Newtyn Management SC 13G/A Merrimack Pharmaceuticals Inc

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

Merrimack pharmaceuticals INC.

(Name of Issuer)

Common Stock, $0.01 par value per share

(Title of Class of Securities)

590328209

(CUSIP Number)

May 3, 2019

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule 13G is filed:

[   ] Rule 13d-1(b)

[X] Rule 13d-1(c)

[   ] Rule 13d-1(d)

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). 

CUSIP No.  590328209
(1) Names of Reporting Persons
	Newtyn Management, LLC
(2) Check the Appropriate Box if a Member of a Group			(a) [    ]
			(b) [    ]
(3) SEC Use Only
(4) Citizenship or Place of Organization
	New York
Number of Shares Beneficially Owned by Each Reporting Person With:
		(5) Sole Voting Power:	0
		(6) Shared Voting Power:	1,191,386*
		(7) Sole Dispositive Power:	0
		(8) Shared Dispositive Power:	1,191,386*
(9) Aggregate Amount Beneficially Owned by Each Reporting Person
	1,191,386*
(10) Check if the Aggregate Amount  in Row (9) Excludes Certain Shares (See Instructions):
	[    ]
(11) Percent of Class Represented by Amount in Row (9)
	8.9%*
(12) Type of Reporting Person (See Instructions)
	IA

* Beneficial ownership percentage is based upon 13,342,784 shares of Common Stock, $0.01 par value per share ("Common Stock"), of Merrimack Pharmaceuticals, Inc., a Delaware corporation (the "Company"), issued and outstanding as of February 27, 2019, based on information reported by the Company in its Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 6, 2019. Newtyn Management, LLC ("Newtyn Management") is the investment manager to Newtyn Partners, LP ("NP") and Newtyn TE Partners, LP ("NTE"). As of May 3, 2019, NP held 671,894 shares of Common Stock and NTE held 519,492 shares of Common Stock.

Newtyn Management, as the investment manager to NP and NTE, possesses the sole power to direct the vote and the sole power to direct the disposition of the 1,191,386 shares of Common Stock held in the aggregate by NP and NTE. As a result of the foregoing, for purposes of Reg. Section 240.13d-3, Newtyn Management may be deemed to beneficially own 1,191,386 shares of Common Stock, or 8.9% of the shares of Common Stock deemed to be issued and outstanding as of May 3, 2019.

CUSIP No.  590328209
(1) Names of Reporting Persons
	Newtyn Partners, LP
(2) Check the Appropriate Box if a Member of a Group			(a) [    ]
			(b) [    ]
(3) SEC Use Only
(4) Citizenship or Place of Organization
	Delaware
Number of Shares Beneficially Owned by Each Reporting Person With:
		(5) Sole Voting Power:	0
		(6) Shared Voting Power:	671,894*
		(7) Sole Dispositive Power:	0
		(8) Shared Dispositive Power:	671,894*
(9) Aggregate Amount Beneficially Owned by Each Reporting Person
	671,894*
(10) Check if the Aggregate Amount  in Row (9) Excludes Certain Shares (See Instructions):
	[    ]
(11) Percent of Class Represented by Amount in Row (9)
	5.0%*
(12) Type of Reporting Person (See Instructions)
	PN

* Beneficial ownership percentage is based upon 13,342,784 shares of Common Stock, $0.01 par value per share ("Common Stock"), of Merrimack Pharmaceuticals, Inc., a Delaware corporation (the "Company"), issued and outstanding as of February 27, 2019, based on information reported by the Company in its Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 6. 2019. As of May 3, 2019, Newtyn Partners, LP ("NP") held 671,894 shares of Common Stock, or approximately 5.0% of the Common Stock deemed issued and outstanding as of May 3, 2019.

