Menlo Therapeutics Inc. June 2019

Developing Serlopitant, a Once-Daily Oral NK1 Receptor Antagonist for Pruritus Safe Harbor Statements

Special Note Regarding Forward-Looking Statements This presentation contains forward-looking statements, including statements about our plans to develop and commercialize our product candidates, our planned clinical trials for serlopitant, the timing of the availability of data from our clinical trials, the timing of our planned regulatory filings, the timing of and our ability to obtain and maintain regulatory approvals for serlopitant and the clinical utility of serlopitant, alone and as compared to other treatment options, the duration of patent protection, and other statements regarding strategy, future operations and plans, as well as assumptions underlying such statements. These statements involve substantial known and unknown risks, uncertainties and other factors, some of which are outside of our control, that may cause our actual results, levels of activity, performance or achievements to be materially different from the information expressed or implied by these forward- looking statements, including risks related to the clinical drug development process, the regulatory approval process, our reliance on third parties, and our ability to defend our intellectual property. We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. Additional information that could lead to material changes in our performance is contained in our filings with the U.S. Securities and Exchange Commission. The forward-looking statements in this presentation represent our views as of the date of this presentation. We anticipate that subsequent events and developments will cause our views to change. However, while we may elect to update these forward-looking statements at some point in the future, we have no current intention of doing so except to the extent required by applicable law. You should, therefore, not rely on these forward-looking statements as representing our views as of any date subsequent to the date of this presentation. Additional Information This presentation concerns a product that is under clinical investigation and which has not yet been approved for marketing by the U.S. Food and Drug Administration. It is currently limited by Federal law to investigational use, and no representation is made as to its safety or effectiveness for the purposes for which it is being investigated.

2 Menlo Investment Highlights

Serlopitant Phase 3 Development in 2 Pruritus Indications + Pipeline • Phase 3 nodularis • Granted Breakthrough Therapy Designation by the FDA • Phase 3 psoriasis • Phase 2 chronic pruritus of unknown origin

Success in Large, Placebo-controlled Phase 2 Pruritus Trials • Hit primary endpoint in 3 of 4 large placebo-controlled Phase 2 trials • In all 4 trials, at every time point, showed improvement in pruritus vs. placebo

Large Market Opportunity in Pruritus • PN: 300-600K patients in the U.S. with no approved therapy • Psoriasis: 7.5M patients diagnosed in the U.S.; >90% experience pruritus

Cash Runway through the end of 2020 • ~$122M cash as of 3/31/19

Solid IP • U.S. composition of matter to 2030, incl. extensions; methods of use to 2033

3 Serlopitant Pipeline and Upcoming Milestones Serlopitant is a highly selective small molecule inhibitor of NK1 Receptor, given once daily, as an oral tablet

Recent and Anticipated Phase Phase Phase Indication Milestones 1 2 3 2019 2020

Prurigo Nodularis Complete File enrollment NDA 2 Phase 3 trials ongoing

Psoriasis EOP2 Mtg Targeting to initiate Phase 3 program in 2019

Chronic Pruritus of Unknown Origin Complete enrollment Phase 2 initiated in January 2019

Trial Results Targeted initiation

4 Serlopitant Met Primary Endpoints in 3 of 4 Phase 2 Pruritus Trials and Demonstrated Improvement Over Placebo at Every Assessed Time Point Chronic Pruritus – TCP-101 – TCP-102 N=257 N=127 0 0 -9mm -10 -10 -15mm -20 -18mm -19mm -20 -30 -28.3% -25mm -34.1% -30 -36mm -40 -41.4% -42.5% -40 p=0.001* -50 p=0.013* VAS % Change fromVAS Baseline 0 1 2 3 4 5 6 0 2 4 6 8

Treatment Week Baseline from Change VAS Avg Treatment Week

Atopic – MTI-103 Psoriasis – MTI-109 N=484 N=203 33% 0 35% 30% -0.5 25% 21% -1 20% 15% * -1.5 p=0.028 -2.01 10% point Responder Rate Responder point

-2 - -2.25 p=0.17* 5%

NRS Change NRS from Baseline -2.5 0% - -2.32 p=0.11 NRS 4

0 2 4 6 - 0 Day 7 2 3 4 5 6 7 8 WI WI Treatment Week Treatment Week

*Primary endpoint Placebo Serlopitant 0.25 mg Serlopitant 1 mg Serlopitant 5 mg

5 Phase 2 Pruritus Studies – Serlopitant 5mg Responder Rate

Chronic Pruritus – TCP-101 Prurigo Nodularis – TCP-102 NRS 4-Point Responder Analysis (Baseline to Week 6) WI-NRS 4-Point Responder Analysis (Baseline to Week 8) 46% 47%

26% 23%

p=0.011 p=0.05 N=53 N=52 N=39 N=43

Atopic Dermatitis – MTI-103 Psoriasis – MTI-109 WI-NRS 4-Point Responder Analysis (Baseline to Week 6) WI-NRS 4-Point Responder Analysis (Baseline to Week 8) 33%

21% 21% 17%

p=0.17 p=0.028* N=158 N=160 N=101 N=102 Placebo Serlopitant 5mg *Primary endpoint.

