April 28, 2011 – The U.S. Food and Drug Administration (FDA) approved the marketing of a new anti-cancer drug, Zytiga (abiraterone acetate), for use in combination with prednisone in the treatment of patients with metastatic prostate cancer who have been previously treated with a paclitaxel-containing chemotherapy regimen and for whom depot treatment has failed. Abiraterone acetate is an oral cytochrome oxidase P450 (CYP450) c17 inhibitor that reduces androgen levels by inhibiting CYP450c17, a key enzyme in androgen synthesis, and has an inhibitory effect on androgens in the testes and elsewhere in the body. The efficacy of abiraterone hydrochloride was confirmed in a phase 3 randomized, placebo-controlled, multicenter study in which 1195 patients with advanced prostate cancer who had previously received paclitaxel chemotherapy and had failed depot therapy were treated with abiraterone acetate 1gm once daily in combination with prednisone 5mg twice daily or placebo in combination with prednisone 5mg twice daily in this trial. The results of the study showed a 35% relative reduction in the risk of death in the abiraterone acetate combined with prednisone treatment group [14.8 months vs. 10.9 months] and a 3.9 month longer median survival compared to the placebo combined with prednisone treatment group. The results of the most recent analysis were consistent with the interim analysis, with a 4.6-month difference in median survival between the two trial groups (15.8 months vs. 11.2 months). The most common adverse reactions (≥5%) reported in the clinical studies were joint swelling or discomfort, hypokalemia, edema, muscle discomfort, hot flashes, diarrhea, urinary tract infection, cough, hypertension, arrhythmia, dysuria, nocturia, dyspepsia, and upper gastrointestinal infection. Two other phase II clinical studies have shown that abiraterone acetate not only reduces prostate-specific antigen (PSA) levels but also helps shrink tumors in prostate cancer that continues to grow despite drug or surgical debulking therapy, offering great promise for the clinical treatment of prostate cancer. Abiraterone acetate is an oral drug that must be taken on an empty stomach. No food should be eaten at least 2h before or 1h after taking the drug. If abiraterone acetate is taken with a meal, this can lead to a 10-fold increase in exposure to abiraterone and increase adverse effects. In conclusion, the availability of abiraterone acetate offers hope to patients with metastatic prostate cancer who have been previously treated with paclitaxel-containing chemotherapy regimens and for whom depot therapy has failed. Currently, abiraterone acetate is not approved for marketing in China.