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

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.

NCT Number	NCT07598708
Lead Sponsor	Centessa Pharmaceuticals (UK) Limited
Conditions	Narcolepsy Type 1, Narcolepsy Type 2
Enrollment	222 participants
Start Date	2026-05-29
Primary Completion	2027-09-30 (estimated)
Study Completion	2027-12-31 (estimated)
Updated on ClinicalTrials.gov	2026-08-11