Orexin-2 receptor (OX2R)

Class

Orexin-2 receptor antagonist

The orexin-2 receptor (OX2R) is a G protein-coupled receptor activated by the neuropeptides orexin-A and orexin-B, which are produced by a small population of hypothalamic neurons that project broadly throughout the brain. Orexin signaling through OX2R (and its counterpart OX1R) stabilizes wakefulness by reinforcing activity in arousal-promoting circuits, including histaminergic and noradrenergic pathways. Because sustained orexin tone helps keep a person awake and alert, blocking OX2R reduces this drive and promotes the onset and maintenance of sleep. This makes OX2R antagonism a rational strategy for conditions where excessive arousal or disrupted sleep architecture is a problem, most notably insomnia. Interest has also extended to mood disorders, since sleep disturbance and arousal dysregulation frequently accompany depression and other psychiatric conditions, and orexin signaling has been implicated in stress and reward circuitry more broadly. Selective OX2R antagonism, as opposed to blocking both orexin receptor subtypes, is intended to dampen the wake-promoting signal while leaving OX1R-mediated functions—which are more closely tied to reward and emotional processing—less affected. This selectivity is a deliberate design choice aimed at achieving sleep-related benefits with a potentially more targeted side-effect profile than dual orexin receptor blockade.