X0306 4 2018-06-12 0 0001290149 Sierra Oncology, Inc. SRRA 0001297500 Pelzer Robert C/O SIERRA ONCOLOGY, INC. 2150 885 WEST GEORGIA ST. VANCOUVER A1 V6C 3E8 BRITISH COLUMBIA, CANADA 1 0 0 0 Stock Option (right to buy) 3.27 2018-06-12 4 A 0 25000 0.00 A 2028-06-12 Common Stock 25000 25000 D The option vests as to 8.333% of the total shares monthly, beginning on July 12, 2018, with 100% of the total shares vested and exercisable on June 12, 2019, subject to the reporting person's provision of service to the issuer on each vesting date. /s/ Sukhi Jagpal as attorney-in-fact for Robert Pelzer 2018-06-14