Leading Innovation in Treatment of Epilepsy and Neuropsychiatric Disorders

February 2015

1 Safe Harbor Statement

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. Words such as “may,” “will,” “expect,” “anticipate,” “estimate,” “intend,” 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 develop and commercialize ganaxolone; status, timing and results of preclinical studies and clinical trials; the potential benefits of ganaxolone; the timing of seeking regulatory approval of ganaxolone; our ability to obtain and maintain regulatory approval; our estimates of expenses and future revenue and profitability; our estimates regarding our capital requirements and our needs for additional financing; our plans to develop and market ganaxolone and the timing of our development programs; our estimates of the size of the potential markets for ganaxolone; our selection and licensing of ganaxolone; our ability to attract collaborators with acceptable development, regulatory and commercial expertise; the benefits to be derived from corporate collaborations, license agreements, and other collaborative or acquisition efforts, including those relating to the development and commercialization of ganaxolone; sources of revenue, including contributions from corporate collaborations, license agreements, and other collaborative efforts for the development and commercialization of products; our ability to create an effective sales and marketing infrastructure if we elect to market and sell ganaxolone directly; the rate and degree of market acceptance of ganaxolone; the timing and amount or reimbursement for ganaxolone; the success of other competing therapies that may become available; the manufacturing capacity for ganaxolone; our intellectual property position; our ability to maintain and protect our intellectual property rights; our results of operations, financial condition, liquidity, prospects, and growth strategies; our spending of the proceeds from this offering; the industry in which we operate; and the trends that may affect the industry or us. We undertake 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 the business of the company in general, see Marinus's Prospectus dated August 1, 2014 and other filings by the company with the U.S. Securities and Exchange Commission. You may access these documents for free by visiting EDGAR on the SEC web site at www.sec.gov.

2 Ganaxolone: First-in-Class Therapeutic for Epilepsy and Neuropsychiatric Disorders

- Synthetic analog of endogenous allopregnanolone New - Novel modulator at GABA receptors, a well characterized target for Mechanism A anti-seizure and antianxiety effects

- $14B global epilepsy market; $4B potential in drug-resistant seizures Large Epilepsy Market - Phase 3 study ongoing in adults with drug-resistant seizures

- Phase 2 studies on-going in pediatric indications PCDH19 and Fragile X Orphan Opportunities - Genetically defined patient populations with high unmet needs

- Positive Phase 2 study completed in drug-resistant seizure patients Robust Data - POC achieved as monotherapy and in pediatric seizures - Demonstrated safety profile in >1000 subjects

- Issued patents covering nanoparticle composition (through 2026), solid Patent and liquid formulations, API method - low cost synthesis process (through Protection 2029)

3 Diversified Clinical Stage Opportunities Large and Pediatric Orphan Indications

Three clinical programs with data milestones anticipated in 2015

Ganaxolone Preclinical Phase 1 Phase 2 Phase 3

Epilepsy Adjunctive Treatment of Focal Onset (Oral Capsules) Epileptic Seizures

Pediatric Epilepsy PCDH19 Female Pediatric Epilepsy (Oral Liquid & Capsule) (orphan)

Developmental Behaviors in Fragile X Syndrome Disorders (orphan, grant funded) (Oral Liquid)

Ganaxolone, with its validated GABAA mechanism, has opportunities in both large and pediatric orphan indications and in chronic and acute care settings

4 Ganaxolone CLINICAL DEVELOPMENT PROGRAM

Large Market, Orphan Indication, Unserved Markets Unmet Needs

5 Epilepsy is a Large Market with 5 Million Patients in the US, EU, Japan

3.0M patients (Focal onset seizures only) # of patients Drugs

1st line Monotherapy Carbamazepine 1.8 million (60%) Phenytoin 2nd line Valproic Acid Monotherapy

New Add on MOA AED 1.2 million (40%) Levetiracetam “Polypharmacy” Lamotrigine Topiramate Dose Add on Titration AED > 1 million patients Oxcarbazepine Efficacy resistant to existing Pregabalin Safety Zonisamide DDI drugs Lacosamide

