ARN-509 is a synthetic biaryl thiohydantoin derivative acting as a competitive inhibitor of the androgen receptor (AR) It binds AR with an IC50 of approximately 16 nmol/L blocking receptor-mediated signaling pathways implicated in prostate cell proliferation Androgen receptor is a nuclear hormone receptor crucial for male sexual differentiation and prostate cancer cell growth Overexpression or hyperactivation of AR frequently occurs in castration-resistant prostate cancer Experimental data indicate that ARN-509 treatment reduces AR-driven transcription and inhibits cell proliferation in prostate cancer cell lines such as LNCaP and VCaP In murine xenograft models oral dosing of ARN-509 diminishes androgen-dependent reporter gene activity reduces tumor cell proliferation and induces apoptosis ARN-509 is utilized in biomedical research to investigate AR signaling and prostate cancer therapeutics