Investigational / not FDA-approved

Orexin A

Hypocretin-1 neuropeptide — ≠ OX2R agonists ≠ DORAs; CSF diagnostic ≠ vial therapy.

Editorial review:

What evidence says

Evidence snapshot

This drawer marks papers. It is not a plan, a dose, or a source. A paper is a bounded report. It is not a protocol. Grades name the object. They are not a safety rating.

Identity lock. Orexin A (hypocretin-1) is a 33-amino-acid hypothalamic neuropeptide (N-terminal pyroglutamate; two disulfide bonds) cleaved from the HCRT prepro-orexin precursor; sequences are identical in human/rat/mouse for orexin A. PubChem CID 56842143; formula C152H243N47O44S4 / MW 3561.1; CAS 205599-75-3. ≠ Orexin B / hypocretin-2. ≠ oral orexin-receptor agonists (e.g. OX2R agonists in narcolepsy trials — different drugs). ≠ dual orexin-receptor antagonists (suvorexant-class insomnia drugs — opposite pharmacology direction). No approved “orexin A peptide vial” therapy in this pack’s framing. This drawer marks papers. It is not use advice.

Bottom line

Sakurai 1998 discovered orexins as feeding/arousal neuropeptides; Chemelli orexin-knockout mice linked the system to narcolepsy; human CSF hypocretin-1 deficiency is a diagnostic cornerstone for narcolepsy type 1. Modern clinical advances in narcolepsy increasingly use receptor agonists/antagonists, not administered orexin-A peptide replacement as a marketed product. Grade peptide biology and CSF diagnostics separately from OX2R-agonist drugs.

Papers

Discovery / circuit biology

PMID 9491897 — Sakurai 1998

Tested: discovery of orexins and orexin receptors as hypothalamic neuropeptides/GPCRs regulating feeding behavior (Cell).

Does not show: a human peptide-replacement drug product.

PMID 10481909 — Chemelli 1999

Tested: narcolepsy phenotype in orexin knockout mice — molecular genetics of sleep regulation.

Does not show: human CSF diagnostics by itself (bridge paper to human disease).

PMID 17299454 — Sakurai 2007

Tested: Nature Reviews Neuroscience synthesis of the orexin/hypocretin neural circuit maintaining sleep and wakefulness.

Does not show: clinical peptide-vial efficacy.

Human narcolepsy / CSF hypocretin-1 (diagnostic biology)

PMID 11558795 — Nishino 2001

Tested: low CSF hypocretin (orexin) and altered energy homeostasis in human narcolepsy.

Does not show: that injecting orexin A is an approved therapy.

PMID 12374492 — Mignot 2002

Tested: role of CSF hypocretin measurement in diagnosing narcolepsy and other hypersomnias.

Does not show: therapeutic peptide replacement outcomes.

PMID 31324898 — Bassetti 2019

Tested: Nature Reviews Neurology clinical-spectrum review of narcolepsy (aetiopathophysiology, diagnosis, treatment).

Does not show: orexin-A vial approval; treatments discussed are clinical standard-of-care objects.

PMID 30546103 — Mahoney 2019

Tested: Nature Reviews Neuroscience neurobiological basis of narcolepsy (orexin-neuron loss framing).

Does not show: exogenous orexin-A peptide RCT success.

PMID 35624073 — Barateau 2022

Tested: clinical review update on narcolepsy.

Does not show: peptide-replacement marketing claims.

Receptor-agonist clinical object (NOT orexin-A peptide)

PMID 37494485 — Dauvilliers 2023

Tested: NEJM trial of an oral orexin receptor 2 agonist in narcolepsy type 1 — small-molecule OX2R agonist ≠ orexin-A peptide.

Does not show: that orexin-A peptide administration was the study intervention.

PMID 41076550 — Rauf 2025

Tested: review of orexin deficiency in narcolepsy — mechanisms, phenotypes, emerging therapeutic frontiers (includes receptor-targeted pipelines).

Does not show: approved orexin-A peptide replacement.

What is not established

Approved therapeutic use of administered orexin-A peptide. Equivalence of orexin A to orexin B, to OX2R agonists, or to dual orexin-receptor antagonists. Consumer sleep or appetite “orexin peptide” claims. Product identity for unregulated orexin-A preparations. This drawer does not provide use advice, schedules, or sourcing.

Selected sources

9491897 10481909 17299454 11558795 12374492 31324898 30546103 35624073 37494485 41076550

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