Skip to Content

Cell Genesys Reports Preclinical Data Demonstrating Superior Anti-Tumor Immunity for Multiantigen Compared to Single-Antigen Immunotherapies

SOUTH SAN FRANCISCO, Calif.--(BUSINESS WIRE)--April 14, 2008--Cell Genesys, Inc. (Nasdaq:CEGE) announced today data from a preclinical study demonstrating that multiantigen immunotherapies provide superior anti-tumor protection, including improved infiltration of immune T-cells into tumors and improved tumor-specific immunologic memory, compared to single-antigen immunotherapies. These data (Abstract # 2853) were presented by Betty Li, research scientist of Cell Genesys, and colleagues at the annual meeting of the American Association for Cancer Research being held in San Diego, California.

Using a murine B16 melanoma model, researchers evaluated the B16-specific immune response generated following either administration of a GM-CSF-secreting B16 whole cell immunotherapy or unrelated, GM-CSF-secreting cell lines that each over-expressed one of the known B16-specific antigens. Researchers observed that mice injected with the B16-specific, multiantigen immunotherapy experienced significantly stronger anti-tumor protection compared to mice injected with either of the B16-specific, single-antigen products. Moreover, higher numbers of tumor-infiltrating T-lymphocytes (TILs) were found in tumors of animals treated with the multiantigen immunotherapy than in the single-antigen products. The higher number of TILs found in animals injected with the multiantigen immunotherapy correlated with significantly prolonged survival observed in these animals compared to mice injected with a single-antigen immunotherapy. The only immune response that was stronger with a single-antigen immunotherapy was the systemic T-cell response against the single over-expressed B-16 specific antigen. When re-challenged 70 days following the initial immunotherapy injection with a lethal dose of live B16 tumor cells, mice that had been injected with the multiantigen immunotherapy demonstrated a more potent B16-specific memory immunologic response than those mice that had been injected with a single-antigen immunotherapy. Fifty percent to 70 percent of mice treated with the multiantigen immunotherapy survived the re-challenge compared to zero percent to 20 percent of animals surviving treated with a single-antigen immunotherapy.

"These preclinical data further underscore the potential advantage of a whole cell immunotherapy such as GVAX that present the immune system with multiple, tumor-specific antigens and activate a robust, broad immune response," stated Peter K. Working, Ph.D., senior vice president of Research and Development at Cell Genesys. "Moreover, in addition to the advantages derived from the multiantigen composition, GVAX(R) cancer immunotherapies also have the advantage of continuously releasing GM-CSF, a protein that activates dendritic and other immune cells at the injection site and serves as a potent product-secreted adjuvant during the immunization process."

About GVAX Immunotherapy for Prostate Cancer

GVAX immunotherapy for prostate cancer is a whole cell, non patient-specific product 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 tumor cell lines that have been modified to secrete GM-CSF (granulocyte-macrophage colony-stimulating factor), an immune stimulatory protein that plays a key role in stimulating the body's immune response, and then irradiated for safety. Cell Genesys, in partnership with Takeda Pharmaceutical Company Limited, is currently evaluating GVAX immunotherapy for prostate cancer in two Phase 3 clinical trials, VITAL-1 and VITAL-2, for the treatment of advanced stage, hormone-refractory prostate cancer. In 2007, the VITAL-1 trial completed enrollment with 626 patients and in January 2008, Cell Genesys announced that the Independent Data Monitoring Committee (IDMC) had completed a pre-planned interim analysis for VITAL-1 and recommended that the study continue. The company currently estimates that there will be sufficient events to trigger the final analysis for VITAL-1 in the second half of 2009. Patients are continuing to be enrolled in the VITAL-2 trial at approximately 100 clinical trial sites located in North America and Europe. Cell Genesys is targeting the completion of enrollment for VITAL-2 with approximately 600 patients in the first half of 2009 and expects that there will be sufficient events to trigger the pre-planned interim analysis in the same time frame. GVAX immunotherapy for prostate cancer is currently being manufactured in Cell Genesys' bioreactor manufacturing facility, located in Hayward, California, a facility that is capable of producing the product during commercialization.

About Cell Genesys

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, which is being developed in partnership with Takeda Pharmaceutical Company Limited, Phase 2 trials of GVAX immunotherapies for pancreatic cancer and for 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

Forward-Looking Statement

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 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 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.

    CONTACT: Cell Genesys, Inc.

             Susan Ferris, 650-266-3200 (Investor Relations)

    SOURCE: Cell Genesys, Inc.

Posted: April 2008