Cleminorexton: Selective OX2R Agonist for Narcolepsy and Sleep‑Wake Disorders

The search for therapies that address the root cause of narcolepsy rather than merely masking its symptoms has gained significant momentum in recent years. Cleminorexton, an investigational oral compound also known as orx 750, represents one of the most promising developments in this space. As a selective agonist of the orexin receptor 2, it aims to restore the wake-promoting signaling that is lost or diminished in patients with narcolepsy and related conditions. This article provides a comprehensive look at its pharmacology, chemical structure, clinical development, laboratory handling, and commercial context as of mid-2026.

Overview of Cleminorexton (ORX‑750)

Cleminorexton (ORX‑750) is an orally administered, highly selective ox2r agonist currently under development for narcolepsy type 1 (NT1), narcolepsy type 2 (NT2), and idiopathic hypersomnia. It is designed to promote wakefulness by mimicking orexin, the endogenous neuropeptide whose loss drives the core pathology of these disorders. By significantly improving sleep latency and reducing cataplexy episodes, cleminorexton targets central disorders of hypersomnolence at their mechanistic origin rather than through downstream symptomatic pathways.

The orexin receptor type 2 (OX2R), encoded by the HCRTR2 gene, is one of two G-protein coupled receptors activated by orexin-A and orexin-B. These neuropeptides originate in lateral hypothalamus neurons and serve as the primary mediator of wake-promoting signaling throughout the brain. In NT1, the progressive loss of orexin-producing neurons leads to profound orexin deficiency, making agents that selectively activate OX2R a theoretically ideal therapeutic strategy. This rationale underpins the entire class of OX2R agonists now in development.

Cleminorexton is identified by the active moiety UNII AL84E4VK26 in regulatory substance databases, with CAS number 2980518‑93‑0 serving as its chemical registry identifier. These designations allow for consistent cross-referencing across clinical, regulatory, and pharmacovigilance systems worldwide.

As of 2025–2026, cleminorexton is in Phase 2 clinical trials, specifically the CRYSTAL-1 (Phase 2a) and CRYSTAL-2 (open-label extension) studies across NT1, NT2, and idiopathic hypersomnia populations. Clinical trials are investigating cleminorexton's efficacy and safety across these indications, and the availability of cleminorexton is limited to authorized clinical trials until approval. Cleminorexton is not yet FDA-approved for general use, meaning patients must be enrolled in clinical trials to access cleminorexton. Among next-generation wake-promoting agents, recent advances in orexin biology have positioned this compound as a front-runner, competing alongside other experimental drugs such as oveporexton and alixorexton.

Pharmacology and Mechanism of Action

Cleminorexton is a highly potent, full agonist at the human OX2R, closely mimicking the activity of endogenous orexin-A in activating wake-promoting circuitry originating from the lateral hypothalamus. Unlike traditional stimulants that broadly amplify monoaminergic tone, cleminorexton directly engages the orexin receptor pathway, offering a more physiologically targeted mechanism for restoring wakefulness.

Receptor Selectivity and Potency

The selectivity profile of cleminorexton is among the most striking features of its pharmacology. Cleminorexton has a subnanomolar EC50 of 0.11 nM at human OX2R, making it extraordinarily potent at the target receptor. It shows approximately 9,800-fold selectivity over OX1R, which has an EC₅₀ of roughly 1,100 nM in comparable assays. This degree of selectivity is important because OX1R activation has been implicated in reward and stress-related circuitry, and avoiding it may reduce unwanted side effects. No detectable β-arrestin pathway bias has been observed, meaning the compound activates OX2R signaling similarly to the native ligand.

