MCRB Form 4: Executive RSU vesting and 1,042-share sale disclosed

Rhea-AI Filing Summary

Seres Therapeutics (MCRB) reported insider equity activity for an executive officer. EVP, Chief Commercial & Strategy Officer Teresa L. Young exercised restricted stock units (RSUs) into common stock on November 15, 2025, receiving 3,998, 132, and 98 shares in three separate transactions. On the same date, she sold 1,042 shares of common stock at a price of $17.30 per share, and held 8,401 shares directly after the reported transactions. The filing notes the sales were made under a pre-arranged Rule 10b5-1 trading instruction adopted on March 5, 2023, with the stated purpose of covering taxes related to RSU vesting.

Insider Trade Summary

Net Seller: 1,042 shares ($18,027)

Net Sell 7 txns

Insider Young Teresa L.

Role See Remarks

Sold 1,042 shs ($18K)

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units	3,998	$0.00	--
Exercise	Restricted Stock Units	132	$0.00	--
Exercise	Restricted Stock Units	98	$0.00	--
Exercise	Common Stock	3,998	$0.00	--
Exercise	Common Stock	132	$0.00	--
Exercise	Common Stock	98	$0.00	--
Sale	Common Stock	1,042	$17.30	$18K

Holdings After Transaction: Restricted Stock Units — 0 shares (Direct); Common Stock — 9,213 shares (Direct)

Footnotes (1)

1. Each restricted stock unit ("RSU") represents a contingent right to receive one share of Issuer common stock. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 instruction adopted by the reporting person on March 5, 2023, solely with the intent to cover taxes in connection with the vesting of the restricted stock units. The RSUs vested in a single installment on November 15, 2025. The RSUs have no expiration date. 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. 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.

Form 4 Insider Transactions: What Each Field Means →

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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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^*

Young Teresa L.

(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		3,998	A	(1)	9,213	D
Common Stock	11/15/2025		M		132	A	(1)	9,345	D
Common Stock	11/15/2025		M		98	A	(1)	9,443	D
Common Stock	11/15/2025		S(2)		1,042	D	$17.3	8,401	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			3,998	(3)	(3)	Common Stock	3,998	$0	0	D
Restricted Stock Units	(1)	11/15/2025		M			132	(4)	(4)	Common Stock	132	$0	664	D
Restricted Stock Units	(1)	11/15/2025		M			98	(5)	(5)	Common Stock	98	$0	878	D

Explanation of Responses:

1. Each restricted stock unit ("RSU") 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 5, 2023, solely with the intent to cover taxes in connection with the vesting of the restricted stock units.

3. The RSUs vested in a single installment on November 15, 2025. The RSUs have no expiration date.

4. 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.

5. 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:

EVP, Chief Commercial & Strategy Officer

	/s/ Thomas J. DesRosier, attorney-in-fact for Teresa L. Young	11/18/2025
	** Signature of Reporting Person	Date
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