spec sheet11 rows
Nivasorexant idorsia's ACT-539313; the first selective orexin-1 receptor antagonist (SO1RA) taken into human trials, aimed at conditions like binge eating and anxiety rather than sleep, since blocking OX1 alone does not strongly promote sleep.
- first selective OX1 antagonist proven druggable in humans
- targets reward/appetite/anxiety circuitry without strong sedation
- explored for binge eating disorder rather than insomnia
- somnolence (most common)
- CYP2C19/3A4 drug-interaction potential
Overview
the drug that shows the 'other half' of orexin biology. blocking OX2 makes you sleepy; blocking OX1 mostly touches reward, appetite, and stress without knocking you out. nivasorexant was the first selective OX1 blocker in the clinic and was tested for binge eating disorder, not insomnia.
- nivasorexant was the first selective OX1 antagonist ever taken into human trials; every earlier orexin drug blocked OX2 (alone or with OX1).
- it was studied for binge eating disorder, not insomnia, because blocking OX1 alone does not strongly make you sleepy.
- the OX1/OX2 split is the key idea it demonstrates: OX2 is the sleep receptor, OX1 is more about reward, appetite, and stress.
- it came out of a happy accident in idorsia's chemistry program that turned a dual antagonist into a selective one.
Mechanism
nivasorexant is a selective -1 receptor (SO1RA); it preferentially blocks OX1R over OX2R. this selectivity matters because the two receptors do different jobs: OX2R is the main sleep/wake receptor (blocking it drives sleep), while OX1R is more tied to reward, motivation, food intake, and the stress/anxiety response. so a selective OX1 blocker is expected to modulate compulsive/appetitive behavior and anxiety without the strong sedation of dual or OX2 blockade, which is exactly the therapeutic angle idorsia pursued. in preclinical work it was active in a rat schedule-induced polydipsia model (a compulsive-behavior assay), supporting its selection as a candidate (williams 2024). it is a cyp substrate and itself a moderate cyp2c19 / weaker cyp3a4 inhibitor at studied doses (berger 2023).
receptor fingerprint
OX1R (-1 / HCRTR1)selective competitive antagonist
OX2R (-2 / HCRTR2)much weaker / spared (selectivity for OX1)
Safetyrisks and cautions, not medical advice
investigational; no approved-label profile. in clinical pharmacology work the most frequently reported adverse event was somnolence, and it showed drug-interaction potential as a cyp2c19 (and to a lesser degree cyp3a4/2c9) inhibitor, so co-medication effects would need attention (berger 2023). because OX1 block is not strongly sleep-promoting, it is not positioned as a hypnotic. not available as a medicine.
History
discovered at idorsia as ACT-539313 out of a dual-antagonist chemotype via a serendipitous medicinal-chemistry finding; it is described as the first SO1RA to enter clinical development and completed a phase 2 proof-of-concept trial in binge eating disorder in 2022 (williams 2024, j med chem). it sits alongside idorsia's daridorexant as the 'selective OX1' complement to the 'dual/OX2' sleep story.
Reputation
scientifically important as the proof-of-concept that selective OX1 blockade is druggable in humans and can target reward/appetite/anxiety rather than sleep; clinically it is early and its binge-eating results were not a blockbuster signal, so it remains investigational. it is the go-to example when explaining why OX1 vs OX2 selectivity matters.
Subjective profileweighing the evidence above
An important proof of concept, since it showed selective orexin-1 blockade is druggable in people, but efficacy in binge eating is still unproven and it is not available as a medicine. Anyone reading it as a sleep drug has it backwards, since blocking OX1 alone does not sedate much.
Resources
This entry is here for reference.
Research
- 1.Discovery of Nivasorexant (ACT-539313): The First Selective Orexin-1 Receptor Antagonist (SO1RA) Investigated in Clinical Trials.
- 2.Effect of nivasorexant (ACT-539313), a selective orexin-1-receptor antagonist, on multiple cytochrome P450 probe substrates in vitro and in vivo using a cocktail approach in healthy subjects.
2 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
does nivasorexant help you sleep?
not really, and that is the point. it selectively blocks OX1, which is not the main sleep receptor; OX2 is. so it modulates reward, appetite, and stress circuits without the strong sedation of dual or OX2 blockers. it was tested for binge eating, not insomnia.
what is a SO1RA?
a selective orexin-1 receptor antagonist. nivasorexant was the first one taken into human trials, versus the DORAs (dual OX1+OX2) and 2-SORAs (selective OX2) that dominate the sleep field.
can i get nivasorexant?
no; it is an investigational compound (idorsia) that completed an early phase 2 trial. it is not approved or marketed.
why does OX1 vs OX2 selectivity matter?
the two receptors do different things. OX2 mainly controls sleep/wake, so blocking it makes you sleepy. OX1 is more about reward, motivation, appetite, and anxiety, so a selective OX1 blocker can target compulsive or appetitive behaviors without knocking you out.
did it work for binge eating disorder?
it completed a phase 2 proof-of-concept in 2022, but it did not produce a strong enough signal to become a marketed therapy; it remains investigational and is mostly important as a mechanistic proof of concept.
Limitations of the evidence
- clinical efficacy still unproven; investigational
Adverse effects
- somnolence (most common)
- CYP2C19/3A4 drug-interaction potential