Cell Genesys Inc has put a halt to its process of developing the treatment for the advanced stages of prostate cancer as a consequence of the high death rates compared to another treatment of the same disease.

The move caused the shares of the San Francisco-based biotechnology company to drop 72% to 78 cents in early-afternoon trading.

The treatment called GVAX immunotherapy had reached the second Phase 3 trial (Vital-2) and the results of it were compared with the combined treatment of Taxotere and prednisone. Of the 48 patients involved in the trial and treatment, 67 who took GVAX perished. Only 47 patients died while undergoing Taxotere treatment.

Although the reason why more patients died when using GVAX treatment than when using Taxotere, Cell Genesys heads decided to cease all the research work at the testing involved in the Vital-2 study.

“Enrollment of new patients into Vital-2 has been suspended as has treatment with GVAX immunotherapy for prostate cancer of patients enrolled in the study," said Stephen A. Sherwin, M.D., chairman.

GVAX treatment is meant to work as a prostate cancer vaccine and drive away existing cancer before strengthening the immune system. The company’s independent data monitoring committee, which notified about the imbalanced number of deaths between the two groups of patients, did not report any new safety issues for GVAX treatment when combined with Sanofi-Aventis SA-made Taxotere.