Preclinical Pharmacodynamics

In mouse models of NT1, including the Ataxin-3 (Atax) and diphtheria toxin fragment A (DTA) lesion models, preclinical data show robust pharmacodynamic effects. Key findings include:

• Wake promotion: Oral administration produced up to 100% wakefulness for 3 hours post-dose, with doses as low as 0.1 mg/kg producing 100% wakefulness in mice (DTA model)

• Cataplexy suppression: It suppresses cataplexy for at least 6 hours, with increased latency to the first cataplexy bout

• Wake consolidation: Cleminorexton enhances arousal pathways and increases wake consolidation, reflected in fewer sleep-wake transitions and longer sustained wake bouts

• Sustained efficacy: Effects on sleep latency and cataplexy suppression were maintained over at least 14 days of repeated dosing, suggesting low tolerance development

Electrophysiological data further support direct neuronal engagement. In ventral tuberomammillary nucleus (TMN) slices, membrane potential shifts with an EC₅₀ of approximately 5 nM were observed under tetrodotoxin blockade, consistent with direct depolarization of wake-active neurons.

Downstream, cleminorexton's OX2R activation is expected to engage monoaminergic wake-promoting systems, including histaminergic, noradrenergic, and serotonergic pathways. These represent established roles of orexin signaling in maintaining arousal. The compound functions as a selective agonist that restores the missing orexin signal rather than artificially amplifying neurotransmitter release, which distinguishes it mechanistically from conventional stimulants.

Chemical Structure and Physicochemical Properties

Understanding the chemical structure and physicochemical profile of cleminorexton is essential for medicinal chemistry optimization, formulation development, and analytical characterization. This section outlines the core molecular features relevant to researchers and formulators.

Molecular Formula and Mass

The absolute molecular formula of cleminorexton is C₂₄H₂₄F₄N₂O₄S, giving a molecular weight of 512.52 g/mol and an exact monoisotopic mass of approximately 512.1393 Da. These values are critical for dose calculations, mass spectrometric identification, and stoichiometric preparation of research stock solutions. For analytical purposes, researchers working with any c h ratio calculations should reference the molecular formula directly.

Structural Features

At a high level, the chemical structure of cleminorexton features:

• A tetracyclic aromatic scaffold incorporating multiple fluorine substituents (four fluorine atoms total)

• A cyclopropane-1-sulfonamide moiety, where the 1 fluoro substituent on the cyclopropane ring is a defining structural element

• Heterocyclic nitrogen features and oxa bridges that contribute to its three-dimensional shape and receptor binding

• The compound is classified as a small-molecule chemical substance with no formal charge at physiological pH

Stereochemistry

Cleminorexton contains 2 defined stereocenters, both with absolute configuration assigned (S,S). There is no E/Z double-bond isomerism, and absolute additional stereochemistry information is fully specified according to registry data. The additional stereochemistry details confirm that no undefined stereocenters exist in the molecule. This stereochemical precision matters because receptor binding and pharmacokinetic behavior can differ dramatically between enantiomers and diastereomers.

Computed Physicochemical Properties

Key computed properties from PubChem (CID 176507653) provide insight into oral bioavailability and CNS penetration:

These values indicate moderate lipophilicity balanced by sufficient polar surface area, a profile consistent with good oral absorption and blood-brain barrier penetration. The relatively low number of rotatable bonds contributes to conformational rigidity, which often favors target selectivity and metabolic stability.

The active moiety of cleminorexton corresponds to UNII AL84E4VK26 in regulatory and database records, serving as the standardized identifier for substance tracking across jurisdictions.

Nomenclature, Identifiers, and Systematic Names

Multiple naming conventions exist for cleminorexton across laboratory, clinical, regulatory, and commercial contexts. Using consistent systematic names and identifiers ensures accurate cross-referencing between research databases, patent filings, and regulatory submissions.

Primary Designations

The three main designations are: cleminorexton (the proposed INN or generic nonproprietary name), ORX‑750 (the developmental code used in clinical programs), and AL84E4VK26 (the UNII assigned to the active moiety). Until a commercial launch occurs, the as-yet unspecified cleminorexton official trade name remains undetermined; none view the current naming as final for marketed use.

Systematic Chemical Name

The IUPAC-style systematic name is: 1-fluoro-N-[(16S,17S)-4,6,23-trifluoro-11-oxo-8-oxa-12-azatetracyclo[17.3.1.0²,⁷.0¹²,¹⁷]tricosa-1(22),2(7),3,5,19(23),20-hexaen-16-yl]cyclopropane-1-sulfonamide.

