Form 8-K - Current report

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): May 8, 2024

Marinus Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)


Delaware	001-36576	20-0198082
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification No.)

, Radnor, PA

5 Radnor Corporate Center, Suite 500

100 Matsonford Rd, Radnor, PA

19087

(Address of principal executive offices)

(Zip Code)

Registrant’s telephone number, including area code: (484) 801-4670

__________________________________________________________________
(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:


☐		Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐		Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐		Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐		Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:


Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, par value $0.001	MRNS	Nasdaq Global Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 2.02. Results of Operations and Financial Condition.

On May 8, 2024, Marinus Pharmaceuticals, Inc. (the “Company”) issued a press release announcing its financial results for the quarter ended March 31, 2024 and certain other information. A copy of the press release is being furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference to this Item 2.02.

The information furnished pursuant to this Item 2.02 shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or otherwise subject to the liabilities of that section, nor shall it be deemed to be incorporated by reference into any of the Company’s filings with the Securities and Exchange Commission under the Exchange Act or the Securities Act of 1933, whether made before or after the date hereof, regardless of any general incorporation language in such a filing, except as expressly set forth by specific reference in such a filing. Except as required by law, the Company undertakes no duty or obligation to publicly update or revise the information so furnished.

Item 8.01. Other Events.

On May 8, 2024, the Company posted an updated corporate presentation on its website at www.marinuspharma.com. A copy of the corporate presentation is filed as Exhibit 99.2 to this Current Report on Form 8-K and is incorporated by reference to this Item 8.01.

Item 9.01. Financial Statements and Exhibits.

(d)Exhibits



Exhibit No.		Description
99.1		Press Release, dated May 8, 2024, of Marinus Pharmaceuticals, Inc.
99.2		Corporate Presentation, dated May 8, 2024.
104		The cover page from this Current Report on Form 8-K, formatted in Inline XBRL.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.


	MARINUS PHARMACEUTICALS, INC.

Date: May 8, 2024	/s/ Steven Pfanstiel
	Steven Pfanstiel
	Chief Operating Officer, Chief Financial Officer and Treasurer

Exhibit 99.1

Marinus Pharmaceuticals Provides Business Update and Reports First Quarter 2024 Financial Results

●

ZTALMY^® (ganaxolone) Q1 2024 net product revenue of $7.5 million representing strong growth of 125% versus Q1 2023

●

Increased full year 2024 projected U.S. ZTALMY net product revenues to between $33 and $35 million

●

Enrollment to be completed mid-May in the Phase 3 TrustTSC trial with topline data anticipated in the first half of Q4 2024

●

Topline results from the Phase 3 RAISE trial expected early summer 2024

●

Cost reduction plans implemented to extend cash runway into late Q1 2025; cash, cash equivalents and short-term investments of $113.3 million as of March 31, 2024

RADNOR, Pa. – May 8, 2024 – Marinus Pharmaceuticals, Inc. (Nasdaq: MRNS), a pharmaceutical company dedicated to the development of innovative therapeutics to treat seizure disorders, today reported business highlights and financial results for the first quarter ended March 31, 2024.

“Our unwavering commitment is to develop innovative treatment options for individuals with seizure disorders,” said Scott Braunstein, M.D., Chairman and Chief Executive Officer of Marinus. “With continued commercial success in CDD and a significant unmet need in drug-resistant epilepsies, we believe there is a robust market opportunity for the ZTALMY franchise. We are actively engaged with the tuberous sclerosis complex community, raising awareness and conducting comprehensive market research in preparation for a potential second half 2025 TSC launch.”

Dr. Braunstein continued, “We plan to announce the RAISE trial topline results this summer and to then engage the FDA to discuss a potential filing strategy. Additionally, we have been prudent in our spend and have implemented cost-reduction measures to extend our cash runway beyond the two upcoming topline data readouts.”

ZTALMY^®(ganaxolone) Oral Suspension CV

●

ZTALMY^® generated net product revenue of $7.5 million for the first quarter of 2024 representing 125% growth versus the first quarter of 2023

●

Increased full year 2024 projected U.S. ZTALMY net product revenues to between $33 and $35 million from a range of $32 and $34 million

●

Achieved profitability on the ZTALMY commercial investment in the first quarter of 2024, ahead of original target

●

Orion Corporation continues to prepare for commercial launches of ZTALMY in select European countries in the second half of 2024

o

Marinus is eligible to receive a €10 million payment on achievement of certain CDD launch milestones

●

Expect to expand ZTALMY access globally in the second half of 2024

Clinical Pipeline

“We are optimistic that we can replicate the success of our pivotal CDD trial of ZTALMY in the TrustTSC study, where we believe refinements made to the Phase 3 titration schedule and low discontinuation rates throughout the trial suggest improved tolerability,” said Joseph Hulihan, M.D., Chief Medical Officer. “Our pipeline is supported by clinical and preclinical data which has demonstrated ganaxolone’s potential in treating seizures resistant to other medications, attributed to its unique ability to modulate both synaptic and extrasynaptic GABA_A receptors. This is particularly valuable in indications such as TSC, where approximately 25% of patients suffer from highly refractory epilepsy.”

Dr. Hulihan added, “We have enrolled 100 patients in the RAISE trial and are preparing for topline results from the full dataset. We then plan to engage with regulatory authorities and RSE stakeholders to discuss the results and potential future development plans for IV ganaxolone.”

Tuberous Sclerosis Complex

●

Enrollment in the global Phase 3 TrustTSC trial of oral ganaxolone in tuberous sclerosis complex (TSC) expected to be completed mid-May of 2024

o

Topline data anticipated in the first half of the fourth quarter of 2024

o

Targeting submission of a supplemental New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) in April 2025 with priority review expected

o

Overall discontinuation rates remain low at approximately 7%

o

Vast majority of patients who have completed the double-blind portion of the trial have transitioned to open-label and remain on therapy

Other Rare Genetic Epilepsies

●

Marinus now anticipates initiating a proof-of-concept study with ZTALMY to treat a range of developmental and epileptic encephalopathies, including Lennox-Gastaut syndrome, in the first half of 2025, pending the TSC topline data

●

IND-enabling studies for a ganaxolone prodrug are now expected to be completed in the first half of 2025

Status Epilepticus

●

Enrolled 100 patients in the Phase 3 RAISE trial of intravenous (IV) ganaxolone in refractory status epilepticus (RSE) with topline results expected in early summer 2024

o

An interim analysis was conducted following enrollment of 83 patients; an independent Data Monitoring Committee recommended the trial may continue without modification

●

The RAISE topline results will inform potential future development of IV ganaxolone, including super refractory status epilepticus

●

Marinus has stopped the Phase 3 RAISE II trial in RSE; future development in RSE will be assessed following review of the RAISE topline data

Ganaxolone development in the RAISE trial is being supported in part by the Department of Health and Human Services; Administration for Strategic Preparedness and Response; Biomedical Advanced Research and Development Authority (BARDA) under contract number 75A50120C00159.

