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Orexin B

Evidence: D

Sleep / Circadian

2 min readLast reviewed July 30, 2026

Key facts

  • Research areaSleep / Circadian
  • Study records161 human
  • Last updated2026-07-30

Evidence Snapshot

Evidence: DMostly Preclinical Evidence
2026-07-30Last updated

What this grade covers

A for identity and receptor pharmacology; B/C for laboratory physiology; E for human therapeutic efficacy, safety, approval, wakefulness, cognition, narcolepsy treatment, or dosing.

Regulatory Context

Orexin B is an endogenous research neuropeptide. No FDA-approved native Orexin B replacement product or verified direct human administration trial was identified. Approved orexin-system drugs and investigational synthetic OX2 agonists are different molecules and do not establish approval or efficacy for native Orexin B.

In Plain English

A quick, research-focused overview. It does not replace, and cannot outrank, the detailed evidence below.

What is it?

Orexin B, also called hypocretin-2, is a second endogenous orexin peptide. Its evidence base is primarily receptor, animal, and cellular research rather than direct human administration.

Why are researchers interested in it?

It is used to study OX2 receptor biology, wakefulness, respiration, feeding, cardiovascular physiology, and other orexin-system functions.

What does the evidence look like?

Evidence grade D. Human, preclinical, regulatory, review, and anecdotal evidence must remain separated.

Biggest things to know

Orexin B is not interchangeable with Orexin A or selective synthetic OX2 receptor agonists. Direct human safety and efficacy evidence is lacking.

Research Takeaway

Orexin B/hypocretin-2 is a native linear 28-amino-acid neuropeptide derived from prepro-orexin.

See all 9 evidence claims →

Quick Summary

Sleep / Circadian

Orexin B, also called hypocretin-2, is a native 28-amino-acid hypothalamic neuropeptide involved in orexin-receptor signaling. Evidence for native Orexin B consists primarily of receptor, structural, cellular, and animal research. No verified direct human administration trial establishes native Orexin B efficacy, safety, pharmacokinetics, or dosing.

Mechanism & Research Overview

Orexin B activates orexin receptors and has greater relative activity at OX2R than at OX1R compared with Orexin A, but this does not make it clinically selective or interchangeable with synthetic OX2 agonists. Native Orexin B, Orexin A, modified peptide analogues, receptor antagonists, and nonpeptide agonists must remain separate evidence categories.

Mechanism pathway

Relationship-support labels describe the type and directness of the research available, not proof of safety or effectiveness. Indirectly supported, inferred and uncertain relationships are not equivalent to directly supported ones.

  1. CompoundOrexin B
  2. Directly supported (Directly supported relationship)
    Biological targetOX2 receptorReceptor
  3. Leads to
    PathwayNeuropeptide & CNS Signaling

Relationship details

  1. Orexin B → OX2 receptor — Directly supportedActivates orexin receptors with greater relative OX2R preference than Orexin A.

Open in the Mechanism & Pathway Explorer→

Evidence Claims

Individual scientific statements drawn from the sources cited below, each shown with the specific evidence boundary that statement does not establish.

identity

Supported

Orexin B/hypocretin-2 is a native linear 28-amino-acid neuropeptide derived from prepro-orexin.

Sources: Solution Structure of Human Hypocretin-2/Orexin-B

identity

Supported

Orexin B and Orexin A are distinct peptides and are not dose-equivalent or clinically interchangeable.

Sources: Orexin B compound record

Mechanism

Supported

Native Orexin B participates in OX1R/OX2R receptor signaling, with greater relative OX2R preference than Orexin A in receptor studies.

Sources: Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior; Characterization of Recombinant Human Orexin Receptors; Structure-Activity Studies of Orexin A and Orexin B

preclinical_evidence

Supported

Evidence for native Orexin B is primarily structural, receptor, cellular, and animal evidence.

Sources: Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior; The hypocretins: hypothalamus-specific peptides with neuroexcitatory activity; Distinct recognition of OX1 and OX2 receptors by orexin peptides

human_evidence

Supported

No verified direct human administration study establishes native Orexin B therapeutic efficacy, safety, pharmacokinetics, or dosing.

Sources: Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior; The hypocretins: hypothalamus-specific peptides with neuroexcitatory activity; Distinct recognition of OX1 and OX2 receptors by orexin peptides

Evidence Boundary

Supported

Human evidence for synthetic nonpeptide OX2 agonists cannot be transferred to native Orexin B.

Sources: Danavorexton OX2R-Agonist Human Study

Evidence Boundary

Supported

Findings from modified Orexin B analogues cannot automatically be attributed to native human Orexin B.

Sources: Signaling Profile of Recombinant Human Orexin-2 Receptor

Regulatory Status

Supported

No FDA-approved native Orexin B replacement drug product was identified.

