A drug used to treat prostate cancer that has spread to other parts of the body and is castration sensitive (has responded to treatments that lower testosterone levels). It is also used to treat prostate cancer that is castration resistant (has not responded to treatments that lower testosterone levels). It is also being studied in the treatment of other types of cancer. Enzalutamide binds to proteins called androgen receptors, which are found in some prostate cancer cells. These proteins bind to androgens (male hormones) and may cause cancer cells to grow. Enzalutamide blocks these proteins and may keep cancer cells from growing. It is a type of antiandrogen. Also called Xtandi.