X0306 4 2020-01-29 0 0001290149 Sierra Oncology, Inc. SRRA 0001793762 Richardson Joshua C/O SIERRA ONCOLOGY, INC. 2150 - 885 WEST GEORGIA STREET VANCOUVER A1 V6C 3E8 BRITISH COLUMBIA, CANADA 1 0 1 0 Common Stock 2020-01-29 4 C 0 1477320 0.00 A 1477320 I By Longitude Venture Partners III, L.P. Series A Convertible Voting Preferred Stock 2020-01-29 4 C 0 19500 D Common Stock 1477320 0 I By Longitude Venture Partners III, L.P. On January 22, 2020, a 1-for-40 reverse split of the Issuer's Common Stock (the "Reverse Split") was effected. These securities reflect the Reverse Split. Each share of Series A Convertible Voting Preferred Stock (the "Series A Preferred Stock") converted into 75.76 shares of the Issuer's Common Stock for no additional consideration, as adjusted for the Reverse Split, automatically upon the 5th trading date following the Issuer's announcement of receiving stockholder approval for the first reverse stock split of the Issuer following November 13, 2019. The Series A Preferred Stock has no expiration date. Longitude Capital Partners III, LLC ("LCP III") is the general partner of Longitude Venture Partners III, L.P. ("LVP III") and may be deemed to have voting, investment and dispositive power with respect to such securities. Patrick G. Enright, Juliet Tammenoms Bakker and the Reporting Person (a member of the Issuer's board of directors), are each members of LCP III and may be deemed to share voting, investment and dispositive power over such securities. Mr. Enright and Ms. Tammenoms Bakker are the managing members of LCP III. Each of LCP III, Mr. Enright, Ms. Tammenoms Bakker and the Reporting Person disclaim beneficial ownership over such securities except to the extent of their respective pecuniary interest therein, and the inclusion of such 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 purpose. Consists of 19,500 shares of Series A Preferred Stock held by LVP III which are convertible into an aggregate of 1,477,320 shares of Common Stock, as adjusted for the Reverse Split. /s/ Sukhi Jagpal as attorney-in-fact for Joshua Richardson 2020-01-31