Immunotherapy

[Guest guest]

Hi Folks,

The article below highlights the success in the area of immunotherapy. We

should all be particularly happy with the results for the CML patients. 10

of the 19 patients participating saw their residual disease levels drop.

Five of the patients achieved PCRU and another five achieved another log

reduction. The follow up data suggests that these results are sustainable.

My fingers are crossed that work in this area continues to go well.

Cheers,

Cheryl-Anne

Cell Genesys Recaps Two Weekend Data Presentations From 2006 ASCO Annual

Meeting

Monday June 5, 7:00 am ET

SOUTH SAN FRANCISCO, Calif., June 5 /PRNewswire-FirstCall/ -- Cell Genesys,

Inc. (Nasdaq: <http://finance./q?s=cege & d=t> CEGE -

<http://finance./q/h?s=cege> News) today provides a recap of

clinical data reports from two GVAXR cancer immunotherapy programs that were

presented this past weekend at the 2006 American Society of Clinical

Oncology (ASCO) Annual Meeting being held in Atlanta, GA.

In the first oral presentation entitled, " A dose-escalation trial of

GM-CSF-gene transduced allogeneic prostate cancer cellular immunotherapy in

combination with a fully human anti-CTLA-4 antibody (MDX-010, ipilimumab) in

patients with metastatic hormone-refractory prostate cancer (HRPC), "

(Abstract #2500), Cell Genesys and collaborator, Medarex, Inc., presented

encouraging data from a Phase 1 clinical trial of the company's' GVAXR

immunotherapy for prostate cancer, administered in combination with

Medarex's fully human anti-CTLA-4 antibody, ipilimumab (MDX-010), in

patients with advanced prostate cancer. Twelve patients have been treated to

date, including six patients who received the combination therapy at the

therapeutic doses currently being evaluated in both GVAX and ipilimumab

Phase 3 clinical trials. Antitumor activity has been observed in five of

these six patients including reductions in prostate-specific antigen (PSA)

levels that are ongoing at two months or longer and qualify in all five

patients as partial responses (greater than 50% sustained reduction) by the

National Cancer Institute (NCI) Working Group criteria with two patients

having greater than 95% reductions. Moreover, clinical evidence of antitumor

activity has been observed in three of these five PSA responders, including

improvement of multiple lesions on bone scan, resolution of abdominal lymph

node disease by CT scan, and improvement in pain due to bone metastases,

respectively. In addition to these findings, four of the six remaining

patients who received the two lower doses of ipilimumab were noted to have

stable disease by PSA with at least two months of follow-up. There have been

no dose-limiting toxicities seen to date with the combination therapy. All

five patients with PSA partial responses have experienced grade 2 or 3

immune-mediated endocrine deficiencies similar in type to those previously

reported with ipilimumab therapy which have been successfully treated with

standard hormone replacement therapy.

In the second oral presentation entitled, " K562/GM-CSF vaccination reduces

tumor burden, including achieving molecular remissions in chronic

myelogenous leukemia (CML) patients with residual disease on imatinib, "

(Abstract #6509), the company reported encouraging long-term follow-up data

from a Phase 2 trial of GVAXR immunotherapy for chronic myelogenous leukemia

(CML). A total of 19 CML patients with molecular evidence of persistent

leukemia following at least one year of GleevecR (imatinib mesylate) therapy

were treated with GVAX immunotherapy while continuing to receive Gleevec.

Updated results show that the addition of GVAX immunotherapy to Gleevec

therapy reduced persistent leukemic disease in 10 of 19 patients as

demonstrated by a complete disappearance (five patients) or a greater than

one log (90%) reduction (five patients) in bcr-abl -- a validated genetic

marker found on the leukemic cells. The new findings reported today also

show that with a median follow up from treatment initiation of 14 months for

all patients, the molecular responses are ongoing in the five patients

showing a one log or greater reduction in bcr-abl. In addition, four of the

5 patients with a complete disappearance of bcr-abl continue to have

undetectable values at the most recent follow up. Of the remaining 10

patients, only one patient has developed cytogenetic progression on therapy

and this patient had the highest level of disease burden at study entry. To

date all patients have tolerated treatment well and completed the planned

follow-up period.

Clinical trials of GVAXR cancer immunotherapies are under way for multiple

types of cancer including prostate cancer, pancreatic cancer, and leukemia.

These products are whole-cell immunotherapies which are designed to

stimulate an immune response against the patient's tumor. The products are

comprised of tumor cells that have been irradiated and genetically modified

to secrete GM-CSF (granulocyte-macrophage colony stimulating factor), an

immune stimulatory hormone which plays a key role in stimulating the body's

response to such immunotherapies. GVAX cancer immunotherapies are being

developed as non patient-specific, " off-the-shelf " pharmaceutical products.

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 - GVAXR cancer immunotherapies

and oncolytic virus therapies. Ongoing clinical trials include Phase 3

trials of GVAX immunotherapy for prostate cancer, Phase 2 trials of GVAX

immunotherapy for pancreatic cancer and 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 <http://www.cellgenesys.com/>

http://www.cellgenesys.com.

Statements made herein about the company, other than statements of

historical fact, including statements about the company's progress, results

and timing of clinical trials and preclinical programs 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, the regulatory approval

process for clinical trials, competitive technologies and products, patents,

continuation of corporate partnerships and the need for additional

financings. For information about these and other risks which may affect

Cell Genesys, please see the company's Annual Report on Form 10-K for the

year ended December 31, 2004 filed on March 14, 2005 as well as Cell

Genesys' reports on Form 10-Q 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: Ina Cu

Investor Relations

650-266-3200