Biogen Idec Showcases Leading Multiple Sclerosis Franchise and Pipeline at the 61st Annual Meeting of the American Academy of Neurology

Biogen Idec (NASDAQ: BIIB) today announced that 25 company-sponsored platform and poster presentations will take place during the 61st Annual Meeting of the American Academy of Neurology (AAN) in Seattle, WA, April 25 through May 2, 2009. These presentations, which are not late-breaking abstracts, will cover five compounds that are marketed or currently in development by Biogen Idec and its partners for the treatment of multiple sclerosis (MS). This includes two approved therapies for MS; TYSABRI® (natalizumab) and AVONEX® (Interferon beta-1a); and additional compounds in development including BG-12 (dimethyl fumarate), PEGylated interferon beta-1a, and daclizumab.

“Biogen Idec is redefining success for patients living with MS. With TYSABRI, we have moved beyond slowing disease progression. We are even seeing some clinical trial patients who are free from MS disease activity or with physical improvement from what was seen at baseline,” said Michael Panzara, MD, MPH, vice president, chief medical officer of neurology, Biogen Idec.

Dr. Panzara continued, “Biogen Idec is at the forefront of development and research with a robust pipeline that includes PEGylated interferon beta-1a, which is expected to enter a Phase III clinical trial by the middle of this year. Biogen Idec has been a pioneer for over a decade in the use of interferon beta to treat MS, and this compound promises to be a significant evolution in that class.

Also, BG-12, an oral compound with potential neuroprotective effects, has shown promising results in early-stage MS and is now well into Phase III trials with over 2000 MS patients currently enrolled. Indeed, with multiple exciting compounds to treat MS at all stages of development, including those at the preclinical stage with the potential to reverse and repair the damage inflicted by the disease, Biogen Idec continues to demonstrate our commitment to improving the lives of MS patients worldwide.”

The following represents select data highlights during the meeting from the company’s portfolio of marketed products.

TYSABRI

There are 14 Biogen Idec-sponsored TYSABRI posters and presentations during the Congress. Key data from these includes an analysis showing that TYSABRI may aid in the repair of MS-related damage to the myelin sheath, as well as possibly protect it from further damage (Natalizumab (Tysabri®) Promotes Remyelination in Patients with Multiple Sclerosis. A Voxel-Wise Magnetization Transfer Imaging Case-Control Study –P03.071). Another key poster will present data from a post-hoc analysis showing that select patients with relapsing MS saw an improvement of physical function as measured on the EDSS scale (Sustained Improvement in Physical Disability with Natalizumab in Patients with Relapsing Multiple Sclerosis –P06.131). A presentation will provide updated TYSABRI safety and utilization information (Natalizumab in Patients with Relapsing Multiple Sclerosis: Updated Utilization and Safety Results including TOUCH™ and TYGRIS – S11.005).

AVONEX

There are six Biogen Idec-sponsored AVONEX posters and presentations during the Congress. A highlight includes a poster on the CHAMPIONS extension study, which is the longest follow-up of CIS patients who start therapy before or shortly after the development of their disease (CHAMPIONS Extension Study: 10 year Follow-up after a Clinically Isolated Syndrome (CIS) in High Risk Patients – P06.137). Another presentation will include further evidence on the potential mechanism of action of AVONEX (Interferon-beta Treatment Increases FoxP3 Expression and CD56bright Natural Killer Cells in Subjects with Multiple Sclerosis – S06.001).

Pipeline programs to be highlighted include PEGylated interferon beta-1a, BG-12 and daclizumab.

“Biogen Idec has one of the most extensive MS pipelines in the industry, with many programs ongoing to target the multiple pathways thought to be critical in treating the disease. To date, many of our pipeline programs have shown compelling results in clinical trials and we look forward to the continued development of these compounds,” said Alfred Sandrock, MD, PhD, senior vice president, Neurology Research and Development, Biogen Idec.

BG-12 (dimethyl fumarate)

There will be two Biogen Idec-sponsored BG-12 posters at the Congress; Dimethyl Fumarate (BG00012) Inhibits Astrogliosis in Rodent EAE Models (P08.054) and Dimethyl Fumarate (BG00012) Inhibits Macrophage Inflammatory Activity In Vivo and In Vitro Models (P09.114). Both posters provide evidence that the compound may have a dual mechanism of action thought to demonstrate anti-inflammatory and neuroprotective properties.

PEGylated Interferon beta-1a

There are two Biogen Idec-sponsored PEGylated interferon beta-1a posters being presented during the Congress. One will focus on safety results from the recently-completed Phase 1 clinical trial (Phase 1 Studies Demonstrate that PEGylated Interferon Beta-1a is Safe, Well Tolerated, and Pharmacologically Active in Healthy Volunteers –P06.129). A second will include data on dosing and administration from the same trial (Pharmacokinetic and Pharmacodynamic Profile of PEGylated Interferon Beta-1a in Healthy Volunteers: Results from 2 Phase 1 Clinical Studies – P06.140). These data support the advancement of the compound into a Phase III clinical trial by mid-year.

Daclizumab

One company-sponsored poster will be presented during the Congress, focusing on results from the Phase II CHOICE trial, showing that reduced T-cell activation may contribute to the compound’s activity in MS (Daclizumab Treatment Reduces Activated T Cells: Results from the CHOICE MS Study – P01.107).

