Exhibit A
JOINT FILING AGREEMENT
In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the persons named below agree to the joint filing on behalf of them of a statement on Schedule 13G (including amendments thereto) with respect to the Common Stock, $0.01 par value per share of Merrimack Pharmaceuticals, Inc., and further agree that this Joint Filing Agreement be included as Exhibit A to such Schedule 13G. In evidence thereof, the undersigned hereby execute this agreement this May 13, 2019.
| NEWTYN MANAGEMENT, LLC | |||
| By: | /s/ Eugene Dozortsev | ||
| Name: Eugene Dozortsev | |||
| Title: Authorized Signatory | |||
| NEWTYN Partners, LP | |||
| By: | Newtyn Management, LLC | ||
| Investment Manager | |||
| By: | /s/ Eugene Dozortsev | ||
| Name: Eugene Dozortsev | |||
| Title: Authorized Signatory | |||
