Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
Crane Alan L
   2. Issuer Name and Ticker or Trading Symbol
MOMENTA PHARMACEUTICALS INC [MNTA] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
President, C.E.O.
(Last)
(First)
(Middle)
C/O MOMENTA PHARMACEUTICALS, 675 WEST KENDALL STREET		 3. Date of Earliest Transaction (Month/Day/Year)
12/30/2005
(Street)

CAMBRIDGE, MA 02142		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option (right to buy) $ 0.99 12/30/2005   D(1)     28,600   (2) 04/06/2014 Common Stock 6,600 $ 0.99 249,000 (4) D  
Stock Option (righ to buy) $ 4.91 12/30/2005   A(1)   28,600     (3) 04/06/2014 Common Stock 28,600 $ 4.91 249,000 (4) D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Crane Alan L
C/O MOMENTA PHARMACEUTICALS
675 WEST KENDALL STREET
CAMBRIDGE, MA 02142		   X     President, C.E.O.  

Signatures

 /s/ Alan L. Crane   01/04/2006
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) On December 30, 2005, in an effort to avoid adverse tax consequences to the Reporting Person under 409A of the Internal Revenue Code, the Issuer and the Reporting Person amended an oustanding stock option to purchase 35,200 shares with an exercise price of $0.99 per share (the "Original Option"). As amended, the portion of the Original Option vested as of December 31, 2004, or 6,600 shares, shall remain in full force and effect and continue to have an exercise price of $0.99. The remaining portion of the Original Option shall be deemed to be cancelled and a replacement option for the purchase of 28,600 shares shall be deemed granted to the Reporting Person with an increased exercise price equal to $4.91 (the "Replacement Option").
(2) As of December 31, 2004, the Original Option was vested as to 6,600 shares, and the Reporting Person may exercise such option as to such number of shares for a per share exercise price of $0.99.
(3) As of January 1, 2006, the Replacement Option was vested as to 11,000 shares, and the Reporting Person may exercise such option as to such number of shares for a per share exercise price of $4.91. The remaining portion of the Replacement Option vests as to 6.25% of the shares at the end of each three-month period following January 1, 2006.
(4) Includes multiple option grants with different prices and vesting dates.

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