An androgen receptor antagonist (Ki = 11 nM); inhibits AR transactivation in U2OS osteosarcoma cells expressing human wild-type and mutant ARs (IC50s = 65, 66, 1,500, and 1,782 nM for wild-type, ARF876L, ARW741L, and ART877A, respectively); prevents androgen-induced AR nuclear translocation in AR-overexpressing HS-HEK293 and LNCaP cells; suppresses androgen-induced proliferation of VCaP cells (IC50 = 230 nM); reduces tumor growth in a VCaP castrated mouse xenograft model at 50 mg/kg per day; inhibits tumor growth without increasing serum testosterone levels in a VCaP intact mouse xenograft model ,