General Business and Financial Update

●

Increased full year 2024 projected U.S. ZTALMY net product revenues to between $33 and $35 million from a range of $32 and $34 million.

●

Company expects that cash, cash equivalents and short-term investments of $113.3 million as of March 31, 2024, inclusive of cost reduction plans, will be sufficient to fund the Company’s operating expenses, capital expenditure requirements and maintain the minimum cash balance of $15 million required under the Company’s debt facility into the first quarter of 2025.

●

The Company has implemented cost reduction plans designed to reduce operating costs while prioritizing advancement towards the Company's near-term goals. Marinus will focus its resources on the continued commercialization and development of ZTALMY, including the TrustTSC trial.

●

Initiated cost reduction activities:

o

Stopped clinical trial enrollment in the RAISE and RAISE II trials

o

Deferred IV ganaxolone manufacturing investments

o

Reduced the Company's workforce by approximately 20%

o

Additional cost reductions across both research and development (R&D) and general and administrative (G&A) functions

o

Other operational changes to increase overall efficiency of the Company’s operations

●

The cost reduction plans allow the Company to retain the appropriate personnel to assess the topline RAISE results and evaluate potential future development plans for IV ganaxolone.

●

The Company will continue to evaluate additional opportunities to further extend cash runway.

●

The Company now expects total GAAP operating expenses, inclusive of selling, general and administrative (SG&A) and R&D, in the range of $135 to $140 million, inclusive of expected stock-based compensation of approximately $20 million. These estimates include the recently initiated cost reduction plans which the Company expects to be fully realized in the third and fourth quarters of 2024.

Financial Results

●

Recognized $7.5 million in net product revenues for the three months ended March 31, 2024, as compared to $3.3 million for the three months ended March 31, 2023.

●

Recognized $0.2 million in Biomedical Advanced Research and Development Authority (BARDA) federal contract revenue for the three months ended March 31, 2024, as compared to $7.0 million for the three months ended March 31, 2023. The decrease was primarily driven by activity associated with start-up of the API onshoring initiative in the first quarter of 2023 and completion of the base period funding in the fourth quarter of 2023.

●

Research and development (R&D) expenses were $24.1 million for the three months ended March 31, 2024, as compared to $27.9 million for the same period in the prior

year; the decrease was due primarily to costs associated with start-up of the API onshoring effort in the first quarter of 2023.

●

Selling, general and administrative (SG&A) expenses were $18.6 million for the three months ended March 31, 2024, as compared to $15.2 million for the same period in the prior year; the primary drivers of the increase were increased commercial spending and headcount costs in the first quarter of 2024.

●

The Company had a net loss of $38.7 million for the three months ended March 31, 2024; cash used in operating activities decreased to $37.5 million for the three months ended March 31, 2024, compared to $41.5 million for the same period a year ago.

●

At March 31, 2024, the Company had cash, cash equivalents and short-term investments of $113.3 million, compared to cash, cash equivalents and short-term investments of $150.3 million at December 31, 2023.

Readers are referred to, and encouraged to read in its entirety, the Company’s Quarterly Report on Form 10-Q for the three months ended March 31, 2024, to be filed with the Securities and Exchange Commission, which includes further detail on the Company’s business plans, operations, financial condition, and results of operations.

Selected Financial Data (in thousands, except share and per share amounts)

	March 31, 2024 (unaudited)		December 31, 2023
ASSETS
Cash and cash equivalents	$	104,253	$	120,572
Short-term investments		9,000		29,716
Other assets		24,097		20,620
Total assets	$	137,350	$	170,908
LIABILITIES AND STOCKHOLDERS’ (DEFICIT) EQUITY
Current liabilities	$	42,758	$	40,624
Long term debt, net		58,072		61,423
Revenue interest financing payable, net		34,642		33,766
Other long-term liabilities		18,312		18,330
Total liabilities		153,784		154,143
Total stockholders’ (deficit) equity		(16,434)		16,765
Total liabilities and stockholders’ (deficit) equity	$	137,350	$	170,908

	Three Months Ended March 31,
	2024 (unaudited)			2023 (unaudited)
Revenue:
Product revenue, net	$	7,509		$	3,332
Federal contract revenue		152			7,048
Collaboration revenue		18			-
Total revenue	$	7,679		$	10,380

Expenses:
Research and development	$	24,118		$	27,933
Selling, general and administrative		18,626			15,204
Cost of product revenue		756			206
Total expenses:	$	43,500		$	43,343
Loss from operations		(35,821	)		(32,963	)
Interest income		1,462			2,343
Interest expense		(4,346	)		(4,147	)
Other income, net		36			37
Net loss applicable to common shareholders	$	(38,669	)	$	(34,730	)
Per share information:
Net loss per share of common stock—basic and diluted	$	(0.68	)	$	(0.67	)
Basic and diluted weighted average shares outstanding		56,851,811			51,769,685

Other comprehensive income (loss)
Unrealized gain on available-for-sale securities		20			74
Total comprehensive loss	$	(38,649	)	$	(34,656)

About Marinus Pharmaceuticals

Marinus is a commercial-stage pharmaceutical company dedicated to the development of innovative therapeutics for seizure disorders. The Company first introduced FDA-approved prescription medication ZTALMY^® (ganaxolone) oral suspension CV in the U.S. in 2022 and continues to invest in the potential of ganaxolone in IV and oral formulations to maximize therapeutic reach for adult and pediatric patients in acute and chronic care settings. For more information, visit www.marinuspharma.com.

