 The orexin neuropeptide signaling system is a central promoter of wakefulness.Blocking the binding of wake-promoting neuropeptides orexin A and orexin B to receptors orexin receptor type 1 (OX1) and orexin receptor type 2 (OX2) is thought to suppress wake drive.Animal studies report the binding affinities for OX1 (0.55 nM) and OX2 (0.35 nM).