NBI-42902 is an orally active, potent functional and competitive antagonist of GnRH receptor with an IC 50 value of 0.79 nM, a K i value of 0.56 nM, respectively. NBI-42902 inhibits GnRH-stimulated inositol phosphate (IP) accumulation, Ca 2+ flux, and ERK1/2 activation. NBI-42902 inhibits serum luteinizing hormone (LH) in castrated male macaques. NBI-42902 can be used for research on sex-hormone-related diseases.