Efficacy of abiraterone acetate in post-docetaxel castration-resistant prostate cancer

Evaluation of: Reid AH, Attard G, Danila DC et al. Significant and sustained antitumor activity in post-docetaxel, castration-resistant prostate cancer with the CYP17 inhibitor abiraterone acetate. J. Clin. Oncol. 28(9), 1489-1495 (2010). Inhibition of cytochrome P17 (CYP17), which is involved in androgen synthesis, is a promising therapeutic strategy for castration-resistant prostate cancer (CRPC). The first multicenter, Phase II study of a CYP17 inhibitor, the small molecule abiraterone acetate, has been conducted on 47 patients that received prior docetaxel chemotherapy for prostate cancer. With 1000 mg once daily, declines of more than 50% in prostate-specific antigen and circulating tumor cell counts were seen in 51 and 63% of patients, respectively. Overall, the drug was well tolerated and had a significant antitumor activity with symptomatic improvements. Reid and colleagues' study highlights abiraterone as a key molecule in CRPC treatment and gives further evidence of the involvement of the androgen receptor signaling axis in the disease. A randomized Phase III trial is ongoing to define the prognostic impact of this drug among the very limited arsenal of drugs currently available for CRPC. In the meantime, other CYP17 inhibitors are expected to show a favorable safety and efficacy profile, as are other novel powerful agents and combinatorial therapeutic strategies.