Geron Reports On Pre-Clinical Studies for Three Product Candidates At 2002 Annual Meeting of the American Association for Cancer Research.

Business Editors & Health/Medical Writers

BIOWIRE2K

MENLO PARK, Calif.--(BW HealthWire)--April 9, 2002

Studies Demonstrate Significant Anti-Tumor Activity Without

Toxicity, Confirming Telomerase to be a Highly Promising Target

for Effective Anti-Cancer Therapies

Geron Corporation (Nasdaq:GERN) today reported positive pre-clinical data from separate studies of three anti-cancer product candidates under development. These studies demonstrate significant and specific anti-tumor activity without toxicity for all three approaches. Together, these studies confirm the effectiveness of inhibiting or targeting telomerase in the treatment of cancer.

Geron's portfolio of telomerase-based anti-cancer therapies, including GRN163, a highly potent and specific telomerase inhibitor; a telomerase promoter-driven oncolytic virus; and ex vivo and in vivo telomerase vaccines were among several key highlights featured from the over 70 telomerase-focused scientific papers and posters presented at this week's American Association for Cancer Research (AACR) Annual Meeting held in San Francisco, California.

Telomerase is an enzyme that is absent in most normal cells and tissues; however, during tumor progression, telomerase is abnormally reactivated and expressed in all major cancer types. While telomerase does not cause cancer, the activation of telomerase enables cancer cells to maintain telomere length and resist apoptosis (programmed cell death), thereby enabling unlimited cell growth and resistance to cytotoxic drugs.

"We are very encouraged by the data we have generated in these studies of our telomerase-based anti-cancer therapies. All three of our product development candidates show promise in pre-clinical studies. In addition, we are very pleased with the progress being made with our telomerase vaccine currently in Phase 1 human clinical trials at Duke and we are on track for our IND (Investigational New Drug) filing for GRN163 by the end of the year," said Tom Okarma, Ph.D., M.D., president and CEO at Geron. "We believe our knowledge and expertise in telomerase, combined with our comprehensive intellectual property estate, give us the advantage in developing telomerase as a highly specific and universal `engine' that will drive multiple successful anti-cancer therapies."

AACR Meeting highlights include:

-- Geron's telomerase inhibitor, GRN163, inhibits growth of

subcutaneous human brain tumors in mice by 70-80 percent and

enters tumor cells when administered into the brains of rats.

Geron reported additional data from its three separate in vivo studies in human brain cancer, demonstrating reduction in tumor size by 70-80 percent in treated mice compared to control groups after short-term treatment with GRN163. Additionally, infusion of fluorescent GRN163 into rat brains demonstrated good uptake into the cancer cells in the absence of a lipid carrier. Dr. Dennis Deen, Ph.D., professor of neurological surgery at University of California, San Francisco, presented the data at the AACR meeting.

In three separate studies, human malignant glioblastoma (brain cancer cells) were implanted under the skin in mice and the resulting tumors were treated with GRN163. In all three studies, short-term treatment (four to nine injections over one to three weeks) with GRN163 resulted in tumor reduction (70-80 percent) compared to the control-treated animals. Importantly, tumor growth was slowed in all of the mice that received GRN163, and in one case, the tumor completely disappeared. Additionally, the results of the rat study demonstrate that GRN163 will have appropriate bioavailability for the treatment of human brain cancers.

An initial report of the in vivo studies featuring GRN163 was presented at the Society of Neuro-Oncology meeting held in November 2001.

-- Telomerase promotor-oncolytic virus induces significant

regression of liver and prostate cancer tumors in mice

following treatment.

Geron researchers conducted tests of its oncolytic virus in mice with pre-existing human liver and prostate cancer. At the end of the 70-day to 100-day period, 80-90 percent of the mice treated with only five intratumoral injections of the telomerase promotor-oncolytic virus (ad2p-hTERT-E1A) showed significant tumor regression. In 43 percent of liver cancer-bearing mice, tumors regressed completely and the mice remained tumor free for the full study duration (70 days). Similarly, 50 percent of prostate cancer-bearing mice became tumor free and remained so over a 100-day period. The surrounding normal cells remained unharmed, demonstrating the high level of specificity of the telomerase promoter in telomerase expressing cancer cells. No toxic effects were observed in the treated mice. Mice treated with a control non-replicating virus did not exhibit tumor regression -- their tumors continued to grow throughout the study.

These studies, taken together with other comprehensive tests done by Geron and various third parties, confirm that a "cancer killing" or "oncolytic" therapeutic virus, when controlled by the telomerase promoter, can effectively kill a wide variety of human cancer cell types and therefore could be used to treat many types of human cancers.

-- Direct, in vivo vaccination with a telomerase DNA therapeutic

vaccine produces a telomerase-specific cytotoxic T cell immune

response.

Geron scientists reported preliminary data from a third anti-cancer therapy approach -- ex vivo and in vivo telomerase therapeutic vaccines.

As with all vaccines, efficacy is dependent upon the antigen used to stimulate the immune response. In the ex vivo study, Geron scientists demonstrated the effectiveness of using telomerase DNA to generate an immune response in mice. In contrast to humans in whom telomerase is expressed primarily in cancers and only rarely in normal tissues, mice demonstrate telomerase activity in many of their normal cells, thereby making it more difficult to generate an immune response to mouse telomerase (mTERT) by vaccination. Geron scientists were successful in inducing an immune response to mTERT first by vaccinating mice with murine derived dendritic cells (DC) genetically modified to express the hTERT (human telomerase) or mTERT gene, separately and in combination.

