Merrimack Pharmaceuticals (MACK) 8-K Entry into a Material Definitive Agreement

Exhibit 3.1

CERTIFICATE OF DESIGNATION

OF

SERIES Z JUNIOR PARTICIPATING PREFERRED STOCK

OF

MERRIMACK PHARMACEUTICALS, INC.

(Pursuant to Section 151 of the General Corporation Law of the State of Delaware)

In accordance with Section 151 of the Delaware General Corporation Law, the undersigned corporation hereby certifies that the following resolution was adopted by the Board of Directors (the “Board”) of Merrimack Pharmaceuticals, Inc., a Delaware corporation (the “Corporation”) at a meeting duly called and held on November 22, 2019:

RESOLVED, that pursuant to the authority granted to and vested in the Board in accordance with the provisions of the Company’s Restated Certificate of Incorporation, as amended and as may be further amended from time to time (the“Certificate of Incorporation”), the Board hereby creates, as of and contingent with the Rights Agreement being signed, a series of junior participating preferred stock of the Company to be designated “Series Z Junior Participating Preferred Stock” with a par value of $0.01 per share, and hereby states the designation and number of shares, and fixes the designations and the qualifications, limitations and restrictions thereof (in addition to the provisions set forth in the Certificate of Incorporation, which are applicable to the Preferred Stock of all classes and series):

Section 1.Designation and Amount. The shares of this series shall be designated as Series Z Junior Participating Preferred Stock (the “Series Z Junior Preferred Stock”), and the number of shares constituting the Series Z Junior Preferred Stock shall be 30,000. Such number of shares may be increased or decreased by resolution of the Board;provided, that no decrease shall reduce the number of shares of Series Z Junior Preferred Stock to a number less than the number of shares then outstanding plus the number of shares reserved for issuance upon the exercise of outstanding options, rights or warrants or upon the conversion of any outstanding securities issued by the Corporation convertible into Series Z Junior Preferred Stock.

Section 2.Dividends and Distributions.

(a) Subject to the rights of the holders of any shares of any series of Preferred Stock (or any other stock) ranking prior and superior to the Series Z Junior Preferred Stock with respect to dividends, the holders of shares of Series Z Junior Preferred Stock shall be entitled to receive, when, as and if declared by the Board out of funds legally available for the purpose, quarterly dividends payable in cash on the last day of March, June, September and December in each year (each such date a “Quarterly Dividend Payment Date”), commencing on the first Quarterly Dividend Payment Date after the first issuance of a share or fraction of a share of Series Z Junior Preferred Stock, in an amount (if any) per share (rounded to the nearest cent), subject to the provision for adjustment hereinafter set forth, equal to 1,000 multiplied by the aggregate per share amount of all cash dividends, and 1,000 multiplied by the aggregate per share amount (payable in kind) of allnon-cash dividends or other distributions, other than a dividend payable in shares of Common Stock, par value $0.01 per share (the “Common Stock”), of the Corporation or a subdivision of the outstanding shares of Common Stock (by reclassification or

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otherwise) declared on the Common Stock since the immediately preceding Quarterly Dividend Payment Date or, with respect to the first Quarterly Dividend Payment Date, since the first issuance of any share or fraction of a share of Series Z Junior Preferred Stock. In the event the Corporation shall at any time declare or pay any dividend on the Common Stock payable in shares of Common Stock, or effect a subdivision or combination or consolidation of the outstanding shares of Common Stock (by reclassification or otherwise than by payment of a dividend in shares of Common Stock) into a greater or lesser number of shares of Common Stock, then in each such case the amount to which holders of shares of Series Z Junior Preferred Stock were entitled immediately prior to such event under the preceding sentence shall be adjusted by multiplying such amount by a fraction, the numerator of which is the number of shares of Common Stock outstanding immediately after such event and the denominator of which is the number of shares of Common Stock that were outstanding immediately prior to such event.

(b) The Corporation shall declare a dividend or distribution on the Series Z Junior Preferred Stock as provided in paragraph (a) of this Section 2 immediately after it declares a dividend or distribution on the Common Stock (other than a dividend payable in shares of Common Stock).

