An antagonist of GnRHR (Ki = 0.9 nM in a radioligand binding assay); selective for GnRHR over CYP3A4 (IC50 = 56 μM) as well as a panel of 100 receptors, ion channels, enzymes, and transporters (IC50s = >10 μM); inhibits GnRH-induced inositol phosphate production in RBL-1 cells expressing human GnRHR (IC50 = 1.5 nM); suppresses production of luteinizing hormone in castrated male cynomolgus macaques at 30 mg/kg