X0306 4 2021-06-03 0 0001382101 SUTRO BIOPHARMA, INC. STRO 0001587487 Wigginton Jon Marc C/O SUTRO BIOPHARMA, INC. 310 UTAH AVENUE, SUITE 150 SOUTH SAN FRANCISCO CA 94080 1 0 0 0 Stock Option (right to buy) 18.21 2021-06-03 4 A 0 18500 0.00 A 2031-06-02 Common Stock 18500 18500 D The option vests as to 8.33% of the total shares monthly, commencing July 3, 2021, with 100% of the total shares vested and exercisable on the earlier of the issuer's 2022 annual stockholders meeting or June 3, 2022, subject to the reporting person's provision of service to the issuer on each vesting date. /s/ Edward C. Albini as attorney-in-fact 2021-06-07