A non-steroidal aromatase inhibitor (IC50s = 5 and 1.4 nM for human placental and rat ovarian microsomal aromatase, respectively); selectively inhibits LH-induced estrogen over progesterone production in hamster ovarian tissue as well as ACTH-induced corticosterone and aldosterone production in rat adrenal tissue (IC50s = 0.03, 160, 100, and 1 μM, respectively); decreases ovarian estrogen levels in rats (0.26 mg/kg); inhibits growth of androstenedione-stimulated mammary D2 cells implanted in mice by 95% (0.5 mg per animal per day) ,