Forward-Looking Statements

To the extent that statements contained in this press release are not descriptions of historical facts regarding Marinus, they are forward-looking statements reflecting the current beliefs and expectations of management made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Words such as "may", "will", "expect", "anticipate", "estimate", "intend", "believe", and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. Examples of forward-looking statements contained in this press release include,

among others, statements regarding our commercialization and marketing plans for ZTALMY; our net product revenue guidance; the potential benefits ZTALMY will provide for physicians and patients; statements regarding our expected clinical development plans, enrollment in our clinical trials, regulatory communications and submissions for ganaxolone, and the timing thereof; our expected data readouts; our expected cash runway; our expectations and beliefs regarding the FDA and EMA with respect to our product candidates; our expectations regarding the development of new formulations and prodrug candidates; our expectations regarding our strategic partners; the expectation that the results from the RAISE trial will be used to determine whether to continue development of IV ganaxolone; expectation that the implemented cost reduction plans will reduce operating costs while prioritizing advancement towards the Company's near-term goals; our financial projections; the potential safety and efficacy of ganaxolone, as well as its therapeutic potential in a number of indications; and other statements regarding the company's future operations, financial performance, financial position, prospects, objectives and other future event.

Forward-looking statements in this press release involve substantial risks and uncertainties that could cause our clinical development programs, future results, performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the Company’s ability to continue as a going concern; unexpected market acceptance, payor coverage or future prescriptions and revenue generated by ZTALMY; unexpected actions by the FDA or other regulatory agencies with respect to our products; competitive conditions and unexpected adverse events or patient outcomes from being treated with ZTALMY, uncertainties and delays relating to the design, enrollment, completion, and results of clinical trials; unanticipated costs and expenses; the company’s cash and cash equivalents may not be sufficient to support our operating plan for as long as anticipated; our ability to comply with the FDA’s requirement for additional post-marketing studies in the required time frames; the timing of regulatory filings for our other product candidates; clinical trial results may not support regulatory approval or further development in a specified indication or at all; actions or advice of the FDA or EMA may affect the design, initiation, timing, continuation and/or progress of clinical trials or result in the need for additional clinical trials; the size and growth potential of the markets for the company’s product candidates, and the company’s ability to service those markets; our ability to develop new formulations of ganaxolone or prodrugs; our ability to obtain, maintain, protect and defend intellectual property for our product candidates; the potential negative impact of third party patents on our or our collaborators’ ability to commercialize ganaxolone; delays, interruptions or failures in the manufacture and supply of our product candidate; the company’s expectations, projections and estimates regarding expenses, future revenue, capital requirements, and the availability of and the need for additional financing; the company’s ability to obtain additional funding to support its clinical development and commercial programs; the potential for our ex-US partners to breach their obligations under their respective agreements with us or terminate such agreements in accordance with their respective terms; the risk that drug product quality requirements may not support continued clinical investigation of our product candidates and result in delays or termination of such clinical trials and product approvals; and the availability or potential availability of alternative products or treatments for conditions targeted by us that could affect the availability or commercial potential of our product candidates. This list is not exhaustive and these and other risks are described in our periodic reports, including the annual report on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K, filed with or furnished to the Securities and Exchange Commission and available at www.sec.gov. Any forward-looking statements that we make in this press release speak only as of the date of this press release. We assume no obligation to update forward-looking statements whether as a result of new information, future events or otherwise, after the date of this press release.

Company Contacts

Investors

Sonya Weigle
SVP, IR, HR & Corporate Affairs

Marinus Pharmaceuticals, Inc.

sweigle@marinuspharma.com

Media

Molly Cameron
Director, Corporate Communications & Investor Relations

Marinus Pharmaceuticals, Inc.

mcameron@marinuspharma.com

Exhibit 99.2

Nasdaq: MRNS @MarinusPharma Photo Credit: Kelly Crews Photography Ryan (center) Living with CDKL5 deficiency disorder Corporate Presentation May 2024

©2024 Marinus Pharmaceuticals. All Rights Reserved I To the extent that statements contained in this presentation are not descriptions of historical facts regarding Marinus, they are forward-looking statements reflecting the current beliefs and expectations of management made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Words such as “may”, “will”, “expect”, “anticipate”, “estimate”, “intend”, “believe”, and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. Examples of forward-looking statements contained in this presentation include, among others, statements regarding our ability to continue as a going concern; our expected revenue and expenses; our commercialization plans for ZTALMY® and clinical development plans for ganaxolone, and the expected timing thereof; the clinical development schedule and milestones; expected dosing in our clinical trials; our expected timing to begin and complete enrollment in our clinical trials; the expected trial design, target patient population and endpoints for our clinical trials; interpretation of scientific basis for ganaxolone use; timing for availability and release of data; the potential safety and efficacy and therapeutic potential of ganaxolone; timing and expectations regarding the potential benefits ZTALMY will provide for patients and physicians; timing and expectations regarding regulatory communications and submissions; expectations regarding our agreement with BARDA; expectations regarding our current and contemplated collaborations with ex-US partners, including the potential benefits and timing thereof; expectations regarding the potential market opportunities for our product candidates; expectations regarding patient populations; expectations regarding potential commercial alliances; expectations regarding our cash flow, cash projections and cash runway; expectations regarding the continued uptake of ZTALMY; expectations regarding the impact of on-going scientific and clinical research investments on our product candidates; expectations regarding operating margins; plans for commercial investments; plans to leverage existing our infrastructure and knowledge; our plans for the global access program and the expected benefits and timing thereof; and our expectations regarding future opportunities of oral and IV ganaxolone. Forward-looking statements in this presentation involve substantial risks and uncertainties that could cause our clinical development programs, future results, performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, uncertainties and delays relating to patient and physician acceptance of ZTALMY; our ability to obtain adequate market access for ZTALMY; our ability to comply with the U.S. Food and Drug Administration’s (“FDA”) requirement for additional post-market studies in the required timeframes; the timing of regulatory filings; the potential that regulatory authorities, including the FDA and the European Medicines Agency (“EMA”), may not grant or may delay approval for our product candidates; uncertainties and delays relating to the design, enrollment, completion, and results of clinical trials; unanticipated costs and expenses; early clinical trials may not be indicative of the results in later clinical trials; clinical trial results may not support regulatory approval or further development in a specified indication or at all; actions or advice of the FDA or EMA may affect the design, initiation, timing, continuation and/or progress of clinical trials or result in the need for additional clinical trials; our ability to obtain and maintain regulatory approval for our product candidates; our ability to obtain, maintain, protect and defend intellectual property for our product candidates; the potential negative impact of third party patents on our collaborators’ or our ability to commercialize ganaxolone; delays, interruptions or failures in the manufacture and supply of our product candidates; the size and growth potential of the markets for our product candidates, and our ability to service those markets; our cash and cash equivalents may not be sufficient to support our operating plan for as long as anticipated; our expectations, projections and estimates regarding expenses, future revenue, capital requirements, and the availability of and the need for additional financing; our ability to obtain additional funding to support our commercial and clinical development programs; our dependence on ex-US partners to commercialize ZTALMY outside of the US; the potential for our ex-US partners to breach our collaboration agreements or terminate the agreements; and the availability or potential availability of alternative products or treatments for conditions targeted by us that could affect the availability or commercial potential of our product candidates. Marinus undertakes no obligation to update or revise any forward-looking statements. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to our business in general, see filings we have made with the Securities and Exchange Commission. You may access these documents for free by visiting EDGAR on the SEC web site at www.sec.gov. Safe Harbor Statement 2

