Cell Genesys GVAX Prostate Cancer Vaccine To Start Phase III Second-Quarter

Cell Genesys' GVAX prostate cancer vaccine is scheduled to enter Phase III at the end of the second quarter under FDA's special protocol assessment program.

The clinical trial program for the vaccine will attempt to demonstrate superiority over taxane chemotherapy.

The SPA applies to the VITAL-1 trial, which will test monotherapy with the GVAX vaccine versus taxane therapy in chemotherapy-naïve, hormone-refractory metastatic prostate cancer patients who are asymptomatic with respect to cancer-related pain. The primary endpoint is survival.

"The SPA indicates that the trial will adequately address the objectives necessary to support a…BLA and that the study forms the basis for a definitive assessment of the effectiveness of the vaccine," Cell Genesys said May 10.

"We…are continuing to make good progress toward achieving our goal of beginning this trial by the end of the second quarter," President & COO Joseph Vallner, PhD, stated.

An initial Phase II trial of GVAX in 55 hormone-refractory prostate cancer patients showed a numerically higher survival rate for GVAX than taxane therapy. Median survival was 31 months in patients receiving high dose GVAX and 23 months in patients on a lower dose.

The study failed to reach statistical significance. Cell Genesys attributed the statistical result to the small number of patients tested and hopes to overcome the statistical hurdle in its larger Phase III program.

Updated results for a second Phase II trial in 80 patients will be reported at the American Society of Clinical Oncology meeting in June. Initial results for the trial, reported at ASCO in 2003, demonstrated clinical activity; median survival (half of the patients dying) was not yet reached for any patient group.

"There was an improvement or stabilization in bone metastatic activity...in 59% of patients" (16 of 27 patients tested at the interim analysis), the company reported. "Prostate-cancer associated antibodies were detected post-vaccination in 83% of patients (15 of 18 tested to date) at levels that are significantly higher than those previously published for other cell-based vaccines," the firm maintained.

Cell Genesys plans to launch a second Phase III trial of the prostate cancer vaccine in late 2004-early 2005. VITAL-2 will enroll symptomatic patients from the same population as VITAL-1, and will compare GVAX plus taxane chemotherapy to taxane therapy alone for palliation of bone pain.

If the GVAX prostate cancer vaccine is ultimately approved, Cell Genesys will look to position the biologic as more effective, safer and more convenient than traditional chemotherapy.

The vaccine's only adverse events to date are redness at the injection site and occasional fever, according to the firm. It is intradermally administered bi-weekly for six months.

Cell Genesys' GVAX platform comprises therapeutic cancer vaccines that are made from whole tumor cells genetically modified to secrete granulocyte-macrophage colony stimulating factor (GM-CSF), a hormone that activates the immune system against cancer cells.

The oncology-focused biotech firm has ongoing trials for GVAX vaccines in four types of cancer besides prostate. Leukemia, non-small cell lung, and pancreatic cancer vaccines are in Phase II, and a myeloma vaccine is in Phase I/II.

The prostate and pancreatic cancer vaccines are non-patient-specific with intended "off-the-shelf" use. The leukemia and myeloma vaccines mix non-patient-specific cancer cells with a patient's own tumor cells, while the lung cancer vaccine uses only patient-specific cells.

The GVAX prostate cancer vaccine appears to be the first therapeutic cancer vaccine with a pivotal trial under the SPA program, which should minimize regulatory issues. Antigenics is attempting to address FDA's concerns about product characterization of its cancer vaccine Oncophage (see ¹ (Also see "Antigenics Oncophage Retrospective Testing For Potency Is Approval Issue" - Pink Sheet, 15 May, 2004.) ).

[Editor's Note: A version of this story first appeared in F-D-C Reports' ² "The Pink Sheet" DAILY May 11. Visit our website, www.ThePinkSheetDAILY.com, to sign up for a free trial.]