A Phase 3 Study to Evaluate the Efficacy and Safety of Samelisant in Patients With Narcolepsy

A Phase 3, Double-blind, Placebo-controlled, Parallel-group, Multicenter Study to Evaluate the Efficacy and Safety of Samelisant Compared to Placebo in Patients With Narcolepsy With or Without Cataplexy

The primary objective of this study is to evaluate the effect of Samelisant on excessive daytime sleepiness (EDS) after 12 weeks of treatment. In addition, the study aims to assess its effectiveness in influencing the weekly frequency of cataplexy episodes (sudden bouts of muscle weakness) that occur while the individual remains conscious. Other objectives include examining the impact of Samelisant on attention and alertness, overall quality of life, the spectrum of narcolepsy symptoms, and daily functioning, as well as evaluating its safety profile.

Study Overview

• Status: Not yet recruiting
• Conditions: Narcolepsy
• Intervention / Treatment: Drug: Samelisant; Drug: Placebo

Detailed Description

This is a Phase 3, randomized, double-blind, placebo-controlled, parallel-group, multicenter study to evaluate the efficacy and safety of Samelisant compared to placebo in the treatment of excessive daytime sleepiness in male or female participants ≥18 years of age with narcolepsy with and without cataplexy.

Participants will be randomized to receive either Samelisant or matching placebo tablets for duration of 12 weeks. Treatment allocation will remain blinded to both participants and investigators throughout the study, except in cases of medical necessity.

• Study Type: Interventional
• Enrollment (Estimated): 240
• Phase: Phase 3

Contacts and Locations

• Study Contact: Name: Study Contact; Phone Number: +9140 2319 3956; Email: narcolepsy@suven.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Key Inclusion Criteria:

1. Body mass index ranging from 18 to 45 kg/m2 (both inclusive).
2. Narcolepsy with or without cataplexy (Narcolepsy Type 1 [NT1] or Narcolepsy Type 2 [NT2]) based on the International Classification of Sleep Disorders 3-TR/ Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR) criteria for the diagnosis of narcolepsy.
3. For NT1 only, current continuing presence of cataplexy as defined by participant report for the last 3 months and have average of ≥4 weekly cataplexy events during the last 2 weeks of the washout period.
4. At the screening Visit and the Baseline Visit, participants who are not on treatment for EDS must have ESS scores ≥12 (as assessed with a look-back period of 1 week).
5. A mean MWT time of <12 minutes across the first 4 sessions at Baseline.
6. Willingness to complete the study protocol with full compliance with procedures and sign an informed consent form.
7. Able to show compliance with sleep diary entries for at least 5 times/week in the final 2 weeks of the screening Period (non-compliant participants will not be included).

Key Exclusion Criteria:

1. Median habitual wake-up time after 9 am as assessed by sleep diary, habitual sleep time of <6 h and median habitual bedtime past 1 am, as determined by sleep diary entries.
2. Use of any investigational therapy within the 30-day period (or 5 half-lives, whichever is longer) prior to enrollment.
3. History of (within past 3 months) or current substance use disorder involving illicit drugs, alcohol, or marijuana, as per DSM-5-TR criteria. Alcohol and/or recreational drugs use within 24 hours of study visits is strictly prohibited.
4. Excessive caffeine (defined as >600 mg/day) use at least 1 week prior to Baseline assessments and during the study.
5. Nicotine dependence that affects sleep (eg, a participant who routinely awakens at night to smoke).
6. If receiving stimulants, modafinil, oxybates, pitolisant, solriamfetol, bupropion or other treatments for narcolepsy, and unwilling or unable to complete weaning 2 weeks prior to Baseline visit (Day 1)
7. Clinically significant ECG abnormalities. Participants are excluded with a screening ECG Fridericia's correction of QT (QTcF) interval ≥450 msec for men and ≥470 msec for women obtained after 5-minute rest in a supine position using a digital ECG.
8. Concurrent use of hypnotics, tranquilizers, centrally acting H1 receptor antagonists, benzodiazepines, anticonvulsants, or clonidine, tricyclic antidepressants that have H1-antihistamine properties (clomipramine, protriptyline).
9. Adjunctive pharmacotherapy directed against cataplexy (including but not limited to venlafaxine, fluoxetine, and gamma hydroxybutyrate) is prohibited.
10. An occupation requiring variable shift work, variable wake times, night shifts, frequent overnight travel or expected overnight travel across > 3 time zones during the study which disrupts sleep patterns and working remotely leading to inconsistent sleep duration.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Samelisant Tablets	Drug: Samelisant; Tablet dosage form, once a day; Other Names: SUVN-G3031
Placebo Comparator: Placebo Tablets	Drug: Placebo; Matching placebo tablets, once a day