Initial Ganaxolone Target Market

Source: AES, Decision Resources 2013 , POS/therapy data UCB, Investor presentation 6 Ganaxolone is Well-Positioned to Address Unmet Needs in Adult and Pediatric Epilepsy

Benefits to  First-in-class with potential to be leader in adjunctive Address Unmet therapy for focal onset seizures Needs1: – 20% seizure reduction (p= 0.014) in drug-resistant population

• Increased – Consistent with Phase 2 efficacy results for approved AEDs Efficacy

 Favorable safety profile (> 1,000 subjects) • Better – Good long-term safety record to date in both pediatric and Tolerability adult subjects with >2 years of dosing • No cardiovascular risk, urinary retention, behavioral • Reproductive side effects or weight gain observed with ganaxolone Safety

 Completed pharmacology and toxicology programs • Minimal Drug- support differentiated safety profile Drug Interactions – No organ or reproductive toxicity identified – Potential for Pregnancy Category B

1Datamonitor, May 2010 , Global Data Dec. 2010 7 New Anti-Epileptic Drugs Have a History of Commercial Success

Sales of AEDs as Adjunctive Therapy Post-launch ® ($ millions, WW sales, years post-launch) Vimpat success demonstrates unmet need $2,500  Novel MOA (Na channel) $2,000  Efficacy < Keppra

$1,500  UCB emphasizes novel MOA and “easy to take” $1,000  Vimpat® successful launch $500 – Priced at 50% premium to branded Keppra $0 0 1 2 3 4 5 6 7 8 9 10 – UCB estimates peak sales of Keppra Topamax Lamictal approximately $1.6B (€1.2B) Vimpat® Sales Since Launch – 150,000 patients prescribed Year ($ millions)(1)

2009 $ 63

2010 $176

2011 $303

2012 $430

2013 $546

(1) Bloomberg average yearly exchange rate used to convert EUR:USD Source: EvaluatePharma.com and equity research July 2009, UCB financials, Decision Resources 2013 8 Ganaxolone is Differentiated from Competition

Ganaxolone Keppra Vimpat Fycompa Target Profile(1) (2000) (2008) (2012)

PAM of extra-synaptic Binds to synaptic Slow inactivation of AMPA (glutamate) Mechanism and synaptic GABA A vesicle protein SV2A VSSC receptor antagonist receptors Reproductive Teratogenicity and Developmental Developmental No abnormalities, Toxicity, developmental toxicity, toxicity, toxicity, Category B Pregnancy Category C Category C Category C Category

Warning: Pts w/ CV conduction CV Risk No CV warning No CV warning No CV warning abnormalities or severe CV disease

Black Box: Serious Psychiatric Warning: Psychiatric No Psychiatric Low incidence (<2%) Psychiatric and Reactions Warning Side Effects Behavioral Reactions

Adjust dose in hepatic Dose adjustments in Renal and disease; monitor in Monitor dose in Dose adjustment in both; not renal disease; not Hepatic recommended in hepatic impairment renal impairment recommended in severe Impairment severe hepatic disease renal or hepatic disease New MOA, efficacy comparable to current and emerging market leaders and differentiation on safety/tolerability

(1) Based on pre-clinical and clinical data to date PAM: positive allosteric modulator 9 Physicians’ Intended Use of Ganaxolone

Physicians reported Uncontrolled focal onset seizure patients they would use ganaxolone for 16- Elderly or young (including children) patients 29% of existing patients to replace: Females of childbearing age or on oral contraceptives • Keppra (behavioral effects)

Patients with co-morbid depression and/or anxiety • Topamax (cognitive blunting) • Depakote (side Patients with metabolic issues effects) • Lamictal (very slow titration, side effects)

Source: Marinus Market Research 10 Ganaxolone is Designed to Modulate GABA through Synaptic and Extrasynaptic Receptors

