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Studies Confirm Proof-of-Principle for Geron´s Human Embryonic Stem Cell (hESC) Derived Hepatocytes

Findings Published in Cloning and Stem Cells Indicate Utility for Predictive Toxicology Tests

MENLO PARK, Calif., April 19, 2007 – Geron Corporation (Nasdaq: GERN) announced today that it has developed standardized hepatocytes from human embryonic stem cells (hESCs) that can model human hepatic drug metabolism.

Published in Cloning and Stem Cells (Vol. 9, No. 1, 51–62), a paper written by Geron’s scientific collaborators at the Roslin Institute describes an improved procedure to differentiate hepatocytes that exhibit characteristic hepatocyte morphology and express several hepatocyte markers, including albumin and HepPar1. The hESC–derived hepatocytes also possess functional activities, including p450 metabolism, albumin production, glycogen storage and uptake and excretion of indocyanine green, that are characteristic of normal human liver function.

"Geron’s hESC–derived hepatocyte technology presents a unique opportunity to address the lack of primary human hepatocytes for in vitro testing during drug discovery," said Thomas B. Okarma, Ph.D., M.D., Geron’s president and chief executive officer. "Pharmaceutical companies currently rely on animal models for preclinical metabolism and toxicity testing that are often not predictive for humans. These new studies provide the proof–of–principle that we could produce a standardized, limitless supply of hepatocytes which would provide the industry with a more representative tool for toxicology and metabolism testing of new drugs in development."

Geron’s hESC–derived hepatocyte technology presents a unique opportunity to address the bottleneck in drug discovery by providing standardized human hepatocytes that are predictive of human metabolism and toxicology. Undifferentiated hESCs maintain pluripotency and stable karyotypes after years in culture, providing a limitless supply of uniform source material. Geron has issued patents covering hepatocyte cells differentiated from hESCs and methods of drug screening using hepatocyte cells differentiated from hESCs.

The lack of human hepatocytes for in vitro assays is a fundamental bottleneck in pharmaceutical drug development. Primary human hepatocytes sourced from cadavers or liver resections have traditionally been used for drug metabolism and hepatotoxicity studies. However, the function, age and availability of these cells vary widely because of differences among the sourced donors.

Additionally, because hepatocyte function cannot be sustained in culture for more than a few days, the availability of primary hepatocytes is dependent on repetitive sourcing, creating supply constraints and further contributing to assay variability. Pharmaceutical companies have had to rely on animal models for preclinical metabolism and toxicity testing, which are often not predictive for man. The expensive and low–throughput nature of animal models has forced such testing to be reserved for compounds in late preclinical development, requiring pharmaceutical companies to invest significant resources in compounds before their metabolism and toxicity profiles are known, which contributes to both high development costs and costly failures of compounds in late preclinical testing.

Through its collaboration with the University of Edinburgh, Geron Bio–Med, Geron’s U.K.–based subsidiary, is sponsoring two development programs: one to develop hESC–derived hepatocytes for application as a tool for predictive toxicology and as a treatment for liver failure, and another to develop hESC–derived bone and cartilage cell types for musculoskeletal diseases including osteoarthritis and osteoporosis.

Geron is developing first–in–class biopharmaceuticals for the treatment of cancer and degenerative diseases, including spinal cord injury, heart failure, diabetes and HIV/AIDS. The company is advancing an anti–cancer drug and a cancer vaccine that target the enzyme telomerase through multiple clinical trials. Geron is also the world leader in the development of human embryonic stem cell–based therapeutics, with its spinal cord injury treatment anticipated to be the first product to enter clinical development. For more information, visit

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 human embryonic stem cell technology 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, 2006.


Media: David Schull, Noonan Russo, 858–717–2310,

Investors: Matthew Haines, Noonan Russo, 212–845–4235,

At Geron: David L. Greenwood, Chief Financial Officer, 650–473–7765,

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