ORX750: OX2R Agonist Clinical Trials in Narcolepsy (NT1, NT2) and Idiopathic Hypersomnia

If you or someone you care about lives with narcolepsy or idiopathic hypersomnia, you already know how profoundly excessive daytime sleepiness can disrupt everyday life. ORX750 is an investigational drug generating significant interest in the sleep medicine community because it targets the root biology of these conditions rather than simply masking symptoms. Here is what the current data, trial designs, and participation details look like as of mid-2026.

Key Takeaways

• ORX750 is an investigational oral orexin-2 receptor agonist developed by Centessa Pharmaceuticals to treat excessive daytime sleepiness in narcolepsy type 1 (NT1), narcolepsy type 2 (NT2), and idiopathic hypersomnia (IH). The drug is not currently approved by the FDA or any other regulatory authority.

• Current clinical trials include a randomized, double blind, placebo controlled study (CRYSTAL-1, phase 2a) and a long-term extension study, with results expected around 2025–2026.

• Study sites span U.S. locations such as North Carolina (Huntersville), Pennsylvania (Willow Grove), Ohio (Dublin), Santa Ana in California, Florida (including Winter Park), South Carolina, and select sites in Canada and Europe.

• Trials enroll adults (18–65) diagnosed with NT1, NT2, or IH. Healthy volunteers are excluded from these treatment-oriented protocols, and ORX750 is not yet available as routine treatment.

• Readers with interest in participation should consult ClinicalTrials.gov listings for the CRYSTAL-1 study and speak with their sleep specialist before making any decisions.

Introduction to ORX750 and the Orexin System

The orexin system plays a central role in keeping you awake and alert. Orexin, sometimes called hypocretin, is a neuropeptide produced in the hypothalamus that acts as a regulator of wakefulness in the brain. In people living with narcolepsy type 1 (NT1), the neurons that produce orexin are almost entirely destroyed, leading to orexin deficiency. This deficiency is a primary target for therapies addressing sleep disorders like narcolepsy and idiopathic hypersomnia.

Narcolepsy type 1 is characterized by excessive daytime sleepiness and cataplexy, a sudden loss of muscle tone triggered by emotions. Narcolepsy type 2 (NT2) involves excessive daytime sleepiness without cataplexy, and while the orexin pathway may not be as severely depleted, downstream signaling is often disrupted. Idiopathic hypersomnia (IH) causes excessive daytime sleepiness despite long sleep duration, meaning a person can sleep ten or more hours and still struggle to stay awake during the day. All three conditions lead to difficulties in staying alert during daily activities, from driving to working to simply having a conversation.

ORX750 is an investigational oral orexin-2 receptor agonist that has been developed to selectively engage orexin receptor 2 (OX2R), mimicking the wake-promoting action of naturally occurring orexin-B. Unlike conventional stimulants or broad-acting wake-promoting agents that push the brain into a generally heightened state, ORX750 is designed to restore a specific biological pathway. This investigational therapy may enable once-daily dosing if pharmacology supports a sustained effect through the waking day. Research is also exploring potential uses of ORX750 in other disorders involving excessive daytime sleepiness beyond narcolepsy type and IH.

ORX750 targets narcolepsy type 1, type 2, and idiopathic hypersomnia, making it one of the broadest orexin-based treatment candidates currently in development.

Study of ORX750: Phase 2a Double-Blind, Placebo-Controlled Trial

The core clinical study of ORX750 in patients is a randomized, double blind, placebo controlled study assessing both safety and efficacy. This phase 2a trial enrolls adults with confirmed diagnoses of narcolepsy type 1 (NT1), narcolepsy type 2 (NT2), and idiopathic hypersomnia (IH), with separate cohorts for each disorder so that outcomes can be evaluated independently across these distinct populations.

The study design includes a crossover approach for treatment. Each participant receives both ORX750 and placebo across two 6-week treatment periods, with appropriate washout in between. This within-person comparison strengthens the data because each participant serves as their own control, reducing the noise from individual variability.

Key details of the phase 2a study plan include:

• Primary efficacy endpoints: Maintenance of wakefulness test (MWT) sleep latency and Epworth Sleepiness Scale (ESS) scores

• NT1-specific endpoint: Weekly cataplexy rate

• Statistical power: Greater than 87.5% power to detect a clinically meaningful change in mean sleep latency of approximately 15 minutes

• Enrollment target: Approximately 248 participants across NT1, NT2, and IH cohorts

• Dosing: Starting at 1 mg in NT1 and 2 mg in NT2 and idiopathic hypersomnia, with dose escalation or de-escalation between cohorts

Early phase data from Phase 1 trials in acutely sleep-deprived healthy volunteers already demonstrated strong wake promoting effects, with ORX750 showing dose-dependent improvements in the maintenance of wakefulness test at doses from 1.0 mg to 5.0 mg. ORX750 demonstrated a favorable safety and tolerability profile in those early phase studies, and the drug demonstrated a potential best-in-class profile in clinical trials when compared to data from other OX2R agonists in development. Topline results from the phase 2a are anticipated in calendar year 2025–2026.

