Sec Form 3 Filing - ORBIMED ADVISORS LLC @ Sierra Oncology, Inc. - 2019-11-22

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person ORBIMED ADVISORS LLC 2. Issuer Name and Ticker or Trading Symbol Sierra Oncology, Inc. [ SRRA] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 601 LEXINGTON AVENUE, 54TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 11/22/2019 (Street) NEW YORK, NY10022 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series A Convertible Preferred Stock ( 1 ) ( 2 ) ( 1 )( 2 ) ( 1 )( 2 ) Common Stock 45,450,000 ( 1 ) ( 2 ) ( 3 ) I See footnote ( 3 ) Series A Warrants $ 0.33 ( 4 )( 5 ) ( 4 )( 5 ) Common Stock 45,450,000 ( 3 ) ( 4 ) ( 5 ) I See footnote ( 3 ) Series B Warrants $ 0.33 ( 6 ) ( 6 ) Common Stock 14,998,500 ( 3 ) ( 6 ) I See footnote ( 3 ) Series A Convertible Preferred Stock ( 1 ) ( 2 ) ( 1 )( 2 ) ( 1 )( 2 ) Common Stock 6,817,500 ( 1 ) ( 2 ) ( 7 ) I See footnote ( 7 ) Series A Warrants $ 0.33 ( 4 )( 5 ) ( 4 )( 5 ) Common Stock 6,817,500 ( 4 ) ( 5 ) ( 7 ) I See footnote ( 7 ) Series B Warrants $ 0.33 ( 6 ) ( 6 ) Common Stock 2,249,775 ( 6 ) ( 7 ) I See footnote ( 7 ) Series A Convertible Preferred Stock ( 1 ) ( 2 ) ( 1 )( 2 ) ( 1 )( 2 ) Common Stock 6,817,500 ( 1 ) ( 2 ) ( 8 ) I See footnote ( 8 ) Series A Warrants $ 0.33 ( 4 )( 5 ) ( 4 )( 5 ) Common Stock 6,817,500 ( 4 ) ( 5 ) ( 8 ) I See footnote ( 8 ) Series B Warrants $ 0.33 ( 6 ) ( 6 ) Common Stock 2,249,775 ( 6 ) ( 8 ) I See footnote ( 8 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other ORBIMED ADVISORS LLC 601 LEXINGTON AVENUE 54TH FLOOR NEW YORK, NY10022 X X OrbiMed Capital GP VII LLC 601 LEXINGTON AVENUE 54TH FLOOR NEW YORK, NY10022 X X OrbiMed Global Healthcare GP LLC 601 LEXINGTON AVENUE 54TH FLOOR NEW YORK, NY10022 X X ORBIMED CAPITAL LLC 601 LEXINGTON AVENUE 54TH FLOOR NEW YORK, NY10022 X X Signatures OrbiMed Advisors LLC; By /s/ Douglas Coon, Chief Compliance Officer 11/26/2019 Signature of Reporting Person Date OrbiMed Capital GP VII; By /s/ Douglas Coon, Chief Compliance Officer 11/26/2019 Signature of Reporting Person Date OrbiMed Capital LLC; By /s/ Douglas Coon, Chief Compliance Officer 11/26/2019 Signature of Reporting Person Date OrbiMed Global Healthcare GP LLC; By /s/ Douglas Coon, Chief Compliance Officer 11/26/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each share of Series A Convertible Preferred Stock will automatically convert into 3,030 shares of the Issuer's Common Stock upon the 5th trading date following the Issuer's receiving stockholder approval for the first reverse stock split of the Issuer following November 13, 2019, provided that, the Issuer will not effect any conversion, subject to certain exceptions, if, as a result of such conversion, the holder, together with its affiliates and other attribution parties, would own more than 9.99% of the total number of shares of Common Stock then issued and outstanding, which percentage may be changed to a higher percentage upon 61 days' notice to the Issuer, and provided further that such limitation on exercise will automatically increase to 19.99% of the total number of shares of Common Stock during the period that any employee, manager, partner, managing director or affiliate of such holder is then serving on the Issuer's board of directors. ( 2 )Mona Ashiya, an employee of OrbiMed Advisors LLC ("OrbiMed Advisors"), is a member of the Issuer's board of directors. The exercise limitation for the Series A Convertible Preferred Stock held by affiliates of OrbiMed Advisors is 19.99%. The Series A Convertible Preferred Stock has no expiration date. ( 3 )These securities are held of record by OrbiMed Private Investments VII, LP ("OPI VII"). OrbiMed Capital GP VII LLC ("OrbiMed GP VII") is the general partner of OPI VII and OrbiMed Advisors, a registered investment advisor under the Investment Advisors Act of 1940, as amended, is the managing member of OrbiMed GP VII. By virtue of such relationships, OrbiMed GP VII and OrbiMed