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Narcolepsy Type 1Phase 2/3NCT07598708

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

A Phase 2/3 study testing cleminorexton in people with Narcolepsy Type 1 and Narcolepsy Type 2, run by Centessa Pharmaceuticals (UK) Limited at 26 sites in United States.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
Search all trials

Trial summary

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]). Read more about this study

Who is it for?
Ages 18 to 70 years
Conditions the study is for
Narcolepsy Type 1, Narcolepsy Type 2
What is being tested?
cleminorexton
Type of treatment
Pill or oral medicine
Could I receive a placebo?
Yes, some participants may receive a placebo
How many people
222 participants
Where
26 sitesUnited States
Study dates
29 May 2026to 31 Dec 2027
Phase
Phase 2/3
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 to 70 years
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • 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

Who cannot join

  • 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

Trial locations and contacts

26 sites in 1 country. Contact the study team or a site near you to ask about taking part.

Centessa Pharmaceuticals contact

617-468-5770

ORX750trials@centessa.com

26 sites in 1 country

United States26 sites, 26 recruiting

  • Atlanta, Georgia

    Atlanta, Georgia, 30328

    Recruiting

  • Austin, Texas

    Austin, Texas, 78731

    Recruiting

  • Birmingham, Alabama

    Birmingham, Alabama, 35213

    Recruiting

  • Brandon, Florida

    Brandon, Florida, 33511

    Recruiting

  • Cincinnati, Ohio

    Cincinnati, Ohio, 45245

    Recruiting

  • Colorado Springs, Colorado

    Colorado Springs, Colorado, 80918

    Recruiting

  • Columbia, South Carolina

    Columbia, South Carolina, 29201

    Recruiting

  • Dallas, Texas

    Dallas, Texas, 75251

    Recruiting

  • Denver, North Carolina

    Denver, North Carolina, 28037

    Recruiting

  • Dublin, Ohio

    Dublin, Ohio, 43017

    Recruiting

  • Flowood Mississippi

    Flowood, Mississippi, 39232

    Recruiting

  • Frisco, Texas

    Frisco, Texas, 75033

    Recruiting

  • Houston, Texas

    Houston, Texas, 77070

    Recruiting

  • Huntersville, North Carolina

    Huntersville, North Carolina, 28078

    Recruiting

  • Lansing, Michigan

    Lansing, Michigan, 48911

    Recruiting

  • Miami, Florida

    Miami, Florida, 33155

    Recruiting

  • Miami, Florida

    Miami, Florida, 33166

    Recruiting

  • Miami, Florida

    Miami, Florida, 33176

    Recruiting

  • Miami, Florida

    Miami, Florida, 33186

    Recruiting

  • Miami Lakes, Florida

    Miami Lakes, Florida, 33014

    Recruiting

  • Orlando, Florida

    Orlando, Florida, 32807

    Recruiting

  • Rincon, Georgia

    Rincon, Georgia, 31326

    Recruiting

  • San Antonio, Texas

    San Antonio, Texas, 78229

    Recruiting

  • St. Petersburg, Florida

    St. Petersburg, Florida, 33707

    Recruiting

  • Stockbridge, Georgia

    Stockbridge, Georgia, 30281

    Recruiting

  • Sugar Land, Texas

    Sugar Land, Texas, 77478

    Recruiting

Other trials in United States

About this study

Official title: 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

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:

Read more
  • 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.

Read the detailed description

The SAPPHIRE Clinical Trial

The Sponsor may in the future, through a protocol amendment, expand the protocol to include participants with idiopathic hypersomnia (IH) in Cohort C.

