X0306 4 2018-10-01 0 0001382101 SUTRO BIOPHARMA INC STRO 0001198325 JANNEY DANIEL ONE EMBARCADERO CENTER, SUITE 3700 SAN FRANCISCO CA 94111 1 0 1 0 Common Stock 2018-10-01 4 C 0 589661 A 589661 I By Alta Partners VIII, L.P. Common Stock 2018-10-01 4 C 0 458331 A 1047992 I By Alta Partners VIII, L.P. Common Stock 2018-10-01 4 C 0 382698 A 1430690 I By Alta Partners VIII, L.P. Common Stock 2018-10-01 4 C 0 514211 A 1944901 I By Alta Partners VIII, L.P. Series B Preferred Stock 2018-10-01 4 C 0 10201769 0.00 D Common Stock 589661 0 I By Alta Partners VIII, L.P. Series C Preferred Stock 2018-10-01 4 C 0 12387324 0.00 D Common Stock 458331 0 I By Alta Partners VIII, L.P. Series D Preferred Stock 2018-10-01 4 C 0 9449318 0.00 D Common Stock 382698 0 I By Alta Partners VIII, L.P. Series E Preferred Stock 2018-10-01 4 C 0 18698578 0.00 D Common Stock 514211 0 I By Alta Partners VIII, L.P. Each share of the issuer's Series B Preferred Stock automatically converted into 0.0578 share of the issuer's Common Stock on October 1, 2018 in connection with the closing of the issuer's sale of its Common Stock in its firm commitment initial public offering (the "IPO") pursuant to a registration statement on Form S-1 (File No. 333-227103) under the Securities Act of 1933, as amended (the "Registration Statement"), and had no expiration date. These securities are held of record by Alta Partners VIII, L.P. ("Alta Partners). Alta Partners Management VIII, LLC ("Alta Management") is the general partner of Alta Partners. The reporting person, a member of the issuer's board of directors, is a managing director of Alta Management, and may be deemed to share voting and investment power over the securities held by Alta Partners. 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. Each share of the issuer's Series C Preferred Stock automatically converted into 0.0370 share of the issuer's Common Stock on October 1, 2018 in connection with the closing of the issuer's sale of its Common Stock in its IPO pursuant to the Registration Statement, and had no expiration date. Each share of the issuer's Series D Preferred Stock automatically converted into 0.0405 share of the issuer's Common Stock on October 1, 2018 in connection with the closing of the issuer's sale of its Common Stock in its IPO pursuant to the Registration Statement, and had no expiration date. Each share of the issuer's Series E Preferred Stock automatically converted into 0.0275 share of the issuer's Common Stock on October 1, 2018 in connection with the closing of the issuer's sale of its Common Stock in its IPO pursuant to the Registration Statement, and had no expiration date. /s/ Edward C. Albini as attorney-in-fact for Daniel Janney 2018-10-01