SC 13G/A 1 sc13ga307422mrsn_02052021.htm AMENDMENT NO. 3 TO THE SCHEDULE 13G

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

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

PURSUANT TO RULE 13d-2(b)

(Amendment No. 3)¹

Mersana Therapeutics, Inc.

(Name of Issuer)

Common stock, par value $0.0001 per share

(Title of Class of Securities)

59045L106

(CUSIP Number)

December 31, 2020

(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)

☐

Rule 13d-1(d)

1 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. 59045L106


	1	NAME OF REPORTING PERSON

			Biotechnology Value Fund, L.P.
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			Delaware
NUMBER OF			5	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			6	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			7	SOLE DISPOSITIVE POWER

					- 0 -
			8	SHARED DISPOSITIVE POWER

					- 0 -
	9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES				☐


	11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

			0%
	12	TYPE OF REPORTING PERSON

			PN

CUSIP No. 59045L106


	1	NAME OF REPORTING PERSON

			BVF I GP LLC
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			Delaware
NUMBER OF			5	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			6	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			7	SOLE DISPOSITIVE POWER

					- 0 -
			8	SHARED DISPOSITIVE POWER

					- 0 -
	9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES				☐


	11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

			0%
	12	TYPE OF REPORTING PERSON

			OO

CUSIP No. 59045L106


	1	NAME OF REPORTING PERSON

			Biotechnology Value Fund II, L.P.
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			Delaware
NUMBER OF			5	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			6	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			7	SOLE DISPOSITIVE POWER

					- 0 -
			8	SHARED DISPOSITIVE POWER

					- 0 -
	9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES				☐


	11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

			0%
	12	TYPE OF REPORTING PERSON

			PN

CUSIP No. 59045L106


	1	NAME OF REPORTING PERSON

			BVF II GP LLC
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			Delaware
NUMBER OF			5	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			6	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			7	SOLE DISPOSITIVE POWER

					- 0 -
			8	SHARED DISPOSITIVE POWER

					- 0 -
	9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES				☐


	11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

			0%
	12	TYPE OF REPORTING PERSON

			OO

CUSIP No. 59045L106


	1	NAME OF REPORTING PERSON

			Biotechnology Value Trading Fund OS LP
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			Cayman Islands
NUMBER OF			5	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			6	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			7	SOLE DISPOSITIVE POWER

					- 0 -
			8	SHARED DISPOSITIVE POWER

					- 0 -
	9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES				☐


	11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

			0%
	12	TYPE OF REPORTING PERSON

			PN

CUSIP No. 59045L106


	1	NAME OF REPORTING PERSON

			BVF Partners OS Ltd.
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			Cayman Islands
NUMBER OF			5	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			6	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			7	SOLE DISPOSITIVE POWER

					- 0 -
			8	SHARED DISPOSITIVE POWER

					- 0 -
	9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES				☐


	11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

			0%
	12	TYPE OF REPORTING PERSON

			CO

CUSIP No. 59045L106


	1	NAME OF REPORTING PERSON

			BVF GP HOLDINGS LLC
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			Delaware
NUMBER OF			5	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			6	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			7	SOLE DISPOSITIVE POWER

					- 0 -
			8	SHARED DISPOSITIVE POWER

					- 0 -
	9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES				☐


	11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

			0%
	12	TYPE OF REPORTING PERSON

			OO

CUSIP No. 59045L106


	1	NAME OF REPORTING PERSON

			BVF Partners L.P.
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			Delaware
NUMBER OF			5	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			6	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			7	SOLE DISPOSITIVE POWER

					- 0 -
			8	SHARED DISPOSITIVE POWER

					- 0 -
	9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES				☐


	11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

			0%
	12	TYPE OF REPORTING PERSON

			PN, IA

CUSIP No. 59045L106


	1	NAME OF REPORTING PERSON

			BVF Inc.
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			Delaware
NUMBER OF			5	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			6	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			7	SOLE DISPOSITIVE POWER

					- 0 -
			8	SHARED DISPOSITIVE POWER

					- 0 -
	9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES				☐


	11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

			0%
	12	TYPE OF REPORTING PERSON

			CO

CUSIP No. 59045L106


	1	NAME OF REPORTING PERSON

			Mark N. Lampert
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☒
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			United States
NUMBER OF			5	SOLE VOTING POWER
SHARES
BENEFICIALLY					- 0 -
OWNED BY			6	SHARED VOTING POWER
EACH
REPORTING					- 0 -
PERSON WITH			7	SOLE DISPOSITIVE POWER

					- 0 -
			8	SHARED DISPOSITIVE POWER

					- 0 -
	9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

			- 0 -
	10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES				☐


	11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

			0%
	12	TYPE OF REPORTING PERSON

			IN

CUSIP No. 59045L106

Item 1(a).

