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

Rhea-AI Filing Summary

Seres Therapeutics, Inc. (MCRB) reported insider equity activity by its Chief Legal Officer, EVP, Co-Chief Executive Officer, and Co-President on 11/15/2025. The filing shows the exercise and settlement of restricted stock units into 132 shares and 112 shares of common stock, each RSU granting one share upon vesting. On the same date, 76 shares of common stock were sold at $17.30 per share under a Rule 10b5-1 trading instruction adopted on March 2, 2023, solely to cover taxes tied to RSU vesting. After these transactions, the reporting person directly owned 7,623 shares of common stock and retained 664 and 1,001 restricted stock units, which vest in scheduled quarterly installments and have no expiration date.

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).

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^*

DesRosier Thomas

(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)
11/15/2025

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	11/15/2025		M		132	A	(1)	7,587	D
Common Stock	11/15/2025		M		112	A	(1)	7,699	D
Common Stock	11/15/2025		S(2)		76	D	$17.3	7,623	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)	11/15/2025		M			132	(3)	(3)	Common Stock	132	$0	664	D
Restricted Stock Units	(1)	11/15/2025		M			112	(4)	(4)	Common Stock	112	$0	1,001	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 March 2, 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 Legal Officer, EVP, Co-Chief Executive Officer, and Co-President

	/s/ Thomas J. DesRosier	11/18/2025
	** 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 insider transaction did Seres Therapeutics (MCRB) report?

The company reported that a senior officer exercised restricted stock units into 132 and 112 shares of common stock on 11/15/2025, then sold 76 shares.

At what price were Seres Therapeutics (MCRB) shares sold in this Form 4?

The filing states that 76 shares of Seres Therapeutics common stock were sold at a price of $17.30 per share on 11/15/2025.

Why were the Seres Therapeutics (MCRB) shares sold by the insider?

The sales were effected under a Rule 10b5-1 trading instruction adopted on March 2, 2023, solely to cover taxes associated with the vesting of restricted stock units.

How many Seres Therapeutics (MCRB) shares does the insider own after the transactions?

Following the reported transactions, the insider directly owned 7,623 shares of Seres Therapeutics common stock.

What restricted stock units remain outstanding for the Seres Therapeutics (MCRB) insider?

After settlement of some units, the insider beneficially owned 664 and 1,001 restricted stock units, each representing a right to receive one share of common stock upon vesting.

How do the Seres Therapeutics (MCRB) restricted stock units vest?

The RSUs vest and settle 25% on specified initial dates in February 2024 and February 2025, with the remainder vesting in 12 equal quarterly installments thereafter, and they have no expiration date.

What is the insider’s role at Seres Therapeutics (MCRB)?

The reporting person serves as Chief Legal Officer, EVP, Co-Chief Executive Officer, and Co-President of Seres Therapeutics.