Eric D. Shaff - 15 Nov 2025 Form 4 Insider Report for Seres Therapeutics, Inc. (MCRB)

Role
Director
Signature
/s/ Thomas J. DesRosier, attorney-in-fact for Eric D. Shaff
Issuer symbol
MCRB
Transactions as of
15 Nov 2025
Net transactions value
-$3,754
Form type
4
Filing time
18 Nov 2025, 16:30:25 UTC
Previous filing
19 Aug 2025
Next filing
18 Feb 2026
SEC
View on sec.gov

Reporting Owners (1)

Name Relationship Address Signature Signature date CIK
Shaff Eric D. Director C/O SERES THERAPEUTICS, INC., 101 CAMBRIDGE PARK DRIVE, CAMBRIDGE /s/ Thomas J. DesRosier, attorney-in-fact for Eric D. Shaff 18 Nov 2025 0001643734

Transactions Table

Type Sym Class Transaction Value $ Shares Change % * Price $ Shares After Date Ownership Footnotes
transaction MCRB Common Stock Options Exercise +390 +3.7% 10,999 15 Nov 2025 Direct F1
transaction MCRB Common Stock Options Exercise +331 +3% 11,330 15 Nov 2025 Direct F1
transaction MCRB Common Stock Sale $3,754 -217 -1.9% $17.30 11,113 15 Nov 2025 Direct F2

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 Restricted Stock Units Options Exercise $0 -390 -17% $0.000000 1,954 15 Nov 2025 Common Stock 390 Direct F1, F3
transaction MCRB Restricted Stock Units Options Exercise $0 -331 -10% $0.000000 2,989 15 Nov 2025 Common Stock 331 Direct F1, F4
* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Buy Plan / Sale Plan: These are also open market purchases/sales of shares, but in this case the transaction is part of a trading plan. Rule 10b5-1 allows insiders to setup a trading plan to buy/sell stocks over a certain period of time. Since the purchases/sales are predetermined, this protects the insiders from violating insider trading law.

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).

Explanation of Responses:

Id Content
F1 Each restricted stock unit represents a contingent right to receive one share of Issuer common stock.
F2 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.
F3 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.
F4 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.