Zytiga, also known by its generic name abiraterone, is a drug that is used to treat men with advanced prostate cancer which has become resistant to hormone therapy.
How Does Zytiga Work?
Zytiga works by blocking the action of an enzyme called 17 α-hydroxylase/C17,20 lyase (CYP17A1). This enzyme is important for the formation of testosterone within the body and, when blocked, overall testosterone production drops.
While other drugs have been developed that block the production of testosterone in the body, they have mostly worked to stop testicular production of testosterone. Zytiga works by essentially eliminating production of testosterone not only from the testicles, but also from the adrenal glands and the tumors themselves.
Because prostate cancer is known to grow in response to testosterone, lowering testosterone levels in the body can result in slowing or sometimes shrinking of prostate cancer.
Is It Approved for Use?
Zytiga is a relatively new drug and has only recently been approved by the Food and Drug Administration (FDA) for use in a subset of men with prostate cancer. Specifically, the FDA has approved its use in men who have prostate cancer that has spread beyond the prostate and which has become resistant to conventional hormone therapy. Its approved use has also been limited to those men who have already taken docetaxel -- an older, more widely used chemotherapy drug.
Zytiga is typically prescribed along with the steroid prednisone, as these drugs were used together in the clinical trials that led to Zytiga's FDA approval.
The FDA approved Zytiga for use in this subset of men with prostate cancer after studies showed increased survival, lowered PSA levels, decreased tumor size, and improved quality of life in men taking the drug.
Sources:
Ang1 JE, Olmos1 D, de Bono JS. CYP17 blockade by abiraterone: further evidence for frequent continued hormone-dependence in castration-resistant prostate cancer. British Journal of Cancer (2009) 100, 671–675.
Effect of abiraterone acetate (AA) on pain control and skeletal-related events (SRE) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) post docetaxel (D): Results from the COU-AA-301 phase III study. Abstract. American Society of Clinical Oncology Annual Meeting 2011.
