An experimental new drug for advanced prostate cancer seems to help men diagnosed with the most aggressive form of the disease that resists current treatments.

According to a report published in the April 10 issue of the journal Science, preliminary tests on 30 men in the first and second phases of clinical trials showed the treatment was safe and could be shrinking tumours.

Of the 30 patients who were given MDV3100, 13 showed declines of more than 50 percent in their PSA or prostate specific antigen levels -- a marker for prostate cancer.

Lower levels of PSA suggest tumours have stopped growing or shrunk.

MDV3100 is an "androgen receptor antagonist" that stops testosterone from getting into cells to keep its anticancer activity, Charles Sawyers of Memorial Sloan-Kettering Cancer Center in New York and his co-authors of the study said.

The findings of early phase I/II trials of the drug, dubbed MDV3100 and made by San Francisco-based Medivation Inc, will be published later this week in the journal Science in a study led by Charles Sawyers of Memorial Sloan-Kettering Cancer Center in New York.

(Agencies via Xinhua April 15, 2009)