Seres Therapeutics (MCRB) grants 75,000-share stock option to officer Henn

Rhea-AI Filing Summary

Seres Therapeutics, Inc. disclosed that officer Matthew R. Henn received a grant of stock options covering 75,000 shares of common stock on March 4, 2026. These options give him the right to buy company shares if they vest and are exercised in the future.

According to the vesting schedule, 25% of the option shares will vest on March 2, 2027, with the remaining shares vesting in 12 equal quarterly installments thereafter. This filing reflects an equity-based compensation award rather than an open-market share purchase or sale.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider Henn Matthew R

Role See Remarks

Type	Security	Shares	Price	Value
Grant/Award	Stock Option (right to buy)	75,000	$0.00	--

Holdings After Transaction: Stock Option (right to buy) — 75,000 shares (Direct)

Footnotes (1)

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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
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).

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)
03/04/2026

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

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
Stock Option (right to buy)	$9.13	03/04/2026		A		75,000		(1)	03/03/2036	Common Stock	75,000	$0	75,000	D

Explanation of Responses:

1. The option will vest as to 25% of the shares on March 2, 2027. The remainder of the shares will vest in 12 equal quarterly installments thereafter.

Remarks:

President and Chief Scientific Officer

	/s/ Thomas J. DesRosier, attorney-in-fact for Matthew R. Henn	03/06/2026
	** 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.
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 did Seres Therapeutics (MCRB) report in Matthew R. Henn’s latest Form 4?

Seres Therapeutics reported a stock option grant to officer Matthew R. Henn for 75,000 shares. The options were granted on March 4, 2026, and represent equity-based compensation rather than a market trade in Seres Therapeutics common stock.

How many Seres Therapeutics (MCRB) shares are covered by Matthew R. Henn’s new option?

The new stock option granted to Matthew R. Henn covers 75,000 shares of Seres Therapeutics common stock. This option represents the right to buy those shares in the future, subject to the stated vesting schedule and any exercise decisions.

What is the vesting schedule for Matthew R. Henn’s Seres Therapeutics (MCRB) stock option?

Twenty-five percent of the option will vest on March 2, 2027, with the remainder vesting in 12 equal quarterly installments. This structure means the award becomes exercisable gradually over several years, aligning ongoing service with potential equity ownership.

Does the Form 4 for Seres Therapeutics (MCRB) show Matthew R. Henn buying or selling shares?

The Form 4 shows an acquisition of stock options as compensation, not a market buy or sell of shares. The transaction is coded as an award (code A), reflecting a grant of derivative securities rather than a direct stock trade.

What transaction code is used for Matthew R. Henn’s Seres Therapeutics (MCRB) option grant?

The transaction uses code “A,” indicating a grant, award, or other acquisition of derivative securities. This code confirms the event is an option award to Matthew R. Henn, not an open-market purchase or sale of Seres Therapeutics common stock.