[Form 4] Seres Therapeutics, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Matthew R. Henn, Chief Scientific Officer and EVP of Seres Therapeutics (MCRB), reported equity changes on a Form 4. Restricted stock units vested and settled on 08/15/2025: 141 RSUs and 97 RSUs were reported as acquired/settled, each representing one share. A subsequent sale on 08/18/2025 disposed of 73 shares at $16.65 per share under a Rule 10b5-1 plan adopted April 13, 2023 to cover taxes related to vesting. Following these transactions the filing shows 4,548 shares beneficially owned and remaining RSU balances of 844 and 976 as reported.

Insights

Financial Analyst

TL;DR: Routine insider vesting and small tax-cover sale; no large disposition or exercise with material market impact.

The Form 4 shows standard compensation settlement activity: two tranches of restricted stock units vested and settled on 08/15/2025 and a small sale of 73 shares at $16.65 executed under a pre-existing 10b5-1 plan to cover tax obligations. The sizes reported are modest relative to typical market-moving insider transactions and reflect compensation mechanics rather than strategic trading.

Corporate Governance Expert

TL;DR: Disclosure aligns with Section 16 rules and uses a documented 10b5-1 plan for tax-related selling.

The reporting includes the required detail on vesting schedules, settlement, and the use of a 10b5-1 instruction adopted April 13, 2023. Signatory authority is documented via attorney-in-fact signature. The filing is consistent with routine governance and insider reporting practices and contains clear explanations of the transactions and vesting cadence.

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
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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

X

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Henn Matthew R

(Last) (First) (Middle)

C/O SERES THERAPEUTICS, INC.

101 CAMBRIDGE PARK DRIVE

(Street)

CAMBRIDGE MA 02140

(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		10% Owner
X	Officer (give title below)		Other (specify below)
	See Remarks

3. Date of Earliest Transaction (Month/Day/Year)
08/15/2025

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	08/15/2025		M		141	A	(1)	4,524	D
Common Stock	08/15/2025		M		97	A	(1)	4,621	D
Common Stock	08/18/2025		S(2)		73	D	$16.65	4,548	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
Restricted Stock Units	(1)	08/15/2025		M			141	(3)	(3)	Common Stock	141	$0	844	D
Restricted Stock Units	(1)	08/15/2025		M			97	(4)	(4)	Common Stock	97	$0	976	D

Explanation of Responses:

1. Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.

2. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted by the reporting person on April 13, 2023, solely with the intent to cover taxes in connection with the vesting of the restricted stock units.

3. The restricted stock units vested and settled as to 25% of the restricted stock units on February 15, 2024. The remainder of the restricted stock units have vested and settled or will vest and settle in 12 equal quarterly installments thereafter. The restricted stock units have no expiration date.

4. The restricted stock units vested and settled as to 25% of the restricted stock units on February 15, 2025. The remainder of the restricted stock units have vested and settled or will vest and settle in 12 equal quarterly installments thereafter. The restricted stock units have no expiration date.

Remarks:

Chief Scientific Officer and EVP

	/s/ Thomas J. DesRosier, attorney-in-fact for Matthew R. Henn	08/19/2025
	** 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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 Number.

FAQ

What transactions did Matthew R. Henn report on the Form 4 for MCRB?

He reported vesting/settlement of 141 and 97 restricted stock units on 08/15/2025 and a sale of 73 shares on 08/18/2025 at $16.65 per share.

Why were shares sold on 08/18/2025 according to the filing?

The sale was effected pursuant to a Rule 10b5-1 instruction adopted April 13, 2023, solely to cover taxes from RSU vesting.

How many shares does the filing show beneficially owned after these transactions?

The Form 4 reports 4,548 shares beneficially owned following the reported transactions.

What is the reporting person’s role at Seres Therapeutics?

Matthew R. Henn is identified as Chief Scientific Officer and Executive Vice President.

Do the restricted stock units have expiration dates?

No; the filing states the restricted stock units have no expiration date and vest in scheduled installments as described.