UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C.  20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. ___)*

Sierra Oncology, Inc.

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

74346L101

 (CUSIP Number)

Steve R. Bailey

c/o Frazier Healthcare Partners

601 Union Street, Suite 3200

Seattle, WA 98101

(206) 621-7200

(Name, Address and Telephone Number of Person Authorized to

Receive Notices and Communications)

February 14, 2017

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. ☐

Note:  Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits.  See §240.13d-7 for other parties to whom copies are to be sent.

*The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No.   74346L101 13D Page 2 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	Frazier Healthcare VI, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	PN

CUSIP No.   74346L101 13D Page 3 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	Frazier Life Sciences VIII, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	PN

CUSIP No.   74346L101 13D Page 4 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	FHM VI, LP
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	PN

CUSIP No.   74346L101 13D Page 5 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	FHM VI, LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

CUSIP No.   74346L101 13D Page 6 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	FHM Life Sciences VIII, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	PN

CUSIP No.   74346L101 13D Page 7 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	FHM Life Sciences VIII, L.L.C.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

CUSIP No.   74346L101 13D Page 8 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	Alan Frazier
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States Citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.   74346L101 13D Page 9 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	Nader Naini
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States Citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.   74346L101 13D Page 10 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	Patrick Heron
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States Citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.   74346L101 13D Page 11 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	James Topper
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States Citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.   74346L101 13D Page 12 of 20 Pages

1	NAMES OF REPORTING PERSONS
	I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
	Nathan Every
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP			(a)	☐
				(b)	☐
3	SEC USE ONLY
4	SOURCE OF FUNDS (SEE INSTRUCTIONS)
	AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(D) OR 2(E)				☐
6	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States Citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER
			0 shares
		8	SHARED VOTING POWER
			8,112,121 shares
		9	SOLE DISPOSITIVE POWER
			0 shares
		10	SHARED DISPOSITIVE POWER
			8,112,121 shares
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	8,112,121 shares
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)				☐
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
	16.28%
14	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

CUSIP No.   74346L101 13D Page 13 of 20 Pages

Item 1. Security and Issuer

This statement relates to the common stock, $0.001 par value (the "Common Stock") of Sierra Oncology, Inc. (the "Issuer") having its principal executive office at 2150 – 885 West Georgia Street, Vancouver, British Columbia, Canada.

Item 2. Identity and Background

This statement is being filed by:

(a) Frazier Healthcare VI, L.P. ("FH VI") and Frazier Life Sciences VIII, L.P. ("FLS VIII");

(b) FHM VI, L.P. ("FM VI L.P."), which is the sole general partner of FH VI; FHM VI, LLC ("FM VI LLC"), which is the sole general partner of FM VI L.P.; FHM Life Sciences VIII, L.P. ("FM VIII L.P."), which is the sole general partner of FLS VIII ; and FHM Life Sciences VIII, L.L.C. ("FM VIII L.L.C."), which is the sole general partner of FM VIII L.P.; and

(c) Alan Frazier ("Frazier"), Nader Naini ("Naini"), Patrick Heron ("Heron"), James Topper ("Topper"), and Nathan Every ("Every") (collectively, the "Members").  The Members are the members of FM VI LLC.  Messrs. Heron and Topper are the sole members of FM VIII L.L.C.

The persons named in this Item 2 are referred to individually herein as a "Reporting Person" and collectively as the "Reporting Persons."

The address of the principal business office of each Reporting Person is:

c/o Frazier Healthcare Partners

601 Union Street, Suite 3200

Seattle, WA 98101

FH VI and FLS VIII are affiliated venture capital funds concentrating in healthcare and related fields.  The sole business of FM VI L.P. and FM VI LLC is to serve as general partner entities for FH VI.  The sole business of FM VIII L.P. and FM VIII L.L.C. is to serve as general partner entities for FLS VIII.  The principal business of each of the Members is to manage FH VI, FM VI L.P., FM VI LLC, FLS VIII, FM VIII L.P., FM VIII L.L.C. and a number of affiliated partnerships with similar businesses.

During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Each of FH VI, FM VI L.P., FLS VIII, and FM VIII L.P. are limited partnerships organized under the laws of the State of Delaware.  FM VI LLC and FM VIII L.L.C. are limited liability companies organized under the laws of the State of Delaware.  Each of the Members is a United States citizen.

Item 3. Source and Amount of Funds or Other Consideration

On February 14, 2017, FLS VIII purchased 5,925,926 shares of Common Stock (the "FLS VIII Shares") pursuant to a registered offering at a purchase price of $1.35 per share (the "Offering").  The working capital of FLS VIII was the source of the funds for the purchase of the FLS VIII Shares in the Offering.  No part of the purchase price paid by FLS VIII was represented by funds or other consideration borrowed or otherwise obtained for the purpose of acquiring, holding, trading or voting the FLS VIII Shares.  In addition, prior to the Offering, FH VI held 2,186,195 shares of the Issuer's Common Stock (the "FH VI Shares", together with the FLS VIII Shares, the "FH Shares").