©2024 Marinus Pharmaceuticals. All Rights Reserved I Ganaxolone Development Pipeline 3 Ganaxolone is a positive allosteric GABAA receptor modulator with a well-defined MOA designed to treat patients suffering from seizure disorders. Ganaxolone is designed to modulate both synaptic and extrasynaptic GABAA receptors to calm over-excited neurons. Ongoing trial Planned future trial PDUFA date March 2022 MAA filing validation Q4 2021 Oral Suspension Intravenous Oral Suspension CDKL5 Deficiency Disorder FDA & EMA approved Topline data early summer 2024 Topline data first half of Q4 2024 Refractory Status Epilepticus RAISE Trial Tuberous Sclerosis Complex TrustTSC Trial Phase 1 Phase 2 Phase 3 Approved Anticipated Milestones Trial to begin 1H 2025 Developmental Epileptic Encephalopathies Including Lennox-Gastaut Syndrome Oral Suspension

©2024 Marinus Pharmaceuticals. All Rights Reserved I Program Indication 1H 2024 2H 2024 1H 2025 2H 2025 CDKL5 deficiency disorder Achieved profitability* Tuberous sclerosis complex Complete Phase 3 TrustTSC enrollment Phase 3 TrustTSC readout Potential filing for FDA Approval Potential Launch Developmental and epileptic Encephalopathies Begin enrollment of Phase 2 trial IV Ganaxolone Refractory status epilepticus Phase 3 RAISE enrollment completed Phase 3 RAISE readout Second-Gen Program Lennox-Gastaut syndrome IND Expected Significant Near-term Milestones Build on Commercial Success 4 Two Topline Data Readouts Expected Before Year-End *on ZTALMY commercial investment

Commercial Overview Not for promotional use

©2024 Marinus Pharmaceuticals. All Rights Reserved I ZTALMY® Has the Potential to Significantly Advance Epilepsy Treatment 6 Differentiated MOA addresses unmet need Well-characterized safety profile FDA-approved in CDD Scalable commercial infrastructure supports rapid expansion and adoption Significant commercial opportunity CDD: CDKL5 deficiency disorder; MOA: mechanism of action

©2024 Marinus Pharmaceuticals. All Rights Reserved I ZTALMY® Performance Metrics and Growth Drivers 7 U.S. net product revenue of $7.5M for the first quarter of 2024 >125% growth from Q1 2023 Continued strong new patient enrollments Continued growth of new prescribers driving demand Achieved profitability on the ZTALMY commercial investment in Q1 2024, ahead of original target Favorable reimbursement dynamics across all payers, including both commercial and government programs Not for promotional use Increased full year 2024 expected U.S. net product revenue to $33M-$35M Growth Opportunities: • >1,000 CDD patients identified through third-party data sources • Indication expansion, including TSC • Ex-U.S. launches (EU, MENA, China)

Tuberous Sclerosis Complex “Many individuals with TSC continue to experience uncontrolled seizures despite a cocktail of multiple antiepileptic drugs. Because new options are always needed, the TSC community welcomes clinical evaluation of new epilepsy treatments.” - Kari Luther Rosbeck, President & CEO of the Tuberous Sclerosis Alliance

©2024 Marinus Pharmaceuticals. All Rights Reserved I Tuberous Sclerosis Complex (TSC) 9 CAUSE • Defect or mutation of TSC1 and/or TSC2 genes INCIDENCE • ~1 in 6,000 live births1 COMMON SYMPTOMS • Seizures, cognitive impairment, behavioral difficulties, skin/kidney/lung abnormalities, etc. EPILEPSY IN TSC • Occurs in ~80-90% of those with TSC2 • Seizures typically begin within first year of life (infantile spasms and/or focal seizures)2 1. Hasbani DM & Crino PB 2018 Hand. Clin. Neurol. 2. Chu-Shore CJ et al. 2010 Epilepsia TSC is one of the most common genetic epilepsies often exhibiting highly refractory seizures despite existing therapies

©2024 Marinus Pharmaceuticals. All Rights Reserved I TSC Phase 2 Trial Results 10 * -200 -100 -80 -60 -40 -20 0 20 40 60 80 100 Percent reduction in TSC-associated seizure frequency =median 16.6% Secondary and Exploratory Analyses Primary Endpoint Results: 16.6% median reduction in TSC-associated seizures The most common adverse events (AEs) reported were somnolence, sedation and fatigue 17.4% (n=4) of patients discontinued due to AEs (total discontinuation rate: 26% (n=6)) 74% (n=17) of patients reported somnolence-related AEs 52% (n=12) of patients required dose adjustments One treatment-related serious adverse event (AE) of seizure was reported in the trial * Secondary endpoint Proportion of patients with a ≥50% reduction in TSC-associated seizure frequency Intent to Treat (n=23) +Cannabidiol (n=12) +Everolimus (n=11) 0 5 10 15 20 25 30 35 40 45 50 36.4 25.0 30.4 Percent of patients % % % Subjects with Focal Seizure Types (n=19) 0 10 20 30 25.2 Percent reduction in focal seizure frequency (median) %

©2024 Marinus Pharmaceuticals. All Rights Reserved I Phase 3 Protocol Refinements Informed by Phase 2 Tolerability 11 Phase 3 Slower titration initially, designed to optimize tolerability and improve efficacy No (n=6) Yes (n=17) 0 5 10 15 20 25 30 Somnolence-related AE Percentreduction in TSC-associated seizure frequency (median) Phase 2 Patients without somnolence related AEs experienced greater seizure reductions 0 7 14 21 28 35 0 50 10 150 20 250 Time (days) Modeled GNX Concentration (ng/mL) 300 Predicted GNX Concentration (Ph2 Titration) Predicted GNX Concentration (Ph3 Titration)

