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* Flagship Ventures Fund IV General Partner LLC (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Seres Therapeutics, Inc. [ MCRB ]	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) 11/23/2020
	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	11/23/2020		J(1)		3,587,820	D	$0.00	4,434,600	I	See Footnote(2)
Common Stock	11/23/2020		J(1)		642,180	D	$0.00	1,283,282	I	See Footnote(3)
Common Stock	11/23/2020		J(1)		966,234	D	$0.00	0	I	See Footnote(4)
Common Stock	11/23/2020		J(5)		1,186,310	D	$0.00	3,258,134	I	See Footnote(6)
Common Stock	11/23/2020		J(7)		1,481,481	D	$0.00	2,962,963	I	See Footnote(8)
Common Stock	11/23/2020		J(7)		43,154	D	$0.00	0	I	See Footnote(9)
Common Stock								2,734,994	I	See Footnote(10)
Common Stock								376,018	I	See Footnote(11)

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* Flagship Ventures Fund IV General Partner LLC (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* Flagship Ventures Fund IV, L.P. (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* Flagship Ventures Fund IV-Rx, L.P. (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* Nutritional Health LTP Fund General Partner LLC (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* Nutritional Health LTP Fund, L.P. (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* Flagship Pioneering Inc. (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* Flagship Pioneering Fund VI General Partner LLC (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* Flagship Pioneering Fund VI, L.P. (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* AFEYAN NOUBAR (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

Explanation of Responses:

1. On November 23, 2020, Flagship Ventures Fund IV, L.P. ("Flagship Fund IV") and Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx") distributed to its limited partners and sole general partner, Flagship Ventures Fund IV General Partner, LLC ("Flagship Fund IV GP"), pro rata and without consideration, 3,587,820 shares and 642,180 shares, respectively, of the Issuer's common stock. Flagship Fund IV GP, in turn, distributed to its members, pro rata and without consideration, the 837,782 shares and 128,452 shares it received from Flagship Fund IV and Flagship Fund IV-Rx, respectively. Noubar B. Afeyan, Ph.D. received 335,171 shares through Flagship Fund IV GP's distribution. The aforementioned distributions were made in accordance with the exemptions afforded by Rule 16a-13 and Rule 16a-9 of the Securities Exchange Act of 1934, as amended.

2. Shares held by Flagship Fund IV. Flagship Fund IV GP is the general partner of Flagship Fund IV. Noubar B. Afeyan, Ph.D. is the sole manager of Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein. Edwin M. Kania, Jr. is retired both from Flagship Pioneering and as a manager of Flagship Fund IV GP.

3. Shares held by Flagship Fund IV-Rx. Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. Noubar B. Afeyan, Ph.D. is the sole manager of Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV-Rx disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

4. Shares held by Flagship Fund IV GP. Noubar B. Afeyan, Ph.D. is the sole manager of Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV GP disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

5. On November 23, 2020, Nutritional Health LTP Fund, L.P. ("Nutritional LTP") distributed to its limited partners, pro rata and without consideration, 1,186,310 shares of the Issuer's common stock. The aforementioned distribution was made in accordance with the exemptions afforded by Rule 16a-13 and Rule 16a-9 of the Securities Exchange Act of 1934, as amended.

6. Shares held by Nutritional LTP. Nutritional Health LTP Fund General Partner LLC ("Nutritional LTP GP") is the general partner of Nutritional LTP. Noubar B. Afeyan Ph.D. is the sole member and manager of Nutritional LTP GP. Each of the reporting persons except for Nutritional LTP disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

7. On November 23, 2020, Flagship Pioneering Fund VI, L.P. ("Flagship Fund VI") distributed to its limited partners and sole general partner, Flagship Pioneering Fund VI General Partner LLC ("Flagship Fund VI GP"), pro rata and without consideration, 1,481,481 shares of the Issuer's common stock. Flagship Fund VI GP, in turn, distributed to its members, pro rata and without consideration, the 43,154 shares it received from Flagship Fund VI. Each of Noubar B. Afeyan, Ph.D. and a trust for the benefit of Dr. Afeyan's children received 12,853 shares through Flagship Fund VI GP's distribution. The aforementioned distributions were made in accordance with the exemptions afforded by Rule 16a-13 and Rule 16a-9 of the Securities Exchange Act of 1934, as amended.

8. Shares held by Flagship Fund VI. Flagship Fund VI GP is the general partner of Flagship Fund VI. Flagship Pioneering, Inc. ("Flagship Pioneering") is the manager of Flagship Fund VI GP. Noubar B. Afeyan Ph.D. is the CEO, sole shareholder and director of Flagship Pioneering. Each of the reporting persons except Flagship Fund VI disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

9. Shares held by Flagship Fund VI GP. Flagship Pioneering is the manager of Flagship Fund VI GP. Noubar B. Afeyan Ph.D. is the CEO, sole shareholder and director of Flagship Pioneering. Each of the reporting persons except Flagship Fund VI GP disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

10. Shares held by Flagship VentureLabs IV LLC ("VentureLabs IV"). Flagship Fund IV is a member of VentureLabs IV and also serves as its manager. Each of the reporting persons except VentureLabs IV disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

11. Shares held by Noubar B. Afeyan, Ph.D. Each of the reporting persons except for Noubar B. Afeyan, Ph.D. disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein. Includes 12,853 shares held through a trust for the benefit of Dr. Afeyan's children. Dr. Afeyan disclaims Section 16 beneficial ownership of these shares except to the extent of his pecuniary interest therein, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such shares for Section 16 or any other purpose.

Remarks:

	Flagship Ventures Fund IV General Partner LLC, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager	11/25/2020
	Flagship Ventures Fund IV, L.P., By: Flagship Ventures Fund IV General Partner LLC, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager	11/25/2020
	Flagship Ventures Fund IV-Rx, L.P., By: Flagship Ventures Fund IV General Partner LLC, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager	11/25/2020
	Nutritional Health LTP Fund General Partner LLC, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager	11/25/2020
	Nutritional Health LTP Fund, L.P., By: Nutritional Health LTP Fund General Partner LLC, its general partner, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager	11/25/2020
	Flagship Pioneering, Inc., By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: CEO, Sole Shareholder & Director	11/25/2020
	Flagship Pioneering Fund VI General Partner LLC, By: Flagship Pioneering, Inc., its manager, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: CEO, Sole Shareholder & Director	11/25/2020
	Flagship Pioneering Fund VI, L.P., By: Flagship Pioneering Fund VI General Partner LLC, its general partner, By: Flagship Pioneering, Inc., its manager, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: CEO, Sole Shareholder & Director	11/25/2020
	Noubar B. Afeyan, Ph.D., by: /s/ Noubar B. Afeyan	11/25/2020
	** 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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