Second-generation antiandrogen therapies that block the production of male sex hormones have been found effective in treating metastatic prostate cancer.
Of 30 men who received low doses of one the drugs in a multisite phase I/II trial designed to evaluate safety, 22 showed a sustained decline in the level of prostate specific antigen (PSA) in their blood.
Phase III clinical trials are planned to evaluate the drug's effect on survival in a large group of patients with metastatic prostate cancer.
The drugs prevent male hormones from stimulating growth of prostate cancer cells.
The new compounds - manufactured by the pharmaceutical company Medivation and known as MDV3100 and RD162 - appear to work well even in prostate cells that have a heightened sensitivity to hormones.
That heightened sensitivity makes prostate cancer cells resistant to existing antiandrogen therapies.
The drugs were discovered in the laboratory of Howard Hughes Medical Institute investigator Charles Sawyers at Memorial Sloan-Kettering Cancer Center in collaboration with chemist Michael Jung at UCLA.
Sawyers's team collaborated on the studies with researchers from the University of California Los Angeles, Oregon Health and Science University, University of Washington and Medivation.
He and his colleagues described the development of the drugs and initial testing in an article posted online April 9, 2009, in Science Express.