EMPA is an orexin 2 receptor (OX2R) antagonist (Ki = 1.1 nM). It is selective for OX2R over OX1R (Ki = 900 nM). EMPA inhibits orexin-A- and orexin-B-induced calcium mobilization (IC50s = 8.8 and 7.9 nM, respectively) and increases orexin-A- and orexin-B-induced inositol phosphate accumulation (EC50s = 1.1 and 2.4 nM, respectively) in CHO(dHFr-) cells expressing recombinant human OX2R. It reduces spontaneous locomotor activity and orexin-B-induced hyperlocomotion in mice when administered at doses ranging between 10 and 300 mg/kg.
