Company: AstraZeneca ( AZN) Drug/indication: Zibotentan for prostate cancer Estimated timing: Fourth quarter Recent stock performance: A rebound in June and July has pushed the stock up 6% for the year. Zibotentan represents the biggest, near-term competitive threat to Dendreon's ( DNDN) prostate cancer immunotherapy Provenge. The phase III study of zibotentan targets the same patient population described in Provenge's FDA-approved label -- men with prostate cancer that no longer respond to hormone treatment but who have minimal bone pain and have not yet started chemotherapy. The study of 580 men compares treatment with zibotentan against best supportive care with a primary endpoint of overall survival. If the study is positive and zibotentan gains FDA approval, doctors will have another treatment choice besides Provenge for this group of prostate cancer patients.