6 Post Hoc Analyses of Completed Phase 2 Studies with Serlopitant

. Observed patterns in three completed Phase 2 studies in pruritus suggest the following types of patients respond better to serlopitant: • patients without inflammatory skin disease • older patients • patients with longer duration of pruritus

TCP-101 Post-hoc Analysis Results

Patients Without a Self-reported History of Patients with a Self-reported History of Inflammatory Skin Disease Inflammatory Skin Disease (1) 52.9% 46.2% 35.7% 33.3% 30.8% 29.6% Placebo 23.1% 22.2% at Week 6 Week at .25 mg point Responder Rate Responder point - 1 mg 5 mg NRS 4

N=27 N=26 N=27 N=18 N=26 N=26 N=28 N=34

(1) Includes patients with a self-reported history of cutaneous erythematosus, dermatitis, , , dry skin, dyshidrotic eczema, eczema, asteatotic eczema, nummular eczema, hand dermatitis, keratosis pilaris, lichen planus, mechanical urticaria, neurodermatitis, photosensitivity reaction, psoriasis, rash, erythematous rash, pruritic rash, seborrheic dermatitis, stasis dermatitis, and urticaria.

7 Consolidated Safety Summary of Serlopitant

. Evaluated in ~1,600 patients and shown to be well-tolerated, including in patients who received treatment up to one year . Most commonly reported treatment emergent adverse events across completed Phase 2 trials were: N=670 N=1261 TEAE Placebo (%) Serlopitant (%) Urinary Tract Infection 2.5% 4.8% Nasopharyngitis 3.7% 4.8% Diarrhea 3.4% 4.7% Headache 6.3% 4.4%

8 Serlopitant for Pruritus Associated with Prurigo Nodularis

Granted Breakthrough Therapy Designation by the FDA Phase 3 Program Ongoing Targeting 2020 NDA Filing

9 Prurigo Nodularis

Prurigo Nodularis (PN) Itch is the Primary Complaint Among 100% of PN Patients (1) . A chronic intensely pruritic Primary Complaint . Scratching leads to nodules which lead to more itch . No approved therapies in US or EU . No effective treatment options 0% 20% 40% 60% 80% 100% Itch

Secondary Complaint

0% 20% 40% 60% 80% 100%

Image courtesy of Prof. Sonja Stander, University Munster Sleep Pain / Burning / Bleeding Lesion / Appearance Other

(1) Company survey of 30 physicians who treat PN patients.

10 Limited Treatment Options Frustrate Patients and Physicians

Living with PN Diagnosis Treatment Management

• Constant itch is • Majority of patients • Treatments are not • Patients resign extremely bothersome diagnosed by always effective and themselves to live with and alters lifestyle dermatologists may have limitations it such as side effects • Severe patients may • “Trial and error” visit physician regularly - topical steroids (every 3-6 months) - antihistamines - intralesional injections - phototherapy - cryotherapy “It can be frustrating...very limited options to treat patients with. And even the options that “Yes, I had some type of relief. But, then, we have, sometimes don't help or help just a it started again. Every time I'd have a little bit. So, these patients you see on an little bit of relief, and then it seems like ongoing basis.” another trigger…” —Dermatologist —PN Patient

11 Attractive Commercial Opportunity in PN

300K – 600K patients in US (1)

~185K PN patients visit physicians each year (1) • 75% of PN patients are diagnosed by a dermatologist On therapy 2-6 months ~5K derms treat majority of PN per year (1) • patients $900 – $2,400 • Estimated 50 person field force could per month(2) reach high-prescribing derms • If approved, serlopitant would be 1st to market in PN

(1) Internal company estimates (2) Estimates based on company payer research and symptom relief analogs

12 PN Phase 2 Study: Data Consistent Across Multiple Endpoints

VAS – Primary Endpoint NRS 0 0 -9mm Placebo Placebo 5 mg 5 mg -10 -15mm -1 -1.5 serlopitant -1.9 serlopitant -20 -19mm -2 -2.4 -18mm * -30 -3 -2.4* -25mm * -36mm* -3.0* -3.7 * -4 -40 *p ≤ 0.05

from Baseline (mm) *p ≤ 0.05 from Baseline (points) (points) Baseline from Average Itch VAS Change Itch VAS Average bars show standard error Change NRS Itch Average bars show standard error -50 -5 0 2 4 6 8 10 0 2 4 6 8 10 Treatment Week Treatment Week

VAS - 40mm Responder Analysis (Baseline to Week 8) WI-NRS - 4 Point Responder Analysis (Baseline to Week 8) Average Itch VAS 54% Worst Itch NRS 47%

25% 26%

PlaceboPlacebo (N=63) VPD-737Serlopitant 5mg (N=64) Placebo Serlopitant p=0.002 Placebo (N=63) p=0.05 VPD-737 5mg (N=64)

13 Ongoing NULARIS Phase 3 Studies in Prurigo Nodularis

MTI-105 (US) & MTI-106 (EU)

