In Vivo: MK-4541 (100 mg/kg; p.o.; 5 times per week for 5 weeks) inhibits prostate tumor growth in athymic nude mice bearing R-3327-G cells. MK-4541 (100 mg/kg, 200 mg/kg; p.o.; 5 times per week for 5 weeks) exhibits anti-androgen effects on the seminal vesicles, reduces plasma testosterone concentrations in intact males, and inhibits Ki67 expression. MK-4541 (15 mg/kg, 50 mg/kg; p.o.; 5 times per week for 8 weeks) causes the loss of musculoskeletal mass and function in adult castrated mice.