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. 4)¹

Merrimack Pharmaceuticals, Inc.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

590328209

(CUSIP Number)

December 31, 2023

(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. 590328209


	1	NAME OF REPORTING PERSON

			22NW Fund, LP
	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. 590328209


	1	NAME OF REPORTING PERSON

			22NW, LP
	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. 590328209


	1	NAME OF REPORTING PERSON

			22NW Fund 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. 590328209


	1	NAME OF REPORTING PERSON

			22NW GP, 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. 590328209


	1	NAME OF REPORTING PERSON

			Aron R. English
	2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP				(a) ☐
						(b) ☐

	3	SEC USE ONLY


	4	CITIZENSHIP OR PLACE OF ORGANIZATION

			USA
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. 590328209

Item 1(a).

Name of Issuer:

Merrimack Pharmaceuticals, Inc., a Delaware corporation (the “Issuer”).

Item 1(b).

Address of Issuer’s Principal Executive Offices:

One Broadway, 14th Floor

Cambridge, MA 02142

Item 2(a).

Name of Person Filing:

This statement is filed by 22NW Fund, LP, a Delaware limited partnership (“22NW Fund”), 22NW, LP, a Delaware limited partnership (“22NW”), 22NW Fund GP, LLC, a Delaware limited liability company (“22NW GP”), 22NW GP, Inc., a Delaware S Corporation (“22NW Inc.”), and Aron R. English. Each of the foregoing is referred to as a “Reporting Person” and collectively as the “Reporting Persons.”

22NW serves as the investment manager of 22NW Fund. 22NW GP serves as the general partner of 22NW Fund. 22NW Inc. serves as the general partner of 22NW. Mr. English is the Portfolio Manager of 22NW, Manager of 22NW GP and President and sole shareholder of 22NW Inc. By virtue of these relationships, 22NW, 22NW GP, 22NW Inc. and Mr. English may be deemed to beneficially own the Shares (as defined below) owned directly by 22NW Fund.

Item 2(b).

Address of Principal Business Office or, if None, Residence:

The address of the principal office of each of the Reporting Persons is 590 1st Ave. S., Unit C1, Seattle, Washington 98104.

Item 2(c).

Citizenship:

22NW Fund, 22NW, 22NW GP and 22NW Inc. are organized under the laws of the State of Delaware. Mr. English is a citizen of the United States of America.

Item 2(d).

Title of Class of Securities:

Common Stock, $0.01 par value per share (the “Shares”).

Item 2(e).

CUSIP Number:

590328209

CUSIP No. 590328209

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)	/ /	Non-U.S. institution in accordance with Rule 240.13d-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.

(a)

Amount beneficially owned:

As of the close of business on December 31, 2023, no Reporting Person beneficially owned any Shares.

(b)

Percent of class:

As of the close of business on December 31, 2023, the Reporting Persons beneficially owned 0% of the outstanding Shares.

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote:

See Cover Pages Items 5-9.

(ii)

Shared power to vote or to direct the vote:

See Cover Pages Items 5-9.

CUSIP No. 590328209

(iii)

Sole power to dispose or to direct the disposition of:

See Cover Pages Items 5-9.

(iv)

Shared power to dispose or to direct the disposition of:

See Cover Pages Items 5-9.

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].

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, 2022.

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. 590328209

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 14, 2024	22NW FUND, LP

	By:	22NW Fund GP, LLC General Partner

	By:	/s/ Aron R. English
		Name:	Aron R. English
		Title:	Manager

22NW, LP

By:	22NW GP, Inc. General Partner

By:	/s/ Aron R. English
	Name:	Aron R. English
	Title:	President and Sole Shareholder

22NW FUND GP, LLC

By:	/s/ Aron R. English
	Name:	Aron R. English
	Title:	Manager

22NW GP, INC.

By:	/s/ Aron R. English
	Name:	Aron R. English
	Title:	President and Sole Shareholder

	/s/ Aron R. English
	ARON R. ENGLISH

MERRIMACK PHARMACEUTICALS INC SC 13G/A