Zytiga (abiraterone acetate) is an orally active inhibitor CYP17 a cytochrome p450 complex that is involved in testosterone production.
Zytiga is specifically indicated in combination with prednisone for the treatment of patients with metastatic castration-resistant prostate cancer who have received prior chemotherapy containing docetaxel.
Zytiga is supplied as a tablet for oral administration. The recommended dose is 1,000 mg administered orally once daily in combination with prednisone 5 mg administered orally twice daily. Zytiga must be taken on an empty stomach.
The FDA approval of Zytiga was based on a randomized, placebo-controlled, multicenter study in 1,195 subjects. The subjects received either Zytiga orally at a dose of 1,000 mg once daily in combination with prednisone 5 mg orally twice daily or placebo once daily plus prednisone 5 mg orally twice daily. Treatment was administered until disease progression (defined as a 25% increase in PSA over the patient’s baseline), initiation of new treatment, unacceptable toxicity or withdrawal. The pre-specified interim analysis was conducted after 552 deaths and showed a statistically significant improvement in overall survival in subjects treated with Zytiga compared to placebo. An updated survival analysis was conducted when 775 deaths occurred. Results from this analysis were consistent with those from the interim analysis. In the interim analysis the median survival was 14.8 months for the Zytiga arm and 10.9 months for the placebo arm. In the updated analysis the median survival was 15.8 months and 11.2 months, respectively.
Adverse events associated with the use of Zytiga may include, but are not limited to, the following:
Abiraterone acetate is converted in vivo to abiraterone, an androgen biosynthesis inhibitor, that inhibits 17 a-hydroxylase/C17,20-lyase (CYP17). This enzyme is expressed in testicular, adrenal, and prostatic tumor tissues and is required for androgen biosynthesis.
For additional information regarding Zytiga or prostate cancer, please visit the Zytiga web page.