X0306 4 2017-02-14 0 0001290149 Sierra Oncology, Inc. SRRA 0001341382 Topper James N C/O FRAZIER HEALTHCARE 601 UNION ST., TWO UNION SQ., STE. 3200 SEATTLE WA 98101 1 0 1 0 Common Stock 2017-02-14 4 P 0 5925926 1.35 A 5925926 I By Frazier Life Sciences VIII, L.P. Common Stock 2186195 I By Frazier Healthcare VI, L.P. The reporting person and Patrick Heron are the managing members of FHM Life Sciences VIII, L.L.C., which is the general partner of FHM Life Sciences VIII, L.P., which is the general partner of Frazier Life Sciences VIII, L.P. ("FLSIII"), the record holder of the securities, and the reporting person may be deemed to share voting and dispositive power over the securities held by FLSIII. The reporting person disclaims beneficial ownership over such securities except to the extent of his pecuniary interest therein, and the inclusion of these 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 purposes. The reporting person, Alan Frazier, Nader Naini, Nathan Every and Patrick Heron are the managing members of FHM VI, LLC, which is the general partner of FHM VI, LP, which is the general partner of Frazier Healthcare VI, L.P. ("FHVI"), the record holder of the securities, and the reporting person may be deemed to share voting and dispositive power over the securities held by FHVI. The reporting person disclaims beneficial ownership over such securities except to the extent of his pecuniary interest therein, and the inclusion of these 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 purposes. /s/ Sukhi Jagpal as attorney-in-fact for James Topper, M.D., Ph.D. 2017-02-16