CHICAGO ( TheStreet) -- Johnson & Johnson's ( JNJ) Zytiga improved survival in "pre-chemo" prostate cancer patients by 33% and more than doubled the time before cancer worsened compared to control, according to results from a phase III study to be presented today at the American Society of Clinical Oncology (ASCO) annual meeting. Zytiga, a pill, was first approved in 2011 as a treatment for prostate cancer patients who have previously been treated with chemotherapy. The new data released for the first time Saturday open a much larger commercial opportunity for J&J because if approved, Zytiga will become a treatment option for men with less advanced prostate cancer.
J&J reported Zytiga sales of $200 million, half of those in the U.S., in the first quarter. The strong Zytiga results are expected to have positive spillover effects for Medivation ( MDVN), which is developing its own prostate cancer pill MDV3100 that is similar -- and perhaps superior to -- Zytiga. Both Zytiga and MDV3100 work similarly by interfering with the way prostate cancer cells feed from testosterone produced in the body. Dendreon ( DNDN), however, may emerge from this year's ASCO meeting with a limp. Based on today's Zytiga results, the pill could steal prostate cancer patients away from its Provenge immunotherapy. In the J&J study, 1,088 patients with prostate cancer who had not yet received chemotherapy were treated with Zytiga plus the steroid prednisone or a placebo plus prednisone. The study was stopped early after an interim analysis found that treatment with Zytiga reduced the risk of prostate cancer worsening or death (also known as progression-free survival) by 57% compared to placebo. The result was highly statistically significant, with a p value of 0.0001, meaning there was less than a one-hundredth of 1% chance that the outcome was derived by chance. Prostate cancer patients treated with placebo reported a median progression-free survival (PFS) of 8.3 months, while the median PFS for Zytiga-treated patients has not yet been reached. " Progression events are coming in slowly, which demonstrates the benefit that Zytiga is having for patients," said Dr. Michael Meyers, a Johnson & Johnson vice president in charge of Zytiga's clinical development.