A new drug that takes a unique approach to blocking prostate cancer tumour growth is showing some success, researchers report.
The new drug, tentatively called MDV3100, is for patients with advanced prostate cancer whose cancer has metastasized, or spread to other areas of the body.
The results of early tests show the drug is safe and well-tolerated and might be shrinking tumours as well, Dr. Chris Tran of Memorial Sloan-Kettering Cancer Center in New York and colleagues report in the journal Science.
Of 30 patients treated with the medication, 13 showed declines of more than 50 per cent in blood levels of PSA, or prostate specific antigen, a biomarker of tumour growth. The researchers call that a "promising" result.
The new drug helps stop testosterone and other male hormones called androgens from getting into cells and driving the cancer.
The current standard treatment for men with advanced prostate cancer is to use "anti-androgens," medications that shut down the "production factory" of the hormones. But tumours can become resistant to those drugs.
This new drug blocks the receptors for those androgens on the tumour cells, the researchers explain.
"Of the first 30 patients treated with MDV3100 in a phase I/II clinical trial, 13 of 30 (43 per cent) showed sustained declines (by more than 50 per cent) in serum levels of prostate specific antigen, a biomarker of prostate cancer," they wrote.
Lower levels of PSA suggest that tumors have stopped growing or have shrunk.
The drug still faces a larger phase III test of effectiveness before it can be proposed for use in patients. An application for a large-scale, international trial has been submitted to the U.S. Food and Drug Administration by Medivation Inc., a California-based biopharmaceutical company that has licensed the drug.
