Filorexant is a dual antagonist of orexin 1 receptor (OX1R) and OX2R (Kis = 2.5 and 0.31 nM, respectively, for the recombinant human receptors). It selectively inhibits OX1R and OX2R over a panel of more than 170 receptors and enzymes. Filorexant inhibits orexin A-induced calcium mobilization in CHO cells expressing recombinant human OX1R or OX2R (Kb = 11 nM for both). It decreases locomotor activity in rats during the dark cycle when administered at a dose of 10 mg/kg. Filorexant (0.5 mg/kg) reduces the time spent awake and decreases the latency to slow-wave sleep stage 1 (SWS1) and SWS2, but not rapid eye movement (REM) sleep, in dogs. It increases the duration of SWS2, but not SWS1 or REM sleep, in the same model.
