X0306 4 2020-09-18 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 Common Stock 2020-09-18 4 S 0 400000 12.00 D 560053 I By Skyline Venture Partners V, L.P. These securities are held of record by Skyline Venture Partners V, L.P. ("Skyline L.P."). Skyline Venture Management V, LLC ("Skyline Management") is the general partner of Skyline L.P. the reporting person, a member of the issuer's board of directors, together with Yasunori Kaneko, are the managing directors of Skyline Management, and each may be deemed to share voting and investment power over the securities held by Skyline L.P. The reporting person disclaims beneficial ownership over such securities except to the extent of his pecuniary interest therein, and the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of the reported securities for purposes of Section 16 or for any other purposes. /s/ Edward C. Albini as attorney-in-fact for John G. Freund 2020-09-22