X0206 3 2017-02-14 0 0001290149 Sierra Oncology, Inc. SRRA 0001456656 Frazier Healthcare VI, L.P. 601 UNION STREET, SUITE 3200 SEATTLE WA 98101 0 0 1 0 0001456655 FHM VI, L.P. 601 UNION STREET, SUITE 3200 SEATTLE WA 98101 0 0 1 0 0001456654 FHM VI, L.L.C. 601 UNION STREET, SUITE 3200 SEATTLE WA 98101 0 0 1 0 0001655827 Frazier Life Sciences VIII, L.P. 601 UNION STREET, SUITE 3200 SEATTLE WA 98101 0 0 1 0 0001698755 FHM LIFE SCIENCES VIII, L.P. 601 UNION STREET, SUITE 3200 SEATTLE WA 98101 0 0 1 0 0001698823 FHM LIFE SCIENCES VIII, L.L.C. 601 UNION STREET, SUITE 3200 SEATTLE WA 98101 0 0 1 0 0001018534 FRAZIER ALAN D 601 UNION STREET, SUITE 3200 SEATTLE WA 98101 0 0 1 0 0001344203 Naini Nader J 601 UNION STREET, SUITE 3200 SEATTLE WA 98101 0 0 1 0 0001531105 Every Nathan R 601 UNION STREET, SUITE 3200 SEATTLE WA 98101 0 0 1 0 0001365617 Heron Patrick J 601 UNION STREET, SUITE 3200 SEATTLE WA 98101 0 0 1 0 Common Stock 2186195 D Common Stock 5925926 D Represents shares held by Frazier Healthcare VI, L.P., an affiliate of Frazier Healthcare Partners. Each of the Reporting Persons disclaims beneficial ownership of the shares except to the extent of their pecuniary interest therein, if any. Represents shares held by Frazier Life Sciences VIII, L.P., an affiliate of Frazier Healthcare Partners. Each of the Reporting Persons disclaims beneficial ownership of the shares except to the extent of their pecuniary interest therein, if any. This statement is filed by: (i) Frazier Healthcare VI, L.P. ("Frazier VI") and Frazier Life Sciences VIII, L.P. ("Frazier VIII"), each a Delaware limited partnership and direct owners of the shares of Common Stock (together, the "Shares"); (ii) FHM VI, L.P., a Delaware limited partnership and general partner to Frazier VI; FHM VI, LLC a Delaware limited liability company and general partner of FHM VI, L.P.; FHM Life Sciences VIII, L.P., a Delaware limited partnership and general partner to Frazier VIII; and FHM Life Sciences VIII, LLC, a Delaware limited liability company and general partner of FHM Life Sciences VIII, L.P.;and (iii) Alan Frazier, Nader Naini, Nathan Every and Patrick Heron, each of who are members of FHM VI, LLC and may be deemed to share voting and investment power with respect to shares held by Frazier VI and Patrick Heron, who is a member of FHM Life Sciences VIII, LLC and may be deemed to share voting and investment power with respect to shares held by Frazier VIII. /s/ Frazier Healthcare VI, L.P. by Steve R. Bailey, Attorney-in-Fact 2017-02-24 /s/ FHM VI, L.P. by Steve R. Bailey, Attorney-in-Fact 2017-02-24 /s/ FHM VI, L.L.C. by Steve R. Bailey, Attorney-in-Fact 2017-02-24 /s/ Frazier Life Sciences VIII, L.P. by Steve R. Bailey, Attorney-in-Fact 2017-02-24 /s/ FHM Life Sciences VIII, L.P. by Steve R. Bailey, Attorney-in-Fact 2017-02-24 /s/ FHM Life Sciences VIII, L.L.C. by Steve R. Bailey, Attorney-in-Fact 2017-02-24 /s/ Alan Frazier by Steve R. Bailey, Attorney-in-Fact 2017-02-24 /s/ Nader Naini by Steve R. Bailey, Attorney-in-Fact 2017-02-24 /s/ Nathan Every by Steve R. Bailey, Attorney-in-Fact 2017-02-24 /s/ Patrick Heron by Steve R. Bailey, Attorney-in-Fact 2017-02-24