Geron and TA Therapeutics Announce Presentation of New Data Supporting Utility of Their Small Molecule Telomerase Activator TAT0002; TAT0002 Selected as Lead Compound for HIV/AIDS Indication

MENLO PARK, Calif.--May 15, 2006--Geron Corporation and TA Therapeutics, Ltd., a joint venture between Geron Corporation and the Biotechnology Research Corporation of Hong Kong (BRC), announced today the presentation of studies demonstrating that their small molecule telomerase activator, TAT0002, enhances the anti-viral activity of CD8 T-cells from HIV/AIDS donors against infected CD4 cells from the same donors. TA Therapeutics is exploring multiple applications for telomerase activators in chronic degenerative and infectious diseases. The company's most advanced program is HIV/AIDS, and it has selected TAT0002 as the lead development candidate for this indication.

The new research was presented at the annual meeting of the American Association of Immunologists in Boston by Steve Fauce, from the laboratory of Rita Effros, Ph.D., professor of pathology and laboratory medicine and a member of the AIDS Institute at the David Geffen School of Medicine at UCLA. The studies are the product of a collaboration between Geron scientists, Dr. Effros and colleagues at UCLA.

As HIV disease progresses, certain immune cells called CD8 cytotoxic T-cells undergo accelerated replicative senescence (cellular aging) and lose their ability to proliferate and kill HIV-infected CD4 T-cells. Previously, Dr. Effros and colleagues demonstrated that introducing the telomerase gene into CD8 cells from HIV/AIDS donors increased: 1) their proliferative capacity, 2) their ability to produce IFN-gamma, and 3) their ability to inhibit virus production and kill HIV-infected T-cells. Dr. Effros' team also showed that Geron's small molecule telomerase activators had similar activity enhancing the ability of certain HIV-specific CD8 T-cells to inhibit virus production when co-cultured with an HLA-matched HIV-infected CD4 T-cell line.

The current work examined the effects of TAT0002 in an autologous "co-culture" setting with T-cells from three independent HIV-positive donors. In this study, CD8 and CD4 T-cells from each donor were separately expanded for 14 days with or without TAT0002. The CD8 and HIV-infected CD4 T-cells from each patient were then cultured together for 10 days at different CD8:CD4 ratios, with or without TAT0002. Virus level was measured by a standard assay. The presence of TAT0002 during the expansion and co-culture periods significantly reduced the mean virus levels for all three donors relative to the vehicle-control treated cells (p=0.003, 0.01 and 0.04 at each of three CD8:CD4 culture ratios). The level of the effect (2-5 fold reduction in virus levels) in this relatively short-term autologous study was greater than that seen previously with the HIV-infected CD4 T-cell line.

"These results are important because they show that significant anti-viral effects of TAT0002 are seen in cells from different HIV-infected persons in an autologous setting that more closely matches the context in which the drug will be used clinically," stated Calvin B. Harley, Ph.D., chief scientific officer of Geron and chair of TA Therapeutics' joint operating committee. "It is also noteworthy that TAT0002 targets the uninfected CD8 T-cells, not the virus itself, so it should not be subject to resistance caused by mutational changes in HIV. We expect TAT0002 will complement conventional anti-viral therapies and may potentially reduce the need for such drugs," added Dr. Harley.

"We are very pleased with the rapid and significant advances made by the TA Therapeutics joint operating team in demonstrating the efficacy, safety and manufacturability of the lead drug candidate," stated Thomas B. Okarma, Ph.D., M.D., president and chief executive officer of Geron. "Our joint venture with BRC has the resources and focus to move TAT0002 through IND-enabling studies in preparation for a future Phase I/II clinical trial in HIV/AIDS."

Geron is a Menlo Park, Calif.-based biopharmaceutical company 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. For more information, visit www.geron.com.

TA Therapeutics Ltd. is a joint venture between Geron Corporation and the Biotechnology Research Corporation, a company established by the Hong Kong University of Science and Technology (HKUST). Website: www.ust.hk

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 and compounds constitute forward-looking statements involving risks and uncertainties, including, without limitation, risks inherent in the development and commercialization of potential products, need for additional capital, reliance on collaborators, need for regulatory approvals or clearances, 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 March 31, 2006.