Geron Corporation (Nasdaq:GERN) today announced the presentation of data from the clinical trial of imetelstat (GRN163L), the company’s telomerase inhibitor drug, in combination with paclitaxel and bevacizumab in patients with breast cancer at the 2010 American Society of Clinical Oncology (ASCO) annual meeting in Chicago.

An interim analysis of the Phase 1 trial was presented by Geron clinical scientists and collaborating principal investigators from Ingalls Memorial Hospital, Harvey, IL and Indiana University Melvin and Bren Simon Cancer Center, Indianapolis, IN.

“We are very encouraged by the data from the trial so far. We have seen good tolerability and exposures of drug, which exceed levels that have been associated with tumor inhibition in several models of human cancers. In addition, a preliminary response rate of 54% is promising in context of the reduced doses of chemotherapy that were administered during treatment cycles,” said Stephen M. Kelsey, M.D., Geron’s executive vice president and chief medical officer, oncology. “We plan to initiate a randomized Phase 2 breast cancer trial this year to test the effect on progression-free survival of adding imetelstat to this combination regimen. The trial will also explore predictive biomarkers to preferentially select breast cancer patients who may benefit from telomerase inhibition.”

Phase 1 Trial Design

Data were presented on patients with locally recurrent or metastatic breast cancer that were given imetelstat by two hour intravenous infusions on days one, eight and 15 of 28 day treatment cycles. Dosing started at 160 mg/m2 and escalation proceeded to 375 mg/m2. The patients also received the chemotherapy combination regimen of 90 mg/m2 paclitaxel (Taxol®) on days one, eight and 15, and 10 mg/kg bevacizumab (Avastin™) on days one and 15, both by intravenous infusion. Endpoints of the trial are safety, pharmacokinetics and efficacy. Safety data were presented on 14 patients and preliminary efficacy data were on 13 patients.

Pharmacokinetic and Efficacy Results

The preliminary confirmed overall response rate was 53.8% (95% confidence interval: 28.7% to 77.6%) based on investigator assessment of disease status using the Response Evaluation Criteria in Solid Tumors (RECIST). Median duration of response was 21.7 weeks (7.3 to 48.3 weeks).

Pharmacokinetic (PK) profile of imetelstat in combination therapy with paclitaxel and bevacizumab was comparable to the PK profile of imetelstat administered alone (from the Phase 1 trial in solid tumors). In the solid tumor trial, the observed level of exposure to imetelstat during the treatment period (AUC) was higher than the exposure that was associated with inhibition of telomerase activity and tumor growth in multiple xenograft animal models of human cancers. Similarly, in this Phase 1 combination trial in breast cancer, modeled AUC values at doses of imetelstat from 240 mg/m2 and above also exceeded the exposure required for efficacy in preclinical models.

Safety Results

Infusions of imetelstat were generally well tolerated and acute dose limiting toxicities were not observed. Neutropenia (low neutrophils) and/or thrombocytopenia (low platelets) in later treatment cycles led to reductions in the dose of imetelstat and/or paclitaxel in 12 (85.7%) patients. Alternative dosing schedules are being evaluated in additional patients to further increase exposure to imetelstat and to enable administration of full doses of standard therapy while minimizing hematological toxicities.

Phase 2 Trial

A randomized Phase 2 clinical trial of imetelstat in patients with metastatic breast cancer is planned for the fourth quarter of 2010. The trial plans to assess the effect on progression-free survival of adding imetelstat to paclitaxel and bevacizumab as first line therapy. The trial will recruit approximately 150 patients from up to 50 medical centers in the U.S.

About Telomerase and Imetelstat (GRN163L)

Telomerase is a critical and broadly applicable tumor target. The enzyme is expressed in a wide range of malignant tumors, and its activity is essential for the indefinite replicative capacity of cancer that enables malignant cell growth. Telomerase is absent or expressed only transiently at low levels in most normal adult tissues.

Imetelstat is a short chain oligonucleotide that binds with high affinity and specificity to the catalytic site of telomerase, resulting in competitive inhibition of enzyme activity. Proprietary manufacturing chemistry and the addition of a 5' lipid chain have enabled the molecule to penetrate cells and tissues throughout the body.

Imetelstat has demonstrated anti-tumor effects in a wide range of preclinical hematological and solid tumor models.

Preclinical studies have also demonstrated that imetelstat can inhibit clonogenic growth of both primary patient samples and subpopulations from cell lines enriched for cancer stem cells from multiple tumor types. These subpopulations show resistance to several conventional chemotherapeutic agents. Cancer stem cells capable of clonogenic growth may play an important role in the rapid regrowth of tumors after initial reduction by standard treatments.

Imetelstat has been tested in six Geron-sponsored Phase 1 clinical trials at 22 U.S. medical centers treating over 180 patients examining the safety, tolerability, pharmacokinetics and pharmacodynamics of the drug, alone or in combination with other standard therapies, in patients with different hematological and solid tumors. Four of the trials have completed patient enrollment. Two randomized Phase 2 clinical trials of imetelstat will start this year in non-small cell lung and breast cancer, and two single arm Phase 2 clinical trials will begin in multiple myeloma and essential thrombocythemia – all malignancies in which cancer stem cells have been shown to play an important role in relapse after standard therapy.

About Geron

Geron is developing first-in-class biopharmaceuticals for the treatment of cancer and chronic degenerative diseases, including spinal cord injury, heart failure and diabetes. The company is advancing an anti-cancer drug and a cancer vaccine that target the enzyme telomerase through multiple clinical trials in different cancers. For more information, visit www.geron.com.

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 statements in this press release regarding potential applications of Geron’s oncology/telomerase 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 quarterly report on Form 10-Q for the quarter ended March 31, 2010.