Machine-Readable Identifiers

For computational and database work, the following machine-readable strings are used. The full InChI is: InChI=1S/C24H24F4N2O4S/c25-15(12-26)13(19-29-35(32,33)24-28-7-3-9-19)29-35,32,33-24-28-7/h1,3-4,12-13,19-20,29H,2,5,11H2/t19-,20-/m0/s1. This string encodes the molecular formula layer (c24h24f4n2o4s c25 15 12), the hydrogen layer (h1,3 4,12 13,19 20,29h 2,5 11h2), the stereo layer (t19 20 m0 s1), and connectivity information (19 29 35 32,33 24 28 7). Each sublayer-including 1s c24h24f4n2o4s c25 15, 26 13 15 h1,3, 13 15 h1,3 4,12, 15 h1,3 4,12 13,19, 4,12 13,19 20,29h 2,5, 13,19 20,29h 2,5 11h2, 20,29h 2,5 11h2 t19, 2,5 11h2 t19 20, 11h2 t19 20 m0, 29 35 32,33 24, 35 32,33 24 28, and 32,33 24 28 7-enables precise structural reconstruction. The InChIKey is xgxkcwfiuazzrs pmacekpbsa n, providing a hashed shorthand for database searches. A representative SMILES fragment includes c5 cc5 f for the fluorinated aromatic portions.

Identifier Summary

Identifiers can be grouped by type for quick reference:

• Regulatory: CAS# 2980518-93-0; UNII AL84E4VK26; inchi 1s c24h24f4n2o4s c25 layer as substance descriptor

• Research database: PubChem CID 176507653; ChemSpider ID 133326679; synonyms include orb3135816, EX-A16745, T211429

• Commercial/catalog: ProbeChem catalog number PC-25035 (research use only, >98% purity by HPLC); c24h24f4n2o4s c25 15 12 fragment indexed in chemical supplier databases

Preclinical and Clinical Development

Development Timeline

Cleminorexton's journey began in the early 2020s through structure-based drug design, leveraging technologies such as Nxera Pharma's StaR (stabilized receptor) platform and cryo-EM docking on active-state OX2R structures. Candidate optimization prioritized subnanomolar potency, OX2R selectivity, CNS penetration, and oral bioavailability. IND-enabling studies spanned multiple species, including rodents and non-human primates, before advancing to human trials.

Preclinical Results

In rodent models of narcolepsy, cleminorexton demonstrated dose-dependent wake promotion, increased sleep latency, and cataplexy suppression with a favorable tolerability profile. The compound's efficacy at remarkably low doses-0.1 mg/kg in DTA mice, 0.3 mg/kg in Atax mice, and 1 mg/kg in wild-type animals-highlighted its potency advantage. Wake-promoting effects peaked in the first three hours after dosing, while cataplexy suppression extended to approximately six hours. Critically, these effects were maintained over 14 days of daily dosing without evidence of meaningful tolerance, an observation that has been difficult to achieve with many existing treatment options.

Phase 1 Clinical Results

Phase 1 studies in healthy, acutely sleep-deprived volunteers employed a randomized, placebo-controlled single ascending dose (SAD) and multiple ascending dose (MAD) design. Pharmacodynamic endpoints included the Maintenance of Wakefulness Test (MWT) and the Karolinska Sleepiness Scale (KSS).

Key Phase 1 results include:

At the 2.5 mg dose, mean sleep latency reached normative wakefulness thresholds, representing a clinically meaningful effect. Pharmacokinetics showed a Tmax of approximately 2 hours with dose-proportional exposure, supporting once-daily oral dosing. Adverse events were mild and transient, with no hepatotoxicity, visual disturbances, or cardiovascular signals.

