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Cell Genesys Announces Publication of Encouraging Phase 1/2 Clinical Results For GVAX(R) Immunotherapy for Prostate Cancer in Early Stage Patients Before Receiving Hormone Therapy

SOUTH SAN FRANCISCO, Calif., July 5 /PRNewswire-FirstCall/ -- Cell Genesys, Inc. (Nasdaq: CEGE) today announced that the results from an initial clinical trial of GVAX(R) immunotherapy for prostate cancer in patients with early-stage disease have been published in a June issue of Clinical Cancer Research by a team led by Jonathan Simons, M.D., professor of Hematology and Oncology, Winship Cancer Institute, Emory University School of Medicine. The Phase 1/2 trial enrolled 21 patients with rising prostate specific antigen (PSA) levels following prostatectomy and who had not received any other treatment for their prostate cancer, including hormone therapy. The results showed that 16 of 21 (76%) patients showed a statistically significant decrease in the rate of rise of PSA (PSA slope) post-treatment compared with the remaining five patients (p<0.001). One patient had a partial PSA response (>50% reduction of PSA) of 7-month duration. GVAX cancer immunotherapy was generally well tolerated, with self-limited injection site reactions, and mild flu-like symptoms being the most frequently reported side effects. In addition to clinical activity, the publication reported immunologic findings confirming that GVAX immunotherapy for prostate cancer resulted in the induction of immune responses as evidenced by the formation of antibodies directed against prostate cancer cells.

Cell Genesys has completed five Phase 1 and Phase 2 clinical trials of GVAX immunotherapy for prostate cancer in approximately 200 patients with various stages of recurrent prostate cancer, and each trial has demonstrated a favorable safety profile. The initial Phase 1 /2 clinical trial in early- stage prostate cancer described in the above publication was conducted at Johns Hopkins Oncology Center. GVAX immunotherapy treatment was administered at a fixed dose in eight weekly intradermal injections in an outpatient setting. As noted above, one patient had a partial PSA response of 7-month duration which was associated with a corresponding decline in the tumor- associated marker, carcinoembryonic antigen (CEA), as well as induction of a high titer antibody response against a prostate cancer antigen. The titer of this antibody decreased when treatment ended, and subsequent tumor progression based on a rising PSA occurred. In addition, several candidate tumor- associated antigens recognized by treatment-induced antibodies were identified in the study, including antigens reported to be involved in modulation of immune response and cancer metastases.

"While our Phase 3 clinical trials and registration strategy for GVAX immunotherapy for prostate cancer are currently focused on the treatment of advanced prostate cancer, we are pleased to also obtain these encouraging results in an earlier-stage of the disease," said Joseph J. Vallner, Ph.D., president and chief operating officer of Cell Genesys. "We believe that GVAX immunotherapy for prostate cancer may have potential for the treatment of prostate cancer at various stages of the disease and we look forward to initiation of future label-expansion studies."

GVAX immunotherapy for prostate cancer is currently being studied in two Phase 3 clinical trials expected to enroll approximately 1200 patients with metastatic hormone-refractory prostate cancer (HRPC), comprising one of the largest Phase 3 clinical programs ever conducted in men with advanced prostate cancer. The first trial (VITAL-1) is enrolling chemotherapy naïve, asymptomatic patients without cancer-related pain and will compare GVAX cancer immunotherapy to Taxotere chemotherapy plus prednisone. The second trial (VITAL-2) is enrolling patients who are symptomatic with cancer-related pain and will compare GVAX cancer immunotherapy plus Taxotere to Taxotere plus prednisone. Each Phase 3 trial is expected to enroll 600 patients and is designed to demonstrate a survival benefit compared to Taxotere plus prednisone. Cell Genesys received Special Protocol Assessments (SPA) from the FDA for each of the VITAL-1 and VITAL-2 Phase 3 studies as well as Fast Track Status for the product itself.

The company's ongoing Phase 3 program is supported by the median survival results from two, independent, multi-center Phase 2 clinical trials in approximately 115 patients that are not only consistent with each other, but also compare favorably to the previously published median survival of 18.9 months for metastatic HRPC patients treated with Taxotere(R) (docetaxel) chemotherapy plus prednisone, the current standard of care. The Phase 3 program is designed to confirm this potential survival benefit for GVAX immunotherapy for prostate cancer.

Cell Genesys' GVAX cancer immunotherapies are whole-cell products which are designed to present the immune system with a broad spectrum of tumor antigens and stimulate an immune response against the patient's tumor. GVAX immunotherapy for prostate cancer is comprised of two prostate cancer cell lines that have been modified to secrete GM-CSF (granulocyte-macrophage colony stimulating factor), an immune stimulatory hormone which plays a key role in stimulating the body's immune response, and then irradiated for safety. GVAX cancer immunotherapy for prostate cancer is being developed as a non patient- specific, "off-the-shelf" pharmaceutical product.

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(R) cancer immunotherapies and oncolytic virus therapies. Ongoing clinical trials include Phase 3 trials of GVAX immunotherapy for prostate cancer, Phase 2 trials of GVAX immunotherapy for pancreatic cancer and leukemia, and a Phase 1 trial of CG0070 oncolytic virus therapy for bladder cancer. Cell Genesys continues to hold an equity interest in its former subsidiary, Ceregene, Inc., which is developing gene therapies for neurodegenerative disorders. Cell Genesys is headquartered in South San Francisco, CA and has its principal manufacturing operation in Hayward, CA. For additional information, please visit the company's website at www.cellgenesys.com.

Statements made herein about the company, other than statements of historical fact, including statements about the company's progress, results and timing of clinical trials and preclinical programs and the nature of product pipelines 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 associated with the success of clinical trials and research and development programs, the regulatory approval process for clinical trials, competitive technologies and products, patents, continuation of corporate partnerships and the need for additional financings. For information about these and other risks which may affect Cell Genesys, please see the company's Annual Report on Form 10-K for the year ended December 31, 2005 filed on March 13, 2006 as well as Cell Genesys' reports on Form 10-Q 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.

Contact: Ina Cu, investor relations of Cell Genesys, +1-650-266-3200.

SOURCE Cell Genesys, Inc.
Web site: http://www.cellgenesys.com
07/05/2006 07:00 EDT http://www.prnewswire.com

"Safe Harbor" Statement under the Private Securities Litigation Reform Act of 1995: Statements in this press release regarding Cell Genesys's business which are not historical facts are "forward-looking statements" that involve risks and uncertainties. For a discussion of such risks and uncertainties, which could cause actual results to differ from those contained in the forward-looking statements, see "Risk Factors" in the Company's Annual Report or Form 10-K for the most recently ended fiscal year.