Purity >98%. Abiraterone is the active metabolite of abiraterone acetate . Abiraterone blocks cytochrome P450 17A1 (also known as steroid 17Alpha-hydroxylase/17,20 lyase) by potently inhibiting both the 17Alpha-hydroxylase and the 17,20 lyase activities (IC50 = 18 and 17 nM, respectively). In mice as well as men, it essentially eliminates plasma testosterone while producing a 3- to 4-fold increase in plasma luteinizing hormone. In clinical trials, abiraterone improves radiographic progression-free survival and significantly delays decline in human metastatic castration-resistant prostate cancer.