ARN-509 is an androgen receptor antagonist with potential antineoplastic activity.ARN-509 binds to AR in target tissues thereby preventing androgen-induced receptor activation and facilitating the formation of inactive complexes that cannot be translocated to the nucleus.This prevents binding to and transcription of AR-responsive genes.This ultimately inhibits the expression of genes that regulate prostate cancer cell proliferation and may lead to an inhibition of cell growth in AR-expressing tumor cells.