News Release

Geron Announces Development Of Defined Culture Medium For The Propagation Of Human Embryonic Stem Cells

Menlo Park, CA – November 19, 2003 – Geron Corporation (Nasdaq: GERN) today announced the development of a defined, serum–free culture system for the propagation of human embryonic stem cells (hESCs). This new culture system relies solely on completely defined components for hESC growth, facilitating safe and scalable expansion of these cells for cell–based therapeutics.

In a presentation at the 2003 annual meeting of the American Institute of Chemical Engineers in San Francisco, Geron presented studies demonstrating that hESCs could be expanded in a culture medium that contains only human–sourced proteins and defined recombinant growth factors. Using these defined conditions, hESCs could be propagated for at least 120 days in culture while maintaining normal morphology, doubling time, and expression of a panel of markers characteristic of hESCs. Moreover, hESCs propagated under these conditions continued to be pluripotent, differentiating into cells representative of endoderm, mesoderm, and ectoderm, the three cell lineages of the human body.

This work extends Geron’s previous development of feeder–free growth conditions for hESCs. Geron had earlier developed protocols to culture hESCs in the absence of direct contact with feeder cells by using extracellular matrix proteins and cell–free media that had been previously conditioned by feeder cells. "This new development allows the replacement of conditioned medium with a fully defined medium that contains only human–sourced proteins and purified growth factors," stated Jane S. Lebkowski, Ph.D., Geron’s vice president of regenerative medicine. "This advance greatly facilitates the scalable production of the cells while essentially eliminating the risk of contamination by non–human infectious agents in the culture process for undifferentiated cells."

"This advance is a major development towards our goal of producing safe and cost–effective cell–based therapeutics for treating degenerative disease," stated Thomas B. Okarma, Ph.D., M.D., Geron’s president and chief executive officer. "In addition to achieving our objective for safety, which will also be a focus of regulatory agencies, this process breakthrough alone has significantly lowered our current manufacturing costs. Geron is now incorporating this defined culture system in all of its manufacturing protocols for the production of therapeutic cells."

Geron is a biopharmaceutical company focused on developing and commercializing therapeutic and diagnostic products for cancer based on its telomerase technology, and cell–based therapeutics using its human embryonic stem cell technology.

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 technologies constitute forward–looking statements that involve risks and uncertainties, including, without limitation, risks inherent in the development and commercialization of potential products, need for future capital 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 quarterly report on Form 10–Q for the quarter ended September 30, 2003.

Contact:
Geron Corporation
David L. Greenwood
Chief Financial Officer
650–473–7765
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