Sec Form 4 Filing - ORBIMED ADVISORS LLC @ Sierra Oncology, Inc. - 2022-01-26

FORM 4 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 AVE., 54TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 01/26/2022 (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 Common Stock 01/26/2022 X 374,962 A $ 13.2 1,511,362 I See footnote (4),( 1 ) Common Stock 01/26/2022 X 56,244 A $ 13.2 226,704 I See footnote (4),( 2 ) Common Stock 01/26/2022 X 56,244 A $ 13.2 226,704 I See footnote( 3 )( 4 )

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 B Warrants $ 13.2 01/26/2022 X 374,962( 5 ) 01/22/2020 ( 6 ) Common Stock 374,962 $ 0 0 I See footnote( 1 )( 4 ) Series B Warrants $ 13.2 01/26/2022 X 56,244( 7 ) 01/22/2020 ( 6 ) Common Stock 56,244 $ 0 0 I See footnote( 2 )( 4 ) Series B Warrants $ 13.2 01/26/2022 X 56,244( 8 ) 01/22/2020 ( 6 ) Common Stock 56,244 $ 0 0 I See footnote( 3 )( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other ORBIMED ADVISORS LLC 601 LEXINGTON AVE., 54TH FLOOR NEW YORK, NY10022 X X OrbiMed Capital GP VII LLC 601 LEXINGTON AVENUE, 54TH FLOOR NEW YORK, NY10022 X X ORBIMED CAPITAL LLC 601 LEXINGTON AVENUE, 54TH FLOOR NEW YORK, NY10022 X X OrbiMed Genesis GP LLC 601 LEXINGTON AVE., 54TH FLOOR NEW YORK, NY10022 X X Signatures OrbiMed Advisors LLC; By /s/Douglas Coon, Chief Compl Ofcr. OrbiMed Capital GP VII; By /s/Douglas Coon, Chief Compl Ofcr. OrbiMed Capital LLC; By /s/Douglas Coon, Chief Compl Ofcr. OrbiMed Genesis GP LLC; By /s/Douglas Coon, Chief Compl Ofcr. 01/28/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )These securities are held of record by OrbiMed Private Investments VII, LP ("OPI VII"). OrbiMed Capital GP VII LLC ("GP VII") is the general partner of OPI VII and OrbiMed Advisors LLC ("OrbiMed Advisors") is the managing member of GP VII. The Reporting Person is an employee of OrbiMed Advisors. By virtue of such relationships, GP VII and OrbiMed Advisors may be deemed to have voting power 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 W. Carter Neild, each of whom disclaims beneficial ownership of the shares held by OPI VII. ( 2 )These securities are held of record by OrbiMed Genesis Master Fund, L.P. ("Genesis"). OrbiMed Genesis GP LLC ("Genesis GP") is the general partner of Genesis and OrbiMed Advisors is the managing member of Genesis. By virtue of such relationships, Genesis 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 W. Carter Neild, each of whom disclaims beneficial ownership of the shares held by Genesis. ( 3 )These securities are held of record by OrbiMed Partners Master Fund Limited ("OPM"). OrbiMed Capital LLC ("OrbiMed Capital") is the investment advisor to OPM. OrbiMed Capital is a relying advisor of OrbiMed Advisors. OrbiMed Advisors and OrbiMed Capital exercise voting and investment power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership of the shares held by OPM. ( 4 )This report on Form 4 is jointly filed by OrbiMed Advisors, GP VII, Genesis GP, and OrbiMed Capital. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of its pecuniary interest therein, if any. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for purpose of Section 16 of the Exchange Act, or for any other purpose. ( 5 )Consists of Series B warrants previously held by OPI VII. ( 6 )The expiration date of the warrants is the date on the seventy-fifth (75th) day anniversary of the announcement by Issuer, via publicly disseminated press release or SEC filing, of the top-line data results from MOMENTUM, its Phase 3 clinical trial of momelotinib for patients with myelofibrosis. ( 7 )Consists of Series B warrants previously held by OPM. ( 8 )Consists of Series B warrants previously held by Genesis.

Remarks: Name and Address of of Reporting Person*: OrbiMed Advisors LLC; OrbiMed Capital GP VII LLC; OrbiMed Genesis GP LLC; OrbiMed Capital LLC; each at 601 Lexington Avenue, 54th Floor, New York, NY 10022.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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