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change from Baseline in total Epworth Sleepiness Scale (ESS) score at Week 12	The ESS is a subjective measure of daytime sleepiness. The participant rates on a 4-point Likert scale how likely it is that he/she would doze in 8 different situations. Scoring of the answers is 0 to 3, with 0 being "would never doze" and 3 being "high chance of dozing". The total ESS score ranges from 0 to 24, with higher scores indicating greater daytime sleepiness. A decrease from baseline in ESS score represents improvement.	Baseline to Week 12

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change from Baseline for Maintenance of Wakefulness Test (MWT) score at Week 12	MWT is an objective test of sleepiness that evaluates a person's ability to remain awake under soporific conditions for a defined period of time. In the MWT, time from start of the test to the time point of falling asleep will be measured, the total score can range from 0 - 30 minutes. Higher values represent a better outcome.	Baseline to Week 12
Change from Baseline in the Clinical Global Impression of Severity of Illness (CGI-S) score as related to excessive daytime sleepiness (EDS) at Week 12	The CGI-S will be used to rate the severity of each participant's illness related to depressive narcolepsy or EDS symptoms on a 7-point scale, which includes the following gradations: 1 = normal, not at all ill; 2 = borderline ill; 3 = mildly ill; 4 = moderately ill; 5 = markedly ill; 6 = severely ill; and 7 = among the most extremely ill.	Baseline to Week 12
Change from Baseline in Weekly Cataplexy Rate (WCR) for Narcolepsy Type 1 (NT1) at Week 12	The WCR is a measure designed to evaluate the average weekly cataplexy frequency in participants who experience cataplexy. Participants who experience cataplexy will complete a daily diary to record the number of cataplexy attacks that occur each day beginning after discontinuation of narcolepsy medication and throughout the 12-week treatment phase of the study.	Baseline to Week 12
Change from Baseline in Narcolepsy Severity Scale for Clinical Trials (NSS-CT) score for Narcolepsy Type 1 (NT1) at Week 12	NSS-CT is a 15-item self-administered scale that requires participants to evaluate themselves with respect to symptoms and quantitative aspects of cataplexy/sleep attacks; impact on social, family, and work life, hallucinations; and sleep paralysis. Each item requires participants to choose among 4 or 6 options. Scores range from 0 to 57 points with the following breakdown: 0 to 14 (mild), 15 to 28 (moderate), 29 to 42 (severe), 43 to 57 (very severe), where degree of severity describes the impact of the narcolepsy on the participant's life.	Baseline to Week 12

Collaborators and Investigators

• Sponsor: Suven Life Sciences Limited

Study record dates

Study Major Dates

• Study Start (Estimated): June 19, 2026
• Primary Completion (Estimated): November 19, 2027
• Study Completion (Estimated): December 19, 2027

Study Registration Dates

• First Submitted: April 13, 2026
• First Submitted That Met QC Criteria: April 13, 2026
• First Posted (Actual): April 20, 2026

Study Record Updates

• Last Update Posted (Actual): April 20, 2026
• Last Update Submitted That Met QC Criteria: April 13, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Narcolepsy; Excessive Daytime Sleepiness; Cataplexy; SUVN-G3031; Samelisant
• Additional Relevant MeSH Terms: Nervous System Diseases; Mental Disorders; Sleep Wake Disorders; Sleep Disorders, Intrinsic; Dyssomnias; Disorders of Excessive Somnolence; Narcolepsy; Cataplexy; samelisant
• Other Study ID Numbers: CTP3S13031H3

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No