Second Positive Phase 3 Trial Results for Zytiga

A second phase 3 clinical trial of Abiraterone (Zytiga) has been successfully completed for earlier stage prostate cancer in men who had not received chemotherapy. The trial has been halted early due to positive results so that the placebo arm could offered treatment with Abiraterone.

In one of those situations when actual clinical practice precedes the normal drug development process a recent announcement from Janssen Research & Development, LLC (Johnson & Johnson) informs that they have un-blinded their Phase 3 study, COU-AA-302, which clearly demonstrates that Zytiga (abiraterone acetate), when taken with prednisone, is effective in treating both mildly symptomatic or asymptomatic men who have metastatic castration-resistant prostate cancer (CRPC) and have not yet had chemotherapy.
The U.S Food and Drug Administration (FDA) approved Zytiga in 2011 for men post chemotherapy failure. According to William N. Hait, MD, PhD, from Global Head, Janssen R&D,
“Since its first approval in the U.S in 2011, Zytiga has been approved in 39 additional countries, many thousands of men have received treatment with it, and it is quickly becoming one of the cornerstones of our oncology offerings.”

The trial, COU-AA-302 which is a double-blind, randomized, international, placebo-controlled study, involved 1,088 men who were given either Zytiga at a dosage of 1,000 mg once a day, as well as prednisone at 5mg twice a day, or a prednisone 5mg twice a day, as well as a placebo.
After analyzing the early data it was recommended by The Independent Data Monitoring Committee (IDMC) that the study be un-blinded and men in the control arm be offeed Zytiga. The Committee made their recommendation after they found the study reached statistical significance on a primary endpoint which was R-PFS and on all secondary endpoints as well as a strong trend for overall survival, all of which constituted compelling evidence of clinical benefit. The actual survival data will continue to mature, however the data will be clouded because of the crossover of men in the placebo arm who will now get Zytiga.
The results from the study have not yet been published, but they will be presented at a medical meeting in the near future, as well as be published in a peer-reviewed journal.

Since the side effect profile of Zytiga is less than chemotherapy, many clinicians have already been using Zytiga with men who have not yet had chemotherapy. The surprise is that most insurance companies have paid for this “off label” treatment. With this new data hopefully those companies that have not been willing to pay for early Zytiga will re-evaluate their position.