The working capital of FH VI and was the source of the funds for the purchase of the FH VI Shares.  No part of the purchase price of the FH VI Shares was represented by funds or other consideration borrowed or otherwise obtained for the purpose of acquiring, holding, trading or voting the FH VI Shares.

CUSIP No.   74346L101 13D Page 14 of 20 Pages

Item 4. Purpose of Transaction

FH VI and FLS VIII acquired the FH Shares for investment purposes.  Depending on market conditions, its continuing evaluation of the business and prospects of the Issuer and other factors, FH VI, FLS VIII and other Reporting Persons may dispose of or acquire additional shares of the Issuer.  Except as set forth above, none of the Reporting Persons has any present plans which relate to or would result in:

(a) The acquisition by any person of additional securities of the Issuer, or the disposition of securities of the Issuer;

(b) An extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries;

(c) A sale or transfer of a material amount of assets of the Issuer or any of its subsidiaries;

(d) Any change in the present board of directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board;

(e) Any material change in the present capitalization or dividend policy of the Issuer;

(f) Any other material change in the Issuer's business or corporate structure;

(g) Changes in the Issuer's charter, bylaws or instruments corresponding thereto or other actions which may impede the acquisition of control of the Issuer by any person;

(h) Causing a class of securities of the Issuer to be delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association;

(i) A class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Securities Exchange Act of 1934, as amended; or

(j) Any action similar to any of those enumerated above.

Item 5. Interest in Securities of the Issuer

(a) FH VI is the record owners of the FH VI Shares.  As the sole general partner of FH VI, FM VI L.P. may be deemed to own beneficially the FH VI Shares.  As the sole general partner of FM VI L.P., FM VI LLC may be deemed to own beneficially the FH VI Shares.  As members of FM VI LLC, each of the Members may be deemed to own beneficially the FH VI Shares.

FLS VIII is the record owners of the FLS VIII Shares.  As the sole general partner of FLS VIII, FM VIII L.P. may be deemed to own beneficially the FLS VIII Shares.  As the sole general partner of FM VIII L.P., FM VIII L.L.C. may be deemed to own beneficially the FLS VIII.  As members of FM VIII L.L.C., each of Messrs. Heron and Topper may be deemed to own beneficially the FLS VIII Shares.

The percentage of outstanding Common Stock of the Issuer which may be deemed to be beneficially owned by each Reporting Person is set forth on Line 13 of such Reporting Person's cover sheet.  Such percentage was calculated based on the 49,850,560 shares of Common Stock outstanding as reported in the Issuer's prospectus filed under Rule 424(b)(5), filed with the Securities Exchange Commission on February 9, 2017.

CUSIP No.   74346L101 13D Page 15 of 20 Pages

(b) Regarding the number of shares as to which such person has:

(i) sole power to vote or to direct the vote: See line 7 of cover sheets

(ii) shared power to vote or to direct the vote: See line 8 of cover sheets

(iii) sole power to dispose or to direct the disposition: See line 9 of cover sheets.

(iv) shared power to dispose or to direct the disposition: See line 10 of cover sheets

(c) Not applicable.

(d) No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, FH Shares beneficially owned by any of the Reporting Persons.

(e) Not applicable.

Item 6. Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer

In connection with the Offering, FH VI, FLS VIII, and Mr. Topper, along with all of the Issuer's executive officers and directors agreed with the underwriters for the Offering, subject to certain exceptions, not to offer or sell any shares of Common Stock for a period of 90 days from February 9, 2017, except with the prior written consent of Jeffries LLC.

Item 7. Material to Be Filed as Exhibits

Exhibit 99.1 – Agreement regarding filing of joint Schedule 13D.

Exhibit 99.2 – Power of Attorney regarding Schedule 13D filings.

CUSIP No.   74346L101 13D Page 16 of 20 Pages

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date:      February 24, 2017

FRAZIER HEALTHCARE VI, L.P.

By: FHM VI, L.P., its General Partner

By: FHM VI, LLC, its General Partner

By: /s/ Steve R. Bailey                                        

Steve R. Bailey, Chief Financial Officer

FHM VI, L.P.

By: FHM VI, LLC, its General Partner

By: /s/ Steve R. Bailey                                        

Steve R. Bailey, Chief Financial Officer

FHM VI, LLC, its General Partner

By: /s/ Steve R. Bailey                                        

Steve R. Bailey, Chief Financial Officer

FRAZIER LIFE SCIENCES VIII, L.P.

By: FHM Life Sciences VIII, L.P., its General Partner

By: FHM Life Sciences VIII, L.L.C., its General Partner

By: /s/ Steve R. Bailey                                        

Steve R. Bailey, Chief Financial Officer

FHM LIFE SCIENCES VIII, L.P.

By: FHM Life Sciences VIII, L.L.C., its General Partner

By:  /s/ Steve R. Bailey                                       

Steve R. Bailey, Chief Financial Officer

FHM LIFE SCIENCES VIII, L.L.C.

