Sec Form 4 Filing - MAYLEBEN TIMOTHY M @ MARINUS PHARMACEUTICALS, INC. - 2024-10-10

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 MAYLEBEN TIMOTHY M 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 _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 5 RADNOR CORPORATE CENTER, SUITE 500, 100 MATSONFORD RD 3. Date of Earliest Transaction (MM/DD/YY) 10/10/2024 (Street) RADNOR, PA19087 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 25,837 ( 1 ) D Common Stock 6,900 ( 2 ) D Common Stock 18,937 ( 2 ) I By Trust ( 3 ) Common Stock 10/10/2024 G 4,980 ( 4 ) D $ 0 13,957 I By Trust ( 3 ) Common Stock 10/10/2024 G 1,660 ( 5 ) D $ 0 12,297 I By Trust ( 3 ) Common Stock 1,660 ( 5 ) I By Trust ( 5 ) Common Stock 10/10/2024 G 1,660 ( 6 ) D $ 0 10,637 I By Trust ( 3 ) Common Stock 1,660 ( 6 ) I By Trust ( 6 )

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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MAYLEBEN TIMOTHY M 5 RADNOR CORPORATE CENTER, SUITE 500 100 MATSONFORD RD RADNOR, PA19087 X Signatures /s/ Debra A. Mohollen, Attorney-in-Fact 10/15/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The reported amount reflects an adjustment to correct a clerical error that previously underreported the Reporting Person's holdings by 1,462 shares of Marinus Pharmaceuticals, Inc. (the "Issuer") common stock. No reportable transactions were omitted from previous filings in connection with the clerical error underlying this correction. ( 2 )The reported amounts reflect an adjustment to correct an administrative error that previously reported that all of the Reporting Person's holdings in Issuer common stock were owned directly by the Reporting Person. Such amounts have been corrected to reflect shares of Issuer common stock held by the Reporting Person directly (i.e., 6,900 shares underlying restricted stock units) and those held by the Timothy M. Mayleben Revocable Trust U/A/D 9/16/16 (i.e., 18,937 shares), of which the Reporting Person is the sole trustee. ( 3 )Represents shares of Issuer common stock held by the Timothy M. Mayleben Revocable Trust U/A/D 9/16/16, of which the Reporting Person is the sole trustee. ( 4 )On October 10, 2024, the Reporting Person transferred an aggregate of 4,980 shares of Issuer common stock from the Timothy M. Mayleben Revocable Trust U/A/D 9/16/16 to members of the Reporting Person's immediate family who do not share the Reporting Person's household for no consideration. ( 5 )On October 10, 2024, the Reporting Person transferred 1,660 shares of Issuer common stock from the Timothy M. Mayleben Revocable Trust U/A/D 9/16/16 to the Ellery A. Mayleben 2017 Trust for no consideration. The Reporting Person is trustee of the trust, and a member of his immediate family is the sole beneficiary of the trust. The Reporting Person disclaims beneficial ownership of these securities, and the filing of this report is not an admission that the Reporting Person is the beneficial owner of these securities for purposes of Section 16 or for any other purpose ( 6 )On October 10, 2024, the Reporting Person transferred 1,660 shares of Issuer common stock from the Timothy M. Mayleben Revocable Trust U/A/D 9/16/16 to the Kasey D. Evans 2017 Trust for no consideration. The Reporting Person is trustee of the trust, and a member of his immediate family is the sole beneficiary of the trust. The Reporting Person disclaims beneficial ownership of these securities, and the filing of this report is not an admission that the Reporting Person is the beneficial owner of these securities for purposes of Section 16 or for any other purpose.

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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