©2024 Marinus Pharmaceuticals. All Rights Reserved I Phase 3 Trial Overview 12 ► Enrollment: ~128 patients, targeting sites in the U.S., Western Europe, Canada, Israel, Australia and China • 90% powered to detect a 25% treatment difference • Statistical significance could be achieved with a treatment difference of approximately 15% • Similar powering assumptions and treatment group size to recent rare epilepsy trials (TSC, LGS, CDD, etc.) ► Primary Endpoint: Percent change in 28-day TSC-associated seizure frequency during 16-week treatment period compared to baseline ► Key Secondary Endpoints: Percent change in TSC-associated seizure frequency during 12-week maintenance period, 50% responder rate, and clinical global impression Ganaxolone Placebo Baseline (4 weeks) Titration (28 days) Maintenance (12 weeks) Eligible Patients with TSC R 1:1 Primary Endpoint Analysis Open-label Ganaxolone Double-blind Phase Upcoming Milestones • Enrollment to be completed mid-May with topline data expected first half of Q4 2024 • Targeting submission of a U.S. sNDA in April 2025 with priority review expected

©2024 Marinus Pharmaceuticals. All Rights Reserved I TrustTSC Baseline Demographics* 13 Age (mean [min-max]) 15 [1-50] Gender 52% male 48% female Failed Therapies* (mean) 4.8 Baseline Seizure Rate (median, per 28 days) 50 DB Discontinuation Rate** ~7% 2 discontinuations (<2%) due to somnolence-related adverse events **From blinded Phase 3 trial data as of May 2024 U.S. Undisclosed Australia Canada China France Germany Israel Spain UK Recruitment by Country Epidiolex®/ CBD mTor inhibitors (everolimus, sirolimus, tacrolimus) 27% 58% ASM: antiseizure medication; DB: double-blind All data are preliminary and may not reflect final trial results *Based on enrollment as of May 2024; failed therapies includes prior and concomitant treatment

©2024 Marinus Pharmaceuticals. All Rights Reserved I 14 Influential Advocacy Community Reflects the values and priorities of the TSC community and addresses the unique challenges associated with rare genetic epilepsy Significant Market Opportunity TSC can be readily diagnosed, and a substantial portion of patients have epilepsy that remains refractory Expand Upon Success in CDD Adapting our proven formula for achieving success on a larger scale to cater to the TSC market Rare Genetic Epilepsy Market Leader CDD ›››TSC Anticipated Commercial Expansion into Tuberous Sclerosis Complex 14

©2024 Marinus Pharmaceuticals. All Rights Reserved I Addressable Patient Population ~2,000 12,700 44%4,5 CDD Patients6 Refractory* CDD Patients Diagnosed TSC Prevalence Epileptic TSC CDD 29,000 84%3 34,000 75%2 48,000 1/6000 incidence1 Unlocking a 4-5x Growth Opportunity for ZTALMY® in TSC 15 1TSC Alliance; 2Marinus ZS Opportunity Assessment, 2020 Market Research; 3Curatolo P - Epilepsy in TSC: Findings from the TOSCA Study; 4Chu-Shore CJ et al.The natural history of epilepsy in tuberous sclerosis complex. Epilepsia.; 563% (Chu-Shore) adjust -19% for Epidiolex & Afinitor Utilization 2010; 6Estimated from Symonds et al. Incidence and phenotypes of childhood-onset genetic epilepsies: a prospective population-based national cohort. Brain. 2019 Aug 1;142(8):2303-2318 *tried/failed 2+ antiseizure medications 15

©2024 Marinus Pharmaceuticals. All Rights Reserved I Plans to Leverage Existing ZTALMY® Infrastructure Expected to Yield Significant Returns in TSC 16 16 COMMERCIAL INFRASTRUCTURE Addition of 12-16 RAMs to reach key targets, including 17 TSC COEs MARKET POSITIONING Distinct TSC positioning: First Phase 3 trial with Everolimus and Epidiolex as concomitant medications EXPANDED TARGETS • ~50% overlap with existing CDD call points • MSL engagements at 51% of TSC COEs/Clinics • 40% of CDD KOLs also treat TSC ACCESS STRATEGY • Expect rapid and broad payer access given reimbursement dynamics across all payers in CDD • Protected class under Medicare Part D • Payer channels are similar (Medicaid 45%, Medicare 20%, Commercial 35%) • Specialty pharmacy process delivers rapid and consistent fulfillment and support STRONG ADVOCACY PARTNERSHIPS • Community and caregiver education • Caregiver activation Existing ZTALMY CDD Commercial Organization PATIENT IDENTIFICATION High diagnosis rates and readily identifiable “refractory” patient populations with well established ICD-10 codes

©2024 Marinus Pharmaceuticals. All Rights Reserved I Significant Growth Potential with Expansion into Larger Indications 17 ~12k refractory patients in the U.S. ~48k patients in the U.S. ~2k patients in the U.S. CDKL5 Deficiency Disorder Approved in the U.S. and EU Tuberous Sclerosis Complex Potential U.S. Approval 2025 Lennox-Gastaut Syndrome Broad potential in refractory epilepsies Developmental and Epileptic Encephalopathies

Second Generation Product Development

©2024 Marinus Pharmaceuticals. All Rights Reserved I Second Generation Ganaxolone 19 Goals Target Oral Pharmacokinetic Profile Increase efficacy Consistent delivery to achieve target plasma concentration Improve tolerability Optimize PK profile to reduce Cmax-related adverse effects Reduce dosing frequency More sustained exposure to allow once- or twice-daily dosing Lower cost of goods Better absorption to reduce API requirements per dose Enhance IP protection Improve formulation characteristics to provide opportunity for new IP AUC Cmax Tmax MEC MTC Current profile Target profile Increase the proportion of time the plasma level exceeds a minimally effective concentration (MEC) Avoid a significant increase in peak level (Cmax) that would exceed the maximum tolerated concentration (MTC) Second-generation ganaxolone development approaches: • Reformulation • Prodrug

©2024 Marinus Pharmaceuticals. All Rights Reserved I Next Steps: Prodrug and Ganaxolone Reformulation 20 Ganaxolone Prodrug Oral prodrug candidate selected Goals: • Optimize PK parameters for efficacy, tolerability and dosing frequency • Increase absorption (oral), solubility (IV) Preclinical IND-enabling trials planned Clinical: IND to follow completion of planned preclinical studies Second generation ganaxolone formulation goals Phase 1 multiple ascending dose (MAD) study of a second generation ganaxolone formulation: • Preliminary results demonstrated linear kinetics through a wide dose range that could allow individualization of treatment in patients with refractory epilepsy • Expect to apply extended-release technologies to the formulation targeting consistent exposure to achieve once or twice daily dosing while allowing physicians to dose titrate to higher serum concentrations of ganaxolone • Linear kinetics • Achieve steady state 100-200 ng/mL • Minimize peak-trough variability • Allow once or twice daily dosing while maintaining adequate trough level at steady state (Average trough levels in Marigold study were ~88 ng/mL)

