X0206 3 2019-04-18 0 0001609809 Seres Therapeutics, Inc. MCRB 0001770404 Chapman Marcus C/O SERES THERAPEUTICS, INC. 200 SIDNEY STREET CAMBRIDGE MA 02139 0 1 0 0 See Remarks Stock Option (Right to Buy) 15.77 2025-03-24 Common Stock 25000 D Stock Option (Right to Buy) 26.20 2026-01-31 Common Stock 12500 D Stock Option (Right to Buy) 9.89 2027-01-25 Common Stock 10000 D Stock Option (Right to Buy) 10.42 2028-01-29 Common Stock 18000 D Restricted Stock Units Common Stock 12000 D Stock Option (Right to Buy) 6.38 2029-01-31 Common Stock 23000 D The option is fully vested and exercisable. The option has vested as to 25% of the shares on February 1, 2017. The remainder of the shares will vest or have vested in 12 equal quarterly installments thereafter. The option has vested as to 25% of the shares on January 26, 2018. The remainder of the shares will vest or have vested in 12 equal quarterly installments thereafter. The option has vested as to 25% of the shares on January 30, 2019. The remainder of the shares will vest or have vested in 12 equal quarterly installments thereafter. These restricted stock units will vest in full on November 1, 2019. Not applicable. Each restricted stock unit represents a contingent right to receive one share of Issuer common stock. This option will vest as to 25% of the shares on February 1, 2020. The remainder of the shares will vest in 12 equal quarterly installments thereafter. Exhibit List: Exhibit 24 - Power of Attorney Principal Financial and Accounting Officer /s/ Thomas J. DesRosier, Attorney-in-fact for Marcus Chapman 2019-04-24