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.”
The androgen receptor is a protein that is important in the development and progression of prostate cancer. ARN-509 is an investigational drug designed to inhibit prostate cancer growth by blocking the androgen receptor. It is being evaluated in studies of men with castration-resistant prostate cancer that has spread (metastasized) to other parts of the body.
In this study, researchers are evaluating ARN-509 in men with castration-resistant prostate cancer that has not metastasized, but whose PSA levels are rising despite therapy, indicating they have a high risk of developing metastatic cancer. Patients will be randomly assigned to receive ARN-509 (two-thirds of the patients) or a placebo (one-third of the patients). ARN-509 is a capsule that is taken orally (by mouth).