Experimental Drug Shows Promise for Treating Prostate Cancer

March 2nd, 2009

Some tumors of the prostate do not respond to standard hormone therapy. Now there is a new drug on the horizon that appears to slow the growth of difficult-to-treat tumors. Two small studies have yielded promising results.

In the first of these studies, a drug called abiraterone shrank tumors by 30% in one-fourth of 31 men whose prostate cancer did not respond to standard therapies and continued to grow. In 35% of the patients taking the experimental drug, their tumors stopped growing.

Standard PSA (prostate-specific antigen) measurements were able to give accurate indications of each response to the new treatment. PSA levels after 12 weeks of treatment with abiraterone lowered PSA levels by 50% or more in 71% of the patients. In two men, the PSA fell so dramatically, it was undetectable.

A leading medical authority at the Cedars-Sinai Medical Center in Los Angeles Radiation Oncology Department called abiraterone currently the most promising prostate cancer drug on the horizon. He explained that the new hormone therapy appears to be active in men not responsive to other hormone treatments.

Abiraterone works differently from other hormone treatments in wide use today. The new drug targets an enzyme called CYP17 that is needed to produce male hormones throughout the body. Current hormonal treatments can only prevent production of male hormones in the testes. Other parts of the body are still able to produce testosterone and related hormones called androgens that fuel the growth of prostate cancer.

The first study involved men who were initially treated surgically or medically to prevent testosterone production in the testes. None had received chemotherapy, sometimes administered when the cancer does not respond well to hormone therapy. Men in the study took abiraterone orally once a day and generally tolerated the drug without serious side effects.

In a second study, men who were given chemotherapy after their hormone treatment no longer worked showed similar encouraging results after taking the experimental drug. Cougar Biosciences is the manufacturer of abiraterone, and they funded this study.

Researchers have begun enrolling men in a larger and longer study. Patients will be randomly assigned to abiraterone or a placebo (sugar pill). If results continue to be promising, the company will apply to the FDA for approval of the drug. Unfortunately, these studies and the approval process can take several years.

In the U.S., prostate cancer was diagnosed in over 180,000 men and 28,000 men died of the disease in 2008. It is the second most common cause of cancer death in the U.S.

Source: WebMD Health News; 3/1/09 written by Charlene Laino and reviewed by Louise Chang, M.D. blog article by Anna Dabney

Entry Filed under: MEDICAL DISCOVERIES,Prostate Cancer,Prostate Cancer,Prostate Cancer