Sec Form 4 Filing - VITULLO NICOLE @ MARINUS PHARMACEUTICALS INC - 2017-01-17

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP 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

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1. Name and Address of Reporting Person VITULLO NICOLE 2. Issuer Name and Ticker or Trading Symbol MARINUS PHARMACEUTICALS INC [ MRNS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O DOMAIN ASSOCIATES, LLC, ONE PALMER SQUARE 3. Date of Earliest Transaction (MM/DD/YY) 01/17/2017 (Street) PRINCETON, NJ08542 4. If Amendment, Date Original Filed (MM/DD/YY) 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 Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 01/17/2017 A 4,500 ( 1 ) A $ 0 7,800 D Common Stock 2,476,886 I By Domain Partners VI, L.P. ( 3 ) Common Stock 17,000 I By DP VI Associates, L.P. ( 3 ) Common Stock 42,550 I By Domain Associates, LLC ( 3 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Stock Option (Right to Buy) $ 1.21 01/17/2017 A 10,500 ( 2 ) 01/17/2027 Common Stock 10,500 $ 0 10,500 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other VITULLO NICOLE C/O DOMAIN ASSOCIATES, LLC ONE PALMER SQUARE PRINCETON, NJ08542 X X Signatures /s/ Lisa A. Kraeutler, Attorney-in-Fact 01/19/2017 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Represents shares of restricted stock which vest on 01/17/2018. Each share of restricted stock represents the right to receive, at settlement, one share of Common Stock. ( 2 )The options vest in 12 equal monthly installments commencing 01/31/2017. ( 3 )The Reporting Person is a managing member of Domain Associates, LLC and a managing member of One Palmer Square Associates VI, LLC, the sole general partner of Domain Partners VI, L.P. and DP VI Associates, L.P. Pursuant to Instruction 4(b)(iv) of Form 4, the Reporting Person has elected to report as indirectly beneficially owned the entire number of securities owned by each such entity, however she disclaims beneficial ownership of any securities, and any proceeds thereof, that exceed her pecuniary interest therein and/or that are not actually distributed to her.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(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).

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