Sec Form 4 Filing - Nutritional Health LTP Fund General Partner LLC @ Seres Therapeutics, Inc. - 2022-07-05

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 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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1. Name and Address of Reporting Person Nutritional Health LTP Fund General Partner LLC 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) (Last) (First) (Middle) 55 CAMBRIDGE PARKWAY, SUITE 800E 3. Date of Earliest Transaction (MM/DD/YY) 07/05/2022 (Street) CAMBRIDGE, MA02142 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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 (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 07/05/2022 P( 1 ) 2,912,748 A $ 3.15 5,875,711 I By Nutritional Health LTP Fund, L.P.( 2 ) Common Stock 07/05/2022 P( 1 ) 5,825,495 A $ 3.15 5,825,495 I By Flagship Pioneering Fund VII, L.P.( 3 ) Common Stock 4,434,600 I By Flagship Ventures Fund IV, L.P.( 4 ) Common Stock 1,283,282 I By Flagship Ventures Fund IV-Rx, L.P.( 5 ) Common Stock 2,962,963 I By Flagship Pioneering Fund VI, L.P.( 6 ) Common Stock 2,734,994 I By Flagship VentureLabs IV LLC( 7 ) Common Stock 376,018 I By Noubar B. Afeyan, Ph.D.( 8 )

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Nutritional Health LTP Fund General Partner LLC 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE, MA02142 X Nutritional Health LTP Fund, L.P. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE, MA02142 X Flagship Pioneering Inc. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE, MA02142 X AFEYAN NOUBAR 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE, MA02142 X Signatures Nutritional Health LTP Fund General Partner LLC, By: /s/ Noubar B. Afeyan, Ph.D., Name: Noubar B. Afeyan, Ph.D., Title: Manager 07/07/2022 Signature of Reporting Person Date Nutritional Health LTP Fund, L.P., By: Nutritional Health LTP Fund General Partner LLC, its general partner, By: /s/ Noubar B. Afeyan, Ph.D., Name: Noubar B. Afeyan, Ph.D., Title: Manager 07/07/2022 Signature of Reporting Person Date Flagship Pioneering, Inc., By: /s/ Noubar B. Afeyan, Ph.D., Name: Noubar B. Afeyan, Ph.D., Title: Chief Executive Officer 07/07/2022 Signature of Reporting Person Date Noubar B. Afeyan, Ph.D., by: /s/ Noubar B. Afeyan, Ph.D. 07/07/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On July 5, 2022, Nutritional Health LTP Fund, L.P. ("Nutritional LTP") and Flagship Pioneering Fund VII, L.P. ("Flagship Fund VII") acquired 2,912,748 shares and 5,825,495 shares, respectively, of the Issuer's Common Stock in a registered direct offering at a price of $3.15 per share. ( 2 )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. ("Dr. Afeyan") 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. ( 3 )Shares held by Flagship Fund VII. Flagship Pioneering Fund VII General Partner LLC ("Flagship Fund VII GP") is the general partner of Flagship Fund VII. Flagship Pioneering, Inc. ("Flagship Pioneering") is the manager of Flagship Fund VII GP. Dr. Afeyan is the Chief Executive Officer, sole shareholder and director of Flagship Pioneering. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein. ( 4 )Shares held by Flagship Ventures Fund IV, L.P. ("Flagship Fund IV"). Flagship Ventures Fund IV General Partner LLC ("Flagship Fund IV GP") is the general partner of Flagship Fund IV. Dr. Afeyan 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. ( 5 )Shares held by Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx"). Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. Dr. Afeyan 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. ( 6 )Shares held by Flagship Pioneering Fund VI, L.P. ("Flagship Fund VI"). Flagship Pioneering Fund VI General Partner LLC ("Flagship Fund VI GP") is the general partner of Flagship Fund VI. Flagship Pioneering is the manager of Flagship Fund VI GP. Dr. Afeyan 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. ( 7 )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. ( 8 )Shares held by Dr. Afeyan. Each of the reporting persons except for Dr. Afeyan 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.

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).

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