Abiraterone works by blocking the effects of an enzyme (called CYP17) that is found in testicular, adrenal, and prostate tumor tissue that is necessary for the production of testosterone and other androgens. By blocking this enzyme, abiraterone reduces the production of testosterone and other androgens which stimulate prostate cancer cells to grow. Abiraterone inhibits androgen at 3 sources—the testes, the adrenal glands, AND the tumor itself.