Sources: 503A Bulk Drug Substances Categories, Updated May 14, 2026; FDA Drug Approvals and Databases; ClinicalTrials.gov Search Portal

Safety

Supported

Human long-term, cardiovascular, neurologic, psychiatric, reproductive, and repeated-administration safety remain unestablished for native Orexin B.

Sources: Contribution of orexin in hypercapnic chemoreflex: evidence from genetic and pharmacological disruption and supplementation studies in mice; The role of orexin-B/orexin 2 receptor in myocardial protection

Safety & Evidence Limitations

Considerations reported in the sources cited on this page — not a complete list of every possible risk, and not medical advice.

  • Safety Consideration

    Potential central nervous system, autonomic, respiratory, cardiovascular, and metabolic effects are incompletely characterized in humans.

  • Safety Consideration

    Modified Orexin B analogues, including [Ala11]orexin-B used in some receptor-selectivity studies, cannot be treated as native Orexin B; findings from such analogues are not automatically attributable to native Orexin B.

  • Safety Consideration

    Long-term and repeated-administration safety are unknown.

  • Safety Consideration

    Potential concerns include excessive arousal, insomnia, anxiety, agitation, or panic; autonomic activation, blood-pressure, heart-rate, and thermoregulatory effects; appetite and metabolic changes; and receptor desensitization or altered sleep architecture. Relative OX2 preference does not establish clinical selectivity or safety.

  • Safety Consideration

    Uncertain CNS delivery and short peptide stability; species-sequence substitution; aggregation, peptide impurities, immunogenicity, sterility, and endotoxins; unknown cardiovascular, neurologic, psychiatric, reproductive, pregnancy, pediatric, and chronic-use risks; and unknown interactions with stimulants, sedatives, antidepressants, wake-promoting drugs, and orexin antagonists.

Research Areas Being Studied

Research areas discussed on this page reflect the Sleep / Circadian category and the sources cited below.

Findings Reported in Studies

Educational summary only — reported in cited studies, not a claim of proven benefit.

Show findings from 1 human study
  • Danavorexton OX2R-Agonist Human Study ():

Study Tables by Evidence Type

16 study records

Human Studies & Clinical Data(1)

Danavorexton OX2R-Agonist Human Study

PMID 36934366

Population / Model
Dose / Duration / Finding

Danavorexton is a synthetic, nonpeptide OX2R agonist studied in humans. It is a distinct molecular class from native Orexin A/Orexin B. Results from danavorexton, oveporexton, or another synthetic receptor agonist cannot establish the identity, stability, brain penetration, dosing, safety, or effectiveness of native orexin peptide products -- used here only as an identity/evidence boundary, not as orexin-peptide evidence.

Show full finding
View sourcePubMed

Animal / Cell / Preclinical Data(10)

Orexin A but not orexin B regulates lipid metabolism and leptin secretion in isolated porcine adipocytes

2018

PMID 29413903 · DOI 10.1016/j.domaniend.2017.12.003

Population / Model
Isolated porcine adipocytes and adipose explants
Dose / Duration / Finding

Orexin A changed several metabolic endpoints, while Orexin B did not show those effects in this model.

Safety note

Species- and tissue-specific negative result; not human systemic evidence.

View sourceDOIPubMed

The role of orexin-B/orexin 2 receptor in myocardial protection

2018

PMID 30467191

Population / Model
Cardiac ischemia/reperfusion models
Dose / Duration / Finding

Orexin B/OX2 receptor signaling was associated with selected myocardial-protection endpoints in preclinical models.

Safety note

Preclinical cardiac results do not establish human cardiovascular benefit or safety.

View sourcePubMed

Contribution of orexin in hypercapnic chemoreflex: evidence from genetic and pharmacological disruption and supplementation studies in mice

2007

PMID 17717124

Population / Model
Mouse respiratory chemoreflex experiments
Dose / Duration / Finding

Orexin signaling contributed to ventilatory responses to carbon dioxide in wakefulness.

Safety note

Respiratory effects are context-dependent and underscore possible autonomic risk.

View sourcePubMed

Distinct recognition of OX1 and OX2 receptors by orexin peptides

2003

PMID 12606634

Population / Model
Receptor-binding and cellular signaling assays
Dose / Duration / Finding

Compared how Orexin A and Orexin B interact with OX1 and OX2 receptor subtypes, supporting distinct pharmacology.

Safety note

In vitro receptor pharmacology does not predict full human safety or clinical effects.

View sourcePubMed

Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior

1998

PMID 9491897

Population / Model
Receptor deorphanization, rodent brain expression, and animal feeding experiments
Dose / Duration / Finding

Identified orexin A and B as endogenous ligands for two receptors and described hypothalamic expression and feeding-related effects.

Safety note

Foundational preclinical biology; not human treatment evidence.

View sourcePubMed

The hypocretins: hypothalamus-specific peptides with neuroexcitatory activity

1998

PMID 9419374

Population / Model
Molecular identification and neuronal studies
Dose / Duration / Finding

Independently described hypocretin-1 and hypocretin-2 as hypothalamic neuroexcitatory peptides.

