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* STARR KEVIN P (Last) (First) (Middle) C/O THIRD ROCK VENTURES, LLC 29 NEWBURY STREET, 3RD FLOOR (Street) BOSTON MA 02116 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol ZAFGEN, INC. [ ZFGN ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X Director 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 09/24/2015
	4. If Amendment, Date of 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

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	09/24/2015		J(1)		1,655,095	D	$0	346,950	I	See footnote(2)
Common Stock	09/24/2015		S		74,949	D	$43.73(3)	272,001	I	See footnote(2)
Common Stock	09/24/2015		S		61,630	D	$44.1(4)	210,371	I	See footnote(2)
Common Stock	09/24/2015		J(5)		476,170	A	$0	476,170	I	See footnote(6)
Common Stock	09/24/2015		J(7)		476,170	D	$0	0	I	See footnote(6)
Common Stock	09/24/2015		J(8)		98,834	A	$0	370,323	D

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

Explanation of Responses:

1. Distribution of shares in kind by Third Rock Ventures, L.P. ("TRV") on a pro rata basis to its partners.

2. The shares are directly held by TRV. The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC") and the Reporting Person is a Manager of TRV GP LLC, as such, each of TRV GP and TRV GP LLC, the other Managers of TRV GP LLC and the Reporting Person exercises shared voting and investment power over the shares held of record by TRV. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein, if any.

3. The shares are directly held by TRV. The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC") and the Reporting Person is a Manager of TRV GP LLC, as such, each of TRV GP and TRV GP LLC, the other Managers of TRV GP LLC and the Reporting Person exercises shared voting and investment power over the shares held of record by TRV. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein, if any.

4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $44.00 to $44.48, inclusive. The Reporting Person undertakes to provide the Issuer, any security holder of the Issuer, or the staff of the SEC, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

5. TRV GP received shares distributed in kind by TRV on a pro rata basis to its partners.

6. The shares are directly held by TRV GP. As such, each of TRV GP LLC and the Reporting Person exercises shared voting and investment power over the shares held of record by TRV GP. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein, if any.

7. Distribution of shares in kind by TRV GP on a pro rata basis to its partners.

8. The Reporting Person received shares distributed in kind by TRV GP on a pro rata basis to its partners.

Remarks:

	/s/ Kevin Gillis by power of attorney for Kevin Starr	09/25/2015
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* 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).
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