Cell Genesys Reports Updated Results From Phase 1 Clinical Trial of GVAX Immunotherapy for Prostate Cancer Used in Combination With Ipilimumab

Update: Yervoy (ipilimumab) Now FDA Approved - March 25, 2011
SOUTH SAN FRANCISCO, Calif.--(BUSINESS WIRE)--Jun 2, 2008 - Cell Genesys, Inc. (Nasdaq:CEGE) today announced interim data from the ongoing Phase 1 clinical trial of GVAX immunotherapy for prostate cancer used in combination with ipilimumab in patients with advanced prostate cancer. Updated data reported includes median follow-up of approximately 22.3 months on the 12 patients enrolled in the escalation cohort of the trial and interim data on the 16 patients enrolled in the expansion cohort of the trial. These data were presented on Saturday, May 31, 2008, by Winald Gerritsen, M.D., Ph.D., director of the University Hospital Vrije Universiteit Cancer Center in Amsterdam, at the annual meeting of the American Society of Clinical Oncology (ASCO) being held in Chicago, Illinois. GVAX immunotherapy for prostate cancer is an investigational product currently in development by Cell Genesys and ipilimumab is an investigational fully human anti-CTLA-4 antibody in development by Medarex, Inc. in partnership with Bristol-Myers Squibb Company.

This Phase 1 clinical trial has now been enrolled with 28 patients, including 12 patients in the escalation cohort and 16 patients in the expansion cohort. As previously reported, of the 12 patients enrolled in the escalation cohort, anti-tumor activity was observed in five of the six patients who received the two highest doses of ipilimumab (3 mg/kg and 5 mg/kg), including prostate-specific antigen (PSA) declines of greater than 50 percent. Four of these five patients maintained this PSA decline for at least six months, with the longest response to date now reported to be approximately 24 months. Of the 16 patients enrolled in the expansion cohort of the trial, 15 have completed dosing with the combination regimen with ipilimumab administered at 3 mg/kg. As of this time in follow-up, seven patients experienced stable PSA that was durable for a median duration of 5.6 months. Of the 12 patients with bone lesions at baseline, five have ongoing stable disease, with the most durable reported to date at nine months.

"These updated results are encouraging with respect to the overall level of anti-tumor activity observed across the two cohorts of patients who received the combination of GVAX immunotherapy for prostate cancer and ipilimumab in this Phase 1 trial," Robert J. Dow, MBChB, senior vice president of Medical Affairs and chief medical officer of Cell Genesys. "Of particular note was the duration of decreased or stable PSA and bone scan in approximately half of these patients with advanced prostate cancer. We plan to continue to follow the patients enrolled in the trial and then, together with our collaborators, determine the next steps for evaluating this combination immunotherapy."

Data from the Phase 1 trial suggest that side effects associated with GVAX immunotherapy for prostate cancer administered in combination with ipilimumab are manageable and most often include low grade fever and fatigue. In addition, immune-mediated adverse events similar in type to those previously reported with ipilimumab administration were observed in this combination therapy trial. Of particular note, patients who experienced PSA declines of greater than 50 percent generally experienced immune-mediated endocrine deficiency, referred to as hypophysitis, which is comparable to that previously reported with ipilimumab administration and which was successfully treated with standard hormone replacement therapy.

The Phase 1 trial of GVAX immunotherapy for prostate cancer used in combination with ipilimumab was designed to evaluate safety and to determine a maximum tolerated dose of ipilimumab when used in combination with GVAX immunotherapy for prostate cancer. Efficacy endpoints include time to clinical disease progression, time to PSA progression and PSA response, immune response to GVAX immunotherapy, reduction in metabolic bone activity and survival. The dose of GVAX immunotherapy for prostate cancer used in this combination trial is comparable to that currently being evaluated in Cell Genesys' ongoing Phase 3 program. In the escalation phase of the trial, three patients were assigned to each of the four ipilimumab dose cohorts (0.3 mg/kg, 1 mg/kg, 3 mg/kg and 5 mg/kg). In the expansion phase of the trial, which enrolled a total of 16 patients, all patients were assigned to receive 3 mg/kg of ipilimumab.

