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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">UNITED STATES<br> SECURITIES AND EXCHANGE COMMISSION</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">WASHINGTON, D.C. 20549</font></b></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">FORM&nbsp;8-K</font></b></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="3" face="Times New Roman" style="font-size:12.0pt;font-weight:bold;">CURRENT REPORT<br> Pursuant to Section&nbsp;13 or 15(d)&nbsp;of the Securities Exchange Act of 1934</font></b></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Date of Report (Date of earliest event reported): <b>September&nbsp;9, 2013</b></font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="5" face="Times New Roman" style="font-size:18.0pt;font-weight:bold;">Merrimack Pharmaceuticals,&nbsp;Inc.</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(Exact Name of Registrant as Specified in its Charter)</font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">001-35409</font></b></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">04-3210530</font></b></p>    </td>   </tr>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(IRS Employer<br>   Identification No.)</font></p>    </td>   </tr>  </table>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">One Kendall Square, Suite&nbsp;B7201</font></b></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Cambridge, MA</font></b></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">02139</font></b></p>    </td>   </tr>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Registrant&#146;s telephone number, including area code: <b>(617) 441-1000</b></font></p>
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<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Check the appropriate box below if the Form&nbsp;8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (<i>see</i> General Instruction A.2. below):</font></p>
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<p style="margin:0in 0in .0001pt .5in;"><font size="2" face="Wingdings" style="font-size:10.0pt;">o</font><font size="1" face="Wingdings" style="font-size:3.0pt;">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; </font><font size="2" style="font-size:10.0pt;">Written communications pursuant to Rule&nbsp;425 under the Securities Act (17 CFR 230.425)</font></p>
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<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Item&nbsp;7.01.&#160; Regulation FD Disclosure.</font></b></p>
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<p style="margin:0in 0in .0001pt;text-indent:24.5pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Merrimack Pharmaceuticals,&nbsp;Inc. (the &#147;Company&#148;) from time to time presents and/or distributes to the investment community at various industry and other conferences slide presentations to provide updates and summaries of its business. The Company is posting to the Investors portion of its website at investors.merrimackpharma.com copies of its current corporate slide presentation and factsheet. These slides are attached to this Current Report on Form&nbsp;8-K as Exhibit&nbsp;99.1 and Exhibit&nbsp;99.2. The Company undertakes no obligation to update, supplement or amend the materials attached hereto as Exhibit&nbsp;99.1 or Exhibit&nbsp;99.2.</font></p>
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<p style="margin:0in 0in .0001pt;text-indent:24.5pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">In accordance with General Instruction B.2 of Form&nbsp;8-K, the information in this Item 7.01 of this Current Report on Form&nbsp;8-K, including Exhibit&nbsp;99.1 and Exhibit&nbsp;99.2, shall not be deemed &#147;filed&#148; for the purposes of Section&nbsp;18 of the Securities Exchange Act of 1934, as amended (the &#147;Exchange Act&#148;), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Exchange Act or the Securities Act of 1933, as amended, except as shall be expressly set forth by reference in such a filing.</font></p>
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<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Item 9.01.&#160; Financial Statements and Exhibits.</font></b></p>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">(d)&nbsp; Exhibits.</font></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt .5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">See Exhibit&nbsp;Index attached hereto.</font></p>
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<p style="margin:0in 0in .0001pt;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Forward Looking Statements</font></b></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">The attached exhibits contain forward-looking statements that involve substantial risks and uncertainties.&#160; All statements, other than statements of historical facts, contained in these exhibits, including statements regarding our strategy, future operations, future financial position, future revenues, projected costs, prospects, plans and objectives of management, are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended.&#160; The words &#147;anticipate,&#148; &#147;believe,&#148; &#147;estimate,&#148; &#147;expect,&#148; &#147;intend,&#148; &#147;may,&#148; &#147;plan,&#148; &#147;predict,&#148; &#147;project,&#148; &#147;target,&#148; &#147;potential,&#148; &#147;will,&#148; &#147;would,&#148; &#147;could,&#148; &#147;should,&#148; &#147;continue&#148; and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.&#160; We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements.&#160; Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make.&#160; These forward-looking statements include, among other things, statements about: our plans to develop and commercialize our most advanced product candidates and companion diagnostics; our ongoing and planned discovery programs, preclinical studies and clinical trials; our anticipated milestones; adequacy of funding for Merrimack&#146;s foreseeable and unforeseeable operating expenses and capital expenditure requirements; and the success or consummation of potential business development activities.&#160; For more information regarding important factors that we believe could cause actual results or events to differ materially from the forward-looking statements that we make, see the &#147;Risk Factors&#148; section of our Quarterly Report on Form&nbsp;10-Q filed with the Securities and Exchange Commission, or SEC, on August&nbsp;8, 2013 and other reports we file with the SEC.&#160; Any forward-looking statement contained in these exhibits reflects Merrimack&#146;s views as of the date of the document with respect to future events and Merrimack assumes no obligation to publicly update or revise these forward-looking statements for any reason, or to update the reasons actual results could differ materially from those anticipated in these forward-looking statements, even if new information becomes available in the future, except as otherwise required by applicable law.</font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">SIGNATURE</font></b></p>
