Exhibit 3.1

FIFTH AMENDED AND RESTATED

CERTIFICATE OF INCORPORATION

OF

MARINUS PHARMACEUTICALS, INC.

FIRST: The name of the corporation is Marinus Pharmaceuticals, Inc. (the “Corporation”).

SECOND: The address of the Corporation’s registered office in the State of Delaware is The Corporation Trust Center, 1209 Orange Street, City of Wilmington, County of New Castle, Delaware 19801. The name of its registered agent at such address is The Corporation Trust Company.

THIRD: The purpose of the Corporation is to engage in any lawful act or activity for which corporations may be organized under the General Corporation Law of the State of Delaware as the same exists or may hereafter be amended (the “DGCL”).

FOURTH: The total number of shares of common stock which the Corporation shall have authority to issue is 1,000, and the par value of each such share is $0.01.

FIFTH: The Board of Directors (the “Board”) shall have the power to adopt, amend or repeal the bylaws of the Corporation.

SIXTH: Election of directors need not be by written ballot unless the bylaws of the Corporation so provide.

SEVENTH: The Corporation expressly elects not to be governed by Section 203 of the DGCL.

EIGHTH: (1)          A director of the Corporation shall not be personally liable to the Corporation or its stockholders (including without limitation their heirs, executors and administrators) for monetary damages for breach of fiduciary duty as a director in accordance with and to the fullest extent permitted by the DGCL as the same exists or may hereafter be amended.

(2)          The Corporation shall indemnify each of the Corporation’s directors and officers in each and every situation where, under Section 145 of the DGCL, as amended from time to time (“Section 145”), the Corporation is permitted or empowered to make such indemnification. The Corporation may, in the sole discretion of the Board, indemnify any other person who may be indemnified pursuant to Section 145 to the extent the Board deems advisable, as permitted by Section 145. The Corporation shall promptly make or cause to be made any determination required to be made pursuant to Section 145.

(3)          Any repeal or modification of this ARTICLE EIGHTH by the stockholders of the Corporation shall not adversely affect any right or protection of a director of the Corporation existing at the time of such repeal or modification.

NINTH: The Corporation reserves the right to amend this Certificate of Incorporation in any manner permitted by the DGCL and all rights and powers conferred herein on stockholders, directors and officers, if any, are subject to this reserved power.