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Long-term Safety Study of ORX750 for Patients with Narcolepsy and Idiopathic Hypersomnia Who Completed a Previous ORX750 Trial

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study involves people with narcolepsy and idiopathic hypersomnia, which are conditions that cause excessive daytime sleepiness and difficulties staying awake during the day. Narcolepsy is a sleep disorder where a person experiences sudden sleep attacks and may have trouble controlling when they fall asleep, while idiopathic hypersomnia is a condition where a person feels extremely sleepy during the day despite getting enough sleep at night. The treatment being tested is ORX750, which is given as a capsule taken by mouth. The purpose of this study is to evaluate the long-term safety and tolerability of ORX750 in people who have already completed a previous clinical trial with this medication.

Participants in this study will be those who finished the full treatment period in an earlier study with ORX750. They will continue taking the medication for an extended period to help researchers understand how safe it is when used over a longer time. During the study, participants will attend regular visits where various health checks will be performed. These checks include blood tests to examine blood cells and body chemistry, measurements of blood pressure and heart rate, weight monitoring, and heart function tests using an electrocardiogram. Researchers will also use questionnaires to assess any thoughts about self-harm and will monitor for any unwanted effects that may occur during treatment.

The study will also measure how well ORX750 works by looking at changes in sleepiness levels. This will be done using a test called the maintenance of wakefulness test, which measures how long a person can stay awake in a quiet, comfortable setting, and a questionnaire that asks about sleepiness during daily activities. Blood samples will be collected at different times to measure the amount of ORX750 in the body. The maximum treatment period for participants will be 63 days, during which they will need to stop taking any other medications used to treat their sleep condition.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and baseline assessments

    This study is designed for individuals who have already completed a previous ORX750 clinical trial. If you are entering from a completed study, you will transition into this long-term extension study.

    Before starting treatment in this extension study, baseline measurements will be recorded. These include laboratory tests such as blood tests, urine tests, vital signs like blood pressure and heart rate, body weight, and a 12-lead electrocardiogram (a test that measures the electrical activity of your heart).

    You will also complete the Columbia-Suicide Severity Rating Scale, which is a questionnaire used to assess any thoughts or feelings related to self-harm.

  2. Step 2

    Treatment period with ORX750

    You will receive ORX750, which is provided as a capsule to be taken by mouth.

    The specific dosage, frequency, and duration of treatment will be determined based on your individual response and the study protocol. This is a long-term extension study, meaning treatment may continue for an extended period.

    During the treatment period, you will be required to attend scheduled visits for ongoing safety and effectiveness assessments.

  3. Step 3

    Safety monitoring throughout the study

    Throughout your participation, safety will be continuously monitored. This includes tracking any adverse events, which are unwanted or harmful effects that may occur during treatment.

    Regular laboratory tests will be performed to check blood chemistry, blood cell counts, and urine composition. These tests help ensure that the medication is not causing harmful changes in your body.

    Your vital signs and body weight will be measured at scheduled visits to monitor any changes.

    Electrocardiograms will be performed at specified times to check your heart's electrical activity.

    The Columbia-Suicide Severity Rating Scale will be administered periodically to monitor your mental well-being.

  4. Step 4

    Effectiveness assessments

    To evaluate how well ORX750 is working, you will undergo the Maintenance of Wakefulness Test at specific timepoints, including at Day 63. This test measures your ability to stay awake in a quiet environment and involves recording the average time it takes you to fall asleep during the first four test sessions.

    You will also complete the Epworth Sleepiness Scale, a questionnaire that asks about your likelihood of falling asleep in different everyday situations. This will be done at baseline and at specified times after starting treatment to measure changes in daytime sleepiness.

    Blood samples will be collected before and after dosing to measure the concentration of ORX750 in your bloodstream. This helps determine how the medication is processed by your body.

  5. Step 5

    Medication restrictions

    If you are a returning participant who did not roll over directly from a previous study, you must be willing and able to stop taking all other medications used to treat narcolepsy or idiopathic hypersomnia (a condition characterized by excessive daytime sleepiness without a clear cause) before starting this study.

  6. Step 6

    Contraception requirements

    If you are male or female and of reproductive potential, you must follow specific contraception requirements throughout the study as outlined in the study protocol.

  7. Step 7

    Study completion

    The study is expected to continue until June 30, 2026. Your participation will last for the duration specified in the study protocol.