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<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.</font></p>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">MERRIMACK   PHARMACEUTICALS,&nbsp;INC.</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Date:   September&nbsp;9, 2013</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">/s/   Jeffrey A. Munsie</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Jeffrey   A. Munsie</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Vice   President and General Counsel</font></p>    </td>   </tr>  </table>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">2<a name="PB_2_053012_5796"></a></font></p>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">EXHIBIT&nbsp;INDEX</font></b></p>
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<p style="margin:0in 0in .0001pt;"><b><font size="1" face="Times New Roman" style="font-size:8.0pt;font-weight:bold;">Exhibit&nbsp;No.</font></b></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:1.0pt;font-weight:bold;">&nbsp;</font></b></p>    </td>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="1" face="Times New Roman" style="font-size:8.0pt;font-weight:bold;">Description</font></b></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">99.1</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Corporate slide presentation of the Company   dated September&nbsp;2013</font></p>    </td>   </tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">99.2</font></p>    </td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Factsheet of the Company dated   September&nbsp;2013</font></p>    </td>   </tr>  </table>
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<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">3<a name="PB_3_053012_2897"></a></font></p>
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{"company-data": {"conformed-name": "MERRIMACK PHARMACEUTICALS INC", "cik": "0001274792", "assigned-sic": "2834", "irs-number": "000000000", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-35409", "film-number": "131084498"}, "business-address": {"street1": "ONE KENDALL SQUARE", "street2": "SUITE B7201", "city": "CAMBRIDGE", "state": "MA", "zip": "02139", "phone": "617-441-1000"}, "mail-address": {"street1": "ONE KENDALL SQUARE", "street2": "SUITE B7201", "city": "CAMBRIDGE", "state": "MA", "zip": "02139"}}
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
FORM 8-K
CURRENT REPORT
Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
Date of Report (Date of earliest event reported):
September 9, 2013
Merrimack Pharmaceuticals, Inc.
(Exact Name of Registrant as Specified in its Charter)
Delaware
001-35409
04-3210530
(State or Other Jurisdiction
of Incorporation
(Commission
File Number)
(IRS Employer
Identification No.)
One Kendall Square, Suite B7201
Cambridge, MA
02139
(Address of Principal Executive Offices)
(Zip Code)
Registrant's telephone number, including area code:
(617) 441-1000
(Former Name or Former Address, if Changed Since Last Report)
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (
see
General Instruction A.2. below):
o
Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
o
Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
o
Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
o
Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))
Item 7.01.  Regulation FD Disclosure.
Merrimack Pharmaceuticals, Inc. (the "Company") from time to time presents and/or distributes to the investment community at various industry and other conferences slide presentations to provide updates and summaries of its business. The Company is posting to the Investors portion of its website at investors.merrimackpharma.com copies of its current corporate slide presentation and factsheet. These slides are attached to this Current Report on Form 8-K as Exhibit 99.1 and Exhibit 99.2. The Company undertakes no obligation to update, supplement or amend the materials attached hereto as Exhibit 99.1 or Exhibit 99.2.
In accordance with General Instruction B.2 of Form 8-K, the information in this Item 7.01 of this Current Report on Form 8-K, including Exhibit 99.1 and Exhibit 99.2, shall not be deemed "filed" for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Exchange Act or the Securities Act of 1933, as amended, except as shall be expressly set forth by reference in such a filing.
Item 9.01.  Financial Statements and Exhibits.
(d)  Exhibits.
See Exhibit Index attached hereto.
Forward Looking Statements
The attached exhibits contain forward-looking statements that involve substantial risks and uncertainties.  All statements, other than statements of historical facts, contained in these exhibits, including statements regarding our strategy, future operations, future financial position, future revenues, projected costs, prospects, plans and objectives of management, are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended.  The words "anticipate," "believe," "estimate," "expect," "intend," "may," "plan," "predict," "project," "target," "potential," "will," "would," "could," "should," "continue" and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.  We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements.  Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make.  These forward-looking statements include, among other things, statements about: our plans to develop and commercialize our most advanced product candidates and companion diagnostics; our ongoing and planned discovery programs, preclinical studies and clinical trials; our anticipated milestones; adequacy of funding for Merrimack's foreseeable and unforeseeable operating expenses and capital expenditure requirements; and the success or consummation of potential business development activities.  For more information regarding important factors that we believe could cause actual results or events to differ materially from the forward-looking statements that we make, see the "Risk Factors" section of our Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission, or SEC, on August 8, 2013 and other reports we file with the SEC.  Any forward-looking statement contained in these exhibits reflects Merrimack's views as of the date of the document with respect to future events and Merrimack assumes no obligation to publicly update or revise these forward-looking statements for any reason, or to update the reasons actual results could differ materially from those anticipated in these forward-looking statements, even if new information becomes available in the future, except as otherwise required by applicable law.
1
SIGNATURE
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
MERRIMACK   PHARMACEUTICALS, INC.
Date:   September 9, 2013
By:
/s/   Jeffrey A. Munsie
Jeffrey   A. Munsie
Vice   President and General Counsel
2
EXHIBIT INDEX
Exhibit No.
Description
99.1
Corporate slide presentation of the Company   dated September 2013
99.2
Factsheet of the Company dated   September 2013
3