Being tested
cleminorexton, Placebo
Keywords
NT1, NT2, Excessive Daytime Sleepiness, Orexin Receptor 2 agonist, Central Disorders of Hypersomnia, Disorders of Excessive Somnolence, Dyssomnias, Nervous System Diseases, Mental Disorders, Hypersomnia, Hypersomnolence, Sleep Wake Disorders, Sleep Disorder, Sleep, Sleepiness, Cataplexy, Narcolepsy Type 1, Narcolepsy Type 2, Orexin, ORX750
Medical subject headings
Disorders of Excessive Somnolence, Dyssomnias, Nervous System Diseases, Mental Disorders, Sleep Wake Disorders, Sleepiness, Cataplexy, Narcolepsy

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • cleminorextonDrug

    Oral cleminorexton capsule

  • PlaceboDrug

    matching placebo capsule

Study groups in NCT07598708
Study groupRoleWhat they receive
Group A - Narcolepsy Type 1 (Dose 1)ExperimentalNot described
Receives: Drug: cleminorexton
Group A - Narcolepsy Type 1 (Dose 2)ExperimentalNot described
Receives: Drug: cleminorexton
Group A - Narcolepsy Type 1 (placebo)Placebo comparatorNot described
Receives: Drug: Placebo
Group B - Narcolepsy Type 2 (Dose 1)ExperimentalNot described
Receives: Drug: cleminorexton
Group B - Narcolepsy Type 2 (Dose 2)ExperimentalNot described
Receives: Drug: cleminorexton
Group B - Narcolepsy Type 2 (placebo)Placebo comparatorNot described
Receives: Drug: Placebo

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Change from baseline in mean sleep latency (average of the first 4 trials) on the Maintenance of Wakefulness Test (MWT)

    Measured: Baseline to week 12

Secondary outcomes (12)

  1. Change from baseline in Epworth Sleepiness Scale (ESS) total score

    Measured: Baseline to Week 12

  2. Weekly Cataplexy Rate (WCR)

    Measurement specific to Group A

    Measured: Week 12

  3. Change from baseline in Narcolepsy Severity Scale for Clinical Trials (NSS-CT)

    Measurement specific to Group A

    Measured: Baseline to Week 12

  4. Change from baseline in Narcolepsy Severity Scale-2 for Clinical Trials (NSS2-CT) total score

    Measurement specific to Group B

    Measured: Baseline to Week 12

  5. Incidence, Severity, and casual relationship of participants with Treatment Emergent Adverse Events (TEAEs)

    Measured: Baseline to Week 12

  6. Number of participants with abnormal changes from baseline in clinical laboratory tests

    Measured: Baseline to Week 12

  7. Number of participants with abnormal changes from baseline in vital signs

    Measured: Baseline to Week 12

  8. Number of participants with abnormal changes from baseline in 12-lead electrocardiograms (ECGs)

    Measured: Baseline to Week 12

  9. Number of participants with at least 1 endorsement of Item 4 or 5 on Columbia-Suicide Severity Rating Scale (C-SSRS)

    Measured: Baseline to Week 12

  10. Cmax: Maximum observed plasma concentration

    Measured: Baseline to Week 12

  11. Tmax: Time of Maximum Concentration for cleminorexton

    Measured: Baseline to Week 12

  12. AUC: Area under the plasma concentration-time curve

    Measured: Baseline to Week 12

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted20 May 2026
  2. Study start29 May 2026
  3. Primary completion30 Sep 2027 (estimated)
  4. Study completion31 Dec 2027 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 2/3
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Masking
Quadruple blind
Who is masked
Participant, Care provider, Investigator, Outcomes assessor
Enrolment
222 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT07598708
Sponsor's protocol ID
ORX750-004
Status last verified
Jul 2026
First submitted
27 Apr 2026
Last updated
3 Nov 2026
Results posted
No
Data monitoring committee
No
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
No

Questions about this trial

What is this clinical trial studying?

A Phase 2/3 study testing cleminorexton in people with Narcolepsy Type 1 and Narcolepsy Type 2, run by Centessa Pharmaceuticals (UK) Limited at 26 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 5 inclusion and 2 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 3 Nov 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 26 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this combined phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Centessa Pharmaceuticals (617-468-5770, ORX750trials@centessa.com), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Change from baseline in mean sleep latency (average of the first 4 trials) on the Maintenance of Wakefulness Test (MWT) (time frame: Baseline to week 12). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT07598708.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 3 Nov 2026; AzTrials last refreshed its copy on 6 Nov 2026.

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