You're getting the first look at the Kaplan-Meier overall survival curves from the phase III "PREVAIL" study of Medivation (MDVN) and Astellas' Xtandi (enzalutamide) in pre-chemo prostate cancer patients. An update from the PREVAIL study was released tonight in advance of a formal presentation on Thursday at a medical conference.
Investors have been eager to see the Xtandi overall survival curves ever since Medivation and Astellas announced positive results and an early stop to the phase III study last November. As you can clearly see, a survival benefit favoring Xtandi (the green line) over placebo (blue line) starts early in the study at about four months and continues until the very end when the curves finally cross with only four patients remaining alive.
As previously disclosed, the overall survival hazard ratio is 0.706, translating into a 29% reduction in the risk of death favoring Xtandi over placebo. Highly statistically significant. At the median, the overall survival benefit favoring Xtandi is 2.2 months over placebo.
Xtandi is competing against Johnson & Johnson's (JNJ) Zytiga in the pre-chemo prostate cancer treatment market. The two drugs have not been studied directly against each other but J&J did conduct its own phase III study of Zytiga plus prednisone versus prednisone alone. Data from this study have been presented at various medical meetings already.
For comparison purposes, here's what the Zytiga overall survival curves look like from its respective phase III study:
Notice: The Zytiga survival curve doesn't start to separate from the control arm until 18 months into the study. The hazard ratio for overall survival from the Zytiga study is 0.79, or a 21% reduction in the risk of death, favoring Zytiga over control. This survival result was not statistically significant because the study was stopped too early.
The full presentation of the Xtandi PREVAIL data on Thursday will be made by Dr. Tomasz Beer of the Knight Cancer Institute at Oregon Health and Science University. Beer previewed his Xtandi presentation with the media earlier today, which is where these slides come from (with the exception of the abiraterone slide, which was shared with me by an investor who keeps better notes than I do.)
Medivation and Astellas did not comment on the new Xtandi data ahead of Thursday's presentation.
The co-primary endpoint of the Xtandi PREVAIL study was radiographic progression-free survival (rPFS.) Here's what those data look like: