Cell Genesys, Inc. today reported updated results from its second multi-center Phase II trial of Gvax immunotherapy for prostate cancer in patients with advanced metastatic hormone-refractory prostate cancer (HRPC). Additional follow-up of the patients who received the dose that is comparable to that being employed in the company's ongoing Phase III program indicates that the median survival has not yet been reached and that the estimated median survival will be no less than 29.1 months.
The company also presented for the first time, an analysis of the survival data for the company's two Phase II trials of Gvax immunotherapy for prostate cancer, based on a published, validated nomogram that uses seven prognostic factors to calculate a patient's predicted survival. This analysis demonstrated a favorable comparison of observed to predicted median survival for both Phase II trials. These new findings were reported yesterday at the 2006 American Society of Clinical Oncology (ASCO) Prostate Cancer Symposium in San Francisco, CA, by Eric J. Small, M.D., professor of Medicine and Urology, University of California San Francisco Comprehensive Cancer Center.
The company's second Phase II trial enrolled a total of 80 patients who were sequentially assigned to escalating dose groups, including 22 patients who were treated with a dose comparable to that being used in the company's Phase III program. As noted above, the median survival has not yet been reached for these 22 patients, and the estimated Kaplan-Meier median survival is expected to meet or exceed 29.1 months based on the patients still in follow-up. Four patients have withdrawn consent to further follow-up and thus were censored in the analysis. The company previously reported final median survival results from its first multi-center Phase III trial of Gvax immunotherapy for prostate cancer in 34 patients with metastatic HRPC that showed an overall median survival of 26.2 months. The survival results from the two, independent multi-center Phase II clinical trials are not only consistent with each other, but also compare favorably to the previously published median survival of 18.9 months for metastatic hormone-refractory prostate cancer patients treated with Taxotere (docetaxel) chemotherapy plus prednisone, the current standard of care for these patients. The company's ongoing Phase III program is designed to confirm this potential survival benefit for Gvax immunotherapy for prostate cancer.
"We are encouraged by the updated survival data from this second Phase II trial of Gvax immunotherapy for prostate cancer and also by the consistency of the survival data from this trial with that reported in our earlier Phase II trial in a similar patient population," stated Joseph J. Vallner, Ph.D., president and chief operating officer of Cell Genesys. "We continue to hope that Gvax immunotherapy for prostate cancer may some day offer an improved and less toxic treatment alternative to chemotherapy for patients with this disease."
In addition to the updated survival data for the second Phase II study, an analysis was also presented of the observed versus predicted median survival results for the two Phase II trials of Gvax immunotherapy for prostate cancer. A published, validated nomogram based on seven prognostic variables including PSA, ECOG performance status, Gleason score sum, alkaline phosphatase, hemoglobin, LDH and presence/absence of visceral metastatic disease was used to calculate each patient's predicted survival (Halabi, et al. Prognostic model for predicting survival in men with HRPC: Journal of Clinical Oncology, 2003; 21(7):1232-7). The median value of the predicted survivals were then calculated for each trial and compared to the observed median survival calculated by the Kaplan-Meier method. In the first Phase II trial, the observed median survival for the 34 patients was 26.2 months, compared with the predicted median survival based on the Halabi nomogram of 19.5 months. In the second Phase II trial, the median survival has not been reached and the estimated median is expected to meet or exceed 29.1 months based on the patients still in follow-up. The predicted median survival for these patients based on the Halabi nomogram was 22.0 months. Cell Genesys believes that the fact that the observed median survival exceeds the predicted median survival in both Phase II trials provides further support for the company's ongoing Phase III program with respect to the potential of Gvax immunotherapy for prostate cancer to demonstrate a survival benefit.
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