification work, we are aiming to optimize the processes for our lentiviral vector and engineered TCR therapeutic candidate manufacturing processes to produce a version 1.5 process for each. Our goal is to achieve a more consistent and efficient manufacturing process and therefore reduce the cost of supply.

              We intend to make a number of changes to our current manufacturing process. Our current version 1.0 manufacturing process is manually intensive, and we are now streamlining some of these manual steps by simplifying the process to select the initial T cells. We are also introducing cryopreservation steps which make the logistics of administering our TCR therapeutic candidates more flexible for patients. Finally, we are changing the growth medium that we use in the later parts of the process to a standard growth medium which prevents the need to make media specific for the process.

              In addition to development of the version 1.5 processes, we are working towards automation of manufacture to produce a version 2.0 process and we intend to bring these activities in-house. We are also working with third-party contractors to develop companion diagnostics for screening of patient tumors for the presence of target peptides for use with our TCR therapeutic candidates.

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Generation 2 Therapeutics

              We believe that there is also further room to enhance the potency and durability of our TCR therapeutic candidates, for instance by adding further active proteins into the lentiviral delivery system. These enhancements are designed to result in generation 2 engineered TCR therapeutic candidates for future clinical programs.

Our TCR Therapeutic Candidates

NY-ESO TCR Therapeutic Candidate

              The following table summarizes the indications for our NY-ESO TCR therapeutic candidate:

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(1)

GSK retains an exclusive option to license NY-ESO TCR for all indications.

              Our first engineered TCR therapeutic candidate, our NY-ESO TCR therapeutic candidate, targets the NY-ESO-1 target peptide. In-house testing to assess the presence of this target peptide across cancer types suggests that this therapy has utility for treating synovial sarcoma, multiple myeloma, melanoma, ovarian and esophageal cancers and Phase 1/2 trials are ongoing in these indications.

              We currently sponsor all of our U.S. clinical trials. We submitted our IND for our NY-ESO TCR therapeutic candidate in December 2010, and clinical trials are running at nine clinical trial sites across the United States, including the National Cancer Institute, University of Pennsylvania, University of Maryland, The Children's Hospital of Philadelphia and Memorial Sloan Kettering Cancer Center. We are now commencing European trials as well.

              Our NY-ESO TCR therapeutic candidate has generally been well tolerated with relatively few related adverse events above grade 3. Adverse events that have been reported in more than 15% of patients and considered at least possibly related to our NY-ESO TCR therapeutic candidate include diarrhea, rash, fever, fatigue, disturbed liver function tests, nausea and anemia. Several events have been classified as serious adverse events. Related serious adverse events occurring in more than one patient include neutropenia, pyrexia, Cytokine-Release Syndrome, Graft Versus Host Disease and dehydration. Graft Versus Host Disease, which impacts the gastrointestinal tract, has only been reported in our myeloma transplant study involving auto-SCT. We have also seen a suspected unexpected serious adverse reaction of grade 4 supraventricular tachycardia, or SVT, in one patient.

Synovial Sarcoma Trial

              Synovial sarcoma, a cancer of the connective tissue, accounts for approximately 6% to 10% of all soft tissue sarcomas. Approximately one third of synovial sarcomas occur in childhood and the peak

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incidence is in the third decade of life, with 70% of sarcomas occurring in patients younger than 40 years old. The majority of patients who develop metastatic soft tissue sarcomas are currently incurable, with 75% to 80% of patients not surviving past two to three years. First line therapy typically involves radiotherapy and chemotherapy, as well as surgical resection where possible. There are limited additional treatment options for unresectable, recurrent and metastatic synovial sarcoma, which is nearly always fatal, and systemic therapy is mainly used to provide palliation and slow disease progression. In 2012, the FDA granted approval for marketing of pazopanib hydrochloride (marketed as Votrient) for treatment of soft tissue sarcoma in patients who had received prior chemotherapy. Based on Votrient's prescribing information, progression-free survival time for patients with synovial sarcoma receiving pazopanib was 4.1 months (0.9 months on placebo), and in 246 patients with all types of soft tissue sarcomas, there were 11 partial responses but no complete responses.

              We are currently conducting a Phase 1/2 open-label clinical trial of our NY-ESO TCR therapeutic candidate in patients with synovial sarcoma. The target peptide to which our NY-ESO TCR therapeutic candidate is directed is believed to be present in 60-70% of synovial sarcoma patients. Patients in this trial all had unresectable, metastatic or recurrent synovial sarcomas with low life expectancy. We are investigating the primary efficacy response using RECIST (Response Evaluating Criteria in Solid Tumors) 1.1 criteria:

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Complete Response (CR):  Disappearance of all target and non-target lesions.



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Partial Response (PR):  At least a 30% decrease in the sum of the diameters of target lesions, taking as reference the baseline sum diameters, without the appearance of new, and/or unequivocal progression of existing, non-target lesions.



•

Stable Disease (SD):  Neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for Progressive Disease (PD).

              Interim results of this trial from March 2014 were presented by the trial investigator at the Connective Tissue Oncology Conference (CTOS) in October 2014. In the first six patients, four patients responded with one CR and three PRs and two patients had SD as the best overall response, as described in the table and graph below:

(1)

Staining describes the degree of NY-ESO present in each patient's
tumor (3+ is the highest).



