Ownership Submission
FORM 3
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

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
OMB APPROVAL
OMB Number: 3235-0104
Expires: January 31, 2005
Estimated average burden hours per response... 0.5

(Print or Type Responses)
1. Name and Address of Reporting Person *
  Henn Matthew R.
 2. Date of Event Requiring Statement (Month/Day/Year)
02/01/2019		 3. Issuer Name and Ticker or Trading Symbol
Seres Therapeutics, Inc. [MCRB]
(Last)
(First)
(Middle)
C/O SERES THERAPEUTICS, INC., 200 SIDNEY STREET		 4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
Chief Scientific Officer
 5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

CAMBRIDGE, MA 02139		 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
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)
Common Stock 4,500
D
 

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(Month/Day/Year)		 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)
Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option (Right to Buy)   (1) 06/25/2025 Common Stock 40,000 $ 18 D  
Stock Option (Right to Buy)   (2) 01/31/2026 Common Stock 12,500 $ 26.2 D  
Stock Option (Right to Buy)   (3) 01/25/2027 Common Stock 30,000 $ 9.89 D  
Restricted Stock Units   (4)   (5) Common Stock 7,500 $ (6) D  
Stock Option (Right to Buy)   (7) 01/29/2028 Common Stock 60,000 $ 10.42 D  
Stock Option (Right to Buy)   (8) 01/24/2029 Common Stock 73,500 $ 6.01 D  

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Henn Matthew R.
C/O SERES THERAPEUTICS, INC.
200 SIDNEY STREET
CAMBRIDGE, MA 02139		       Chief Scientific Officer  

Signatures

/s/ Eric D. Shaff, Attorney-in-fact 02/11/2019
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(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).
(1) The option has vested as to 25% of the shares on June 26, 2016. The remainder of the shares will vest or have vested in 12 equal quarterly installments thereafter.
(2) The option has vested as to 25% of the shares on February 1, 2017. The remainder of the shares will vest or have vested in 12 equal quarterly installments thereafter.
(3) The option has vested as to 25% of the shares on January 26, 2018. The remainder of the shares will vest or have vested in 12 equal quarterly installments thereafter.
(4) These restricted stock units have vested and settled or will vest and settle as to 20% of the restricted stock units on January 26, 2018, 30% on January 26, 2019 and 50% on January 26, 2020.
(5) Not applicable.
(6) Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.
(7) The option has vested as to 25% of the shares on January 30, 2019. The remainder of the shares will vest in 12 equal quarterly installments thereafter.
(8) The option vests as to 25% of the shares on January 25, 2020. The remainder of the shares will vest in 12 equal quarterly installments thereafter.
 
Remarks:
Exhibit List: Exhibit 24 - Power of Attorney

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, See Instruction 6 for procedure.

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.