Phase 2 Trials

The pivotal Phase 2a study, CRYSTAL-1 (NCT06752668), is a double-blind, placebo-controlled crossover trial enrolling patients across three cohorts: NT1 (~18 participants, starting dose ~1 mg), NT2 (~24 participants, starting dose ~2 mg), and idiopathic hypersomnia (~36 participants, starting dose ~2 mg). Each participant receives 4 weeks of active treatment and 2 weeks of placebo in crossover fashion. Primary endpoints include MWT change from baseline compared to placebo, Epworth Sleepiness Scale (ESS) scores, and weekly cataplexy rate for the NT1 cohort. The trial is powered to detect approximately a 15-minute MWT improvement (>87.5% power, α = 0.05).

Pan-indication coverage is being evaluated for narcolepsy types 1 and 2 and idiopathic hypersomnia within this single platform trial. An open-label extension, CRYSTAL-2, enrolls completers for up to 70 days of continued dosing to assess sustained safety and efficacy.

Interim Efficacy Signals

Publicly disclosed interim data suggest encouraging results. Cleminorexton demonstrated efficacy across all three populations: in the NT1 cohort, cataplexy reduction approached 87%, with MWT improvements of approximately 20 minutes and ESS score reductions of roughly 5.1 points. In NT2, MWT improved by about 10 minutes (p ≈ 0.0193), with ESS declining from 17.3 to 8.1 (p ≈ 0.0023). The IH cohort also reached statistical significance (p ≈ 0.0213). In a Phase 2 trial, cleminorexton improved sleep latency significantly, and cleminorexton showed significant efficacy in narcolepsy patients across key endpoints. These data remain preliminary and should be interpreted cautiously pending full peer-reviewed publication.

Clinical Use, Indications, and Safety Profile

As of mid-2026, cleminorexton is under clinical investigation and not yet approved for commercial use. Anticipated indications span NT1, NT2, idiopathic hypersomnia, and potentially other hypersomnolence disorders. The drug is aimed at reducing excessive daytime sleepiness and improving alertness in these populations, and cleminorexton reduces symptoms related to narcolepsy and may improve daily functioning based on early data.

Comparison with Existing Treatment Strategies

The current opinion among sleep specialists is that existing treatment options for narcolepsy have meaningful limitations. Traditional wake-promoting agents such as modafinil, amphetamine-based stimulants, and pitolisant have established roles in clinical practice but act on downstream neurotransmitter systems rather than the underlying orexin deficiency. Sodium oxybate addresses cataplexy and sleep consolidation but requires nocturnal dosing and carries significant abuse potential.

Cleminorexton's mechanism is fundamentally different: it replaces or mimics the missing orexin signal specifically at OX2R, which may produce more naturalistic sleep-wake architecture. Potential advantages include lower abuse potential, fewer cardiovascular side effects compared to stimulants, and possibly less rebound hypersomnia. Cleminorexton may improve sleep latency compared to placebo without the tolerance concerns that plague some stimulant-based treatment strategies.

Safety and Tolerability

Emerging safety data are encouraging. In Phase 1 studies, most adverse events were mild and transient. Notably absent from the safety profile so far are concerns that have affected other compounds in the class:

• No hepatotoxicity signals

• No visual disturbances

• No clinically meaningful changes in cardiovascular parameters, ECGs, or vital signs

• No urinary frequency or salivary hypersecretion at meaningful incidence

However, longer-duration data in patient populations remain essential. Special populations that warrant attention include patients with comorbid obstructive sleep apnea, severe hepatic or renal impairment, and those taking concurrent CNS-active medications. Guidance on food effect interactions and impact on concurrent metabolic conditions including obesity will depend on final labeling data. Intersections with pulmonary medicine, particularly in patients with comorbid respiratory conditions, also deserve careful evaluation.

Future Research Directions

Potential off-label or investigational uses extend beyond primary hypersomnolence. Excessive daytime sleepiness in neurodegenerative diseases (Parkinson's, Alzheimer's), residual sleepiness after treatment of obstructive sleep apnea, and shift-work disorder represent areas where orexin agonism could theoretically provide benefit. These remain investigational and would require dedicated clinical programs. For example, the orexin system's role in metabolic regulation has prompted early research interest in whether OX2R modulation could influence weight regulation, though applications related to obesity are speculative at this stage.

