Sierra Oncology (SRRA) SC 13G ProNAi Therapeutics Inc

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO RULE 13d-1(b), (c), AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO

RULE 13d-2

(Amendment No.     )*

ProNAi Therapeutics, Inc.

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

74346L101

(CUSIP Number)

December 31, 2015

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

¨ Rule 13d-1(b)

¨ Rule 13d-1(c)

x Rule 13d-1(d)

* 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 the disclosures provided in a prior cover page.

The information required in 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 13G

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 (SEE INSTRUCTIONS) (a)  ¨        (b)  ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER 0 shares
		6	SHARED VOTING POWER 2,186,195 shares
		7	SOLE DISPOSITIVE POWER 0 shares
		8	SHARED DISPOSITIVE POWER     2,186,195 shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,186,195 shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.27%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)     PN

Page 2 of 14 Pages

CUSIP No. 74346L101 13G

1	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) FHM VI, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a)  ¨        (b)  ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER 0 shares
		6	SHARED VOTING POWER 2,186,195 shares
		7	SOLE DISPOSITIVE POWER 0 shares
		8	SHARED DISPOSITIVE POWER     2,186,195 shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,186,195 shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.27%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN

Page 3 of 14 Pages

CUSIP No. 74346L101 13G

1	NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) FHM VI, L.L.C.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a)  ¨        (b)  ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER 0 shares
		6	SHARED VOTING POWER 2,186,195 shares
		7	SOLE DISPOSITIVE POWER 0 shares
		8	SHARED DISPOSITIVE POWER 2,186,195 shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,186,195 shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.27%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) OO

Page 4 of 14 Pages

CUSIP No. 74346L101 13G

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 (SEE INSTRUCTIONS) (a)  ¨        (b)  ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION United States Citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER 0 shares
		6	SHARED VOTING POWER 2,186,195 shares
		7	SOLE DISPOSITIVE POWER 0 shares
		8	SHARED DISPOSITIVE POWER 2,186,195 shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,186,195 shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.27%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) IN

Page 5 of 14 Pages

CUSIP No. 74346L101 13G

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 (SEE INSTRUCTIONS) (a)  ¨        (b)  ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION United States Citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER 0 shares
		6	SHARED VOTING POWER 2,186,195 shares
		7	SOLE DISPOSITIVE POWER 0 shares
		8	SHARED DISPOSITIVE POWER 2,186,195 shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,186,195 shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.27%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) IN

Page 6 of 14 Pages

CUSIP No. 74346L101 13G

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 (SEE INSTRUCTIONS) (a)  ¨        (b)  ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION United States Citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER 0 shares
		6	SHARED VOTING POWER 2,186,195 shares
		7	SOLE DISPOSITIVE POWER 0 shares
		8	SHARED DISPOSITIVE POWER 2,186,195 shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,186,195 shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.27%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) IN

Page 7 of 14 Pages

CUSIP No. 74346L101 13G

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 (SEE INSTRUCTIONS) (a)  ¨        (b)  ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION United States Citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER 0 shares
		6	SHARED VOTING POWER 2,186,195 shares
		7	SOLE DISPOSITIVE POWER 0 shares
		8	SHARED DISPOSITIVE POWER 2,186,195 shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,186,195 shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.27%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) IN

Page 8 of 14 Pages

CUSIP No. 74346L101 13G

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 (SEE INSTRUCTIONS) (a)  ¨        (b)  ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION United States Citizen
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER 0 shares
		6	SHARED VOTING POWER 2,186,195 shares
		7	SOLE DISPOSITIVE POWER 0 shares
		8	SHARED DISPOSITIVE POWER 2,186,195 shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,186,195 shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.27%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) IN

Page 9 of 14 Pages

CUSIP No. 74346L101 13G

Schedule 13G

Item 1(a). Name of Issuer: ProNAi Therapeutics, Inc. (the “Issuer”)

Item 1(b). Address of Issuer’s Principal Executive Offices:

2150-885 West Georgia Street

Vancouver, British Columbia A1 V6C 3E8

Item 2(a). Name of Persons Filing:

Frazier Healthcare VI, L.P. (“FH VI”), FHM VI, L.P. (“FHM L.P.”) and FHM VI, L.L.C. (“FHM L.L.C.”), Alan Frazier (“Frazier”), Nader Naini (“Naini”), Patrick Heron (“Heron”), James Topper (“Topper”), Nathan Every (“Every”), (each, a “Reporting Person” and collectively, the “Reporting Persons”). FHM L.P. is the sole general partner of FH VI. FHM L.L.C. is the sole general partner of FHM L.P. Frazier, Naini, Heron, Topper, and Every (collectively, the “Members”) are all of the members of FHM L.L.C.