About GVAX Immunotherapy for Prostate Cancer

GVAX immunotherapy for prostate cancer is a whole-cell, non patient-specific product designed to present the immune system with a broad spectrum of tumor antigens and stimulate an immune response against the patient's tumor. GVAX immunotherapy for prostate cancer is comprised of two prostate tumor cell lines that have been modified to secrete GM-CSF (granulocyte-macrophage colony-stimulating factor), an immune stimulatory protein that plays a key role in stimulating the body's immune response, and then irradiated for safety. Cell Genesys, in partnership with Takeda Pharmaceutical Company Limited, is currently evaluating GVAX immunotherapy for prostate cancer in two Phase 3 clinical trials, VITAL-1 and VITAL-2, for the treatment of advanced stage, hormone-refractory prostate cancer. In 2007, the VITAL-1 trial completed enrollment with 626 patients and in January 2008, Cell Genesys announced that the Independent Data Monitoring Committee (IDMC) had completed a pre-planned interim analysis for VITAL-1 in the timeframe originally estimated and recommended that the study continue. The company currently estimates that there will be sufficient events to trigger the final analysis for VITAL-1 in the second half of 2009. Patients are continuing to be enrolled in the VITAL-2 trial at approximately 100 clinical trial sites located in North America and Europe. Cell Genesys is targeting the completion of enrollment for VITAL-2 with approximately 600 patients in the first half of 2009 and expects that there will be sufficient events to trigger the pre-planned interim analysis in the same time frame. GVAX immunotherapy for prostate cancer is currently being manufactured in Cell Genesys' bioreactor manufacturing facility, a facility that is capable of producing the product during commercialization.

About Ipilimumab

Ipilimumab, formerly referred to as MDX-010, is a fully human antibody that binds CTLA-4 (cytotoxic T lymphocyte-associated antigen 4), a molecule on T-cells that plays a critical role in regulating immune responses. The absence or presence of CTLA-4 can augment or suppress the immune system's T-cell response in fighting disease. Ipilimumab is designed to block the activity of CTLA-4, thereby sustaining an active immune response in its attack on cancer cells. Ipilimumab is being developed through a joint partnership between Medarex and Bristol-Myers Squibb. The two companies are pursuing a broad clinical development program with ipilimumab evaluating its potential use in advanced melanoma, as well as prostate, lung, pancreatic, bladder, breast, lymphoma and leukemia cancers. More than 2,000 patients have been treated with ipilimumab as a monotherapy or in combination with other agents in clinical trials. Further information regarding the ipilimumab program can be found in Medarex's public disclosure filings with the U.S. Securities and Exchange Commission (SEC).

About Cell Genesys

Cell Genesys is focused on the development and commercialization of novel biological therapies for patients with cancer. The company is currently pursuing two clinical stage product platforms-GVAX(R) cancer immunotherapies and oncolytic virus therapies. Ongoing clinical trials include Phase 3 trials of GVAX immunotherapy for prostate cancer, which is being developed in partnership with Takeda Pharmaceutical Company Limited, Phase 2 trials of GVAX immunotherapies for pancreatic cancer and for leukemia, and a Phase 1 trial of CG0070 oncolytic virus therapy for bladder cancer. Cell Genesys continues to hold an equity interest in its former subsidiary, Ceregene, Inc., which is developing gene therapies for neurodegenerative disorders. Cell Genesys is headquartered in South San Francisco, CA and has its principal manufacturing operation in Hayward, CA. For additional information, please visit the company's website at www.cellgenesys.com.

Statements made herein about the company, other than statements of historical fact, including statements about the progress, results, findings and timing of the company's clinical trials and preclinical programs, current and potential corporate partnerships, the nature of product pipelines and anticipated operating results and cash expenditures are forward-looking statements and are subject to a number of uncertainties that could cause actual results to differ materially from the statements made, including risks associated with the success of clinical trials and research and development programs, the regulatory approval process for clinical trials, competitive technologies and products, patents, the ability to raise capital, operating expense levels and the ability to establish and retain corporate partnerships and other risks. For information about these and other risks which may affect Cell Genesys, please see the company's reports on Form 10-Q, 10-K, and 8-K and other reports filed from time to time with the Securities and Exchange Commission. The company assumes no obligation to update the forward-looking information in this press release.

Contact

Cell Genesys, Inc.
Susan Ferris, 650-266-3200
Investor Relations

Posted: June 2008

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