X0306 4 2022-01-25 0 0001290149 Sierra Oncology, Inc. SRRA 0001713663 Longitude Capital Partners III, LLC 2740 SAND HILL ROAD SECOND FLOOR MENLO PARK CA 94025 0 0 1 0 0001674099 Longitude Venture Partners III, L.P. 2740 SAND HILL ROAD SECOND FLOOR MENLO PARK CA 94025 0 0 1 0 0001431159 Tammenoms Bakker Juliet 2740 SAND HILL ROAD SECOND FLOOR MENLO PARK CA 94025 0 0 1 0 0001253886 ENRIGHT PATRICK G 2740 SAND HILL ROAD SECOND FLOOR MENLO PARK CA 94025 0 0 1 0 Common Stock 2022-01-25 4 X 0 487451 13.20 A 1964771 I See footnote Series B Warrants 13.20 2022-01-25 4 X 0 1477125 13.20 D 2020-01-22 2022-04-10 Common Stock 487451 0 I See footnote These securities are held directly by Longitude Venture Partners III, L.P. ("LVP III"). Longitude Capital Partners III, LLC ("LCP III") is the general partner of 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 Joshua Richardson, 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 Joshua Richardson 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 1,477,125 Series B Warrants held by LVP III which are exercisable for an aggregate of 487,451 shares of Common Stock. Longitude Venture Partners III, L.P.; By /s/ Patrick G. Enright, Managing Member 2022-01-27 Longitude Capital Partners III, LLC; By /s/ Patrick G. Enright, Managing Member 2022-01-27 /s/ Juliet Tammenoms Bakker 2022-01-27 /s/ Patrick G. Enright 2022-01-27