Sec Form 3 Filing - Longitude Capital Partners III, 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 Longitude Capital Partners III, LLC 2. Issuer Name and Ticker or Trading Symbol Sierra Oncology, Inc. [ SRRA] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 2740 SAND HILL ROAD, SECOND FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 11/22/2019 (Street) MENLO PARK, CA94025 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 59,085,000 ( 1 ) ( 2 ) ( 3 ) ( 4 ) I See Footnote ( 3 ) ( 4 ) Series A Warrants $ 0.33 ( 5 )( 6 ) ( 5 )( 6 ) Common Stock 59,085,000 ( 3 ) ( 4 ) ( 5 ) ( 6 ) I See Footnote ( 3 ) ( 4 ) Series B Warrants $ 0.33 ( 7 ) ( 7 ) Common Stock 19,498,050 ( 3 ) ( 4 ) ( 7 ) I See Footnote ( 3 ) ( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Longitude Capital Partners III, LLC 2740 SAND HILL ROAD, SECOND FLOOR MENLO PARK, CA94025 X Longitude Venture Partners III, L.P. 2740 SAND HILL RD 2ND FLOOR MENLO PARK, CA94025 X Tammenoms Bakker Juliet 2740 SAND HILL RD 2ND FLOOR MENLO PARK, CA94025 X ENRIGHT PATRICK G 2740 SAND HILL RD 2ND FLOOR MENLO PARK, CA94025 X Signatures Longitude Venture Partners III, L.P.; By /s/ Patrick G. Enright, Managing Member 11/26/2019 Signature of Reporting Person Date Longitude Capital Partners III, LLC; By /s/ Patrick G. Enright, Managing Member 11/26/2019 Signature of Reporting Person Date /s/ Juliet Tammenoms Bakker 11/26/2019 Signature of Reporting Person Date /s/ Patrick G. Enright 11/26/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each share of Series A Convertible Preferred Stock will convert into 3,030 shares of the Issuer's Common Stock (a) at the option of the holder and (b) automatically upon the 5th trading date following the Issuer's announcement of 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, and the holder will not have the right to convert, subject to certain exceptions, the Series A Convertible Preferred Stock for shares of common stock 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 at the holder's election to a lower percentage at any time or to a higher percentage upon 61 days' notice to the Issuer, ( 2 )(Continued from Footnote 1) and provided further that such limitation on exercise will automatically increase to 19.99% of the total number of shares of Common Stock then issued and outstanding 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. As Joshua Richardson is a member of the Issuer's board of directors and affiliated with Longitude Venture Partners III, L.P. ("LVP III"), the conversion limitation for Series A Convertible Preferred Stock held by LVP III is 19.99%. The Series A Convertible Preferred Stock has no expiration date. ( 3 )The Reporting Person's beneficial ownership of the Issuer's Common Stock is comprised of 19,500 Series A Convertible Preferred Stock, 59,085,000 Series A Warrants and 59,085,000 Series B Warrants held by the Reporting Person. Longitude Capital Partners III, LLC ("LCP III") is the general partner of LVP III and may be deemed to have voting, investment and dispositive power with respect to such securities. Patrick G. Enright, Juliet Tammenoms Bakker and Joshua Richardson (a member of the Issuer's board of directors), are each members of LCP III and may be deemed to share voting, investment and dispositive power over such securities. Patrick G. Enright and Juliet Tammenoms Bakker are the managing members of LCP III. ( 4 )(Continued from Footnote 3) Each of LCP III, Patrick G. Enright, Juliet Tammenoms Bakker and Joshua Richardson disclaim beneficial ownership over such securities except to the extent of their respective pecuniary interest therein, and the inclusion of such 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. ( 5 )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"), provided that, at each holder's election, 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, ( 6 )(Continued from Footnote 5) 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 A Warrant will expire five years from the date it first becomes exercisable. ( 7 )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.

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