CRYSTAL-1 Clinical Trial Overview

CRYSTAL-1 is the named, multicenter clinical trial evaluating ORX750 in adults aged 18 to 65 with narcolepsy type 1 NT1, narcolepsy type 2 NT2, and idiopathic hypersomnia IH. Sites span the United States and Canada, making it one of the more geographically accessible trials in this space.

The trial is designed to further characterize the drug's safety, optimal doses, and efficacy after initial phase 2a work. Participants undergo standardized sleep lab assessments, including overnight polysomnography and daytime wakefulness test sessions, with consistent use of validated scales across every site.

The study description, participation criteria, and contact details are publicly available on ClinicalTrials.gov (NCT06752668). CRYSTAL-1 was first posted around December 2024 and has an estimated primary completion date of November 30, 2026, though these dates may evolve as enrollment and data collection progress. The methods used in CRYSTAL-1 are generally aligned with current regulatory expectations, giving the results the rigor needed for potential future approval pathways.

Long-Term Extension (LTE) Study of ORX750

After completing the treatment period in the phase 2a trial, participants may enter a long-term extension (LTE) study. The study design is a Phase 2, long-term extension study with a non-randomized, open-label design, meaning all participants receive oral ORX750 with no placebo and no masking. Healthy volunteers are not included.

The LTE began enrollment around August 12, 2025, with estimated completion around April 30, 2026. The trial aims to enroll 90 participants with narcolepsy and IH, all of whom must have previously completed an ORX750 clinical study.

Main objectives of the LTE include:

• Evaluate long-term safety and tolerability, with systematic tracking of treatment emergent adverse events (TEAEs), including serious TEAEs

• Monitor sustained effects on excessive daytime sleepiness via MWT and ESS

• Assess stability of cataplexy control in NT1 over months of continued dosing

• Collect pharmacokinetic data (Cmax, Tmax, AUC at steady state)

The study will assess safety, tolerability, and efficacy of ORX750 over follow-up periods extending to approximately 63–70 days per participant. Key registry dates illustrate active oversight: first submission to ClinicalTrials.gov in July 2025 and last verification in April 2026, confirming that data updates remain current. The Phase 2 study plans to enroll 90 participants, providing a meaningful dataset on what happens when treatment extends beyond the limited observation window of a crossover trial.

Eligibility and Participation Criteria

ORX750 studies focus on adults aged 18 to 65 with confirmed diagnoses of narcolepsy type 1, narcolepsy type 2, or idiopathic hypersomnia based on established sleep-medicine criteria. The trial includes participants aged 18 to 65 years, and a child or adolescent under 18 is not eligible to participate.

Healthy volunteers are explicitly excluded from these treatment-focused protocols. To meet the eligibility criteria and inclusion criteria, each person must have:

• Documented excessive daytime sleepiness with appropriate polysomnography and multiple sleep latency test (MSLT) findings

• A confirmed diagnosis of NT1 (with documented cataplexy), NT2, or IH per ICSD standards

• Stable baseline medications or willingness to taper under medical supervision

• Controlled comorbid conditions and a BMI within the specified range (generally 17–37)

Common exclusion criteria include:

• Uncontrolled cardiovascular disorder

• Significant psychiatric instability

• Prior serious adverse reaction to an OX2R agonist or related compounds

• Any condition that, in the investigator's judgment, would compromise participation

If you are considering participation, discuss your eligibility with your sleep specialist and local study coordinator rather than self-diagnosing or altering medications on your own. Recruitment status changes frequently, so verify current availability before planning visits.

Study Locations: North Carolina, Pennsylvania, Ohio, and Beyond

ORX750 trials are active across multiple U.S. states and internationally. Examples of investigative sites include north carolina huntersville, pennsylvania willow grove, and ohio dublin. Additional sites have been established in Santa Ana, California; Miami and Orlando in Florida, including Florida Winter Park; and in south carolina. Sites in Stockbridge, Georgia; Auburn, Alabama; and Toronto in Canada round out the geographic footprint.

European locations in Italy (Bologna, Verona) and Spain (Móstoles, Madrid; Álava) are also listed for the LTE study, enabling broader access for people living with these conditions.

Each site operates under the same core protocol but may differ in local contact information, visit scheduling, and capacity to enroll new participants. Some sites may have an active status while others are not currently loading new participants.

For the most current list of recruiting sites, site-specific phone numbers, and recruitment status, check ClinicalTrials.gov and search for CRYSTAL-1 or NCT06752668.

How ORX750 Is Evaluated: Endpoints and Assessments

Understanding how researchers measure whether ORX750 works requires a look at both objective and subjective endpoints. Here is how the data are structured.

