Cell Genesys Halts VITAL-2 GVAX Trial in Advanced Prostate Cancer

Conference Call Scheduled for 8:30 a.m. ET Today
SOUTH SAN FRANCISCO, Calif.--(Business Wire)--
Cell Genesys, Inc. (Nasdaq:CEGE) today announced that it has
terminated VITAL-2, the second of two Phase 3 clinical trials of GVAX
immunotherapy for prostate cancer, which compares GVAX immunotherapy
in combination with Taxotere(R) (docetaxel) to Taxotere plus
prednisone in patients with advanced-stage prostate cancer. The
Company ended the trial as recommended by its Independent Data
Monitoring Committee (IDMC) which, in a routine safety review meeting
held this week, observed an imbalance in deaths between the two
treatment arms of the study. To date, VITAL-2 enrolled 408 patients.
The IDMC based its recommendation on 114 deaths of which 67 occurred
in the GVAX plus Taxotere combination treatment arm and 47 deaths
occurred in the Taxotere control arm. At this time, a specific cause
for the imbalance in deaths has not been identified and the IDMC
reported no new safety issues for GVAX when administered in
combination with Taxotere. The Company plans to fully analyze the
clinical data from these patients to attempt to understand the
potential cause for the higher rate of deaths observed in the GVAX
immunotherapy plus Taxotere combination arm, including an assessment
of potential imbalances between the two arms of the study such as
baseline characteristics and prognostic factors, as well as other
treatment variables. In light of the IDMC's observation with respect
to VITAL-2, the Company has requested that the IDMC perform a
previously unspecified futility analysis of VITAL-1, the other Phase 3
clinical trial of GVAX immunotherapy for prostate cancer. The Company
expects the results of the VITAL-1 futility analysis in approximately
one month.

"Patient safety is always our paramount concern and so we have
immediately responded to the recommendation of the IDMC. We are
currently notifying all participating clinical trial sites and
regulatory agencies that enrollment of new patients into VITAL-2 has
been suspended as has treatment with GVAX immunotherapy for prostate
cancer of patients enrolled in the study," stated Stephen A. Sherwin,
M.D., chairman and chief executive officer of Cell Genesys.
"Notwithstanding this disappointing outcome, we would like to
acknowledge the courage and commitment of the patients and physicians
who have participated in this trial."

Dr. Sherwin continued, "The observation in the VITAL-2 trial is
very surprising to us, and we have therefore asked the IDMC to conduct
a previously unplanned futility analysis of VITAL-1 in order to
determine the overall prospects for our ongoing development program
for this product. Moreover, with the cessation of VITAL-2, we expect
to make commensurate adjustments to our business operations and we
will provide further details regarding this in the near future. As a
reminder, the company ended the second quarter of 2008 with $166
million in cash."

VITAL-2 was a multi-center, randomized, controlled Phase 3
clinical trial designed to evaluate the safety and efficacy of GVAX
immunotherapy for prostate cancer used in combination with Taxotere
chemotherapy compared to the use of Taxotere chemotherapy and
prednisone in hormone-refractory prostate cancer (HRPC) patients with
metastatic disease who are symptomatic with cancer-related pain. The
primary endpoint of the trial was an improvement in survival. VITAL-2
was initiated in June 2005 and to date had enrolled 408 patients at
115 clinical trial sites located in North America and the European
Union. VITAL-1, the other Phase 3 clinical trial of GVAX immunotherapy
for prostate cancer, is designed to compare GVAX cancer immunotherapy
as a monotherapy to Taxotere chemotherapy plus prednisone in earlier
stage HRPC patients with metastatic disease who are asymptomatic with
respect to cancer-related pain. The primary endpoint of the trial is
an improvement in survival. In 2007, the VITAL-1 trial completed
enrollment with 626 patients. In January 2008, Cell Genesys announced
that the IDMC had completed a pre-planned interim analysis for VITAL-1
and recommended that the study continue, providing no further
information to the company other than the recommendation to continue
the trial.

Conference Call and Webcast

Members of the Cell Genesys management team will host a conference
call today, Wednesday, August 27, 2008, at 8:30 a.m. ET to discuss the
IDMC's recommendation. Investors may listen to the webcast of the
conference call live on the investor section of the Cell Genesys
website, www.cellgenesys.com. Alternatively, investors may listen to a
replay of the call by dialing (800) 475-6701 from locations in the
U.S. and (320) 365-3844 from outside the U.S. The call-in replay and
webcast will be available for at least 72 hours following the call.
Please refer to reservation number 958709.

About GVAX Immunotherapy for Prostate Cancer

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 cytokine that plays a key role in stimulating the body's
immune response, and then irradiated for safety. GVAX immunotherapy
for prostate cancer is designed to be administered through intradermal
injections on an outpatient basis.

About Cell Genesys

Cell Genesys (Nasdaq: CEGE) is focused on the development and
commercialization of novel biological therapies for patients with
cancer. The company's lead product platform is GVAX(R) immunotherapy
for cancer, which holds the potential to treat multiple types of
cancer including prostate cancer, leukemia, pancreatic cancer and lung
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, California, and has manufacturing operations in
Hayward, California. 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 company's progress,
results, findings, analysis and timing of clinical trials and
preclinical programs, the timing of completion of and results from the
VITAL-1 futility analysis discussed above and the nature of product
pipelines 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, regulatory
requirements and the regulatory approval process for clinical trials,
manufacture and commercialization of the company's products,
competitive technologies and products, the need for and reliance on
partnerships with third parties, and the need for additional
financings. 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.

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

Copyright Business Wire 2008