Prostate cancers initially need the male hormone testosterone for growth. Hormone therapies that lower the level of testosterone are among the most effective treatments for prostate cancers that have spread to other organs (metastasized). The benefits of hormone treatments do not last, however. Over time, many prostate cancers continue to grow despite hormonal therapies; these are called “castration-resistant prostate cancers.”
Abiraterone acetate is a standard treatment prescribed for men with castration-resistant prostate cancer, but often the cancer eventually continues to grow. In this study, researchers are finding the highest dose of an investigational drug called AT13387 that can be given safely in men with castration-resistant prostate cancer that continues to grow despite abiraterone therapy. In the second part of the study, researchers will evaluate the safety and preliminary effectiveness of AT13387 when combined with abiraterone and steroids in men for whom abiraterone therapy is starting to fail.
AT13387 is designed to inhibit cancer cell growth by blocking HSP90, a protein required for cell growth. It is given intravenously (by vein); abiraterone is given orally (by mouth).