Initial Statement of Beneficial Ownership (3)

FORM 3	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0104 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person ^*

Cieplinska Agnieszka

2. Date of Event Requiring Statement (MM/DD/YYYY) 1/8/2020

3. Issuer Name and Ticker or Trading Symbol

MOMENTA PHARMACEUTICALS INC [MNTA]

(Last) (First) (Middle)

C/O MOMENTA PHARMACEUTICALS, INC., 301 BINNEY ST.

4. Relationship of Reporting Person(s) to Issuer (Check all applicable)

_____ Director _____ 10% Owner
___X___ Officer (give title below) _____ Other (specify below)
VP FINANCE, CONTROLLER (PAO) /

(Street)

CAMBRIDGE, MA 02142

(City) (State) (Zip)

5. If Amendment, Date Original Filed(MM/DD/YYYY)

6. Individual or Joint/Group Filing(Check Applicable Line)

_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

*Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)*
1. Title of Derivate Security (Instr. 4)	2. Date Exercisable and Expiration Date (MM/DD/YYYY)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivate Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security		6. Nature of Indirect Beneficial Ownership (Instr. 5)
Stock Option (Right to Buy)	⁽¹⁾	4/12/2029	Common Stock	25000	$13.85	D

Explanation of Responses:
(1)	The stock option will vest and become exercisable with respect to 6,250 shares on the first anniversary of the grant date, and the remainder will vest in equal quarterly installments thereafter. All vesting is subject to Agnieszka Cieplinska's continued service to the Company through the applicable vesting date.

Remarks:
Exhibit List: Exhibit 24 - Power of Attorney

Reporting Owners
Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
Cieplinska Agnieszka C/O MOMENTA PHARMACEUTICALS, INC. 301 BINNEY ST. CAMBRIDGE, MA 02142			VP FINANCE, CONTROLLER (PAO)