Efficacy Endpoints

Objective tests like the MWT measure how long a person can stay awake under controlled conditions. Patients on ORX750 showed over a 20-minute increase in sleep latency, and ORX750 improved mean sleep latency by over 20 minutes compared to baseline in early evaluations. At higher doses evaluated in Phase 1 trials, sleep latency reached levels compared favorably with normative wakefulness, suggesting the drug can meaningfully restore the ability to stay awake.

Subjective measures tell the other half of the story. ORX750 improved mean ESS scores from 19.6 to 5.1 in NT1 patients, a shift from severe sleepiness to near-normal alertness. In NT2, mean ESS scores improved from 17.3 to 8.1 with ORX750, further supporting efficacy across narcolepsy type 2 (NT2) and related conditions.

For cataplexy control, participants showed an 87% reduction in weekly cataplexy rate. ORX750 reduced weekly cataplexy rate by 87% in NT1 patients, which, if confirmed in larger trials, would represent a substantial clinical advance. ORX750 is the first OX2R agonist to show significant efficacy in IH, a disorder that currently has very limited approved treatment options.

Safety Monitoring

Safety assessments are conducted at each clinic visit and include physical exams, vital signs, ECGs, laboratory tests, suicidal ideation screening (C-SSRS), and systematic collection of adverse events. The drug was well tolerated in early phase trials. Common adverse events include pollakiuria, insomnia, dizziness, and headache, all of which were generally mild to moderate and transient. No hepatotoxicity or visual disturbances were reported at the doses evaluated.

In the placebo controlled study and open-label follow-up, researchers compare short-term versus long-term outcomes for NT1 nt2 and idiopathic hypersomnia to build a comprehensive picture of the drug's safety over time.

Frequently Asked Questions (FAQ)

Is ORX750 available as a prescription outside clinical trials?

As of mid-2026, ORX750 remains an investigational OX2R agonist and is not approved by the FDA, Health Canada, or other regulators for routine clinical use. It can only be accessed through participation in authorized clinical trials. No pharmacy currently dispenses this drug, and any claims suggesting otherwise should be treated with skepticism.

Can healthy volunteers enroll in ORX750 studies?

Current ORX750 programs focus on patients with narcolepsy and idiopathic hypersomnia. Healthy volunteers were included in early phase 1 studies to establish basic pharmacokinetics and safety, but the ongoing phase 2a and long-term extension trials are limited to individuals with a confirmed diagnosis of NT1, NT2, or IH who meet specific eligibility criteria.

How is ORX750 different from current stimulant medications?

While stimulants act broadly on dopamine or related neurotransmitter systems, ORX750 is designed to more directly engage the orexin-2 receptor, aiming to restore a biological pathway that is deficient in NT1 and possibly dysregulated in NT2 and IH. Other OX2R agonists like oveporexton (TAK-861) and alixorexton (ALKS-2680) are also in development, but ORX750's selective profile, oral bioavailability, and early safety data have positioned it competitively among these agonists.

Will participation in an ORX750 trial affect my existing sleep medications?

Many protocols require tapering or stabilizing certain medications before the baseline assessment period. Any changes must be carefully supervised by the study investigator and a participant's usual sleep specialist. Do not adjust your current medications independently based on trial information you read online.

Where can I find official and up-to-date information about ORX750 studies?

The most reliable sources are the ClinicalTrials.gov entries for CRYSTAL-1 (NCT06752668) and the LTE study (NCT07096674), as well as official study websites like crystal1study.com. For clinical guidance, speak with a licensed sleep medicine clinician rather than relying on informal online sources. Centessa Pharmaceuticals also periodically publishes updates through press releases and conference presentations.

Frequently Asked Questions

What is ORX750 and what conditions does it target?

ORX750 is an investigational oral orexin-2 receptor agonist developed by Centessa Pharmaceuticals to treat excessive daytime sleepiness in narcolepsy type 1, narcolepsy type 2, and idiopathic hypersomnia. It is not currently FDA-approved.

How does ORX750 work differently from other wake-promoting medications?

ORX750 selectively targets orexin receptor 2 to restore a specific biological pathway, mimicking naturally occurring orexin-B. Unlike conventional stimulants, it targets the root cause rather than broadly heightening brain activity.

What is the current status of ORX750 clinical trials?

ORX750 is in phase 2a clinical trials including the CRYSTAL-1 randomized, double-blind, placebo-controlled study with approximately 248 participants. Topline results are anticipated in 2025-2026.

Who is eligible to participate in ORX750 clinical trials?

Adults aged 18-65 with confirmed diagnoses of narcolepsy type 1, narcolepsy type 2, or idiopathic hypersomnia are eligible. Healthy volunteers are excluded. Trial sites are located across the U.S., Canada, and select European locations.

What does the phase 2a trial design measure?

The trial measures maintenance of wakefulness test sleep latency, Epworth Sleepiness Scale scores, and weekly cataplexy rates in narcolepsy type 1. Participants receive both ORX750 and placebo in separate 6-week periods with washout between them.