X0508 4 2024-06-18 0001267813 MARINUS PHARMACEUTICALS, INC. MRNS 0001573553 Fischer Seth H. Z. 5 RADNOR CORPORATE CENTER, SUITE 500 100 MATSONFORD RD RADNOR PA 19087 true false false false 0 Common Stock 2024-06-18 4 A 0 2300 0 A 12926 D Stock Option (Right to Buy) 1.40 2024-06-18 4 A 0 10450 0 A 2034-06-18 Common Stock 10450 10450 D Represents the grant of restricted stock units (RSUs). The RSUs vest in full on July 15, 2025, subject to the reporting person's continued service with Marinus Pharmaceuticals, Inc. (the Issuer). Each RSU represents the right to receive one share of common stock of the Issuer. The option vests and becomes exercisable in full on July 15, 2025, subject to the reporting person's continued service with the Issuer. /s/ Debra A. Mohollen, Attorney-in-Fact 2024-06-20