Discovery of ARD-69 as a Highly Potent Proteolysis Targeting Chimera (PROTAC) Degrader of Androgen Receptor (AR) for the Treatment of Prostate Cancer

We report herein the discovery of highly potent PROTAC degraders of androgen receptor (AR), as exemplified by compound 34 (ARD-69). ARD-69 induces degradation of AR protein in AR-positive prostate cancer cell lines in a dose- and time-dependent manner. ARD-69 achieves DC50 values of 0.86, 0.76, and 10.4 nM in LNCaP, VCaP, and 22Rv1 AR+ prostate cancer cell lines, respectively. ARD-69 is capable of reducing the AR protein level by >95% in these prostate cancer cell lines and effectively suppressing AR-regulated gene expression. ARD-69 potently inhibits cell growth in these AR-positive prostate cancer cell lines and is >100 times more potent than AR antagonists. A single dose of ARD-69 effectively reduces the level of AR protein in xenograft tumor tissue in mice. Further optimization of ARD-69 may ultimately lead to a new therapy for AR+, castration-resistant prostate cancer.