Flash Info Biotech

SOUTH SAN FRANCISCO, Calif.–(BUSINESS WIRE)–Cell Genesys, Inc. (Nasdaq:CEGE) announced today that immunological data
from the ongoing Phase 1 clinical trial of GVAX immunotherapy for
prostate cancer in combination with ipilimumab (MDX-010) suggest an
association between an increase in T-cell immunity and anti-tumor
activity as measured by a decrease in prostate-specific antigen (PSA)
serum levels. These data (Abstract #2538) were presented by Saskia JAM
Santegoets, Ph.D., from the Department of Medical Oncology and Pathology
of Vrije Universiteit Medical Center located in Amsterdam, Netherlands,
at the annual meeting of the American Association for Cancer Research
(AACR) being held in San Diego, California. GVAX immunotherapy for
prostate cancer is an investigational product currently in development
by Cell Genesys, and ipilimumab is a fully human anti-CTLA-4 antibody,
an investigational product currently in development by Medarex, Inc. in
partnership with Bristol-Myers Squibb Company.

The data presented are based on an analysis of blood samples from the
first 12 patients involved in the dose escalation portion of the Phase 1
combination trial. The samples were collected from each patient prior to
dosing and then at monthly intervals following the initiation of dosing.
Researchers analyzed the samples to determine the potential impact of
the combination regimen on T-cells, dendritic cells and antibody
response. An association was observed between the dose-dependent
increase in T-cell activation and decreases in PSA levels. Patients
receiving the three highest doses of ipilimumab in combination with GVAX
immunotherapy showed an increase in the percentage of memory T-cells as
measured through peripheral blood T-cell monitoring. Patients receiving
the two highest doses of ipilimumab in combination with GVAX
immunotherapy had an increase in HLA-DR on T-cells, indicating T-cell
activation. Additionally, researchers observed an increase in activated
dendritic cells as indicated by the activation marker, CD40. No anti-PSA
antibodies were detected in any of the 12 patients.

“These data presented today affirm that GVAX
immunotherapy for prostate cancer used in combination with ipilimumab
induces a cellular immune response and that the immune response may be
associated with durable objective PSA responses, which we previously
reported in June 2007 for the first 12 patients treated in this trial,”
said Peter K. Working, Ph.D., senior vice president, Research and
Development. “We look forward to presenting
updated results from this trial at the 2008 American Society of Clinical
Oncology (ASCO) annual meeting, including preliminary results for the 16
additional patients who have been enrolled in the expansion cohort of
the trial.”

The Phase 1 trial reported on today was designed to evaluate safety and
to determine a maximum tolerated dose of ipilimumab when used in
combination with GVAX immunotherapy for prostate cancer. To date, 28 men
with metastatic hormone refractory prostate cancer (HRPC) have been
enrolled in the trial, including 12 patients in the dose escalation
cohort and 16 patients in the expansion cohort. 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, four doses of ipilimumab were
evaluated, including 0.3 mg/kg, 1 mg/kg, 3 mg/kg and 5 mg/kg.

As previously reported at the June 2007 ASCO meeting, investigators
presented follow-up data for the first 12 patients treated in this Phase
1 clinical trial of GVAX immunotherapy for prostate cancer used in
combination with ipilimumab. These data indicate that five of the six
patients who received the two highest doses of antibody experienced PSA
declines of greater than 50 percent, which in four patients were
maintained for at least six months. In addition, four of these six
patients had clinical responses, as measured by bone scan, abdominal CAT
scan and bone pain. As previously reported, the five patients with PSA
declines of greater than 50 percent experienced either Grade 2 or 3
immune-mediated endocrine deficiencies similar in type to those
previously reported with ipilimumab administration, and were
successfully treated with standard hormone replacement therapy. One
patient who received the 5 mg/kg dose of ipilimumab developed a Grade 3
dose-limiting pulmonary alveolitis that responded to steroid treatment.
The induction of patient-specific antibody immune responses to a broad
array of previously identified cancer-associated antigens, including
PSMA, NY-ESO-1 and filamin-B was also observed. These latter results are
consistent with those of similar analyses from a separate study carried
out in patients who received GVAX immunotherapy alone for prostate
cancer in a Phase 2 trial as recently reported at the February 2008 ASCO
Symposium on Genitourinary Cancer. Those data indicated that GVAX
immunotherapy for prostate induced a broad array of patient-specific
antibody responses that were in certain cases associated with increased
patient survival.

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 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 (MDX-010)

Ipilimumab, also known 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^®
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.