By:  /s/ Steve R. Bailey                                       

Steve R. Bailey, Chief Financial Officer

CUSIP No.   74346L101 13D Page 17 of 20 Pages

                      *                                       

Alan Frazier

                      *                                        Nader Naini

                      *                                        Patrick Heron

                      *                                        James Topper

                      *                                        Nathan Every

     *By:  /s/ Steve R. Bailey                                

Steve R. Bailey, as Attorney-in-Fact

This Schedule 13D was executed by Steve R. Bailey on behalf of the individuals listed above pursuant to a Power of Attorney a copy of which is attached as Exhibit 99.2.

CUSIP No.   74346L101 13D Page 18 of 20 Pages

EXHIBIT 99.1

AGREEMENT

Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, the undersigned hereby agree that only one statement containing the information required by Schedule 13D need to be filed with respect to the ownership by each of the undersigned of shares of Common Stock of Sierra Oncology, Inc.

Dated:   February 24, 2017

FRAZIER HEALTHCARE VI, L.P.

By: FHM VI, L.P., its General Partner

By: FHM VI, LLC, its General Partner

By: /s/ Steve R. Bailey                                        

Steve R. Bailey, Chief Financial Officer

FHM VI, L.P.

By: FHM VI, LLC, its General Partner

By: /s/ Steve R. Bailey                                        

Steve R. Bailey, Chief Financial Officer

FHM VI, LLC, its General Partner

By: /s/ Steve R. Bailey                                        

Steve R. Bailey, Chief Financial Officer

FRAZIER LIFE SCIENCES VIII, L.P.

By: FHM Life Sciences VIII, L.P., its General Partner

By: FHM Life Sciences VIII, L.L.C., its General Partner

By: /s/ Steve R. Bailey                                        

Steve R. Bailey, Chief Financial Officer

FHM LIFE SCIENCES VIII, L.P.

By: FHM Life Sciences VIII, L.L.C., its General Partner

By:  /s/ Steve R. Bailey                                       

Steve R. Bailey, Chief Financial Officer

FHM LIFE SCIENCES VIII, L.L.C.

By:  /s/ Steve R. Bailey                                       

Steve R. Bailey, Chief Financial Officer

CUSIP No.   74346L101 13D Page 19 of 20 Pages

                      *                                       

Alan Frazier

                      *                                        Nader Naini

                      *                                        Patrick Heron

                      *                                        James Topper

                      *                                        Nathan Every

     *By:  /s/ Steve R. Bailey                                    

Steve R. Bailey, as Attorney-in-Fact

This Schedule 13D was executed by Steve R. Bailey on behalf of the individuals listed above pursuant to a Power of Attorney a copy of which is attached as Exhibit 99.2.

CUSIP No.   74346L101 13D Page 20 of 20 Pages

EXHIBIT 99.2

POWER OF ATTORNEY

KNOW ALL BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints Steve R. Bailey with full power to act singly, his true and lawful attorney-in-fact, with full power of substitution, to: (i) sign any and all instruments, certificates and documents that may be necessary, desirable or appropriate to be executed on behalf of himself as an individual or in his capacity as a general partner of any partnership or limited liability company, pursuant to Section 13 or 16 of the Securities Exchange Act of 1934, as amended, and any and all regulations promulgated thereunder, (ii) file the same (including any amendments thereto), with all exhibits thereto, and any other documents in connection therewith, with the Securities and Exchange Commission, and any stock exchange or similar authority and (iii) take any other action of any type whatsoever in connection with the foregoing which, in the opinion of such attorney-in-fact, may be of benefit to, in the best interest of, or legally required by, the undersigned, it being understood that the documents executed by such attorney-in-fact on behalf of the undersigned pursuant to this power of attorney shall be in such form and shall contain such terms and conditions as such attorney‑in‑fact may approve in such attorney‑in‑fact's discretion, granting unto said attorney-in-fact full power and authority to do and perform each and every act and thing necessary, desirable or appropriate.

Each of the undersigned hereby grant to the attorney-in-fact full power and authority to do and perform any and every act and thing whatsoever requisite, necessary or proper to be done in the exercise of any of the rights and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally present with full power of substitution or revocation, hereby ratifying and confirming all that such attorney-in-fact or such attorney-in-fact's substitute or substitutes, shall lawfully do or cause to be done by virtue of this power of attorney and the rights and powers herein granted.

This power of attorney shall remain in full force and effect until revoked by the undersigned in a signed writing delivered to the attorney-in-fact.

IN WITNESS WHEREOF, this Power of Attorney has been signed as of the 16th day of February, 2016.

/s/ Alan Frazier                                

    Alan Frazier

/s/ Nader Naini                                 

    Nader Naini

/s/ Patrick Heron                              

    Patrick Heron

/s/ James Topper                              

    James Topper

/s/ Nathan Every                              

    Nathan Every