Ownership Submission
FORM 3
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
  22NW, LP
 2. Date of Event Requiring Statement (Month/Day/Year)
03/13/2019		 3. Issuer Name and Ticker or Trading Symbol
MERRIMACK PHARMACEUTICALS INC [MACK]
(Last)
(First)
(Middle)
1455 NW LEARY WAY, SUITE 400, 		 4. 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
 5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

SEATTLE, WA 98107		 6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)		 2. Amount of Securities Beneficially Owned
(Instr. 4)		 3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)		 4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Common Stock (1) 1,092,263
I
By: 22NW Fund, LP (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(Month/Day/Year)		 3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)		 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)		 6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
22NW, LP
1455 NW LEARY WAY, SUITE 400
SEATTLE, WA 98107		     X   See Explanation of Responses
22NW Fund, LP
1455 NW LEARY WAY
SUITE 400
SEATTLE, WA 98107		     X   See Explanation of Responses
22NW Fund GP, LLC
1455 NW LEARY WAY, SUITE 400
SEATTLE, WA 98107		     X   See Explanation of Responses
English Aron R.
1455 NW LEARY WAY, SUITE 400
SEATTLE, WA 98107		     X   See Explanation of Responses

Signatures

22NW Fund, LP; By: 22NW, LP; By: 22NW Fund GP, LLC; By: /s/ Aron R. English, Managing Member 03/20/2019
**Signature of Reporting Person Date
22NW, LP; By: 22NW Fund GP, LLC; By: /s/ Aron R. English, Managing Member 03/20/2019
**Signature of Reporting Person Date
22NW Fund GP, LLC; By: /s/ Aron R. English, Managing Member 03/20/2019
**Signature of Reporting Person Date
/s/ Aron R. English 03/20/2019
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(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).
(1) This Form 3 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.

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