SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* POLARIS VENTURE MANAGEMENT CO III LLC (Last) (First) (Middle) 1000 WINTER STREET SUITE 3350 (Street) WALTHAM MA 02451-1215 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol MOMENTA PHARMACEUTICALS INC [ MNTA ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 02/22/2005
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

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
Common Stock	02/22/2005		S		6,125	D	$7.02	120,141	I	See footnotes(1)(4)(5)(6)
Common Stock	02/22/2005		S		240,150	D	$7.02	4,622,866	I	See footnotes(2)(4)(5)(6)
Common Stock	02/22/2005		S		3,725	D	$7.02	72,923	I	See footnotes(3)(4)(5)(6)

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 Securities Underlying Derivative Security (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: 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

1. Name and Address of Reporting Person* POLARIS VENTURE MANAGEMENT CO III LLC (Last) (First) (Middle) 1000 WINTER STREET SUITE 3350 (Street) WALTHAM MA 02451-1215 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* POLARIS VENTURE PARTNERS III LP (Last) (First) (Middle) 1000 WINTER STREET SUITE 3350 (Street) WALTHAM MA 02451-1215 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* POLARIS VENTURE PARTNERS FOUNDERS FUND III LP (Last) (First) (Middle) 1000 WINTER STREET SUITE 3350 (Street) WALTHAM MA 02451-1215 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* POLARIS VENTURE PARTNERS ENTREPRENEURS FUND III LP (Last) (First) (Middle) 1000 WINTER STREET SUITE 3350 (Street) WALTHAM MA 02451-1215 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Arnold Stephen D (Last) (First) (Middle) 1000 WINTER STREET SUITE 3350 (Street) WALTHAM MA 02451-1215 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Flint Jonathan A (Last) (First) (Middle) 1000 WINTER STREET SUITE 3350 (Street) WALTHAM MA 02451-1215 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* MCGUIRE TERRANCE (Last) (First) (Middle) 1000 WINTER STREET SUITE 3350 (Street) WALTHAM MA 02451-1215 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* SPOON ALAN G (Last) (First) (Middle) 1000 WINTER STREET SUITE 3350 (Street) WALTHAM MA 02451-1215 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. These shares are owned directly by Polaris Venture Partners Entrepreneurs' Fund III, L.P. ("PVPEF III"), of which Polaris Venture Management Co. III, LLC ("PVM III") is the General Partner. As such, PVM III may be deemed to share voting and investment powers with respect to the shares owned by PVPEF III.

2. These shares are owned directly by Polaris Venture Partners III, L.P. ("PVP III") of which PVM III is the General Partner. As such, PVM III may be deemed to share voting and investment powers with respect to the shares owned by PVP III.

3. These shares are owned directly by Polaris Venture Partners Founders' Fund III, L.P. ("PVPFF III"), of which PVM III is the General Partner. As such, PVM III may be deemed to share voting and investment powers with respect to the shares owned by PVPFF III.

4. PVM III is the General Partner of PVP III, PVPEF III and PVPFF III, and Stephen D. Arnold, Jonathan A. Flint, Terrance G. McGuire and Alan G. Spoon, the managing members of PVM III, may be deemed to share voting and dispositive power over the shares held by PVP III, PVPEF III and PVPFF III. Such persons disclaim beneficial ownership of shares held by PVP III, PVPEF III and PVPFF III except to the extent of any pecuniary interest therein.

5. North Star Ventures directly or indirectly provides investment advisory services to various venture capital funds, including PVM III, the General Partner of PVPEF III, PVPFF III and PVP III. The respective General Partners of these funds exercise sole voting and investment power with respect to the shares held by such funds.

6. Continued from footnote 5. The members of North Star Ventures are members of PVM III, the General Partner of PVPEF III, PVPFF III and PVP III. As members of PVM III, they may be deemed to share voting and investment powers with respect to the shares held by such funds. These principals disclaim beneficial ownership of all such shares except to the extent of their proportionate pecuniary interest therein.

	/s/ Kevin Littlejohn Authorized Signatory	02/24/2005
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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