    You must be available to complete all scheduled measurements and follow all study requirements throughout your participation.

Who can join the trial?

9 criteria

  • You must have narcolepsy (a condition causing sudden sleep attacks and excessive daytime sleepiness) of type 1 or type 2, or idiopathic hypersomnia (a condition causing extreme daytime sleepiness without a known cause), and you must have finished the full treatment period in the previous study called ORX750-0201.
  • You must be able and willing to attend all scheduled visits and follow all study procedures, and you must agree to complete all required measurements and follow study rules.
  • If you are male or female, you must follow the birth control requirements described in the study plan.
  • If you are a new participant joining this study: you must be between 18 and 65 years old.
  • If you are a new participant joining this study: your body mass index (a measure of body fat based on your height and weight) must be between 17.0 and 37.
  • If you are a new participant joining this study: your estimated glomerular filtration rate (a measure of how well your kidneys are filtering waste from your blood) must be at least 60, which indicates healthy kidney function.
  • If you are a new participant joining this study: you must be willing and able to stop taking all medications used to treat narcolepsy or idiopathic hypersomnia.
  • If you are a new participant joining this study: you must be willing and able to follow additional study requirements.
  • If you are continuing from the previous study: you must provide written permission to participate by your final treatment visit on Day 42 of the previous study, before any procedures for this long-term study begin.

Who cannot join the trial?

3 criteria

  • The source data does not contain specific exclusion criteria, which are reasons why a patient cannot participate in the study
  • Without detailed exclusion criteria information, it is not possible to list the specific conditions or situations that would prevent someone from joining this clinical trial
  • Typically, exclusion criteria may include things like certain other medical conditions, use of specific medications, pregnancy status for women, or recent participation in other studies, but these specific details are not provided in the available information
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Investigated drugs

ORX750 is an investigational medication being studied for the treatment of narcolepsy and idiopathic hypersomnia. Narcolepsy is a sleep disorder that causes excessive daytime sleepiness and sudden sleep attacks, while idiopathic hypersomnia is a condition where people feel extremely sleepy during the day despite getting enough sleep at night. This medication is being tested to see if it can help people with these conditions stay more awake and alert during the day. In this study, researchers want to understand how safe the medication is when people take it for a long period of time and whether it continues to work well over time.

What is already known about the treatment

ORX750 – ORX750 is an investigational medication currently being studied in clinical trials for the treatment of narcolepsy and idiopathic hypersomnia, which are sleep disorders characterized by excessive daytime sleepiness. This drug is administered as part of research studies to evaluate its long-term safety and effectiveness in helping patients manage their symptoms of excessive sleepiness. While the exact mechanism of action has not been fully disclosed in available trial information, medications for these conditions typically work by affecting brain chemicals that control wakefulness and sleep-wake cycles. ORX750 is still in the experimental phase and is not yet approved for general medical use outside of clinical trials.

Investigated diseases

  • Narcolepsy

    Narcolepsy is a chronic sleep disorder characterized by overwhelming daytime drowsiness and sudden attacks of sleep. People with this condition often find it difficult to stay awake for long periods of time, regardless of the circumstances. The disorder disrupts the normal sleep-wake cycle, causing individuals to fall asleep suddenly during daily activities. Additional symptoms may include sudden loss of muscle tone, vivid dreams during sleep onset, and brief inability to move or speak while falling asleep or waking up. The condition typically begins in adolescence or young adulthood and persists throughout life. Narcolepsy significantly affects daily functioning, work performance, and social activities.

  • Idiopathic Hypersomnia

    Idiopathic hypersomnia is a sleep disorder characterized by excessive daytime sleepiness despite adequate or prolonged nighttime sleep. People with this condition experience persistent drowsiness and difficulty waking up, often feeling groggy for extended periods after awakening. Unlike narcolepsy, individuals with idiopathic hypersomnia typically do not experience sudden sleep attacks or loss of muscle tone. Sleep periods can be very long, sometimes lasting 10 hours or more at night, yet the person still feels unrefreshed upon waking. Daytime naps are usually long and unrefreshing, failing to improve alertness. The condition typically develops in young adulthood and continues as a chronic disorder affecting daily life and productivity.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IVTrial ID2025-522987-34-00Protocol codeORX750-202Estimated enrolment148 patientsSponsorCentessa Pharmaceuticals UK Limited

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