13D Filing: JFL Capital Management and Merrimack Pharmaceuticals Inc (NASDAQ:MACK)

The following constitutes
the Schedule 13D filed by the undersigned (the “Schedule 13D”).

Item 1.

Security and Issuer.

This statement relates
to the common stock, $0.01 par value per share (the “Shares”), of Merrimack Pharmaceuticals, Inc., a Delaware corporation
(the “Issuer”). The address of the principal executive offices of the Issuer is One Kendall Square, Suite B7201, Cambridge,
Massachusetts 02139.

Item 2.

Identity and Background.

(a)       This
statement is filed by:

(i)

JFL Partners Fund LP, a Delaware limited partnership (“JFL Partners”), with respect to the Shares directly and beneficially owned by it;

(ii)

JFL Capital Management LP, a Texas limited partnership (“JFL GP”), as the general partner of JFL Partners;

(iii)

JFL Capital Holdings LLC, a Delaware limited liability company (“JFL Holdings”), as the general partner of JFL GP;

(iv)

JFL Capital Management LLC, a Delaware limited liability company (“JFL Capital Management”), as the investment manager of JFL Partners and a certain managed account (the “JFL Account”); and

(v)

Joseph F. Lawler, M.D., Ph.D., as the Managing Member of each of JFL Holdings and JFL Capital Management.

Each of the foregoing
is referred to as a “Reporting Person” and collectively as the “Reporting Persons.” Each of the Reporting
Persons is party to that certain Joint Filing Agreement, as further described in Item 6. Accordingly, the Reporting Persons are
hereby filing a joint Schedule 13D.

(b)       The
address of the principal office of each of the Reporting Persons is 2110 Ranch Road 620 S, #341732, Lakeway, Texas 78734.

(c)       The
principal business of JFL Partners is investing in securities. The principal business of JFL GP is serving as the general partner
of JFL Partners. The principal business of JFL Holdings is serving as the general partner of JFL GP. The principal business of
JFL Capital Management is serving as the investment manager of JFL Partners and the JFL Account. The principal occupation of Dr.
Lawler is serving as the Managing Member of each of JFL Holdings and JFL Capital Management.

(d)       No
Reporting Person has, during the last five years, been convicted in a criminal proceeding (excluding traffic violations or similar
misdemeanors).

(e)       No
Reporting Person has, during the last five years, been party to a civil proceeding of a judicial or administrative body of competent
jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations
of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to
such laws.