(c) Dividends due pursuant to paragraph (a) of this Section 2 shall begin to accrue and be cumulative on outstanding shares of Series Z Junior Preferred Stock from the Quarterly Dividend Payment Date next preceding the date of issue of such shares, unless the date of issue of such shares is prior to the record date for the first Quarterly Dividend Payment Date, in which case dividends on such shares shall begin to accrue from the date of issue of such shares, or unless the date of issue is a Quarterly Dividend Payment Date or is a date after the record date for the determination of holders of shares of Series Z Junior Preferred Stock entitled to receive a quarterly dividend and before such Quarterly Dividend Payment Date, in either of which events such dividends shall begin to accrue and be cumulative from such Quarterly Dividend Payment Date. Accrued but unpaid dividends shall not bear interest. Dividends paid on the shares of Series Z Junior Preferred Stock in an amount less than the total amount of such dividends at the time accrued and payable on such shares shall be allocated pro rata on ashare-by-share basis among all such shares at the time outstanding. The Board may fix a record date for the determination of holders of shares of Series Z Junior Preferred Stock entitled to receive payment of a dividend or distribution declared thereon, which record date shall be not more than 60 days prior to the date fixed for the payment thereof.

Section 3.Voting Rights. The holders of shares of Series Z Junior Preferred Stock shall have the following voting rights:

(a) Subject to the provision for adjustment hereinafter set forth, each share of Series Z Preferred Stock shall entitle the holder thereof to 1,000 votes on all matters submitted to a vote of the stockholders of the Corporation. In the event the Corporation shall at any time declare or pay any dividend on the Common Stock payable in shares of Common Stock, or effect a subdivision or combination or consolidation of the outstanding shares of Common Stock (by reclassification or otherwise than by payment of a dividend in shares of Common Stock) into a greater or lesser number of shares of Common Stock, then in each such case the number of votes per share to which holders of shares of Series Z Junior Preferred Stock were entitled immediately prior to such event shall be adjusted by multiplying such number by a fraction, the numerator of which is the number of shares of Common Stock outstanding immediately after such event and the denominator of which is the number of shares of Common Stock that were outstanding immediately prior to such event.

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(b) Except as otherwise provided herein, by the Certificate of Incorporation, including any other Certificate of Designation creating a series of Preferred Stock or any similar stock, the bylaws of the Corporation or by applicable law, the holders of shares of Series Z Junior Preferred Stock and the holders of shares of Common Stock and any other capital stock of the Corporation having general voting rights shall vote together as one class on all matters submitted to a vote of stockholders of the Corporation.

(c) Except as set forth herein, or as otherwise required by law, holders of Series Z Junior Preferred Stock shall have no special voting rights and their consent shall not be required (except to the extent they are entitled to vote with holders of Common Stock as set forth herein) for taking any corporate action.

Section 4.Certain Restrictions.

(a) Whenever quarterly dividends or other dividends or distributions payable on the Series Z Junior Preferred Stock as provided in Section 2 are in arrears, thereafter and until all accrued and unpaid dividends and distributions, whether or not declared, on shares of Series Z Junior Preferred Stock outstanding shall have been paid in full, the Corporation shall not:

(i) declare or pay dividends, or make any other distributions, on any shares of stock ranking junior (either as to dividends or upon liquidation, dissolution orwinding-up) to the Series Z Junior Preferred Stock;

(ii) declare or pay dividends, or make any other distributions, on any shares of stock ranking on a parity (either as to dividends or upon liquidation, dissolution orwinding-up) with the Series Z Junior Preferred Stock, except dividends paid ratably on the Series Z Junior Preferred Stock and all such parity stock on which dividends are payable or in arrears in proportion to the total amounts to which the holders of all such shares are then entitled; or

(iii) redeem or purchase or otherwise acquire for consideration shares of any stock ranking junior (either as to dividends or upon liquidation, dissolution orwinding-up) to the Series Z Junior Preferred Stock, provided that the Corporation may at any time redeem, purchase or otherwise acquire shares of any such junior stock in exchange for shares of any stock of the Corporation ranking junior (as to dividends and upon dissolution, liquidation orwinding-up) to the Series Z Junior Preferred Stock.

(b) The Corporation shall not permit any subsidiary of the Corporation to purchase or otherwise acquire for consideration any shares of stock of the Corporation unless the Corporation could, under paragraph (a) of this Section 4, purchase or otherwise acquire such shares at such time and in such manner.

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Section 5.Reacquired Shares. Any shares of Series Z Junior Preferred Stock purchased or otherwise acquired by the Corporation in any manner whatsoever shall be retired and canceled promptly after the acquisition thereof. The Corporation shall take all such actions as are necessary to cause all such shares to become authorized but unissued shares of Preferred Stock that may be reissued as part of a new series of Preferred Stock subject to the conditions and restrictions on issuance set forth herein or in the Certificate of Incorporation, including any Certificate of Designation creating a series of Preferred Stock or any similar stock, or as otherwise required by law.