This ex vivo approach generated a telomerase-specific immune response sufficient to cause the death of mouse tumor cells expressing mTERT, which culminated in significant inhibition of tumor growth in some of the vaccinated mice. These results demonstrate that telomerase vaccination can induce an anti-telomerase immune response that can recognize and kill tumor cells expressing the enzyme.

Also reported at the meeting, Dr. Johannes Vieweg and colleagues from Duke University showed that human dendritic cells transfected with native or a modified form of hTERT RNA were remarkably effective in vitro in stimulating a strong anti-telomerase immune response that was able to lyse human tumor cells.

Encouraged by the results of the ex vivo vaccination experiments, Geron scientists conducted a separate study demonstrating that an in vivo (direct) DNA vaccination is also able to generate a significant telomerase-specific immune response in mice.

The in vivo results suggest that direct methods of vaccination can also successfully induce an immune response against telomerase. This method of cancer immunization would be much simpler and less expensive than the ex vivo approach because it would eliminate the need for an individualized, patient-specific therapy based on cultured dendritic cells.

GERON'S ONCOLOGY PRODUCT PORTFOLIO

GRN163 Telomerase Inhibitor

Developed by Geron scientists, GRN163 is a short-chain nucleic acid-like compound, known as an oligonucleotide, that acts as a telomerase template antagonist. This type of oligonucleotide is from a relatively new class of compounds with high potential for the treatment of disease and diagnostic applications. The compound binds tightly to the RNA template in the active site of telomerase, blocking activity of the enzyme. GRN163 is chemically modified to produce improved cellular uptake and biodistribution as well as resistance to degradation and enhanced binding affinity to telomerase. GRN163 inhibits purified telomerase at extremely low concentrations and does not inhibit other critical enzymes. This suggests that, unlike most other cancer therapies today, GRN163 may have little or no toxicity in normal (telomerase negative) tissue. Scale up synthesis plans and IND-enabling safety and efficacy animal studies are ongoing in support of an IND filing for GRN163 scheduled for late 2002.

Oncolytic Viruses

Geron's oncolytic (cancer-killing) virus therapies utilize the telomerase promoter and an adenovirus, one of the viruses responsible for the common cold. The telomerase promoter-driven oncolytic virus is engineered to selectively replicate in and kill targeted cancer cells expressing telomerase, leaving healthy normal tissues (that are telomerase negative) largely unharmed. The virus replicates until the cancer cell can no longer contain the virus and bursts. The tumor cell is destroyed and the newly created viruses spread to neighboring cancer cells, repeating the same lytic cycle. Telomerase-driven oncolytic viruses have the potential to treat many types of primary and metastatic cancers. Geron has granted a non-exclusive license to Genetic Therapy Inc. (GTI), a subsidiary of Novartis AG, to use the telomerase promoter technology in oncolytic virus-based products.

Therapeutic Vaccines

Geron's therapeutic vaccine development program focuses on delivering telomerase to special immune cells called dendritic cells that instruct the immune system (T lymphocytes) to detect cells that express telomerase and kill them. This approach exploits the presence of telomerase in all major cancer types. A Phase 1 study in prostate cancer patients at Duke University Medical Center is currently underway using this ex vivo immunotherapy approach. Geron is also developing an in vivo therapeutic cancer vaccine using telomerase DNA. This is a direct method of immunizing cancer patients, developed to stimulate an immune response within the patient's own body. The advantage of using a direct, in vivo vaccine is in eliminating the need for manipulating dendritic cells in culture, thereby enabling cost-effective and simple vaccination procedures to be potentially available for all cancer patients. Merix Bioscience and Dendreon Corporation hold licenses or options for incorporating the telomerase antigen into their respective ex vivo cancer vaccine procedures. Geron retains rights to the in vivo vaccine.

INTELLECTUAL PROPERTY AND TELOMERASE

Geron's telomerase-based oncology programs are supported by a broad intellectual property portfolio of over 56 issued or allowed U.S. patents, 44 granted foreign patents and over 182 patent applications pending around the world.

Issued U.S. patents include claims covering the cloned genes that encode the RNA component (hTR) and the catalytic protein component (hTERT) of human telomerase, as well as cells that are immortalized by expression of recombinant hTERT. Aspects of Geron's oncology product development programs covered by issued and pending patent applications include cancer diagnostics based on detecting the expression of telomerase in cancer cells, the use of telomerase as a cancer vaccine, the use of the hTERT promoter in cancer-killing genes and viruses, and telomerase inhibitors for use as cancer therapeutics.

Geron also owns issued U.S. patents and/or pending patent applications directed to both small molecules and oligonucleotide template antagonist telomerase inhibitors, as well as particular nucleic acid chemistry developed at Geron.

Geron is a biopharmaceutical company focused on developing and commercializing therapeutic and diagnostic products for applications in oncology and regenerative medicine, and research tools for drug discovery. Geron's product development programs are based upon three patented core technologies: telomerase, human embryonic stem cells and nuclear transfer.

This news release may contain forward-looking statements made pursuant to the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995. Investors are cautioned that such forward-looking statements in this press release regarding future applications of Geron Corporation's technology constitute forward-looking statements involving risks and uncertainties, including, without limitation, risks inherent in the development and commercialization of potential products, dependence on collaborative partners, and the maintenance of our intellectual property rights. Actual results may differ materially from the results anticipated in these forward-looking statements. Additional information on potential factors that could affect our results and other risks and uncertainties are detailed from time to time in Geron's periodic reports, including the annual report on Form 10-K for the year ended December 31, 2001.

Additional information about the company can be obtained at http://www.geron.com.