Marella Thorell - 04 Mar 2026 Form 4 Insider Report for Seres Therapeutics, Inc. (MCRB)

Role: EVP and Chief Financial Officer
Signature: /s/ Thomas J. DesRosier, Attorney-in-Fact for Marella Thorell
Issuer symbol: MCRB
Transactions as of: 04 Mar 2026
Net transactions value: $0
Form type: 4
Filing time: 06 Mar 2026, 16:33:50 UTC
Previous filing: 15 Oct 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Thorell Marella	EVP and Chief Financial Officer	C/O SERES THERAPEUTICS, INC., 101 CAMBRIDGE PARK DRIVE, CAMBRIDGE	/s/ Thomas J. DesRosier, Attorney-in-Fact for Marella Thorell	06 Mar 2026	0001826323

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	MCRB	Stock Option (right to buy)	Award		+22,500		$0.000000^*	22,500	04 Mar 2026	Common Stock	22,500	$9.13	Direct	F1

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	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:

EVP and Chief Financial Officer