Geron Corporation (Nasdaq:GERN) announced today the presentation of studies which show that insulin-producing cells can be differentiated from human embryonic stem cells (hESCs). In these studies, presented at the Cell Transplant Society Meeting in Boston, Geron scientists reported improvements in the differentiation and characterization of the cells and early engraftment results from transplant studies in animal models.

Anish Sen Majumdar Ph.D., Geron's director of immunology, reported on the differentiation of islet cells from hESCs. Geron scientists have developed a three-step differentiation protocol that yields a population containing cells with many of the features of islet cells. During the differentiation protocol, appropriate temporal expression of markers characteristic of progressively more mature precursors of islet cells were observed. The final product contained cell aggregates where insulin- and glucagon-expressing cells were found in close apposition. Insulin and glucagon are important hormones produced by pancreatic islets that regulate blood glucose levels. Cells within the aggregates also expressed c-peptide, a secretory cleavage product of insulin, indicative of bonafide production of insulin by the hESC-derived cells. Moreover, these cells appropriately increased insulin and c-peptide production upon exposure to increasing concentrations of glucose, a property of insulin-producing beta islet cells.

In studies performed in collaboration with Drs. Greg Korbutt and Ray Rajotte at the University of Alberta in Edmonton, Canada, the hESC-derived islet-like cells were transplanted into streptozotocin-induced diabetic mice, a rodent model of diabetes. Histological examination of the grafts showed the presence of c-peptide-producing cells three months after transplantation. Human c-peptide was also found in the serum of these transplanted animals after challenge with high glucose.

"We are excited about this progress," stated Jane S. Lebkowski, Geron's senior vice president of regenerative medicine. "Differentiation of pancreatic islet cells from embryonic stem cells is very challenging and protocols reported from work with mouse embryonic stem cells have not proven useful for human embryonic stem cells. We are focused on improving the yield and purity of hESC-derived islet cells to advance our preclinical studies in models of diabetes."

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 human embryonic stem cell technologies involve risks and uncertainties, including, without limitation, risks inherent in the development and commercialization of potential products, reliance on collaborators, 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, 2004.