 Ganaxolone is a synthetic analog of allopregnanolone − Unlike allopregnanolone, ganaxolone does not convert to

an active steroid GABAergic GABA Receptors Neuron  Ganaxolone is designed to Allopregnanolone Ganaxolone modulate over-excited neurons via GABA both extrasynaptic and synaptic

GABAA receptors

 Ganaxolone mechanism has been validated: − adult drug-resistant epilepsy − use as monotherapy − pediatric seizures Postsynaptic Neuron

11 Completed Phase 2 Study of Ganaxolone as Adjunctive Treatment in Drug-Resistant Adult Focal Onset Seizures

 N=147 randomized 2:1 (98 ganaxolone, 49 PBO; 1500mg/day) at 24 U.S. sites  Oral suspension dosed 500mg 3x/day  Highly refractory population − Mean ~25 yrs since diagnosis − ~75% on > 2 concomitant AEDs

Randomization Down titrate to exit Study 600 or enter OLE 601

Baseline Titration Maintenance

Wk -8 Wk 0 Wk 2 Wk 10 BL

 95% reached target 1500mg/day, 131 completers, 95% of eligible entered Open Label Extension (OLE)

12 Ganaxolone Demonstrated Statistically Significant Seizure Reduction in Phase 2 Study

% Seizure Reduction Over Baseline (ITT)  Statistically significant reduction in seizures from GNX PBO GNX-PBO baseline vs. placebo (US FDA n=98 n=49 Difference approvable efficacy endpoint) Mean -17.6% +2.0% 19.6% (SD) (48.9) (63.2) p=0.014  Secondary efficacy measures supported primary, including Median -26.0% -10.2% 15.7% Responder Analysis - proportion with 50% improvement over Responder Analysis (ITT) baseline (EU approvable 30 p= 0.057 efficacy endpoint) 25 20  Open-label extension study 23.5 26.3 PBO results supported findings in 15 double-blind study 10 14.6 13.0 GNX

% Responders % 5 0 Titr. + Maint. Maint. Only

Source: 1042- 600 CSR Tables 14.2.1.4.2, 14.2.3.2; 1042-0601 CSR Table 14.2.1.1 13 Ganaxolone has a Differentiating Tolerability and Safety Profile Based on Phase 2 Results Ganaxolone Placebo n=98 n=49 % Incidence SAEs 5 8 Safety Insights: % Subjects w/ AE 84 78  Likely to be preferred D/C due to AEs 7 6 for women due to Dizziness 16 8 reproductive safety & Fatigue 16 8 lack of steroidal side effects Sleepiness 13 2 Adverse Events Injury 17 22  Likely to be preferred >5% for for older patients due Headache 8 12 Ganaxolone to low risk for (Double Blind Abnormal 6 6 cardiovascular or renal Study) Coordination complications Convulsion (seizure) 5 8  Favorable safety and Nasopharyngitis 5 10 tolerability profile may Fall 5 12 make ganaxolone the preferred choice for Safety Tests – No trends or clinically meaningful changes in ECG, polypharmacy therapy Double Blind and chemistry or vital signs, no evidence of weight gain Open Label Study

Safety Profile was consistent in long-term extension to Phase 2

Source: 1042-600 Study CSR, 1042-0601 Table 14.3.1.2 14 Ganaxolone Demonstrated Efficacy as a Monotherapy in Drug-Resistant Subjects Undergoing Surgical Evaluation

 Double-blind, randomized, placebo-controlled, Phase 2 trial (N= 52) with subjects undergoing evaluation for surgical treatment of drug- resistant focal onset seizures

 Subjects were treated with ganaxolone monotherapy 625 mg 3x/day for 8 days

 Primary endpoint: “study exit due to emergence of seizures” -- 62% of ganaxolone subjects remained at Day 8 compared with 39% of placebo subjects (p=0.08)(1,2)

(1) As measured from Day 2 (Kaplan-Meier Curve) (2) On secondary endpoint, Discontinuation due to any reason, 50% GNX subjects remained compared with 25% PBO subjects (p=0.04) Source: Marinus CSR 1042-0104; Laxer et al., Epilepsia, 41(9):1187-1 194, 2000 15 Current Phase 3 Trial of Ganaxolone as Adjunctive Treatment of Focal Onset Seizures

