X0206 3 2020-07-28 1 0001290149 Sierra Oncology, Inc. SRRA 0001819240 Thomson Christina C/O SIERRA ONCOLOGY, INC. 2150 885 WEST GEORGIA ST. VANCOUVER A1 V6C 3E8 BRITISH COLUMBIA, CANADA 0 1 0 0 General Counsel No securities are beneficially owned. /s/ Sukhi Jagpal, as attorney-in-fact for Mary Christina Thomson 2020-07-29