GVAC Lung Cancer Vaccine

Cell Genesys' GVAX® lung cancer vaccine is a patient-specific vaccine designed to induce a systemic immune response against the patient's lung cancer. The vaccine is made by directly modifying the patient's tumor cells using a semi-automated closed system designed to enable safe and sterile manufacturing of each patient's vaccine. After surgical removal of a patient's tumor, the GVAX® cancer vaccine is prepared by culturing and genetically modifying the patient's tumor cells to secrete GM-CSF, an immune stimulatory hormone. The cells are then irradiated for safety prior to vaccinating the patient.

Based on encouraging data from the company's initial trial of GVAX® lung cancer vaccine, Cell Genesys will conduct two Phase 2 clinical trials evaluating GVAX® lung cancer vaccine. The first of these Phase 2 trials, initiated in April 2003, is sponsored by Cell Genesys and is enrolling patients with all subtypes of non small-cell lung cancer. Patients are being randomized to receive GVAX® lung cancer vaccine with or without low-dose cyclophosphamide, a chemotherapeutic agent which in the doses to be employed has been shown to enhance the immune response. The second Phase 2 trial, which is expected to be sponsored and partially funded by the Southwest Oncology Group (SWOG), a cooperative clinical trials group of the National Cancer Institute (NCI), will focus on patients with the bronchoalveolar carcinoma (BAC) subtype of non small-cell lung cancer. This trial is expected to begin in the second quarter of 2004. The two trials may enroll up to approximately 75 patients each.

At the International Conference on Gene Therapy of Cancer in December 2002, final data were reported from the company's initial Phase 1/2 trial of GVAX® lung cancer vaccine in patients with advanced non small-cell lung cancer. Patients received the treatment vaccine in an outpatient clinical setting over a three-month period and were monitored for the subsequent six months. Of the 33 advanced stage patients, most of whom had failed prior chemotherapy and/or radiation therapy, three patients (9 percent) experienced complete responses (complete disappearance of all tumors) with a median duration of response of 17.8 months. The median survival of all 33 treated patients was 11.6 months (measured from the initiation of vaccine manufacturing), which compares favorably to the approved second-line taxane chemotherapy for such patients. Of these three patients, two were noted to have the BAC subtype of lung cancer. In addition to these complete responses, seven patients (21 percent) achieved stable (non progressive) disease with a median response duration of 7.7 months. Median survival was significantly longer in patients whose vaccine products secreted higher levels of GM-CSF which all GVAX® vaccines are engineered to produce (median survival of 17.1 months for GM-CSF >40 ng./106 cells/24 hr. versus median survival of 7.4 months for GM-CSF <40ng./106 cells/24 hr., p= .04).

Cell Genesys constructed a 35,000 square-foot manufacturing facility in Memphis, TN, which is being used for the manufacturing of the company's patient-specific GVAX® lung cancer vaccines for the ongoing Phase 2 clinical trial, and is also expected to be used for the Phase 3 clinical trial and potential market launch.

(The data referenced in the preceding paragraphs represent the most recently announced data pertaining to this program.)

Information About GVAX® Lung Cancer Vaccine Clinical Trials Currently Under Way:

• D-0031: A Phase 2 Randomized Study of GM-CSF Gene-Modified Autologous Tumor Vaccine (CG8123) ("GVAX® Lung Cancer Vaccine") with and without Low-Dose Cyclophosphamide in Advanced Stage Non Small-Cell Lung Cancer.

** POSTED JUNE 30, 2004 **