January 3, 2018

VIA EDGAR SUBMISSION

Securities and Exchange Commission

Division of Corporation Finance

100 F Street, NE

Washington, DC 20549

Attention: Ada D. Sarmento.

 

Re:	Merrimack Pharmaceuticals, Inc.

Registration Statement on Form S-3

File No. 333-222093

Request for Acceleration

Ladies and Gentlemen:

Pursuant to Rule 461 under the Securities Act of 1933, as amended, Merrimack Pharmaceuticals, Inc. hereby requests acceleration of the effective date of its Registration Statement on Form S-3 (File No. 333-222093), so that it may become effective at 4:30 p.m., Eastern time, on January 5, 2018, or as soon as practicable thereafter.

 

Very truly yours,
By:		/s/ Jeffrey A. Munsie
		Jeffrey A. Munsie General Counsel