Geron Announces Initiation of Clinical Trial for Its Telomerase Inhibitor Drug GRN163L in Patients With Solid Tumor Malignancies.

MENLO PARK, Calif. -- Geron Corporation (Nasdaq:GERN) announced today that it has initiated clinical testing of its lead anti-cancer compound, GRN163L, in patients with solid tumor malignancies at The University of Chicago Cancer Research Center.

This Phase I, dose-escalation trial of GRN163L is primarily designed to demonstrate the safety and tolerability of GRN163L administered intravenously (IV) on a weekly basis in patients with refractory or relapsed solid tumor malignancies. This study will also evaluate the tolerability of IV infusions of GRN163L at various rates of administration, and enable an assessment of the pharmacokinetic profile of GRN163L at escalating doses and at decreasing infusion durations. A secondary endpoint of the trial is the preliminary evaluation of anti-tumor activity of GRN163L in this patient population.

"This second trial of GRN163L is open for patient enrollment at The University of Chicago, under the leadership of principal investigator, Mark Ratain, M.D.," said Melissa Kelly Behrs, Geron's vice president of oncology. "Dr. Ratain is a recognized leader in the areas of clinical pharmacology and clinical drug development, with extensive clinical research experience in a broad array of solid tumor types."

"We are excited to be extending the clinical evaluation of this first-in-class drug, GRN163L, in the solid tumor setting," said Mark Ratain, M.D., Leon. O. Jacobson Professor, Department of Medicine and Associate Director for Clinical Sciences, Cancer Research Center at The University of Chicago. "Preclinical studies of GRN163L alone, and in combination with approved chemotherapeutic agents, indicate the importance of telomerase as a target for the treatment of cancer, and the potential utility of GRN163L in the treatment of patients with essentially any type of solid tumor malignancy. We are, therefore, very hopeful that our patients may benefit from this new drug."

Phase I/II Clinical Trial of GRN163L in CLL Patients

A Phase I/II clinical trial of GRN163L is also ongoing in patients with advanced chronic lymphocytic leukemia (CLL). This trial is open for patient enrollment at Long Island Jewish Medical Center, North Shore University Hospital, and the Weill Medical College of Cornell University.

For more information about the GRN163L clinical trials in CLL and solid tumors, visit the U.S. National Library of Medicine website at http://www.ClinicalTrials.gov to access a brief synopsis for each study. A link to this site is also provided on Geron's website at http://www.geron.com.

About GRN163L

GRN163L is a potent inhibitor of telomerase. Inhibition of telomerase activity by GRN163L in cancer cells results in telomere shortening, and leads to cell cycle arrest or apoptosis. GRN163L is a 13-mer oligonucleotide N3' -- P5' thio-phosphoramidate (NPS oligonucleotide) that is covalently attached to a C16 (palmitoyl) lipid moiety. GRN163L binds directly with high affinity to the template region of the RNA component of human telomerase (hTR), which lies in the active or catalytic site of hTERT, the telomerase reverse transcriptase. GRN163L binding to hTR results in direct, competitive inhibition of telomerase enzymatic activity. The mechanism of action of the drug is not antisense mediated.

GRN163L has been characterized preclinically and shown to inhibit telomerase in human tumor cells of many cancer types, in both cell culture systems and animal models. These studies continue to demonstrate broad anti-tumor activity of GRN163L, alone and in combination with other anti-tumor agents, and support the potential utility of GRN163L in the treatment of patients with hematologic and solid tumor malignancies.

Geron is a biopharmaceutical company focused on developing and commercializing three groups of products: i) therapeutic products for oncology that target telomerase; ii) pharmaceuticals that activate telomerase in tissues impacted by senescence, injury or degenerative disease; and iii) cell-based therapies derived from its human embryonic stem cell platform for applications in multiple chronic diseases.

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 potential applications of Geron's telomerase technology and future clinical trial results constitute forward-looking statements that involve risks and uncertainties, including, without limitation, risks inherent in the development and commercialization of potential products, uncertainty of clinical trial results or regulatory approvals or clearances, need for future capital, dependence upon collaborators and 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, 2005.