Item 1(a).  Name Of Issuer.  Merrimack Pharmaceuticals, Inc. (the “Company”)
Item 1(b).  Address of Issuer’s Principal Executive Offices.
	One Kendall Square, Suite B7201 Cambridge, MA
Item 2(a).  Name of Person Filing.
	This report on Schedule 13G (this "Schedule 13G") is being jointly filed by (a) Newtyn Partners, LP ("NP"), a Delaware limited partnership and (b) Newtyn Management, LLC, a New York limited liability company and the investment manager to (y) NP, which is the holder of 671,894 shares of Common Stock, $0.01 par value per share ("Common Stock"), of the Company reported on this Schedule 13G, and (z) Newtyn TE Partners, LP ("NTE"), which is the holder of 519,492 shares of Common Stock of the Company reported on this Schedule 13G (NP and Newtyn Management the "Reporting Persons"). The 1,191,386 shares of Common Stock held in the aggregate by NP and NTE, which constitutes 8.9% of the shares of Common Stock deemed to be issued and outstanding as of May 3, 2019, may be deemed to be beneficially owned indirectly by Newtyn Management, LLC, as the investment manager to NP and NTE. As of May 3, 2019, NP held 671,894 shares of Common Stock, or approximately 5.0% of the Common Stock deemed issued and outstanding as of May 3, 2019.
Item 2(b).  Address of Principal Business Office or, if None, Residence.
	The address for each of Newtyn Management and NP is 405 Park Avenue, Suite 1104, New York, New York 10022.
Item 2(c).  Citizenship.
	Newtyn Management, LLC is organized under the laws of the State of New York. Newtyn Partners, LP is a Delaware limited partnership
Item 2(d).  Title of Class of Securities.
	Common Stock, $0.01 par value per share.
Item 2(e).  CUSIP No.
	590328209

Item 3.  If This Statement Is Filed Pursuant to Section 240.13d-1(b) or 240.13d-2(b) or (c), check whether the Person Filing is a:
	Not Applicable.

Item 4.  Ownership.
	Newtyn Management, LLC
	(a)     Amount Beneficially Owned:		1,191,386*
	(b)    Percent of Class:		8.9%*
	(c)     Number of Shares as to which such person has:
		(i)     Sole power to vote or to direct the vote:	0
		(ii)     Shared power to vote or to direct the vote:	1,191,386*
		(iii)     Sole power to dispose or to direct the disposition of:	0
		(iv)     Shared power to dispose or to direct the disposition of:	1,191,386*

 ___________________________________________________________

Newtyn Partners, LP
(a)     Amount Beneficially Owned:		671,894*
(b)    Percent of Class:		5.0%*
(c)     Number of Shares as to which such person has:
	(i)     Sole power to vote or to direct the vote:	0
	(ii)     Shared power to vote or to direct the vote:	671,894*
	(iii)     Sole power to dispose or to direct the disposition of:	0
	(iv)     Shared power to dispose or to direct the disposition of:	671,894*

___________________________________________________________

 *     This Schedule 13G is being jointly filed by (a) NP and (b) Newtyn Management, the investment manager to (y) NP, which is the holder of 671,894 shares of Common Stock of the Company reported on this Schedule 13G, and (z) NTE, which is the holder of 519,492 shares of Common Stock of the Company reported on this Schedule 13G.

The 1,191,386 shares of Common Stock held in the aggregate by NP and NTE, which constitutes approximately 8.9% of the shares of Common Stock deemed to be issued and outstanding as of May 3, 2019, may deemed to be beneficially owned indirectly by Newtyn Management, LLC, as the investment manager to NP and NTE.

As of May 3, 2019, NP held 671,894 shares of Common Stock, or approximately 5.0% of the Common Stock deemed issued and outstanding as of May 3, 2019. 

The foregoing beneficial ownership percentage is based upon information reported by the Company in its Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 6, 2019.

Item 5.  Ownership of Five Percent or Less of a Class.
	If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following:  [   ]
Item 6.  Ownership of More Than Five Percent on Behalf of Another Person.
	Not Applicable.
Item 7.  Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable.
Item 8.  Identification and Classification of Members of the Group.
	Not Applicable.
Item 9.  Notice of Dissolution of Group.
	Not Applicable.
Item 10.  Certification.
	By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

SIGNATURE

          After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

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

Attention: Intentional misstatements or omissions of fact constitute

Federal criminal violations (See 18 U.S.C. 1001)

Exhibit Index

Exhibit

A. Joint Filing Agreement dated as of May 13, 2019.