On August 31st, 2012, the Food and Drug Administration (FDA) approved MDV3100 (now known as Xtandi) for treatment of prostate cancers in men who have previously failed hormone and chemo therapies. (See the full story in the August 31st issue of the Prostate Cancer Foundation, PCF, NewsPulse). In its Phase III clinical trials, Xtandi increased median survival by 4.8 months (18.4 versus 13.6 months) over patients receiving the placebo. Overall, some patients had lengthy remissions well beyond the average time while others did not respond. These positive results led to the Phase III clinical trial being stopped early and the drug then being offered to patients in the placebo arm of the study due to its effectiveness in causing remissions and its high patient tolerability. [This was also the case during the Phase III clinical trials for Zytiga (abiraterone acetate) in 2011.] Xtandi has a novel mechanism of action. It does not shut off the production of testosterone but instead blocks testosterone’s effects by directly blocking the activity of the androgen (hormone) receptor at three distinct points, thus interfering with the “engine” of prostate cancer progression. By comparison, Zytiga affects cancer progression by shutting off the cell’s supply of testosterone, the “fuel” that drives the “engine”. Both Zytiga and Xtandi are administered orally and are currently being evaluated in Phase III trials in patients who have failed hormone therapy but have not yet received chemotherapy. Further efforts will concentrate on testing both drugs in men with early recurrence of prostate cancer. In addition, both drugs are also being tested in a pre-surgical condition, prior to prostatectomy, with the intent of potentially curing primary, high-risk prostate cancer. Having both drugs available represents an important advance in patient treatment. The nine-year research and development period for Xtandi has been relatively short when compared to twelve years or more for other drugs. Xtandi will be distributed jointly by its co-developers, San Francisco’s Medivation, Inc. and the Japanese company, Astellas Pharma, Inc.