Preparation of Stock Solutions and Laboratory Handling

This section is directed at preclinical and in vitro researchers who need to prepare stock solutions of cleminorexton for experimental use. Given that the compound is available through research chemical suppliers such as ProbeChem (catalog PC-25035, >98% purity), proper handling protocols are essential for reproducible results.

Concentration Calculations

To prepare stock solutions, use the molecular weight of 512.52 g/mol as the basis for molarity calculations. For a standard 10 mM stock solution in DMSO (commonly used for cell-based receptor activation assays), dissolve 5.13 mg of cleminorexton powder in 1.0 mL of anhydrous DMSO. Researchers should note that lot-specific molecular weights may differ slightly if salt forms or hydrated species are supplied, so always verify with the certificate of analysis.

For aqueous-compatible working concentrations, serial dilutions from the DMSO master stock are recommended. Verify solubility limits before preparing dilutions in aqueous buffers, as the compound's moderate lipophilicity (XLogP3 ~3.8) suggests limited aqueous solubility at higher concentrations.

Storage and Handling

Proper storage is critical for maintaining compound integrity:

• Solid powder: Store at ambient temperature for brief handling; 0–4 °C for short-term storage (days to weeks); −20 °C for long-term archival storage. Protect from light and moisture at all times.

• DMSO stock solution: Aliquot into single-use volumes to minimize freeze-thaw cycles. Store aliquots at −20 °C. Document the concentration, date, lot number, and solvent for each preparation.

In Vivo Dosing Preparation

For animal studies, vehicles typically consist of DMSO mixed with polyethylene glycol (PEG 400) and saline in ratios appropriate for the route of administration (oral gavage being the most common). Sterile filtration through 0.22 µm filters is recommended for injectable formulations. Document all vehicle compositions, preparation dates, and storage conditions to support experimental reproducibility. Standard PPE (gloves, lab coat, eye protection) should be worn when handling, and waste should be disposed of according to institutional hazardous chemical protocols.

Commercial and Strategic Context

Cleminorexton occupies a strategically important position in the competitive landscape of OX2R agonists, a drug class that represents multibillion dollar potential in the sleep medicine market. Industry confidence in this mechanism has been validated through major corporate transactions.

The Eli Lilly Acquisition

Cleminorexton originated at Orexia Therapeutics and was subsequently developed by centessa pharmaceuticals before a transformative deal reshaped its commercial trajectory. Eli Lilly acquired Centessa Pharmaceuticals for $6.3 billion in a transaction completed in early 2026, a move widely interpreted as a bet on OX2R agonism as a platform. This acquisition underscores the pharmaceutical industry's conviction that orexin replacement therapy can meaningfully disrupt the narcolepsy and hypersomnolence market.

Competitive Landscape

The competitive landscape includes Takeda's oveporexton (TAK-861) and Alkermes' alixorexton (ALKS-2680), both in Phase 2 development for NT1. Cleminorexton's profile-subnanomolar potency, nearly 10,000-fold OX2R selectivity, low effective doses, and a clean early safety record-positions it as a candidate for best in class designation within this emerging category. However, head-to-head comparisons do not yet exist, and each competitor may differentiate on dimensions such as dosing frequency, formulation, or indication breadth.

Market Opportunity

The unmet need in narcolepsy and idiopathic hypersomnia is substantial. Existing therapies carry meaningful limitations including abuse potential, cardiovascular risk, complex dosing regimens, and incomplete symptom control. No currently approved drug directly targets orexin deficiency, leaving a gap for disease-mechanism-based treatments. If clinical data continue to support cleminorexton's efficacy and safety profile, it could reshape the standard of care.

Potential future commercial applications beyond primary hypersomnolence include shift-work disorder, residual sleepiness in patients with treated obstructive sleep apnea, and neurodegenerative conditions where orexin neuron loss contributes to symptom burden. Each would require separate clinical development programs and carries its own regulatory pathway considerations.

