By ecancer reporter Jo Armstrong

Presentation: LBA5: Abiraterone acetate (AA) plus low dose prednisone (P) improves overall survival (OS) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) who have progressed after docetaxel-based chemotherapy (chemo): Results of COU-AA-301, a randomised double-blind placebo-controlled phase III study - J De Bono

Top-line phase III clinical trial data on abiraterone acetate (AA) in the treatment of castration-resistant prostate cancer (CRPC) was presented at this year's ESMO conference in Milan.

AA, which is a selective androgen biosynthesis inhibitor that acts by blocking CYP17 and potently inhibits persistent androgen synthesis (PAS) from adrenal and intratumoral (autocrine/paracrine) sources, is the latest breakthrough for the treatment of advanced cases and is the first in class intracrine androgen antagonist for patients whose cancer has stopped responding to androgen deprivation therapy.

Clinical responses observed in phase I-II studies suggested that some CRPCs remain dependent on AR signalling. The COU-AA-301 study of 1,195 patients previously treated with docetaxel with mCRPC from 13 countries, showed that AA 1000mg plus prednisolone (5mg bid) resulted in significant improvements in overall survival (OS), time to PSA progression (TTPP), radiographic PFS (rPFS) and PSA response versus placebo plus prednisolone (p<0.0001).

Mineralocorticoid related AEs were more common in the AA arm vs placebo, but Grade 3/4 hypokalaemia and Grade 3/4 hypertension were infrequent. Liver function test abnormalities and cardiac disorders were observed in 10.4% AA vs 8.1% placebo and 12.5% AA vs 9.4% placebo, respectively.

This study concluded that AA resulted in prolonged OS by targeting PAS following medical/surgical castration in patients with mCRPC who have progressed after docetaxel-based chemotherapy.