Status Epilepticus

©2024 Marinus Pharmaceuticals. All Rights Reserved I Status Epilepticus Overview 22 Status Epilepticus = Condition resulting from either the failure of the mechanisms responsible for seizure termination or from the initiation of mechanisms which lead to: • abnormally prolonged seizures (after time point t 1 ) • can have long-term consequences (after time point t2 ) 1. DeLorenzo RJ et al 1995 J Clin Neurophysiol 2. Naylor DE. Epilepsia Open. 2023 3. Rossetti AO, et al. J Neurol Neurosurg Psychiatry. 2006 4. Jayalakshmi S, et al. Seizure. 2015 5. Penberthy LT, et al. Seizure. 2005 6. Guterman EL, et al. JAMA Neurol 2021 • Disabling cognitive deficits3 • 2.9x increased risk for development of epilepsy3 Associated with significant morbidity in survivors: • Underlying SE etiology3 • More refractory SE4 • Therapeutic coma exposure3 • Increased age3 • Substantial direct healthcare cost5 especially as SE progresses6 Incidence of SE in the United States: ~150,000 SE episodes per year1 • Disabling cognitive deficits2 • Increased risk for development of epilepsy2 Increased mortality associated with: Significant healthcare utilization:

©2024 Marinus Pharmaceuticals. All Rights Reserved I Pharmacokinetics/Pharmacodynamics Well Suited for Acute SE Treatment 23 Experimental PK – plasma and brain1 Brain and plasma concentration after ganaxolone 3 mg/kg IM in mice Human PD – EEG changes2 EEG bispectral index in healthy volunteers following IV ganaxolone 1. Zolkowska D, Wu CY, Rogawski MA. Intramuscular allopregnanolone and ganaxolone in a mouse model of treatment‐resistant status epilepticus. Epilepsia. 2018 Oct;59:220-7. 2. Data on file, Marinus Pharmaceuticals, inc. Human PK2 Following 30 mg ganaxolone bolus (over 5 minutes): Cmax 1,240 ng/mL Tmax 0.08 hrs Ganaxolone activates the extrasynaptic GABAA receptor, is associated with high brain concentrations, and delivers a rapid onset of action.

©2024 Marinus Pharmaceuticals. All Rights Reserved I Treatment Period Loading Dose Maintenance Taper Phase 2 Refractory Status Epilepticus Trial (RSE) Design 24 • Diagnosis of convulsive or non-convulsive SE • Failed at least one 2nd line IV AED but had not progressed to 3rd line IV anesthetics Bolus plus continuous infusion 2-4 day infusion 18-hour taper Screening Post-treatment Follow-up 24 hour Weeks 2, 3, 4 SE Patients Cohort Dose of ganaxolone/day N Low 500mg/day 5 Medium 650mg/day 4 High 713mg/day 8 Goals of a new treatment Limitations of current treatments Endpoints • Rapid cessation • Maintenance of seizure control • Prevent progression to IV anesthetics • 1st line Benzodiazepines ineffective in 45%-50%; limited by cardiovascular and respiratory side effects • 2nd line Ineffective in over 50% of established SE; further decreased response in refractory SE • 3rd line IV Anesthetics: high morbidity, mortality ~35%; increased duration of hospitalization and costs of care • Primary: Percent of patients who did not require escalation of treatment with IV anesthetic within the first 24 hours after ganaxolone initiation • Secondary: Additional efficacy, safety and tolerability 8 males, 9 females Mean age: 57 years old (range: 23-88) 17 patients enrolled

©2024 Marinus Pharmaceuticals. All Rights Reserved I Phase 2 Trial Results Demonstrated Rapid Onset And Durability of Effect 25 Data presented at AES 2019 AEDs – antiepileptic drugs Cohort No escalation to IV anesthetics within 24 hours from infusion initiation (Primary Endpoint) Status-free through 24 hours from infusion initiation (investigator determination) No escalation to additional IV AEDs or IV anesthetics for status relapse at any time through 24 hours after ganaxolone discontinuation No SE Relapse at anytime during the 4-wk follow up period High (713 mg/day) (n=8) 100% (8 of 8) 88% (7 of 8) 100% (8 of 8) 100% (6 of 6) (1ET, 1 died) Medium (650 mg/day) (n=4) 100% (4 of 4) 100% (4 of 4) 75% (3 of 4) 67% (2 of 3) (1 ET) Low (500 mg/day) (n=5) 100% (5 of 5) 100% (5 of 5) 60% (3 of 5) 50% (1 of 2) (1 died) Immediate Prior AED Administered 4 Hours (mean) to ganaxolone treatment SE Cessation Occurred Rapidly in All Dose Groups (median = 5 minutes) Safety Summary: • 2 treatment emergent serious adverse events noted as severe sedation • 13 treatment emergent adverse events: 5 moderate (4 somnolence; 1 hypercarbia); 6 mild (2 hypotension, 2 somnolence, 1 urinary retention, 1 hypercarbia) Trial data published in Epilepsia

©2024 Marinus Pharmaceuticals. All Rights Reserved I RAISE: Phase 3 Trial in Refractory Status Epilepticus 26 STUDY POPULATION INTERVENTION CO-PRIMARY ENDPOINTS KEY SECONDARY ENDPOINTS Onset of Action: Proportion of patients with SE cessation within 30 minutes Durability of Effect: Proportion of patients with no progression to IV anesthesia for 36 hours Onset of Action: Time to SE cessation Durability of Effect: No progression to IV anesthesia for 72 hours Status epilepticus patients aged ≥12 years who have failed 2 or more antiseizure treatments for the acute treatment of SE* Background Standard of Care + IV Ganaxolone 1:1 randomization Background Standard of Care + Placebo DOSING REGIMEN • Interim analysis conducted at 2/3 of total enrollment (N=83) • DMC recommendation: Trial may continue without modification • Completed enrollment of 100 patients with topline results expected in early summer 2024 Interim Analysis and Topline Results