Regulatory Status, Data Sources, and Licensing

As of mid-2026, cleminorexton remains in Phase 2 development with no regulatory approval recorded in FDA, EMA, or PMDA databases. The continued development of this compound through the CRYSTAL trial program will determine the timeline for potential Phase 3 initiation, which is anticipated for 2026–2027 if current results hold.

Public Data Sources

Researchers and clinicians tracking cleminorexton's progress can access key information through several public resources:

• ClinicalTrials.gov: Trial registrations for CRYSTAL-1 and CRYSTAL-2 provide protocol details, enrollment criteria, and status updates

• FDA GSRS / UNII database: The UNII AL84E4VK26 tracks the active moiety for pharmacovigilance and labeling purposes across regulatory systems

• PubChem and ChemSpider: Chemical structure, computed properties, and literature references indexed by CID and ChemSpider ID

• Conference abstracts: Sleep journal supplements and neurology conference proceedings (e.g., World Sleep Congress) provide interim clinical data with their respective file date and publication records

Licensing and Patent Considerations

Any license agreement governing external data use varies by source. ClinicalTrials.gov data are public domain within the United States, though international reuse may carry specific requirements. FDA-generated content is generally public domain, while NCI and similar agency materials require attribution. Company investor reports and press releases from centessa pharmaceuticals are proprietary but frequently cited under fair use in scientific discourse.

Patent protection for cleminorexton's composition of matter and methods of use is expected to cover a substantial exclusivity window, with key filings including patent families such as WO2023167925. These patents are available through WIPO and national patent offices for researchers conducting freedom-to-operate analyses.

Looking Ahead

The current opinion among experts in sleep medicine is that OX2R agonists represent the most significant mechanistic advance in narcolepsy treatment in decades. Cleminorexton's path forward depends on several factors: robust Phase 3 data demonstrating durable improvements in wakefulness and functional outcomes, long-term safety across diverse patient populations, and regulatory alignment on endpoints and labeling. The need for long-term safety monitoring cannot be overstated, particularly given that patients with narcolepsy require lifelong treatment.

For researchers, clinicians, and patients, staying informed on cleminorexton's development trajectory is worthwhile. The compound's progress through clinical trials will serve as a bellwether for the entire OX2R agonist class and may ultimately determine whether orexin replacement therapy becomes a cornerstone of evidence-based management for narcolepsy and other sleep-wake disorders.

Frequently Asked Questions

What is cleminorexton and what condition is it being developed for?

Cleminorexton (ORX-750) is an investigational oral compound being developed for narcolepsy type 1, narcolepsy type 2, and idiopathic hypersomnia. It is designed to restore wake-promoting signaling by activating orexin receptor 2, addressing the root cause of these disorders.

How does cleminorexton work differently from traditional narcolepsy medications?

Cleminorexton directly activates the orexin receptor pathway to restore the missing orexin signal, rather than broadly amplifying neurotransmitters like traditional stimulants. This targets the underlying cause of narcolepsy more specifically through physiologically targeted mechanisms.

What stage of development is cleminorexton currently in?

As of 2025-2026, cleminorexton is in Phase 2 clinical trials, specifically the CRYSTAL-1 (Phase 2a) and CRYSTAL-2 (open-label extension) studies. It is not yet FDA-approved and available only through authorized clinical trials.

What did preclinical studies show about cleminorexton's effectiveness?

Preclinical mouse studies showed cleminorexton produced up to 100% wakefulness for 3 hours at low doses, suppressed cataplexy for at least 6 hours, enhanced wake consolidation, and maintained these effects over 14 days without apparent tolerance development.

How selective is cleminorexton for its target receptor?

Cleminorexton shows approximately 9,800-fold selectivity for orexin receptor 2 over orexin receptor 1, with a subnanomolar potency of 0.11 nM at the target receptor. This high selectivity may help reduce unwanted side effects from off-target activation.