ASC-J9, is antitumor agent. ASC-J9 suppresses castration-resistant prostate cancer growth via degradation of full-length and splice variant androgen receptors. Research results suggested that targeting both fAR- and AR3-mediated PCa growth by ASC-J9 may represent the novel therapeutic approach to suppress castration-resistant PCa. ASC-J9 ameliorates spinal and bulbar muscular atrophy phenotype via degradation of androgen receptor.