Name of Issuer:

Mersana Therapeutics, Inc., a Delaware corporation (the “Issuer”).

Item 1(b).

Address of Issuer’s Principal Executive Offices:

840 Memorial Drive

Cambridge, Massachusetts 02139

Item 2(a).

Name of Person Filing

Item 2(b).

Address of Principal Business Office or, if None, Residence

Item 2(c).

Citizenship

Biotechnology Value Fund, L.P. (“BVF”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF I GP LLC (“BVF GP”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

Biotechnology Value Fund II, L.P. (“BVF2”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF II GP LLC (“BVF2 GP”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

Biotechnology Value Trading Fund OS LP (“Trading Fund OS”)

PO Box 309 Ugland House

Grand Cayman, KY1-1104

Cayman Islands

Citizenship: Cayman Islands

CUSIP No. 59045L106

BVF Partners OS Ltd. (“Partners OS”)

PO Box 309 Ugland House

Grand Cayman, KY1-1104

Cayman Islands

Citizenship: Cayman Islands

BVF GP Holdings LLC (“BVF GPH”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF Partners L.P. (“Partners”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF Inc.

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

Mark N. Lampert (“Mr. Lampert”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: United States

Each of the foregoing is referred to as a “Reporting Person” and collectively as the “Reporting Persons.”

Item 2(d).

Title of Class of Securities:

Common stock, par value $0.0001 per share (the “Shares”).

Item 2(e).

CUSIP Number:

59045L106

CUSIP No. 59045L106

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:

	/x/	Not applicable.

(a)	/ /	Broker or dealer registered under Section 15 of the Exchange Act.

(b)	/ /	Bank as defined in Section 3(a)(6) of the Exchange Act.

(c)	/ /	Insurance company as defined in Section 3(a)(19) of the Exchange Act.

(d)	/ /	Investment company registered under Section 8 of the Investment Company Act.

(e)	/ /	An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E).

(f)	/ /	An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F).

(g)	/ /	A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G).

(h)	/ /	A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act.

(i)	/ /	A church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act.

(j)	/ /	Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

(k)	/ /	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with Rule 240.13d-1(b)(1)(ii)(J), please specify the type of institution: ____

Item 4.

Ownership

As of the close of business on December 31, 2020, the Reporting Persons no longer beneficially owned any Shares of the Issuer.

Item 5.

Ownership of Five Percent or Less of a Class.

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following [X].

CUSIP No. 59045L106

Item 6.

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

Not Applicable.

Item 7.

Identification and Classification of the Subsidiary That 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.

See Exhibit 99.1 to the Schedule 13G filed by the Reporting Persons with the Securities and Exchange Commission on February 14, 2020.

Item 9.

Notice of Dissolution of Group.

Not Applicable.

Item 10.

Certifications.

By signing below each of the undersigned certifies that, to the best of its knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

CUSIP No. 59045L106

SIGNATURE

After reasonable inquiry and to the best of his knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: February 11, 2021

BIOTECHNOLOGY VALUE FUND, L.P.		BIOTECHNOLOGY VALUE TRADING FUND OS LP

By:	BVF I GP LLC., its general partner	By:	BVF Partners L.P., its investment manager
		By:	BVF Inc., its general partner
By:	/s/ Mark N. Lampert
	Mark N. Lampert	By:	/s/ Mark N. Lampert
	Chief Executive Officer		Mark N. Lampert
			President

BVF I GP LLC
		BVF GP HOLDINGS LLC
By:	/s/ Mark N. Lampert
	Mark N. Lampert	By:	/s/ Mark N. Lampert
	Chief Executive Officer		Mark N. Lampert
			Chief Executive Officer

BIOTECHNOLOGY VALUE FUND II, L.P.
		BVF PARTNERS L.P.
By:	BVF II GP LLC, its general partner
		By:	BVF Inc., its general partner
By:	/s/ Mark N. Lampert
	Mark N. Lampert	By:	/s/ Mark N. Lampert
	Chief Executive Officer		Mark N. Lampert
			President

BVF II GP LLC
		BVF INC.
By:	/s/ Mark N. Lampert
	Mark N. Lampert	By:	/s/ Mark N. Lampert
	Chief Executive Officer		Mark N. Lampert
			President

BVF PARTNERS OS LTD.
		/s/ Mark N. Lampert
By:	BVF Partners L.P., its sole member	MARK N. LAMPERT
By:	BVF Inc., its general partner

By:	/s/ Mark N. Lampert
	Mark N. Lampert
	President