Testosterone stimulates the growth of prostate cancer cells. Abiraterone works by inhibiting an enzyme in the body called cytochrome P450 17 (CYP17). This enzyme helps make testosterone. By blocking CYP17 activity, abiraterone decreases the amount of testosterone produced in the body.
The majority of testosterone in the body is produced by the testes. However, some testosterone is made by the adrenal glands and in the prostate cancer cells. Abiraterone decreases testosterone made in the cancer cells and the adrenal gland. Therefore, this drug may work in prostate cancer that has been resistant to other medical or surgical treatments that only worked to decrease testosterone made by the testes.
In clinical studies, abiraterone was shown to extend life by up to four months in men with late-stage prostate cancer who were previously treated with docetaxel (Taxotere®), a chemotherapy treatment. In these studies, men given abiraterone in addition to prednisone survived, on average, 14.8 months compared to 10.9 months in men who received a placebo (a "sugar pill" that does not contain any active ingredients) plus prednisone.
Zytiga Web site. Available at: http://www.zytiga.com/. Accessed June 16, 2011.
Food and Drug Administration (FDA) news release. FDA approves Zytiga for late-stage prostate cancer. Available at http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm253055.htm. Accessed June 16, 2011.
Food and Drug Administration, Center for Drug Evaluation and Research. Electronic orange book: approved drug products with therapeutic equivalence evaluations. FDA Web site. Available at: http://www.fda.gov/cder/ob/. Accessed June 17, 2011.
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