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A Study to Investigate the Effects of Cleminorexton Compared With Placebo in the Treatment of Participants With Central Disorders of Hypersomnolence

A Randomized, Double-blind, 3-Arm Parallel Design Study to Investigate the Efficacy, Safety, Tolerability, and Pharmacokinetics of Cleminorexton Compared With Placebo in Participants With Central Disorders of Hypersomnolence

Who can join

Ages 18 to 70 · All sexes

Key Inclusion Criteria:

* 18-70 years of age
* Body Mass Index (BMI) within the range ≥ 17.0 and ≤ 45 kg/m\^2 (inclusive)
* Meets the diagnostic criteria of Narcolepsy Type 1 (NT1) or Type 2 (NT2) according to International Classification of Sleep Disorders, 3rd edition, Text Revision edition (ICSD-3-TR) criteria
* Is willing and able to discontinue all medications used for the treatment of narcolepsy
* Is willing and able to adhere to additional protocol requirements

Key Exclusion Criteria:

* Medical disorder other than NT1 or NT2, that is associated with excessive daytime sleepiness (EDS)
* Presence of significant cardiovascular, pulmonary, gastrointestinal, hepatic, renal, hematological, malignancy, endocrine, neurological or psychiatric disease

About the study

Narcolepsy Type 1 (NT1) and Narcolepsy Type 2 (NT2) are rare conditions that make people feel very sleepy during the day (often referred to as excessive daytime sleepiness \[EDS\]). People living with these conditions might find it hard to stay alert and pay attention when they are at school, working, driving, or performing other daily activities.

While all conditions result in feeling sleepy, there are some differences in other common symptoms:

* NT1: People with NT1 often feel very tired during the day and experience cataplexy. Cataplexy is a sudden loss of muscle strength, which can cause someone to collapse or lose control of their muscles for a short time. This is often triggered by strong emotions, such as laughter or surprise. They may also have trouble sleeping well at night. * NT2: People with NT2 feel sleepy during the day, just like NT1, but they do not have cataplexy.

Orexin is a protein in the brain that helps coordinate a system that plays an important role in helping people to stay awake during the daytime. Cleminorexton is designed to mimic the action of orexin. The purpose of this study is to see how safe and tolerable cleminorexton is in NT1 and NT2 and learn about what the drug does to the body. Another goal of the study is to see if cleminorexton can help people with NT1 and NT2 feel less sleepy and make other symptoms better.

What is being tested

• cleminorexton (drug)
• Placebo (drug)

Sponsor: Centessa Pharmaceuticals (UK) Limited · Participants: 222 · Started: May 29, 2026

Contact the study team

• Centessa Pharmaceuticals · Phone: 617-468-5770

Official record on ClinicalTrials.gov — NCT07598708

Locations in the U.S.

Conditions

• Disorders of Excessive Somnolence
• Neurologic Diseases
• Mental Disorders
• Sleep Disorders
• Sleepiness
• Narcolepsy

From ClinicalTrials.gov, data retrieved Sep 29, 2026. Each study sets its own eligibility; the study team decides who can join.