Cell Genesys Announces Final Results From Phase 3 Program Of GVAX Immunotherapy For Prostate Cancer

Cell Genesys, Inc. (NASDAQ:CEGE) announced today results from further analyses of VITAL-1, the Company's recently terminated Phase 3 clinical trial which compared GVAX immunotherapy for prostate cancer to Taxotere® (docetaxel) chemotherapy plus prednisone and enrolled 626 advanced prostate cancer patients with asymptomatic castrate-resistant metastatic disease. VITAL-1 was terminated in October 2008 based on the results of a futility analysis conducted at the Company's request by the study's Independent Data Monitoring Committee (IDMC) which indicated that the trial had less than a 30 percent chance of meeting its predefined primary endpoint of an improvement in overall survival. However, the final Kaplan-Meier survival curves for the two treatment arms suggest a late favorable effect of GVAX immunotherapy on patient survival compared to chemotherapy, with the curve for GVAX patients crossing above the chemotherapy curve at approximately the same time median survival was reached in both treatment arms (21 months). Additionally, the data suggest that patients with Halabi predicted survival (HPS) greater than or equal to 18 months may have a more favorable response to the immunotherapy. Treatment with GVAX immunotherapy was generally well-tolerated and had a very favorable side-effect profile compared to Taxotere chemotherapy particularly with respect to a lower frequency of grade 3 or higher toxicity of nine percent versus 43 percent. These results will be presented today at the American Society of Clinical Oncology's Genitourinary Cancer Symposium being held in Orlando, Florida. The abstract, #LBA150, can be found at http://www.asco.org.

"We believe that the further analyses of the VITAL-1 trial presented today indicate that GVAX immunotherapy for prostate cancer has clinical activity and a favorable safety profile compared to Taxotere chemotherapy, the standard of care for men with advanced prostate cancer," stated Stephen A. Sherwin, M.D., chairman and chief executive officer of Cell Genesys. "While we and our investigators were very disappointed with the failure of the trial to meet its primary endpoint of improvement in survival, we sincerely hope that we have contributed to a better understanding of how to best evaluate immunotherapy treatments in prostate cancer, both with respect to the potential delayed benefit of immunotherapy compared to a more rapidly acting chemotherapy, as well as the need to evaluate immunotherapies in patients with more favorable prognoses. The Company has recently taken steps to facilitate further studies of GVAX immunotherapy for prostate cancer and related GVAX products by academic investigators."

Earlier in the meeting, researchers also reported findings from further analyses of VITAL-2, the Company's second Phase 3 clinical trial of GVAX immunotherapy for prostate cancer used in combination with Taxotere (see abstract #7 at http://www.asco.org). VITAL-2, which compared GVAX immunotherapy for prostate cancer in combination with Taxotere to Taxotere plus prednisone and enrolled 408 patients with symptomatic castrate-resistant metastatic prostate cancer, was prematurely terminated in August 2008 following the recommendation of the trial's IDMC which in a routine safety meeting observed an imbalance in deaths between the two treatment arms of the study. Updated analyses show no significant toxicities in the GVAX plus Taxotere arm that could explain the imbalance in deaths. Eighty-five percent of deaths were reported as due to prostate cancer in both arms, and there was no trend in the causes of death in the remaining patients. These observations are consistent with the hypothesis that the decision to omit concomitant prednisone in the GVAX immunotherapy treatment arm to avoid the immunosuppressive effects of prednisone may have contributed to an unfavorable outcome compared to the combination of chemotherapy and prednisone. Additionally, it is important to note that further analyses of VITAL-2 have indicated that the imbalance in deaths between the two treatment arms has decreased from 20 deaths as reported at that the time of the IDMC's initial analysis (August, 2008) to 9 deaths at the time of the final analysis (December, 2008).

About VITAL-1 and VITAL-2

VITAL-1 was a Phase 3 clinical trial designed to compare GVAX cancer immunotherapy as a monotherapy to Taxotere chemotherapy plus prednisone in castrate-resistant prostate cancer (CRPC) patients with metastatic disease who were asymptomatic with respect to cancer-related pain. The primary endpoint of the trial was an improvement in survival. In 2007, the VITAL-1 trial completed enrollment with 626 patients at 131 sites in North America and the European Union. In January 2008, Cell Genesys announced that the IDMC had completed a pre-planned interim efficacy analysis for VITAL-1 and recommended that the study continue, providing no further information to the Company other than the recommendation to continue the trial. On August 27, 2008, the Company announced that it had requested the IDMC to conduct a previously unplanned futility analysis of VITAL-1. Based on the results of that analysis, the Company terminated the VITAL-1 trial in October 2008. VITAL-2 was a Phase 3 trial designed to compare GVAX immunotherapy in combination with Taxotere to Taxotere plus prednisone in CRPC patients with metastatic disease who were symptomatic with respect to cancer-related pain. The primary endpoint of the trial was also improvement in survival. VITAL-2 was initiated in June 2005 and had enrolled 408 patients at 115 clinical trial sites located in North America and the European Union prior to study termination. On August 27, 2008, the Company announced its decision to terminate enrollment and treatment with GVAX immunotherapy in VITAL-2 as recommended by its IDMC which, in a routine safety review meeting held at that time to review both VITAL-1 and VITAL-2, observed an imbalance in deaths between the two treatment arms of the VITAL-2 study.

About GVAX Immunotherapy for Prostate Cancer

GVAX immunotherapy for prostate cancer is comprised of two prostate tumor cell lines that have been modified to secrete GM-CSF (granulocyte-macrophage colony-stimulating factor), an immune stimulatory cytokine that plays a key role in stimulating the body's immune response, and then irradiated for safety. GVAX immunotherapy for prostate cancer is designed to be administered through intradermal injections on an outpatient basis.

About Cell Genesys

Cell Genesys is a biotechnology company that was focused on the development and commercialization of novel biological therapies for patients with cancer. Following the termination of the Phase 3 trials of GVAX immunotherapy for prostate cancer, the Company's lead product program, the Company implemented a substantial restructuring plan in October, 2008, and is currently evaluating strategic alternatives for the business. Cell Genesys is headquartered in Hayward,, California. For additional information, please visit the company's website at http://www.cellgenesys.com.

Statements made herein about the company, other than statements of historical fact, including statements about the progress, results, findings and timing of the company's clinical trials and preclinical programs, are forward-looking statements and are subject to a number of uncertainties that could cause actual results to differ materially from the statements made, including risks and uncertainties associated with the timing of the termination of VITAL-1 and the premature termination of VITAL-2, the timing of the further analyses of VITAL-2 and VITAL-2, the success of clinical trials and research and development programs generally, the regulatory approval process for clinical trials, and competitive technologies and products, and other risks. For information about these and other risks which may affect Cell Genesys, please see the company's reports on Form 10-Q, 10-K, and 8-K and other reports filed from time to time with the Securities and Exchange Commission. The company assumes no obligation to update the forward-looking information in this press release.