Section 6.Liquidation, Dissolution orWinding-Up.

(a) Upon any liquidation, dissolution orwinding-up of the Corporation, voluntary or otherwise, no distribution shall be made to the holders of stock ranking junior (either as to dividends or upon liquidation, dissolution orwinding-up) to the Series Z Junior Preferred Stock unless, prior thereto, the holders of Series Z Junior Preferred Stock shall have received an amount per share (the “Series Z Liquidation Preference”), subject to the provision for adjustment hereinafter set forth, equal to 1,000 multiplied by the aggregate amount to be distributed per share to holders of shares of Common Stock plus an amount equal to any accrued and unpaid dividends. In the event the Corporation shall at any time declare or pay any dividend on the Common Stock payable in shares of Common Stock, or effect a subdivision or combination or consolidation of the outstanding shares of Common Stock (by reclassification or otherwise than by payment of a dividend in shares of Common Stock) into a greater or lesser number of shares of Common Stock, then in each such case the aggregate amount to which holders of shares of Series Z Junior Preferred Stock were entitled immediately prior to such event under the preceding sentence shall be adjusted by multiplying such amount by a fraction, the numerator of which is the number of shares of Common Stock outstanding immediately after such event and the denominator of which is the number of shares of Common Stock that were outstanding immediately prior to such event.

(b) If there are not sufficient assets available to permit payment in full of the Series Z Liquidation Preference and the liquidation preferences of all other classes and series of stock of the Corporation, if any, that rank on a parity with the Series Z Junior Preferred Stock in respect thereof, then the assets available for such distribution shall be distributed ratably to the holders of the Series Z Junior Preferred Stock and the holders of such parity shares in proportion to their respective liquidation preferences.

(c) Neither the merger nor consolidation of the Corporation into or with another entity nor the merger or consolidation of any other entity into or with the Corporation shall be deemed to be a liquidation, dissolution orwinding-up of the Corporation within the meaning of this Section 6.

Section 7.Consolidation, Merger, Etc. If the Corporation shall enter into any consolidation, merger, combination or other transaction in which the shares of Common Stock are exchanged for or changed into other stock or securities, cash and/or any other property, then in any such case each share of Series Z Junior Preferred Stock shall at the same time be similarly exchanged or changed into an amount per share, subject to the provision for adjustment hereinafter set forth, equal to 1,000 multiplied by the aggregate amount of stock, securities, cash and/or any other property (payable in kind), as the case may be, into which or for which each share of Common Stock is changed or exchanged. In the event the Corporation shall at any time

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declare or pay any dividend on the Common Stock payable in shares of Common Stock, or effect a subdivision or combination or consolidation of the outstanding shares of Common Stock (by reclassification or otherwise than by payment of a dividend in shares of Common Stock) into a greater or lesser number of shares of Common Stock, then in each such case the amount set forth in the preceding sentence with respect to the exchange or change of shares of Series Z Junior Preferred Stock shall be adjusted by multiplying such amount by a fraction, the numerator of which is the number of shares of Common Stock outstanding immediately after such event and the denominator of which is the number of shares of Common Stock that were outstanding immediately prior to such event.

Section 8.Amendment. While any Series Z Junior Preferred Stock is issued and outstanding, the Certificate of Incorporation shall not be amended in any manner, including in a merger or consolidation, which would alter, change or repeal the powers, preferences or special rights of the Series Z Junior Preferred Stock so as to affect them adversely without the affirmative vote of the holders of at leasttwo-thirds of the outstanding shares of Series Z Junior Preferred Stock, voting together as a single class.

Section 9.Rank. The Series Z Junior Preferred Stock shall rank, with respect to the payment of dividends and upon liquidation, dissolution andwinding-up, junior to all other series of Preferred Stock, unless the terms of any such series shall provide otherwise, and shall rank senior to the Common Stock as to such matters.

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IN WITNESS WHEREOF, this Certificate of Designation is executed on behalf of the Corporation by its duly authorized officer this 3rd day of December, 2019.

MERRIMACK PHARMACEUTICALS, INC.
By:	/s/ Gary L. Crocker
	Name: Gary L. Crocker
	Title: President

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