A late-stage trial of Johnson & Johnson's Zytiga has been unblinded due its effectiveness in patients with castration-resistant prostate cancer.

The healthcare giant's Janssen unit says that its second Zytiga (abiraterone) Phase III study will be unblinded, based on the unanimous recommendation of an independent data monitoring committee. The 1,088-patient study was evaluating the drug versus placebo (both plus prednisone) for the treatment of metastatic castration-resistant prostate cancer (CRPC) who have not received chemotherapy.

Janssen said the analysis of the trial revealed "differences in radiographic progression-free survival, overall survival and secondary endpoints that constitute evidence of clinical benefit as well as continued evidence of favourable safety" in patients receiving the Zytiga/prednisone combo. Based on the findings, the IDMC recommended that patients in the placebo arm be offered treatment with the drug - the results will be presented at an upcoming medical meeting.

Zytiga was approved in the USA and Europe last year for the treatment of metastatic CRPC who have received prior chemotherapy. Janssen now plans to submit for regulatory approval around the world beginning in the second half of 2012 for chemotherapy-naive patients.

If approved in this additional indication, Zytiga would proide a serious challenge to Dendreon’s prostate cancer immunotherapy Provenge (sipuleucel-T) which was approved by the US Food and Drug Administration in 2010.