Seres Therapeutics (MCRB) officer trades RSUs and sells 75 shares

Rhea-AI Filing Summary

Seres Therapeutics officer Teresa L. Young reported multiple Form 4 transactions involving restricted stock units and common stock. She acquired 231 shares of common stock on February 15, 2026 through exercises of restricted stock units at $0.00 per share, then sold 75 common shares at $8.47 per share. The sale was executed under a pre-arranged Rule 10b5-1 instruction adopted on March 5, 2023 to cover taxes related to vesting of restricted stock units.

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

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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^*

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)
02/15/2026

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	02/15/2026		M		231	A	(1)	8,632	D
Common Stock	02/15/2026		S(2)		75	D	$8.47	8,557	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)	02/15/2026		M			133	(3)	(3)	Common Stock	133	$0	531	D
Restricted Stock Units	(1)	02/15/2026		M			98	(4)	(4)	Common Stock	98	$0	780	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 5, 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:

EVP, Chief Commercial & Strategy Officer

	/s/ Thomas J. DesRosier, attorney-in-fact for Teresa L. Young	02/18/2026
	** 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.
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FAQ

What insider transactions did Seres Therapeutics (MCRB) report for Teresa L. Young?

Seres Therapeutics reported that officer Teresa L. Young exercised restricted stock units into 231 common shares and sold 75 common shares. The transactions occurred on February 15, 2026, and were reported on a Form 4 insider trading filing.

How many Seres Therapeutics (MCRB) shares did Teresa L. Young sell and at what price?

Teresa L. Young sold 75 shares of Seres Therapeutics common stock at a price of $8.47 per share. This open-market sale was disclosed as part of her Form 4 insider transaction report for February 15, 2026.

Were Teresa L. Young’s Seres Therapeutics (MCRB) stock sales under a Rule 10b5-1 plan?

Yes. The filing states the sales were effected pursuant to a Rule 10b5-1 instruction adopted on March 5, 2023. The plan’s stated intent was solely to cover taxes arising from the vesting of restricted stock units.

What do the restricted stock units in the Seres Therapeutics (MCRB) Form 4 represent?

Each restricted stock unit represents a contingent right to receive one share of Seres Therapeutics common stock. The units vest over time, with initial 25% tranches vesting on February 15, 2024 and February 15, 2025, followed by 12 equal quarterly installments.

How many Seres Therapeutics (MCRB) common shares did Teresa L. Young hold after the reported transactions?

After the February 15, 2026 transactions, Teresa L. Young held 8,557 shares of Seres Therapeutics common stock directly. This figure was disclosed as the total shares beneficially owned following the open-market sale.

Were the Seres Therapeutics (MCRB) restricted stock units reported in the Form 4 subject to expiration?

The filing notes that the restricted stock units have no expiration date. They vest and settle according to specified schedules beginning February 15, 2024 and February 15, 2025, with remaining portions vesting in 12 equal quarterly installments thereafter.