(2)

This patient's response was PD at month two.

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                  Source: Melinda Merchant, M.D., Ph.D. CTOS, October 2014

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Time Course of Tumor Reduction

                      

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                      Source: Melinda Merchant, M.D., Ph.D. CTOS, October 2014

              The clinical course of the patient with a CR is illustrated below. In the first row prior to treatment with our NY-ESO TCR therapeutic candidate (referred to below as "Baseline"), the patient scans show several measurable and multiple other lesions throughout the lungs. In the second row (referred to below as Day +2) and reflecting the position two days after administration of our TCR therapeutic candidate, the lesions appear worse owing to inflammation caused by T-cell activity. In the final row 101 days after administration of our TCR therapeutic candidate (referred to below as "Day 101"), the lesions have disappeared from the patient scans.

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Source: Melinda Merchant, M.D., Ph.D. CTOS, Berlin, October 2014

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              The clinical course of one of the patients with a partial response is illustrated below. In the first picture prior to treatment with our NY-ESO TCR therapeutic candidate, there is a large, un-resectable lesion behind the knee. In the second picture, at one month after administration of our TCR therapeutic candidate, there is a noticeable reduction in the size of the lesion. By the third picture, at two months after administration of our TCR therapeutic candidate, there was a an approximately 70% reduction in lesion size. The lesion could then be resected.

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Source: Melinda Merchant, M.D., Ph.D. CTOS, Berlin, October 2014

              As of October 2014, our NY-ESO engineered T cells have demonstrated persistence in four patients beyond three months and in two patients at one year following administration.

Our Updated Clinical Data

              As of April 20, 2015, a total of 11 patients had been infused with our NY-ESO TCR therapeutic candidate. Of the first 10 patients, six have responded with the best overall response described in the table below. The one CR remained between month three and up to month nine before small lesions reappeared and the patient relapsed. In the five PRs, three PRs continued for four to six

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months and two PRs have been more recently reported at one and three months. This is illustrated by the graph below.

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Surgical resection of primary but still with PR of lung lesions

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Progression of disease from nadir or CRà resection of NY-ESO+ lung mets

#

Low cell dose, late cytokine release syndrome with tumor infiltrating NY-ESO-1+ cells, tumor progression

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Source: Crystal Mackall, National Cancer Institute

              As of February 28, 2015, of the first 10 patients, four patients were diagnosed with grade 1 to 3 Cytokine-Release Syndrome, which resolved with supportive therapy and none required steroid treatment. We have reported one suspected unexpected serious adverse reaction relating to a grade 4 SVT. The patient had a lesion in the chest close to the heart and had had an episode of SVT, prior to

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administration of our NY-ESO TCR therapeutic candidate. Following administration, the patient had two further episodes of SVT, which resolved with treatment. These SVT episodes were thought possibly related to our TCR therapeutic candidate causing inflammation of the chest lesion and consequent irritation of the right atrium provoking the SVT. The chart below lists all serious adverse events of grade 3 or above that were thought possibly related to our TCR therapeutic candidate and were observed in patients during the trial and through February 2, 2015 by the principal investigator in the trial.

              Based on the positive responses to date, we are extending the trial to include an additional 30 patients in U.S. sites. In the second quarter of 2015, the first of three cohorts of 10 patients is planned to open in the United States. These cohorts are designed to standardize the optimal cell dose, determine the optimal level of the NY-ESO target peptide on screening and the regimen of chemotherapy given to patients before administration of our NY-ESO TCR therapeutic candidate.

Multiple Myeloma Trials (Transplant and Non-transplant)

              Multiple myeloma is a cancer that forms in a type of white blood cell (plasma cells) and is characterized by the proliferation of those plasma cells within bone marrow. Its prevalence in the United States is reported to be approximately 77,600 cases with approximately 24,000 new cases in 2014. Average five-year survival rates are estimated to be less than 45% with survival rates depending on factors such as age, stage of diagnosis and suitability for auto-SCT, which is used as part of the treatment for eligible patients with multiple myeloma. Despite recent therapeutic advances, multiple myeloma remains an incurable but treatable cancer. Patients are typically treated with repeat rounds of combination therapy with the time intervals to relapse becoming shorter with each successive line of therapy. The majority of patients eventually have a relapse which cannot be further treated. At this late stage, median survival is only six to nine months and treatment is primarily palliative to reduce symptoms and manage quality of life.

              We have conducted a Phase 1/2, open-label, two-site clinical trial in 25 multiple myeloma patients who were eligible for an auto-SCT. This Phase 1/2 clinical trial was open to patients with high risk or relapsed multiple myeloma, who have few remaining treatment options and low life expectancy. Prior to enrollment in the clinical trial, patients had received on average three prior therapies and the trial included six patients that had a prior auto-SCT. Sixty percent of tumors contained cytogenetic abnormalities that represent negative prognostic indicators.

              We assessed disease response in accordance with the International Uniform Response Criteria for myeloma assessment and the additional criteria of nCR which was consistent with the methods employed by the Bone Marrow Transplantation Clinical Trials Ne