Edgar Filing: GAY ROBERT C

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

OMB APPROVAL

OMB Number:

3235-0104

Expires:

January 31, 2005

Estimated average burden hours per response...

0.5

(Print or Type Responses)

1. Name and Address of Reporting Person ^*

Â GAY ROBERT C

2. Date of Event Requiring Statement (Month/Day/Year)
01/31/2012

3. Issuer Name and Ticker or Trading Symbol
MERRIMACK PHARMACEUTICALS INC [MACK]

(Last)

(First)

(Middle)

C/O MERRIMACK PHARMACEUTICALS, INC.,Â ONE KENDALL SQUARE, SUITE B7201

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

__X__ Director	_____ 10% Owner
_____ Officer (give title below)	_____ Other (specify below)

5. If Amendment, Date Original Filed(Month/Day/Year)

(Street)

CAMBRIDGE,Â MAÂ 02139

6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ 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)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
	Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

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)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security		6. Nature of Indirect Beneficial Ownership (Instr. 5)
Series B Convertible Preferred Stock	Â ⁽¹⁾	Â ⁽¹⁾	Common Stock	113,586	$ ⁽¹⁾	D	Â
Series D Convertible Preferred Stock	Â ⁽²⁾	Â ⁽²⁾	Common Stock	142,857	$ ⁽²⁾	D	Â
Series B Convertible Preferred Stock	Â ⁽¹⁾	Â ⁽¹⁾	Common Stock	113,586	$ ⁽¹⁾	I	See footnote ⁽³⁾
Series D Convertible Preferred Stock	Â ⁽²⁾	Â ⁽²⁾	Common Stock	142,857	$ ⁽²⁾	I	See footnote ⁽³⁾
Stock Option (right to buy)	Â ⁽⁴⁾	10/22/2017	Common Stock	60,000	$ 2.59	D	Â
Stock Option (right to buy)	Â ⁽⁴⁾	09/21/2018	Common Stock	20,000	$ 1.81	D	Â
Stock Option (right to buy)	Â ⁽⁴⁾	11/04/2019	Common Stock	20,000	$ 2.12	D	Â
Stock Option (right to buy)	Â ⁽⁴⁾	05/02/2021	Common Stock	53,000	$ 5.54	D	Â
Common Stock Warrant (right to buy)	Â ⁽⁴⁾	12/17/2015	Common Stock	8,766	$ 3	D	Â
Common Stock Warrant (right to buy)	Â ⁽⁴⁾	12/17/2015	Common Stock	8,766	$ 3	I	See footnote ⁽⁵⁾

Reporting Owners

Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
GAY ROBERT C C/O MERRIMACK PHARMACEUTICALS, INC. ONE KENDALL SQUARE, SUITE B7201 CAMBRIDGE,Â MAÂ 02139	Â X	Â	Â	Â

Signatures

/s/ Jeffrey A. Munsie, attorney-in-fact		02/01/2012
^**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)	Each share of Series B Convertible Preferred Stock will automatically convert into approximately 1.5435 shares of Common Stock upon the closing of the issuer's initial public offering. The shares have no expiration date.
(2)	Each share of Series D Convertible Preferred Stock will automatically convert into one share of Common Stock upon the closing of the issuer's initial public offering. The shares have no expiration date.
(3)	These shares are held by the Robert C. Gay 1998 Family Trust, of which Dr. Gay is the grantor. Dr. Gay disclaims beneficial ownership of these shares, except to the extent of his pecuniary interest therein, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any such shares for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.
(4)	This security is fully vested.
(5)	This warrant is held by the Robert C. Gay 1998 Family Trust, of which Dr. Gay is the grantor. Dr. Gay disclaims beneficial ownership of this warrant and the shares underlying this warrant, except to the extent of his pecuniary interest therein, and the inclusion of this warrant in this report shall not be deemed an admission of beneficial ownership of this warrant or any shares underlying this warrant for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, See Instruction 6 for procedure.

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.