About Biogen Idec

Biogen Idec creates new standards of care in therapeutic areas with high unmet medical needs. Founded in 1978, Biogen Idec is a global leader in the discovery, development, manufacturing, and commercialization of innovative therapies. Patients in more than 90 countries benefit from Biogen Idec's significant products that address diseases such as lymphoma, multiple sclerosis, and rheumatoid arthritis. For product labeling, press releases and additional information about the company, please visit www.biogenidec.com.

About TYSABRI

TYSABRI is a treatment approved for relapsing forms of MS in the US and relapsing-remitting MS in the European Union. According to data that have been published in the New England Journal of Medicine, after two years, TYSABRI treatment led to a 68% relative reduction (p<0.001) in the annualized relapse rate compared to placebo and reduced the relative risk of disability progression by 42-54% (p<0.001).

TYSABRI is also approved in the US to induce and maintain clinical response and remission in adult patients with moderately-to-severely active Crohn's disease (CD) with evidence of inflammation in those patients who have had an inadequate response to, or are unable to tolerate, conventional CD therapies and inhibitors of TNF-alpha. According to the US full prescribing information, among patients who responded to TYSABRI, 54% sustain their response through every visit for one year compared to 20% of patients receiving placebo (p<0.001), for a treatment difference of 34%.

TYSABRI increases the risk of progressive multifocal leukoencephalopathy (PML), an opportunistic viral infection of the brain that usually leads to death or severe disability. Cases of PML have been reported in patients taking TYSABRI who were recently or concomitantly treated with immunomodulators or immunosuppressants, as well as in patients receiving TYSABRI as monotherapy. Other serious adverse events that have occurred in TYSABRI-treated patients included hypersensitivity reactions (e.g., anaphylaxis) and infections. Serious opportunistic and other atypical infections have been observed in TYSABRI-treated patients, some of whom were receiving concurrent immunosuppressants. Herpes infections were slightly more common in patients treated with TYSABRI. In MS and CD clinical trials, the incidence and rate of other serious adverse events, including serious infections, were similar in patients receiving TYSABRI and those receiving placebo. Common adverse events reported in TYSABRI-treated MS patients include headache, fatigue, infusion reactions, urinary tract infections, joint and limb pain and rash. Other common adverse events reported in TYSABRI-treated CD patients include respiratory tract infections and nausea. Clinically significant liver injury has been reported in patients treated with TYSABRI in the post-marketing setting.

TYSABRI is approved in more than 40 countries. Biogen Idec and Elan Corporation, plc (NYSE: ELN) are in a 50-50 partnership for the development and promotion of TYSABRI.

For more information about TYSABRI please visit www.tysabri.com, www.biogenidec.com or www.elan.com or call 1-800-456-2255.

About AVONEX

AVONEX is the most prescribed treatment for relapsing forms of MS worldwide, with approximately 135,000 patients on therapy. It is used worldwide as a treatment for relapsing forms of MS to slow the progression of disability and reduce relapses. AVONEX is also approved for patients who have their first clinical MS attack and have a brain MRI scan consistent with MS.

The most common side effects associated with AVONEX multiple sclerosis treatment are flu-like symptoms, including myalgia, fever, fatigue, headache, chills, nausea, vomiting, pain and asthenia.

AVONEX should be used with caution in patients with depression or other mood disorders and in patients with seizure disorders. AVONEX should not be used by pregnant women. Patients with cardiac disease should be closely monitored. Patients should also be monitored for signs of hepatic injury. Routine periodic blood chemistry and hematology tests are recommended during treatment with AVONEX. Rare cases of anaphylaxis have been reported. Please see complete prescribing information available at www.AVONEX.com.

About PEGylated Interferon beta-1a

PEGylated interferon beta-1a is currently in clinical development.

About BG-12

BG-12 is currently in Phase III clinical development. The CONFIRM (COmparator and aN oral Fumarate In Relapsing-remitting MS) trial is currently enrolling patients in North America, Europe and rest of world. CONFIRM is two-year, randomized, multi-center, double-blind, placebo-controlled, dose-comparison study to determine the safety and efficacy of BG-12 in subjects with relapsing-remitting MS. CONFIRM will also include a glatiramer acetate (Copaxone®) reference comparator arm. It was recently announced that the DEFINE (Determination of the Efficacy and safety of oral Fumarate IN rElapsing-remitting MS) study fully enrolled 1,241 patients. For more information about CONFIRM, please email ms@dandersoncompany.com.

About Daclizumab

Daclizumab is currently in Phase II clinical development. Biogen Idec is developing daclizumab for MS in collaboration with PDL BioPharma, Inc.

Safe Harbor

This press release contains forward-looking statements about our marketed products and our products in development. Drug development and commercialization involves a high degree of risk, and all of our products are subject to a number of risks and uncertainties. Important risk factors include the risk that we may be unable to adequately address concerns or questions raised by FDA or other regulatory authorities, the occurrence of adverse safety events with our products, that concerns may arise from additional data, that we may not be able to get the drugs in development approved and that the incidence and/or risk of any safety issues with respect to our products may be higher than observed in clinical trials. The company may also encounter other unexpected hurdles. Additional risks and uncertainties are described in Item 1.A. Risk Factors in our reports on Form 10-K and Form 10-Q and in other reports we file with the SEC. These forward-looking statements speak only as of the date of this press release, and we do not undertake any obligation to publicly update any forward-looking statements, whether as a result of new information, future events, or otherwise.