Item 2(b). Address of Principal Business Office or, if None, Residence: The address of each of the Reporting Persons is:

c/o Frazier Healthcare Ventures

601 Union Street, Suite 3200

Seattle, WA 98101

Item 2(c). Citizenship: FH VI and FHM L.P. are limited partnerships organized under the laws of the State of Delaware. FHM L.L.C. is a limited liability company organized under the laws of the State of Delaware. Each of the Members is a United States Citizen.

Item 2(d). Title of Class of Securities: Common Stock, $0.001 par value per share (the “Common Stock”).

Item 2(e). CUSIP Number: 74346L101

Item 3. If this statement is filed pursuant to Rule 13d-1(b), or 13d-2(b) or (c), Check Whether the Person Filing is a:

Not applicable.

Item 4. Ownership.

(a) Amount beneficially owned:

FH VI is the record owner of 2,816,195 shares of Common Stock (the “Record Shares”). As the general partner of FH VI, FHM L.P. may be deemed to own beneficially the Record Shares. As the general partner of FHM L.P., FHM L.L.C. likewise may be deemed to own beneficially the Record Shares. As individual members of FHM L.L.C., each of the Members may be deemed to own beneficially the Record Shares. Each Reporting Person disclaims beneficial ownership of all the Record Shares other than those shares which such person owns of record.

Page 10 of 14 Pages

CUSIP No. 74346L101 13G

(b) Percent of class:

See Line 11 of the cover sheets. In accordance with Rule 13d-1(j), the percentages relating to beneficial ownership of Common Stock are based on 30,058,105 shares of Common Stock outstanding as of November 4, 2015 as set forth in the Issuer’s 10-Q filed on November 5, 2015 and as adjusted pursuant to Rule 13d-3(d)(1).

(c) Number of shares as to which the person has:

(i) sole power to vote or to direct the vote: See line 5 of cover sheets.

(ii) shared power to vote or to direct the vote: See line 6 of cover sheets.

(iii) sole power to dispose or to direct the disposition: See line 7 of cover sheets.

(iv) shared power to dispose or to direct the disposition: See line 8 of cover sheets.

Item 5. Ownership of Five Percent or Less of a Class.

Not applicable.

Item 6. Ownership of More than Five Percent on Behalf of Another Person.

Not applicable.

Item 7. Identification and Classification of the Subsidiary which Acquired the Security Being Reported on By the Parent Holding Company or Control Person.

Not applicable.

Item 8. Identification and Classification of Members of the Group.

Not applicable.

Item 9. Notice of Dissolution of Group.

Not applicable

Item 10. Certification.

Not applicable. This Schedule 13G is not filed pursuant to Rule 13d-1(b) or Rule 13d-1(c).

Page 11 of 14 Pages

CUSIP No. 74346L101 13G

SIGNATURES

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.

Dated February 12, 2016	Frazier Healthcare VI, L.P.
	By FHM VI, L.P., its General Partner
	By FHM VI, L.L.C., its General Partner
	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer
Dated February 12, 2016	FHM VI, L.P.
	By: FHM VI, L.L.C., its General Partner
	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer
Dated February 12, 2016	FHM VI, L.L.C.
	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer
	*
	Alan Frazier
	*
	Nader Naini
	*
	Patrick Heron
	*
	James Topper
	*
	Nathan Every
	*By:	/s/ Steve R. Bailey
		Steve R. Bailey, as Attorney-in-Fact

This Schedule 13G 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 2.

Page 12 of 14 Pages

CUSIP No. 74346L101 13G

EXHIBIT 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 13G need to be filed with respect to the ownership by each of the undersigned of shares of Common Stock of ProNAi Therapeutics, Inc.

Dated February 12, 2016	Frazier Healthcare VI, L.P.
	By FHM VI, L.P., its General Partner
	By FHM VI, L.L.C., its General Partner
	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer
Dated February 12, 2016	FHM VI, L.P.
	By: FHM VI, L.L.C., its General Partner
	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer
Dated February 12, 2016	FHM VI, L.L.C.
	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer
	*
	Alan Frazier
	*
	Nader Naini
	*
	Patrick Heron
	*
	James Topper
	*
	Nathan Every
	*By:	/s/ Steve R. Bailey
		Steve R. Bailey, as Attorney-in-Fact

This Schedule 13G 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 2.

Page 13 of 14 Pages

CUSIP No. 74346L101 13G

EXHIBIT 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 suchattorney-in-fact may approve in suchattorney-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 12th 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

Page 14 of 14 Pages