X0306 4 2019-04-15 0 0001274792 MERRIMACK PHARMACEUTICALS INC MACK 0001694297 22NW, LP 1455 NW LEARY WAY, SUITE 400 SEATTLE WA 98107 0 0 1 1 See Explanation of Responses 0001640809 22NW Fund, LP 1455 NW LEARY WAY SUITE 400 SEATTLE WA 98107 0 0 1 1 See Explanation of Responses 0001770575 22NW Fund GP, LLC 1455 NW LEARY WAY, SUITE 400 SEATTLE WA 98107 0 0 1 1 See Explanation of Responses 0001770436 English Aron R. 1455 NW LEARY WAY, SUITE 400 SEATTLE WA 98107 0 0 1 1 See Explanation of Responses Common Stock 2019-04-15 4 P 0 30110 5.7300 A 1205246 I By: 22NW Fund, LP Common Stock 2019-04-16 4 P 0 20450 5.9480 A 1225696 I By: 22NW Fund, LP Common Stock 2019-04-17 4 P 0 16200 5.9973 A 1241896 I By: 22NW Fund, LP 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. 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. 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. 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. 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 2019-04-17 22NW, LP; By: 22NW Fund GP, LLC; By: /s/ Aron R. English, Managing Member 2019-04-17 22NW Fund GP, LLC; By: /s/ Aron R. English, Managing Member 2019-04-17 /s/ Aron R. English 2019-04-17