©2024 Marinus Pharmaceuticals. All Rights Reserved I ► SRSE-specific dosing approach • ↓Cmax but ↑ AUC • 3-month oral wean • Ganaxolone 833mg/day x48h ➛ 1,050mg/day x 168h • Captisol® 50gm/day ➛ 63gm/day Approach to SRSE 27 29 patients with SRSE treated with IV ganaxolone to date 14 with regimen similar to RSE dosing 15 with new regimen specific to SRSE 0 24 48 72 96 120 144 168 192 0 250 500 750 1000 Time (h) Simulated GNX Plasma Concentration (ng/mL) Simmulated plasma levels during SRSE treatment Simmulated plasma levels in RAISE trial 3-month oral taper

©2024 Marinus Pharmaceuticals. All Rights Reserved I Super Refractory Status Epilepticus: Ganaxolone Experience to Date 28 New onset refractory status epilepticus (NORSE) Febrile illness-related epilepsy syndrome (FIRES) Lennox-Gastaut syndrome PCDH-19 related epilepsy Autoimmune encephalitis Herpes encephalitis Vascular disorder Mitochondrial disorder Congenital malformation Post-traumatic (remote) Response Prior regimen New regimen Total SE resolution 5 (36%) 8 (53%) 13 (45%) Partial response 6 (21%) 3 (20%) 6 (21%) Did not respond 9 (43%) 3 (20%) 9 (31%) Unknown 0 1 (7%) 1 (3%) Total 14 15 29 Ages Diagnoses Outcomes Age range Number of patients 1-4 years 3 5-12 years 6 13-17 years 4 18 + 16 Total 29

Financial Update

©2024 Marinus Pharmaceuticals. All Rights Reserved I Financial Overview 30 Analyst Coverage*: Cantor Fitzgerald: Charles C. Duncan, Ph.D. T.D. Cowen: Joseph Thome, Ph.D. H.C. Wainwright & Co: Douglas Tsao Jefferies: Andrew Tsai JMP Securities: Jason N. Butler, Ph.D. Ladenburg Thalmann: Michael Higgins Oppenheimer: Jay Olson RBC: Brian Abrahams RW Baird: Brian Skorney Leerink Partners: Marc Goodman Truist: Joon Lee, M.D., Ph.D. *Note: Opinions, estimates, and forecasts of the individual analysts regarding Marinus do not represent opinions, estimates, and forecasts of Marinus. The listing above does not imply endorsement or concurrent with their information, conclusions, or recommendations. Nasdaq: MRNS 2024 Full Year Guidance Revenues: • U.S. ZTALMY Net Product Revenue: $33 - $35 million Operating Expenses • FY 2024 GAAP operating expenses (SG&A and R&D) of between $135 - $140 million; including ~$20 million of non-cash stock-based compensation Financial Summary (at Mar. 31, 2024): • $113.3 million in cash, cash equivalents, and short-term investments • Cash runway into Q1 2025 • $75 million in debt; interest only through May 2024, matures 2026 • 54.9 million shares outstanding; 68.0 million shares on a fully dilutive basis1 1 Fully dilutive total includes impact of pre-funded warrants and outstanding stock options and RSU’s

©2024 Marinus Pharmaceuticals. All Rights Reserved I Driving Global Access of ZTALMY® (ganaxolone) 31 Europe: Collaboration agreement with Orion Corporation for ganaxolone in CDD, TSC, RSE • Up to €90 million of development, commercial, and sales milestones1 ; tiered royalties in the low double-digits up to the high teens (oral suspension) and low 20s (IV) • Marinus is eligible to receive a €10 million payment on achievement of certain CDD launch milestones China: Collaboration agreement with Tenacia Biotechnology for ganaxolone in CDD, TSC, SE • Up to $256 million of development, commercial, and sales milestones2 ; tiered double-digit royalties MENA: Distribution agreement with Biologix Fzco for ganaxolone • Revenue sharing arrangement with regulatory milestones Marinus Access Program Program initiated in Q4 2023 to expand global access to ZTALMY in non-partnered markets for appropriate patients with seizures associated with CDD 1Subject to achievement of certain clinical and commercial launch milestones related to CDD, TSC, and RSE and annualized sales thresholds for the oral and IV products 2Subject to achievement of regulatory approvals for CDD and TSC

Intellectual Property

©2024 Marinus Pharmaceuticals. All Rights Reserved I Multiple Layers Of Potential Protection 33 Orphan drug designations for CDD and PCDH19 provide 7 and 10 years regulatory exclusivity in U.S. and EU, respectively. Orphan drug designation for SE provides 7 years regulatory exclusivity in U.S. U.S. Patents/ Patent Applications Expiration Date Status Epilepticus Method of Use Patent granted on clinical regimen 2040 Patent granted on clinical regimen using broader ganaxolone dosing 2040 Applications pending on dosing regimens for SRSE and ESE 2041/2042 Formulation Licensed Captisol® patents Through 2033 Applications pending on IV formulation 2036 CDKL5 Deficiency Disorder Method of Use Patent granted (licensed) for method of treating CDKL5 deficiency disorder 2037 Application pending on dosing regimen 2038/2041/2042 Formulation Patents granted (oral suspension) 2031 (if PTE granted) Tuberous Sclerosis Complex Method of Use Patent granted on a method of treating TSC-related epilepsy 2040 Application pending on new dosing regimens 2041/2042 Formulation Patents granted (oral suspension) 2031 (if PTE granted) Second Generation Ganaxolone Formulation Application pending on second generation formulations 2042/2043

Appendix

©2024 Marinus Pharmaceuticals. All Rights Reserved I A Comprehensive Commercial Strategy to Grow the ZTALMY® Brand 35 Patient identification Activate the caregiver community Focused education to HCPs to establish ZTALMY as the standard of care for CDD seizure management Continuously enhance the patient experience • Elevate by educating HCPs on the importance of determining the genetic etiology of patients with refractory epilepsy syndromes • Increased investment in third party data expected to allow targeting of approximately 2x more CDD patients • Inspire through newly added “Shining Moments ” educational programing delivered directly to the caregiver community focused on ZTALMY and CDD the community • Promotional education targeted to HCPs with a high propensity of having CDD patients and prescribing ZTALMY • Data driven analytics and HCP segmentation strategies to deliver the right message, to the right HCP, at the right time • Refine the ZTALMYOne patient support program to meet the evolving needs of the CDD community Drive best in class practices, establish Marinus as a leader in refractory epilepsy, and build capabilities for future launches Not for promotional use

