X0306 4 2022-09-08 0 0001609809 Seres Therapeutics, Inc. MCRB 0001767321 Henn Matthew R. C/O SERES THERAPEUTICS, INC. 200 SIDNEY STREET CAMBRIDGE MA 02139 0 1 0 0 See Remarks Stock Option (Right to Buy) 10.84 2022-09-08 4 A 0 35000 0.00 A 2022-09-08 2027-07-18 Common Stock 35000 35000 D On June 19, 2017, the Reporting Person was granted an option to purchase 70,000 shares of the Issuer's common stock. Subject to the Reporting Person's continued service to the Issuer through each applicable vesting date, the option vests and becomes exercisable in two equal installments upon the satisfaction of certain performance criteria. On September 8, 2022, the Issuer's Board of Directors determined that the performance criteria for the first installment were met, resulting in vesting of the option as to 35,000 shares. Chief Scientific Officer and EVP /s/ Thomas J. DesRosier, attorney-in-fact for Matthew R. Henn 2022-09-09