Trial Design  Double-blind, randomized, two Cohort study  ~300 drug-resistant patients in Cohort 2  ~60 sites: US, Australia, Bulgaria, Germany, Poland and Russia  Primary efficacy endpoint: % change in seizure frequency from baseline through endpoint  Key secondary endpoint: Proportion of Responders (50% improvement over baseline)

Cohort 2 (N=300)

Randomization Period 2 wk. Ganaxolone: 12 weeks 1800 mg Baseline titration

(8 weeks) 2 wk. titration Placebo: 12 weeks

Cohort 1 DB treatment completed:  46 subjects randomized to ganaxolone or placebo  1-week titration + 8-week maintenance (ganaxolone 4 weeks 1200mg, 4 weeks 1800 mg or Placebo)  PK, efficacy, safety

16 Ganaxolone CLINICAL DEVELOPMENT PROGRAM

Large Market, Orphan Indication, Unserved Market Unmet Needs

17 PCDH19 Female Pediatric Epilepsy Orphan indication with onset in early childhood

 Mutation of PCDH19 gene associated with low levels of allopregnanolone, affecting 15-30K in US

 Genetic test available

 Disorder includes focal and generalized seizures, developmental delay, intellectual disability, behavioral problems

 Seizure clusters last from one day to weeks, sensitive to fever and illness

 Hospitalization often required

 In earlier trials of ganaxolone in children with intractable seizures, 41% (12/29) showed ≥50% improvement at study end (Week 8)

 Open-label, Phase 2 clinical trial (under epilepsy IND)

 ~10 females (2-10 yrs old), confirmed PCDH19 mutation

 Ganaxolone oral suspension or capsules administered up to 26 weeks

 Primary Endpoint: % change in seizure frequency per 28 days relative to baseline

18 Behaviors in Fragile X Syndrome Orphan indication linked to GABA dysfunction

 Mutation of fmr1 gene causes syndrome of intellectual disability, cognitive impairment, anxiety, seizures, over- sensitivity to stimuli

 Studies using the fmr1 knock-out mouse model confirm:

– Deficit in extrasynaptic GABAA receptors – Decrease in GABAergic enzymes and proteins

 Fragile X Syndrome (FXS) estimated to affect 100,000 children and adults in the U.S.

 Randomized, placebo-controlled, crossover, Phase 2 grant funded study: n=60; children & adolescents 6-17 years; doses up to 1800 mg/day Ganaxolone may increase signaling at existing receptors to normalize GABA-mediated inhibition

19 Our Strategy

Maximize value of ganaxolone as a first-in-class innovative therapeutic with a portfolio of diversified indications

Execute Expand Broaden Commer- Establish registra- orphan dose forms cialize in partners tion indications (IV) US Ex-US studies

20 Ganaxolone: First-in-Class Therapeutic for Epilepsy and Neuropsychiatric Disorders

- Synthetic analog of endogenous allopregnanolone New - Novel modulator at GABA receptors, a well characterized target for Mechanism A anti-seizure and antianxiety effects

- $14B global epilepsy market; $4B potential in drug-resistant seizures Large Epilepsy Market - Phase 3 study ongoing in adults with drug-resistant seizures

- Phase 2 studies on-going in pediatric indications PCDH19 and Fragile X Orphan Opportunities - Genetically defined patient populations with high unmet needs

- Positive Phase 2 study completed in drug-resistant seizure patients Robust Data - POC achieved as monotherapy and in pediatric seizures - Demonstrated safety profile in >1000 subjects

- Issued patents covering nanoparticle composition (through 2026), solid Patent and liquid formulations, API method - low cost synthesis process (through Protection 2029)

21 Leading Innovation in Treatment of Epilepsy and Neuropsychiatric Disorders

www.marinuspharma.com 484-801-4674

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