X0306 4 2021-06-03 0 0001382101 SUTRO BIOPHARMA, INC. STRO 0001296771 Freund John Gordon SKYLINE VENTURES 525 UNIVERSITY AVE., SUITE 1350 PALO ALTO CA 94301 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