Sec Form 4 Filing - Fischer Seth H. Z. @ MARINUS PHARMACEUTICALS, INC. - 2025-02-07

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 Fischer Seth H. Z. 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) 02/07/2025 (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 02/07/2025 D( 1 ) 12,707 D $ 0.55 ( 1 ) 2,300 ( 2 ) D Common Stock 02/11/2025 D( 1 ) 2,300 ( 3 ) D $ 0.55 ( 1 ) 0 D

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) $ 1.4 02/11/2025 D( 4 ) 10,450 ( 4 ) 06/18/2034 Common Stock 10,450 $ 0 0 D Stock Option (Right to Buy) $ 9.74 02/11/2025 D( 4 ) 20,900 ( 4 ) 01/18/2034 Common Stock 20,900 $ 0 0 D Stock Option (Right to Buy) $ 5.94 02/11/2025 D( 4 ) 16,200 ( 4 ) 01/26/2033 Common Stock 16,200 $ 0 0 D Stock Option (Right to Buy) $ 10.4 02/11/2025 D( 4 ) 12,375 ( 4 ) 02/04/2032 Common Stock 12,375 $ 0 0 D Stock Option (Right to Buy) $ 12.6 02/11/2025 D( 4 ) 16,500 ( 4 ) 01/15/2031 Common Stock 16,500 $ 0 0 D Stock Option (Right to Buy) $ 8.28 02/11/2025 D( 4 ) 25,000 ( 4 ) 01/08/2030 Common Stock 25,000 $ 0 0 D Stock Option (Right to Buy) $ 15.84 02/11/2025 D( 4 ) 8,750 ( 4 ) 02/26/2029 Common Stock 8,750 $ 0 0 D Stock Option (Right to Buy) $ 24.76 02/11/2025 D( 4 ) 8,750 ( 4 ) 12/06/2027 Common Stock 8,750 $ 0 0 D Stock Option (Right to Buy) $ 4.84 02/11/2025 D( 4 ) 2,625 ( 4 ) 01/17/2027 Common Stock 2,625 $ 0 0 D Stock Option (Right to Buy) $ 6.92 02/11/2025 D( 4 ) 3,850 ( 4 ) 09/06/2026 Common Stock 3,850 $ 0 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Fischer Seth H. Z. 5 RADNOR CORPORATE CENTER, SUITE 500 100 MATSONFORD RD RADNOR, PA19087 X Signatures /s/ Debra A. Mohollen, Attorney-in-Fact 02/11/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On December 29, 2024, the Issuer entered into an Agreement and Plan of Merger (the "Merger Agreement") with Immedica Pharma AB, a corporation organized and existing under the laws of Sweden ("Parent"), and Matador Subsidiary, Inc. a Delaware corporation and a wholly owned subsidiary of Parent ("Purchaser"). Pursuant to the terms of the Merger Agreement and the Offer (as defined in the Merger Agreement), each share of the Issuer's common stock (the "Common Stock") held by the Reporting Person was acquired, subject to adjustment, at a purchase price of $0.55 per share (the "Offer Price") in cash. ( 2 )The reported amount reflects an adjustment to correct a clerical error that previously underreported the Reporting Person's holdings by 2,081 shares of Common Stock. No reportable transactions were omitted from previous filings in connection with the clerical error underlying this correction. ( 3 )Represents 2,300 shares underlying Restricted Stock Units (the "RSUs"). Pursuant to the terms of the Merger Agreement, at the effective time of the merger (the "Effective Time"), each outstanding RSU was terminated in exchange for a lump sum cash payment equal to (i) the Offer Price multiplied by (ii) the number of shares of Common Stock underlying the RSU. ( 4 )Pursuant to the terms of the Merger Agreement, at the Effective Time, each outstanding out-of-the-money stock option (i.e., a stock option that has an exercise price per share that is greater than the Offer Price) was terminated and the Reporting Person was not entitled to any payment in respect thereof.

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