N~280 per trial Serlopitant . PN of ≥6 weeks 5 mg . Trial 1: ~50 sites in US Primary endpoint . Trial 2: ~50 sites in Europe WI-NRS 4-point •Screening pruritus responder rate at ≥7 on WI-NRS Week 10 •Excludes active Placebo pruritic skin disease

2-4 week screening 10-week treatment 3-5 week follow-up

Over 160 patients enrolled in each trial as of 5/2/19 Data expected H1 2020

14 Serlopitant for Pruritus Associated with Psoriasis

Phase 3 Targeted for 2019

15 Psoriasis

. Psoriasis is a chronic inflammatory disease of multiple systems causing areas of thickened skin, itch and pain . No cure; treatments aim to improve symptoms . ~7.5M diagnosed in the U.S.(1)

Itch is the Most Frequent Current Standard of Care Does not Patient Complaint(2) Target Itch for Majority of Patients

Moderate-Severe Psoriasis(1) • 59% not treated • 9% biologics 25% Mod / (3) • 13% oral systemic Severe Psoriasis • 17% topicals 75% Mild Psoriasis

Mild Psoriasis(4) • 49% not treated • 42% topicals only

(1) Armstrong, Dermatol Ther 2016 (2) Quality of Life & Work Productivity Impairment among Psoriasis Patients: Findings from National Psoriasis Foundation Survey 2003–2011 (3) National Psoriasis Foundation (4) Armstrong, JAMA Derm 2013

16 Large Market Opportunity for Pruritus with Psoriasis

~7.5M diagnosed patients in the US (1)

74% with moderate to severe itch (2) (~5.5M)

~75% not well controlled with current therapy(2) (~4M) On therapy 4-8 months ~100-150 person field force per year (3) could target high- prescribing derms and $900 – $1,200 PCPs per month(3)

(1) Armstrong, Dermatol Ther 2016 (2) Company market research (3) Internal company estimates

17 PSORIXA Phase 2 Study in Psoriasis – Data Announced Dec. 2018

MTI-109

Serlopitant N=204 5 mg . Plaque-type PsO for Primary endpoint ≥6 months, ≤10% BSA . Pruritus ≥ 4 weeks WI-NRS 4-point . WI-NRS ≥ 7 w/in 24 responder rate at Week 8 hours of initial Placebo screening

2-4-week screening 8-week treatment 2-week follow-up

ClinicalTrials.gov ID: NCT03343639 PsO = Psoriasis

18 Psoriasis Phase 2 Study: Data Consistent Across Multiple Endpoints

Primary Endpoint - WI-NRS 4-Point Responder Analysis WI-NRS 4-Point Responder Analysis (Change from Baseline) (Baseline to Week 8) 35% 33% 30% 33% 25% 21% p=0.028 20% 15% 21% 10%

point Responder Rate Responder point 5% - 0% NRS 4 - WI p=0.028 *

Secondary Endpoint: WI-NRS 4-Point Responder Analysis WI-NRS (Change From Baseline) (Baseline to Week 4) 0 -0.5 21% -1 -1.5 -2.02 -2 11% -2.5 -2.77 -3 NRS Change NRS from Baseline -

p=0.039 WI *

*Follow-up visit at Week 10. Treatment through Week 8 only. Placebo Serlopitant 5mg

19 Serlopitant for Chronic Pruritus of Unknown Origin (CPUO)

Phase 2 Initiated in Q1 2019

20 Chronic Pruritus of Unknown Origin – A Large and Underserved Market

CPUO . Defined as pruritus lasting 6 weeks or longer, with no identified underlying disease • Also referred to as idiopathic pruritus or pruritus of undetermined origin • Overlaps with pruritus of the elderly / . Large market • 8-15%(1) of ~80M chronic pruritus patients(2) . No approved therapies in US or EU

In patients with severe pruritus that cannot be eliminated by identifying and treating an underlying cause…, topical therapy and lifestyle changes are unlikely to be sufficient, and systemic therapy should be considered. Given a paucity of data from randomized trials to evaluate various therapies, therapeutic choices are largely based on clinical experience and anecdotal reports. Sedating antihistamines are commonly used as first-line therapy but often have only modest efficacy….

Yosipovitch. NEJM. 2013

(1) Weisshaar, 2012 (2) Lifetime prevalence. Matterne, Acta Der Venereol, 2013

21 Phase 2 Study in CPUO

MTI-117

Serlopitant N~200 5 mg Primary endpoint . Chronic pruritus of unknown origin ≥6 WI-NRS 4-point months responder rate at . WI-NRS ≥7 prior to Placebo Week 10 screening

2- or 4-week 10-week treatment 3-week follow-up screening Primary endpoint at week 10

Data Expected mid-2020

22 Financial Information and Conclusion

23 Key Financial Highlights

Quarter Ended March 31, 2019

Cash & investments ~$122M

Operating expenses $20M Including $1M non-cash stock-based compensation

Common shares outstanding 23.7M

Forward-Looking Information

2019 Estimated operating expenses* $78M-$88M Including ~$3M-$6M non-cash stock-based compensation

Estimated cash runway Through 2020

*Provided 2/27/19

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