Safety note

Foundational discovery work does not establish administered-human safety.

View sourcePubMed

Characterization of Recombinant Human Orexin Receptors

PMID 10498827

Population / Model
Dose / Duration / Finding

Orexin A activates both OX1R and OX2R with high functional activity at each. Orexin B activates OX2R efficiently but has substantially weaker functional activity at OX1R than Orexin A, so the two peptides must not be treated as interchangeable or dose-equivalent.

Show full finding
View sourcePubMed

Signaling Profile of Recombinant Human Orexin-2 Receptor

PMID 18599270

Population / Model
Dose / Duration / Finding

Cell and receptor-signaling research supports OX2R-mediated arousal signaling, receptor signaling and desensitization. These findings remain preclinical/cellular and do not establish human administered-Orexin-B efficacy or safety.

View sourcePubMed

Solution Structure of Human Hypocretin-2/Orexin-B

PMID 10583376

Population / Model
Dose / Duration / Finding

Orexin B, also called hypocretin-2, is an endogenous linear 28-amino-acid neuropeptide generated from prepro-orexin. The mature human peptide is C-terminally amidated. Human and rodent Orexin B sequences are not identical; species-specific sequence must be verified.

Show full finding
View sourcePubMed

Structure-Activity Studies of Orexin A and Orexin B

PMID 14971895

Population / Model
Dose / Duration / Finding

Structure-activity relationships for Orexin A and Orexin B are concentrated in the C-terminal region. Orexin B is often described as relatively OX2-preferring, but it is not an absolutely selective OX2R ligand, and results from a synthetic selective OX2R agonist cannot be assigned to native Orexin B.

Show full finding
View sourcePubMed

Regulatory Documents & Official Trial Registries(4)

503A Bulk Drug Substances Categories, Updated May 14, 2026

2026
Population / Model
Dose / Duration / Finding

Neither Orexin A nor Orexin B was identified as a current individually evaluated substance in the reviewed FDA 503A bulk-substance category list or FDA significant-safety-risk table as of this update. Absence from those lists is not approval, a safety determination, or authorization to compound.

Show full finding
View source

Orexin B compound record

2026
Population / Model
Chemical identity database record
Dose / Duration / Finding

PubChem records Orexin B as a defined endogenous peptide compound.

Safety note

An identity record does not indicate FDA approval or human-administration evidence.

View source

ClinicalTrials.gov Search Portal

Population / Model
Dose / Duration / Finding

General trial-registry search portal used as part of this review's regulatory/trial-landscape check.

View source

FDA Drug Approvals and Databases

Population / Model
Dose / Duration / Finding

No FDA-approved Orexin A or Orexin B peptide drug or indication was identified in the reviewed FDA drug databases.

View source

Review Articles / Secondary Sources(1)

Orexin (hypocretin) receptor agonists and antagonists for treatment of sleep disorders: rationale for development and current status

2013

PMID 23359095 · DOI 10.1007/s40263-012-0036-8

Population / Model
Narrative review of orexin biology and drug development
Dose / Duration / Finding

Reviews the role of orexin signaling in wakefulness, narcolepsy, and receptor-targeted drug development.

Safety note

Review evidence must not be presented as a primary trial of Orexin A or B.

View sourceDOIPubMed

Anecdotal Reported Patterns — Not Medical Advice

Anecdotal Reported Patterns — Not Medical Advice

Reported dosing patterns are included for educational context only. They are self-reported, unverified, not medical advice, and not instructions for human use. Community-submitted patterns are not yet available in this Phase 1 prototype; this section is a placeholder reserved for moderated, aggregated community data.

Lab Markers to Discuss With a Clinician

Educational topics only — not self-monitoring instructions.

FAQ

Orexin B, also called hypocretin-2, is a second endogenous orexin peptide. Its evidence base is primarily receptor, animal, and cellular research rather than direct human administration.

Disclaimer

This page concerns native Orexin B/hypocretin-2. Evidence from Orexin A, modified Orexin B analogues, synthetic OX2 agonists, or orexin antagonists is included only when needed to define an evidence boundary. It does not provide treatment, administration, or dosing guidance.

Educational use only. This content is provided for informational and research-summary purposes only. It is not medical advice, not a treatment recommendation, not a dosing guide, and not a substitute for care from a licensed medical professional. Nothing here is intended to diagnose, treat, cure, prevent, or mitigate disease. Reported dosing patterns, when shown elsewhere on the site, must be labeled either as Study / Trial Dosing or Anecdotal Reported Patterns — Not Medical Advice. Community reports are self-reported, unverified, and not scientific proof.

Community-reported experiences, once enabled, must be displayed only as moderated, anonymized, or aggregated data. They are anecdotal, self-reported, unverified, and should never be presented as proof of safety, efficacy, or expected results.

Content status: Published. Last updated 2026-07-30.

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