Cell Genesys reports antitumor activity in Phase I/II GVAX lung cancer vaccine trial

SAN FRANCISCO, Calif., May 13, 2001—Cell Genesys, Inc. (Nasdaq: CEGE) today reported interim clinical data from its multicenter Phase I/II GVAX® lung cancer vaccine trial which demonstrates objective evidence of antitumor activity including a major response rate of 18 percent in patients with advanced non small-cell lung cancer who have failed chemotherapy and/or radiation therapy. These data were presented on behalf of the GVAX® Lung Cancer Clinical Investigators by John Nemunaitis, M.D. of U.S. Oncology at the American Society of Clinical Oncology (ASCO) Meeting in San Francisco, Calif. The presentation was one of 17 selected for ASCO’s Official Press Program from the more than 3,300 submitted to the meeting.

The interim clinical trial data includes results on 30 currently evaluable patients with advanced or early-stage lung cancer. Of 22 patients with advanced-stage lung cancer, three patients, two of whom had failed chemotherapy and one who failed radiation therapy, showed a complete disappearance of metastatic tumors following treatment with GVAX® lung cancer vaccine. One other patient who failed radiation and chemotherapy had partial (greater than 50 percent) reduction in his tumor. In addition to these major responses, four patients currently have stable (non-progressive) disease. All of these responses are continuing with a median follow-up time of approximately five months. In addition to the responses in patients with advanced disease, seven of eight patients with early-stage lung cancer who received GVAX® vaccine following surgery, currently remain free of disease with a median follow-up time of seven months.

“We are very encouraged by what we have seen to date with GVAX® lung cancer vaccine, particularly with respect to the major tumor responses in patients with metastatic lung cancer who have failed chemotherapy,” stated Dr. Nemunaitis. “These findings are all the more noteworthy given that lung cancer patients who fail chemotherapy have little chance of responding to further chemotherapy or other treatment.”

“These exciting clinical results with our GVAX® lung cancer vaccine are yet another reason we have increased our investment in the clinical and manufacturing development required to bring a GVAX® product to market,” stated Joseph J. Vallner, Ph.D., executive vice president and chief operating officer of Cell Genesys. “GVAX® vaccines have demonstrated objective evidence of antitumor activity in all five types of cancer in which they have been tested—lung, prostate, pancreatic, kidney and melanoma—as well as a very favorable safety profile compared to chemotherapy which has been documented in over 300 patients treated to date.”

The currently ongoing Phase I/II trial of GVAX® lung cancer vaccine for which the interim results were reported has recently completed enrollment. A final report on the trial is expected during the next year. In this trial, patients were administered up to six vaccine treatments every other week for three months as an intradermal (under the skin) injection. Patients received no other anticancer treatments during the trial evaluation period. As has been demonstrated in all GVAX® cancer vaccine trials to date, the vaccine was shown to be safe and well tolerated—a side effect profile which compares favorably to other cancer treatments such as chemotherapy. No dose limiting toxicities have been observed. In addition to the antitumor activity noted above, the interim trial results also demonstrate that GVAX® lung cancer vaccine induces an anti-lung cancer cellular immune response as well as the formation of new anti-lung cancer antibodies in the blood.

Update on Initial Trial of GVAX® Lung Cancer Vaccine

An earlier Phase I/II trial of GVAX® lung cancer vaccine in patients with advanced non small-cell lung cancer which was conducted by Dr. Glenn Dranoff and colleagues at Dana-Farber/Partners Cancer Care, an affiliate of Harvard Medical School, was reported at the Ninth World Conference on Lung Cancer in Tokyo, Japan in September 2000. This trial demonstrated antitumor immunity in 18 of 25 patients. In addition, two patients who received GVAX® lung cancer vaccine following surgery remain in complete remission more than three years after GVAX® treatment.

Future Clinical Trials for GVAX® Lung Cancer Vaccine

The GVAX® lung cancer vaccine trials to date, including the current study, have employed a patient-specific product format in which the vaccine is directly prepared from the patient’s own tumor cells in an overnight process. In the near future, Cell Genesys plans to launch a clinical trial in advanced lung cancer to evaluate a non patient-specific GVAX® product which will be centrally manufactured by Cell Genesys and then mixed with patients’ own irradiated tumor cells prior to vaccination. This new product format for GVAX® lung cancer vaccine is expected to have significant development and commercialization advantages compared to the first generation product used in the trial reported today. Given the encouraging results demonstrated in ongoing clinical trials for prostate and pancreatic cancer, Cell Genesys is emphasizing non patient-specific GVAX® products which can be developed and commercialized as “off-the-shelf” pharmaceuticals.

Background on GVAX® Cancer Vaccines

GVAX® cancer vaccines are comprised of tumor cells which have been genetically modified to secrete granulocyte-macrophage colony stimulating factor (GM-CSF), a hormone which plays a key role in stimulating the body's immune response to vaccines. The genetically modified tumor cells are then irradiated for safety and used to vaccinate patients to stimulate an immune response against their tumor. The company's lead GVAX® cancer vaccine program targets patients with recurrent hormone refractory prostate cancer and is currently being evaluated in two multicenter Phase II trials. A series of Phase I/II trials was recently initiated utilizing the company’s new high-potency GVAX® prostate cancer vaccine. Additionally, a Phase I/II trial for GVAX® vaccine for myeloma was recently initiated, and a Phase II trial of GVAX® pancreatic cancer vaccine and a Phase I/II trial of GVAX® vaccine for leukemia are expected to commence in mid 2001.

Cell Genesys Profile

Cell Genesys is focused on the development and commercialization of cancer vaccines and gene therapies to treat major, life-threatening diseases. The company is conducting clinical trials of GVAX® cancer vaccines in prostate cancer, pancreatic cancer, lung cancer and myeloma and expects to initiate new studies in acute leukemia during 2001. Preclinical stage programs include gene therapies for cancer, hemophilia and cardiovascular disorders. Cell Genesys’ majority-owned subsidiary, Ceregene, is focused on gene therapies for central nervous system disorders. Cell Genesys also continues to hold a 10.5 percent equity interest in its former subsidiary, Abgenix, an antibody product company. For additional information, please visit the company's web site at www.cellgenesys.com.

Statements made herein about Cell Genesys and its subsidiaries, other than statements of historical fact, including statements about the progress and reports of GVAX® clinical trials and progress and reports of preclinical programs, marketability and success of potential products and nature of product pipelines, licenses and intellectual property 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 research and development programs, the success and results of clinical trials, the regulatory approval process, competitive technologies and products, patents and 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 dated April 2, 2001 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.