Cancer vaccine reports positive data

Cell Genesys, from South San Francisco, CA, US has reported positive long-term follow-up data from a Phase 1 clinical trial of Gvax melanoma vaccine, a patient-specific vaccine made directly from patient tumor biopsies.

Data from this trial, which completed enrollment in mid-1999, involved patients with metastatic melanoma, the majority of whom had failed prior treatment including surgery, radiation, chemotherapy and/or interferon. Of the 35 patients enrolled in this study, 10 patients (29%) remain alive with a minimum follow-up of 36 months, including four patients without evidence of recurrent disease following surgical resection of their tumor. One complete response, one partial response and one mixed response were observed following the initial treatment period, and the overall median survival was 15 months. Treatment with Gvax vaccine was safe and well tolerated in the outpatient setting, and vaccine was successfully manufactured in 97% of the enrolled patients.

'The trial reported in September 1 issue of the Journal of Clinical Oncology, corroborates a growing body of clinical data from multiple Gvax cancer vaccine trials which have demonstrated prolonged survival and increased time to disease progression in some patients and a side effect profile that compares favorably to standard cancer treatments. While we will continue to prioritise our more advanced clinical programs for Gvax prostate and lung cancer vaccines, the data for Gvax melanoma vaccine clearly indicate the potential broad applicability of this product platform,' stated Dr Joseph J. Vallner, president and coo of Cell Genesys. 'The melanoma trial also provides another example of the ability to successfully manufacture patient-specific Gvax products as we are currently doing in our lung cancer program. However, our focus will remain on Gvax products that can be developed as non patient-specific, off-the-shelf products.'

In addition to the encouraging long-term follow-up data noted above, the Phase 1 trial also demonstrated the ability of a Gvax cancer vaccine to elicit a specific immune response directed against the patient's own tumor. Twenty-five patients were evaluated for enhanced antitumor immunity as measured by delayed-type hypersensitivity (DTH) skin reactions following treatment with Gvax melanoma vaccine, and 17 of the 25 patients (68%) demonstrated induction of immunologic reactivity against their tumors by the DTH test. In addition, microscopic examination of surgically resected metastatic tumor showed an active immune response with T- and B-lymphocyte infiltration and tumor necrosis (cell death) in 10 of 16 cases (63%). These findings demonstrate the induction of both cellular (T cell) and antibody (B cell) immunity by the Gvax vaccine and are consistent with the immunologic findings previously reported for other cancer vaccine products.

What is a cancer vaccine?

Cell Genesys' Gvax cancer vaccines are comprised of tumor cells which have been irradiated and 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 used to vaccinate patients to stimulate an immune response against their tumor. Cell Genesys' cancer vaccines have demonstrated antitumor effects against every type of human cancer tested to date, and the company is currently evaluating these products in five types of cancerprostate, lung, pancreatic, leukemia and myeloma. Currently, Cell Genesys is evaluating non patient-specific, off-the-shelf products for prostate cancer, pancreatic cancer, leukaemia and myeloma and a patient-specific, individualised product for lung cancer.