New Drug May Help Men with Hard-To-Treat Prostate Cancer

An investigational drug called abiraterone acetate can prolong survival of men with metastatic castration-resistant prostate cancer (CRPC) whose disease is progressing after receiving docetaxel-based chemotherapy, according to new findings.

Increased androgen synthesis in tumors is one mechanism of escape from conventional hormone treatments. Abiraterone acetate is an inhibitor of Cyp17, which blocks androgen biosynthesis in the testes, adrenal glands, as well as in the tumor, Dr. Scher's group explained in a poster presented at the symposium. The result is plasma testosterone levels in the 1-2 ng/mL range which is significantly lower than is achieved with standard therapies.

In a phase 3 multinational study, investigators randomized 797 such patients to receive abiraterone acetate plus prednisone and 398 to receive placebo plus prednisone. The median follow-up was 12.8 months.

Abiraterone acetate prolonged survival by a median of approximately four months, lead researcher Howard I. Scher, MD, of Memorial Sloan Kettering Cancer Center (MSKCC) in New York, reported at the fourth annual Genitourinary Cancers Symposium. Abiraterone acetate recipients had a 35% decreased risk of death relative to the placebo group.
Dr. Scher, who is Chief of Genitourinary Oncology Service at MSKCC Sidney Kimmel Center for Urologic and Prostate Cancers, and his collaborators also observed improvements in secondary end points attributable to abiraterone acetate, such as time to PSA progression, radiographic progression-free survival, and PSA response rate. Notable as well, was that the safety profile (adverse events or toxicities observed in patients receiving abiraterone acetate was very similar to placebo treated patients, Dr. Scher said. The events that occurred more frequently in abiraterone treated patients were fluid retention, hypokalemia, and hypertension which are related to the known mechanism of action of the drug.
These results establish that considering CRPC to be hormone refractory may deny patients a safe and life-prolonging treatment, Dr. Scher told attendees.

Johnson & Johnson, which is developing the new drug, funded the study.