Sec Form 4 Filing - Ashiya Mona @ Sierra Oncology, Inc. - 2022-07-01

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 Ashiya Mona 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) C/O SIERRA ONCOLOGY, INC., 1820 GATEWAY DR., SUITE 110 3. Date of Earliest Transaction (MM/DD/YY) 07/01/2022 (Street) SAN MATEO, CA94404 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 07/01/2022 D 1,511,362 D $ 55 0 I See footnotes( 1 )( 2 ) Common Stock 07/01/2022 D 226,704 D $ 55 0 I See footnotes( 2 )( 3 ) Common Stock 07/01/2022 D 226,704 D $ 55 0 I See footnotes( 2 )( 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 Stock Option (right to buy) $ 13.87 07/01/2022 D 1,500 ( 5 ) 11/29/2029 Common Stock 1,500 $ 0( 6 ) 0 D( 7 ) Stock Option (right to buy) $ 13.98 07/01/2022 D 6,874 ( 8 ) 06/09/2030 Common Stock 6,874 $ 0( 6 ) 0 D( 7 ) Stock Option (right to buy) $ 18.11 07/01/2022 D 6,000 ( 9 ) 06/08/2031 Common Stock 6,000 $ 0( 6 ) 0 D( 7 ) Series A Warrants $ 13.2 07/01/2022 D 1,136,250 11/13/2019 11/13/2024 Common Stock 1,136,250 $ 0( 10 ) 0 I See footnotes( 1 )( 2 ) Series A Warrants $ 13.2 07/01/2022 D 170,437 11/13/2019 11/13/2024 Common Stock 170,437 $ 0( 10 ) 0 I See footnotes( 2 )( 3 ) Series A Warrants $ 13.2 07/01/2022 D 170,437 11/13/2019 11/13/2024 Common Stock 170,437 $ 0( 10 ) 0 I See footnotes( 2 )( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Ashiya Mona C/O SIERRA ONCOLOGY, INC. 1820 GATEWAY DR., SUITE 110 SAN MATEO, CA94404 X X Signatures /s/ Mona Ashiya; By: Mary Christina Thomson, Attorney-In-Fact 07/01/2022 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 )Each of the Reporting Person, OrbiMed Advisors, GP VII, OrbiMed Genesis GP LLC ("Genesis GP"), and OrbiMed Capital LLC ("OrbiMed Capital") 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. ( 3 )These securities are held of record by OrbiMed Genesis Master Fund, L.P. ("Genesis"). Genesis GP is the general partner of Genesis and OrbiMed Advisors is the managing member of Genesis GP. 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. ( 4 )These securities are held of record by OrbiMed Partners Master Fund Limited ("OPM"). 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. ( 5 )The option fully vested on November 29, 2020. ( 6 )Pursuant to the terms of the merger agreement between issuer, GlaxoSmithKline plc ("GSK") and a subsidiary of GSK, this option was cancelled on the effective date of the merger in exchange for a cash payment equal to, on a per share basis, the offer price of $55.00 less the exercise price. ( 7 )Pursuant to an agreement with OrbiMed Advisors and GP VII, the Reporting Person is obligated to transfer any securities issued under any such stock options or other awards, or the economic benefit thereof, to OrbiMed Advisors and GP VII, which will in turn ensure that such securities or economic benefits are provided to OPI VII. ( 8 )The option fully vested on June 9, 2021. ( 9 )The option fully vested on June 8, 2022. ( 10 )Pursuant to the terms of the merger agreement between issuer, GSK and a subsidiary of GSK (the "Merger"), the Company's outstanding warrants will be treated in accordance with their respective terms. At the effective time of the Merger, (1) any of the Company's outstanding Series A warrants will be cancelled and represent only the right to receive an amount in cash, without interest, equal to the Black Scholes Value (as defined in the Series A Warrants) which is calculated under the terms of the Series A warrants to be $45.98 per share of our common stock subject to the Series A warrants.

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