Drug shrinks stubborn prostate tumors

July 22, 2008 9:09:33 AM PDT
Doctors may soon have a new weapon in fighting prostate cancer that doesn't respond to other treatments.

A pill now under development by a Southern California company is showing promise in dramatically shrinking tumors in men with advanced prostate cancer who had not responded to other treatments.

That's according to a study published in the Journal of Clinical Oncology.

The phase 1 clinical trial showed that Cougar Biotechnology Inc's drug abiraterone delayed a worsening of the disease by a median of 400 days.

Prostate cancer is the second-leading cancer killer of men after lung cancer. Each year, 680,000 men worldwide are diagnosed with the disease and about 220,000 will die from it.

All the volunteers in the study had an aggressive form of prostate cancer in which some researchers believe the tumor tissue is able to produce its own supply of the hormones that fuel the disease.

Johan deBono, of Britain's Institute of Cancer Research, the lead scientists on the trials, says, "This drug prevents the cancer from making its own hormones that allow the cancer cells to survive."

Prostate cancer is the second-leading cancer killer of men after lung cancer. Each year, 680,000 men worldwide are diagnosed with the disease and about 220,000 will die from it.

All the volunteers in the study had an aggressive form of prostate cancer in which some researchers believe the tumor tissue is able to produce its own supply of the hormones that fuel the disease.

The drug targets an enzyme called CYP17, which plays a key role in this process, he said.

About 70 to 80 percent of the men in the study showed declines in PSA levels and their tumors shrank, even when the cancer had spread to other parts of the body, de Bono said.

Prostate-specific antigen, or PSA, is a protein produced only by prostate cells. PSA goes up as the prostate enlarges, but it also rises if there is a tumor in the gland.

Abiraterone works not only in blocking the generation of these hormones in the testes, but also elsewhere in the body, including generation of the hormones in the cancer itself.

The researchers said some volunteers have been on the drug for up to two-and-a-half years and were able to control the disease with few side effects. They included fatigue and weight gain, they added.

The drug is now in Phase III trials. Cougar Biotechnologies hopes to have it on the market by 2011. It has gone from Phase I to Phase III in under three years.


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