Cell Genesys is slashing three-quarters of its workforce after announcing it is terminating its VITAL-1 Phase III clinical trial of its prostate cancer immunotherapy agent GVAX and is halting further development of the drug.

The announcement is based on results that indicate the trial’s endpoint is not going to be reached.

The move comes less than two months after the company announced it was terminating its other Phase III trial of GVAX immunotherapy, VITAL-2, for prostate cancer, due to a higher than expected number of patient deaths.

The latest termination is based of the results of a futility analysis of the VITAL-1 trial, which was requested following the dropping of the VITAL-2 trial in August.

Results from this analysis indicated the VITAL-1 trial had less than a 30% chance of meeting its predefined primary endpoint of an improvement in survival.

The company announced in a statement that further development of the drug for treatment of prostate cancer would be put on hold pending a review of the programme with its collaborator Takeda Pharmaceutical.

As a result, staff numbers are expected to be reduced by 75% by the end of the year with further reductions anticipated in the first half of 2009 as additional activities are phased out, the company said.

“We are, needless to say, extremely disappointed with the outcome of the futility analysis for the VITAL-1 Phase III clinical trial, but remain committed to learning as much as we can about the potential role for immunotherapy in the treatment of cancer,” said Stephen Sherwin, Chairman and Chief Executive of Cell Genesys.

“The significant changes in our business which we are implementing today are painful by necessary and will enable us to consider the appropriate strategic alternatives for our company.”