Roche and Kosan Biosciences Incorporated announced plans to initiate a phase II trial of KOS-862 in prostate cancer, while terminating a phase II trial in colorectal cancer.

Prostate cancer has been selected for further clinical development because of the high response rates recently reported for the epothilone class of drugs in this indication. The KOS-862 trial in colorectal cancer will be terminated due to unanticipated cumulative drug toxicities in patients who had been previously treated with oxaliplatin. A planned phase Ib combination trial of KOS-862 with Xeloda to support the colorectal trial will not be initiated, a company release said.

"Although we have concluded the colorectal cancer trials, the response rate of patients with prostate cancer towards other epothilones leads us to be optimistic about the potential efficacy of KOS-862 in this type of tumour," said Daniel V Santi, chairman and CEO of Kosan.

William M Burns, head of Roche's Pharmaceuticals Division, added, "Roche is confident in the potential of epothilones as important anticancer agents. We are pleased that the Roche-Kosan collaboration continues to move KOS-862 through the appropriate efficacy trials, while advancing next-generation epothilone analogs through the pipeline."

Roche and Kosan entered into an alliance for the co-development of KOS-862 and its back up compounds in September 2002. The partners expect to file an IND application and initiate a phase I clinical trial for a second epothilone compound in 2004. Currently, Roche and Kosan are discussing extending their relationship to generate and develop additional epothilone drug candidates.

Kosan Biosciences has two lead product candidates- KOS-862 and 17-AAG, including its proprietary formulation designated KOS-953. Both compounds are derived from an important class of natural products known as polyketides.