©2024 Marinus Pharmaceuticals. All Rights Reserved I 36 Ganaxolone Placebo 0 10 20 30 40 Median Percent Reduction 28-day Frequency of Major Motor Seizures 30.7% 6.9% *Wilcoxon Rank-Sum Test **Hodges-Lehman Estimate of Median Dif erence Patients taking ganaxolone experienced a significant reduction in seizure frequency Ganaxolone reduced the frequency of monthly major motor seizures by a median of 30.7% compared with 6.9% for placebo (p=0.0036)* Δ = 27.1% (47.9 - 9.6)** *Hodges-Lehmann estimate of median difference (95% confidence interval) **Wilcoxon rank-sum test Phase 3 Marigold data published in The Lancet Neurology First international CDKL5 guidelines published in Frontiers in Neurology Phase 3 CDD Marigold Trial Data and Safety Summary Not for promotional use Treatment Emergent Adverse Events (TEAE) Preferred Term Placebo (n=51) Ganaxolone (n=50) Any TEAE, n (%) 45 (88.2) 43 (86.0) Somnolence 8 (15.7) 18 (36.0) Pyrexia 4 (7.8) 9 (18.0) Upper Respiratory Tract Infection 3 (5.9) 5 (10.0) Constipation 3 (5.9) 3 (6.0) Salivary Hypersecretion 1 (2.0) 3 (6.0) Sedation 2 (3.9) 3 (6.0) Includes AEs that occurred >5% of subjects in ganaxolone arm and ganaxolone > placebo Preferred Term Placebo (n=51) Ganaxolone (n=50) Any Serious TEAE, n (%) 5 (9.8) 6 (12.0) Bronchitis 0 (0.0) 1 (2.0) Rhinovirus Infection 0 (0.0) 1 (2.0) Urinary Tract Infection 0 (0.0) 1 (2.0) Pneumonia Mycoplasmal 1 (2.0) 0 (0.0) Pneumonia Viral 1 (2.0) 0 (0.0) Respiratory Syncytial Virus Bronchiolitis 1 (2.0) 0 (0.0) Oxygen Saturation Decreased 0 (0.0) 1 (2.0) Food Refusal 0 (0.0) 1 (2.0) Pneumonia Aspiration 0 (0.0) 1 (2.0) Hypoxia 1 (2.0) 0 (0.0) Faecaloma 1 (2.0) 0 (0.0) Hypotonia 1 (2.0) 0 (0.0) Seizure 1 (2.0) 0 (0.0) Unresponsive to Stimuli 1 (2.0) 0 (0.0) Serious Treatment Emergent Adverse Events

©2024 Marinus Pharmaceuticals. All Rights Reserved I Average Ganaxolone Levels Correlate with Seizure Reduction 37 • Logarithms of plasma ganaxolone level and percentage change in major motor seizure frequency were negatively correlated • Patients in the Medium and High ganaxolone level groups had an average ganaxolone concentration of 120 ng/mL and a median 38.5% reduction in seizure frequency • Incidence of CNS-related adverse events was similar across ganaxlone dose level groups Loge percentage change in major motor seizure frequency was calculated as loge (percentage change + 100) 3.0 3.5 4.0 4.5 5.0 5.5 6.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Loge GNX Level (ng/mL) Loge Percent Change Major Motor Seizure Frequency Equivalent % Change in Major Motor Seizure Frequency r = -0.512 p = 0.001 *Pearson correlation * 145 48.4 -10.0 -45.4 -66.9 -79.9 -87.8 Equivalent GNX Level (ng/mL) 20.1 33.1 54.6 90.0 148 245 403 Low (40 ng/m L*) Medium (70 ng/m L*) High (170 ng/m L*) -100 -75 -50 -25 0 25 50 75 100 Percent Change in Major Motor Seizure Frequency **p = 0.01 *m ean GNX level w it h in Grou p **Kru skal-W allis Test n =13 n =13 n =12 Goal of reformulation is to drive consistent plasma ganaxolone levels to the mid- and upper-end of the target range

©2024 Marinus Pharmaceuticals. All Rights Reserved I Patients who remained in the clinical trial at 2 years experienced sustained reduction in MMSF1 ► Following the pivotal trial, 88 out of 101 patients entered an open-label extension study to evaluate the ongoing safety and efficacy of ZTALMY.1 ► The primary objective of the OLE was to collect additional safety and tolerability data. Safety findings were consistent with the double-blind phase; no new safety findings had emerged at the time of analysis. 1,2 ► Additional efficacy assessments were also performed. Open-label design and small sample size preclude conclusions about efficacy. 38 Reduction in monthly major motor seizure frequency through 2 years of the OLE* Phase 3 Open Label Extension Data in CDD Not for promotional use Patients achieved average seizure reductions of approximately 50% at two years of treatment *Data as of June 30, 2022 1. Data on file. Marinus Pharmaceuticals, Inc. 2. Specchio N, Amin S, Hulihan J, et al. Extended duration safety and efficacy of ganaxolone for the treatment of CDKL5 deficiency disorder: preliminary open-label extension analysis (Marigold Study). American Epilepsy Society. Dec 4-8, 2020. Virtual conference. Trial data published in Epilepsia

©2024 Marinus Pharmaceuticals. All Rights Reserved I Phase 1 Single Ascending Dose (SAD) Study 39 39 Mean Cmax (ng/mL) Mean AUC0-t (h*ng/mL) 41% 31% 38% 18% 18% 14% Study design Ganaxolone reformulation demonstrated linear kinetics at single doses from 100-1200 mg • Single dose PK study in healthy adult volunteers • Evaluated PK profile of 100, 200, 400, 600, 900 and 1200 mg of reformulated ganaxolone • Ganaxolone reformulation administered as sprinkle mixed with water or yogurt Test Reference Test Reference

Document and Entity Information	May 08, 2024
Document and Entity Information [Abstract]
Document Type	8-K
Document Period End Date	May 08, 2024
Entity File Number	001-36576
Entity Registrant Name	Marinus Pharmaceuticals, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-0198082
Entity Address State Or Province	PA
Entity Address, Address Line One	5 Radnor Corporate Center
Entity Address, Adress Line Two	Suite 500
Entity Address, Address Line Three	100 Matsonford Rd
Entity Address, City or Town	Radnor
Entity Address, Postal Zip Code	19087
City Area Code	484
Local Phone Number	801-4670
Title of 12(b) Security	Common Stock, par value $0.001
Trading Symbol	MRNS
Security Exchange Name	NASDAQ
Entity Emerging Growth Company	false
Entity Central Index Key	0001267813
Amendment Flag	false
Written Communications	false
Soliciting Material	false
Pre-commencement Tender Offer	false
Pre-commencement Issuer Tender Offer	false