SEC Form 4

FORM 4		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 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* 22NW, LP (Last) (First) (Middle) 1455 NW LEARY WAY, SUITE 400 (Street) SEATTLE WA 98107 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol MERRIMACK PHARMACEUTICALS INC [ MACK ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) X Other (specify below) See Explanation of Responses
	3. Date of Earliest Transaction (Month/Day/Year) 04/15/2019
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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
Common Stock(1)	04/15/2019		P		30,110	A	$5.73(3)	1,205,246	I	By: 22NW Fund, LP(2)
Common Stock(1)	04/16/2019		P		20,450	A	$5.948(4)	1,225,696	I	By: 22NW Fund, LP(2)
Common Stock(1)	04/17/2019		P		16,200	A	$5.9973(5)	1,241,896	I	By: 22NW Fund, LP(2)

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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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

1. Name and Address of Reporting Person* 22NW, LP (Last) (First) (Middle) 1455 NW LEARY WAY, SUITE 400 (Street) SEATTLE WA 98107 (City) (State) (Zip)

1. Name and Address of Reporting Person* 22NW Fund, LP (Last) (First) (Middle) 1455 NW LEARY WAY SUITE 400 (Street) SEATTLE WA 98107 (City) (State) (Zip)

1. Name and Address of Reporting Person* 22NW Fund GP, LLC (Last) (First) (Middle) 1455 NW LEARY WAY, SUITE 400 (Street) SEATTLE WA 98107 (City) (State) (Zip)

1. Name and Address of Reporting Person* English Aron R. (Last) (First) (Middle) 1455 NW LEARY WAY, SUITE 400 (Street) SEATTLE WA 98107 (City) (State) (Zip)

Explanation of Responses:

1. This Form 4 is filed jointly by 22NW Fund, LP ("22NW Fund"), 22NW, LP ("22NW"), 22NW Fund GP, LLC ("22NW GP") and Aron R. English (collectively, the "Reporting Persons"). Each of the Reporting Persons may be deemed to be a member of a Section 13(d) group that collectively beneficially owns more than 10% of the Issuer's outstanding shares of Common Stock. Each of the Reporting Persons disclaims beneficial ownership of the securities of the Issuer owned directly by other members of the Section 13(d) group and this report shall not be deemed an admission that the Reporting Persons are the beneficial owners of such securities for purposes of Section 16 or for any other purpose. Further, each of the Reporting Persons expressly disclaims beneficial ownership of the securities reported herein except to the extent of his or its pecuniary interest therein.

2. Securities owned directly by 22NW Fund. As the general partner and investment adviser to 22NW Fund, 22NW may be deemed to beneficially own the securities owned directly by 22NW Fund. As the general partner of 22NW, 22NW GP may be deemed to beneficially own the securities owned directly by 22NW Fund. Mr. English, as the Portfolio Manager of 22NW and Managing Member of 22NW GP, may be deemed to beneficially own the securities owned directly by 22NW Fund.

3. The reported price in Column 4 is a weighted average price. These shares of Common Stock were purchased in multiple transactions at prices ranging from $5.49 to $5.90, excluding commissions. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock purchased at each separate price within the range set forth in this footnote.

4. The reported price in Column 4 is a weighted average price. These shares of Common Stock were purchased in multiple transactions at prices ranging from $5.80 to $6.00, excluding commissions. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock purchased at each separate price within the range set forth in this footnote.

5. The reported price in Column 4 is a weighted average price. These shares of Common Stock were purchased in multiple transactions at prices ranging from $5.98 to $6.00, excluding commissions. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock purchased at each separate price within the range set forth in this footnote.

	22NW Fund, LP; By: 22NW, LP; By: 22NW Fund GP, LLC; By: /s/ Aron R. English, Managing Member	04/17/2019
	22NW, LP; By: 22NW Fund GP, LLC; By: /s/ Aron R. English, Managing Member	04/17/2019
	22NW Fund GP, LLC; By: /s/ Aron R. English, Managing Member	04/17/2019
	/s/ Aron R. English	04/17/2019
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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