A drug used to treat prostate cancer that has spread to other parts of the body and did not get better with other treatment, including docetaxel. 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. Blocking these proteins may keep cancer cells from growing. Enzalutamide is a type of antiandrogen. Also called Xtandi.