Cell Genesys Initiates Second Phase 3 Clinical Trial Of GVAX® Vaccine For Prostate Cancer

SOUTH SAN FRANCISCO, CA, July 5, 2005 -- Cell Genesys, Inc. (Nasdaq: CEGE) today announced the initiation of a second multicenter Phase 3 clinical trial of GVAX® vaccine for prostate cancer in patients with metastatic hormone-refractory prostate cancer.

This second Phase 3 trial, referred to as VITAL-2, is the other key component of the company's product registration strategy which builds on promising findings from two previously reported Phase 2 trials of the vaccine in over 100 patients with advanced prostate cancer.

The trial will compare GVAX® vaccine for prostate cancer plus Taxotere® (docetaxel) chemotherapy to Taxotere® plus prednisone with respect to survival benefit and is expected to enroll approximately 600 patients at approximately 100 medical centers across North America and Europe.

In May 2005, Cell Genesys received a Special Protocol Assessment (SPA) from the U.S. Food and Drug Administration (FDA) for this trial, which provided FDA confirmation that the trial design would adequately support a product registration application.

"The initiation of our second Phase 3 clinical trial for GVAX® vaccine for prostate cancer represents an important milestone for our lead product development program and our business as a whole," stated Joseph J. Vallner, Ph.D., president and chief operating officer of Cell Genesys. "We are very encouraged by the results we have seen to date with GVAX® vaccine for prostate cancer which includes a potential survival benefit in two separate Phase 2 trials and we hope that this product may someday provide a promising alternative to currently available therapies for patients with advanced prostate cancer."

Cell Genesys is conducting two Phase 3 clinical trials of GVAX® vaccine for prostate cancer in hormone-refractory prostate cancer patients with radiologic evidence of metastatic disease. The first trial (VITAL-1 for Vaccine ImmunoTherapy with Allogeneic prostate cancer cell Lines), which was initiated in July 2004, is enrolling chemotherapy naïve, asymptomatic patients without cancer-related pain and is comparing GVAX® vaccine to Taxotere® chemotherapy plus prednisone.

The trial is expected to enroll 600 patients and is designed to demonstrate superiority in the duration of survival for the GVAX® vaccine treatment arm. Cell Genesys received a SPA from the FDA for this trial in May 2004. More than 70 clinical trial sites in the United States are now open and patient accrual is ongoing.

The second trial (VITAL-2) which is now underway, is enrolling symptomatic patients with cancer-related pain and is comparing GVAX® vaccine plus Taxotere® to Taxotere® chemotherapy plus prednisone. This trial is also designed to demonstrate superiority in the duration of survival for the GVAX® vaccine plus Taxotere® treatment arm. Both the VITAL-1 and VITAL-2 trials will enroll patients with all levels of Gleason scores (a measure of the aggressiveness of prostate cancer) including the highest risk patients.

Cell Genesys has previously conducted two Phase 2 trials of GVAX® vaccine for prostate cancer in patients with advanced prostate cancer. At the Annual Meeting of the American Society of Clinical Oncology (ASCO) held last month, Cell Genesys reported additional promising results from a second Phase 2 trial of GVAX® vaccine for prostate cancer in patients with metastatic hormone-refractory prostate cancer.

The results for the 22 patients who received the highest dose - a dose comparable to that being employed in the company's ongoing Phase 3 program - indicate that the median survival has not been reached and the final median survival will be no less than 24.1 months based on the current median follow-up time for these patients.

Previously reported findings from the company's first Phase 2 trial of GVAX® vaccine for prostate cancer indicated an overall median survival of 26.2 months. The median survival results from both Phase 2 trials compare favorably to the recently reported median survival of 18.9 months for hormone-refractory metastatic prostate cancer patients treated with Taxotere® plus prednisone, the current standard of care.

Clinical trials of GVAX® cancer vaccines are under way for multiple types of cancer in addition to prostate cancer, including leukemia and pancreatic cancer.

GVAX® vaccines are whole-cell vaccines that are designed to stimulate an immune response against the patient's tumor. The vaccines are comprised of tumor cells that have been genetically modified to secrete GM-CSF, an immune stimulatory hormone that plays a key role in stimulating the body's immune response to vaccines and are being developed as non patient-specific "off-the-shelf" pharmaceutical products. GVAX® cancer vaccines have demonstrated a favorable side effect profile in over 600 patients treated in clinical trials to date.

Cell Genesys is focused on the development and commercialization of novel biological therapies for patients with cancer. The company is currently pursuing two clinical stage product platforms - GVAX® cancer vaccines and oncolytic virus therapies.

Ongoing clinical trials include Phase 3 trials of GVAX® vaccine for prostate cancer, Phase 2 trials of GVAX® vaccines for leukemia and pancreatic cancer, and a Phase 1 trial of CG0070 oncolytic virus therapy for bladder cancer and potentially other types of cancer.

GVAX® Prostate Cancer Vaccine Vs Docetaxel and Prednisone in Patients with Metastatic Hormone-Refractory Prostate Cancer This study is currently recruiting patients.