Advisors may be deemed to have voting and investment power over the securities held by OPI VII and, as a result, may be deemed to have beneficial ownership over such securities. OrbiMed Advisors exercises voting and investment power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and Jonathan T. Silverstein. Each of OrbiMed GP VII, OrbiMed Advisors, Carl L. Gordon, Sven H. Borho, and Jonathan T. Silverstein disclaims beneficial ownership of the shares held by OPI VII, except to the extent of its or his pecuniary interest therein, if any. ( 4 )Each Series A Warrant will be exercisable for one share of Common Stock. The Series A Warrants are exercisable on the first trading day following the date the Issuer obtains stockholder approval of an amendment to its certificate of incorporation increasing the aggregate number of authorized shares of its Common Stock, such that the Issuer shall have sufficient authorized but unissued shares of Common Stock, solely for the purpose of enabling the Issuer to issue shares of its Common Stock upon exercise of the Series A Warrants and the Series B Warrants (the "Warrant Exercise Date"). ( 5 )The holder will be prohibited, subject to certain exceptions, from exercising the Series A Warrant for shares of Common Stock if, as a result of such exercise, the holder, together with its affiliates and other attribution parties, would own more than 9.99% of the total number of shares of Common Stock then issued and outstanding, which percentage may be changed at the holder's election to a higher percentage upon 61 days' notice to the Issuer. Each Series A Warrant will expire five years from the date it first becomes exercisable. ( 6 )Each Series B Warrant will be exercisable for 0.33 shares of Common Stock. The Series B Warrants are exercisable on the Warrant Exercise Date, provided that, at each holder's election, the holder will be prohibited, subject to certain exceptions, from exercising the Series B Warrant for shares of Common Stock if, as a result of such exercise, the holder, together with its affiliates and other attribution parties, would own more than 9.99% of the total number of shares of Common Stock then issued and outstanding, which percentage may be changed at the holder's election to a lower percentage at any time or to a higher percentage upon 61 days' notice to the Issuer. Each Series B warrant will expire on the 75th day anniversary of the Issuer's announcement of top-line data from MOMENTUM, its planned Phase 3 clinical trial of momelotinib for patients with myelofibrosis. ( 7 )These securities are held of record by OrbiMed Genesis Master Fund, L.P. ("Genesis"). OrbiMed Global Healthcare GP LLC ("Healthcare GP") is the general partner of Genesis and OrbiMed Advisors is the managing member of Healthcare GP. By virtue of such relationships, Healthcare GP and OrbiMed Advisors may be deemed to have voting power and investment power over the securities held by Genesis and as a result, may be deemed to have beneficial ownership over such securities. OrbiMed Advisors exercises voting and investment power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and Jonathan T. Silverstein, each of whom disclaims beneficial ownership of the shares held by Genesis. ( 8 )These securities are held of record by OrbiMed Partners Master Fund Limited ("OPM"). OrbiMed Capital LLC ("OrbiMed Capital") is the sole holder of manager shares and sole voting member of OPM. By virtue of such relationships, OrbiMed Capital may be deemed to have voting power and investment power over the securities held by OPM and as a result, may be deemed to have beneficial ownership over such securities. OrbiMed Capital exercises voting and investment power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and Jonathan T. Silverstein, each of whom disclaims beneficial ownership of the shares held by OPM. OrbiMed Capital is a relying advisor of OrbiMed Advisors.

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