In vitro activity: Almorexant inhibits the increase in intracellular Ca2+ induced by 10 nM human orexin-A in Chinese hamster ovary cells with IC50 of 16 nM (rat) and 13 nM (human) for the OX1 receptor and 15 nM (rat) and 8 nM (human) for the OX2 receptor.

Kinase Assay: In binding kinetic analyses, [(3)H]almorexant had fast association and dissociation rates at hOX(1), whereas it had a fast association rate and a remarkably slow dissociation rate at hOX(2).

Cell Assay: Almorexant (also known as ACT078573) is a novel, potent, orally bioactive, competitive and dual orexin receptor antagonist with IC50 of 6.6 nM and 3.4 nM for OX1 and OX2 receptor, respectively. It has the potential for treating insomnia. In the inositol phosphates assay, almorexant acts as a competitive antagonist of hOX1R but a noncompetitive-like antagonist of hOX2R. Furthermore, almorexant shows effects on sleep in multiple species, including man.