Cell Genesys, Inc. has reported immune response data from two previously conducted Phase 2 clinical trials of GVAX immunotherapy for prostate cancer.
Evaluation of antibody responses in patients with advanced prostate cancer from these studies shows that the GVAX cell-based immunotherapy induces antibody responses to a broad array of prostate cancer- associated antigens, including some not previously known to be associated with prostate cancer. In addition, the antibody responses to this non patient- specific product were predominantly patient-specific and unique from patient to patient, indicating the potential advantage of a cell-based multi-antigen product such as GVAX to generate the broadest and most relevant immune response. Serological analysis of gene expression (SEREX) technology was also used to identify target antigens involved in response to the immunotherapy. More than 148 proteins to which antibody responses were induced were identified and many of these proteins had not been identified previously as prostate cancer-associated antigens. These findings were presented today by Dr. Thomas Harding and colleagues from Cell Genesys at the annual meeting of the American Association for Clinical Research being held in Los Angeles, CA.
GVAX immunotherapy for prostate cancer is currently being studied both as a single agent and in combination with docetaxel chemotherapy in two Phase 3 clinical trials targeted to enroll approximately 1200 patients with metastatic hormone-refractory prostate cancer (HRPC). This ongoing Phase 3 program is supported by the median survival results from two, independent, multi-center Phase 2 clinical trials. Cell Genesys recently reported final, updated results from its second multi-center Phase 2 trial of GVAX immunotherapy for prostate cancer, which evaluated escalating doses of the immunotherapy in 80 patients with metastatic hormone-refractory prostate cancer (HRPC). Additional follow-up of the 22 patients who received the dose that is comparable to that being employed in the company's ongoing Phase 3 program revealed that their median survival is 35.0 months. Four patients have withdrawn consent to further follow-up and thus were censored in the analysis. The company also has previously reported final median survival results from its first multi-center Phase 2 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 2 clinical trials compare favorably to the previously published median survival of 18.9 months for metastatic hormone-refractory prostate cancer patients treated with Taxotere(R) (docetaxel) chemotherapy plus prednisone, the current standard of care for these patients. The company's ongoing Phase 3 program is designed to confirm this potential survival benefit of GVAX immunotherapy for prostate cancer.
"The immune response data reported today provide added support for the concept that a whole-cell immunotherapy, such as GVAX immunotherapy for prostate cancer, is an ideal multi-antigen source that is capable of eliciting an immune response to a broad array of tumor-associated antigens," stated Peter K. Working, Ph.D., senior vice president of Research and Development at Cell Genesys. "That the majority of antibody responses are unique to individual patients is further evidence that the non patient-specific format of GVAX immunotherapies is capable of inducing unique, patient-specific immune responses. Moreover, the fact that many of these antigens have not before been associated with prostate cancer, further suggests that a multivalent antigen immunotherapy like GVAX immunotherapy may provide the best potential for inducing an effective anti-tumor immune response, especially for heterogeneous cancers such as prostate cancer."