An orally bioavailable androgen receptor (AR) antagonist with potential antineoplastic activity. Upon oral administration, proxalutamide binds to AR in target tissues, inhibits androgen-induced receptor activation, and facilitates the formation of inactive complexes that cannot translocate to the nucleus. This prevents binding to and transcription of AR-responsive genes that regulate prostate cancer cell proliferation. In addition, proxalutamide induces AR downregulation, thereby further preventing AR-mediated signaling. This ultimately leads to an inhibition of growth in AR-expressing prostate cancer cells. AR is overexpressed in prostate cancer and plays a key role in prostate cancer cell proliferation.