MENLO PARK, Calif., December 10, 2012 - Geron Corporation (Nasdaq: GERN) today announced positive clinical results from the Phase 2 trial of imetelstat, the company's first-in-class telomerase inhibitor, in patients with essential thrombocythemia (ET). ET is a chronic blood disorder that is representative of a group of diseases known as myeloproliferative neoplasms (MPNs). The data, which showed rapid and durable hematologic and molecular responses in patients treated with imetelstat, were presented Sunday evening in an oral session at the 54^th Annual Meeting of the American Society of Hematology (ASH) in Atlanta, GA, by Prof. Dr. med. Gabriela M. Baerlocher of the University Hospital and University of Bern, Switzerland, and a principal investigator of the trial. To view the presentation slides, please visit www.geron.com/PDFs/Geron-Imetelstat-ETPh2-ASH-2012.pdf.

"The observed hematologic response rate of 100%, accompanied by a molecular response rate of 86% among the patients who had a JAK2 V617F mutation, is very impressive considering that these were patients who did not respond to or tolerate other therapies," said Prof. Baerlocher. "The 60 to 90% reduction in JAK2 V617F allelic burden in patients who had the molecular responses, and the rapidity with which these responses were observed, exceeded our expectations. It is also encouraging that all of the patients who were eligible to remain on imetelstat beyond a year have elected to do so."

Study Rationale and Design
Geron's multi-center, single arm, open-label Phase 2 study of imetelstat in patients with ET has been designed to provide proof-of-concept for the potential use of the drug as a treatment for hematologic myeloid malignancies, including myelofibrosis, myelodysplastic syndromes and acute myelogenous leukemias. The study has leveraged non-clinical observations that imetelstat distributes well to bone marrow and selectively inhibits the proliferation of malignant progenitors from patients with ET.

Hematologic responses were measured by reductions in platelet counts. Molecular responses were measured by reductions in mutant JAK2 allelic burden in circulating granulocytes. A decrease in the relative proportion of mutant JAK2 to wild type JAK2 is consistent with selective inhibition of the neoplastic progenitor cells responsible for the disease. The European LeukemiaNet criteria were used to grade both hematological and molecular responses.

Efficacy Results
The results from the first 14 patients enrolled in the ET study were reported. All were refractory to or intolerant of conventional therapies (hydroxyurea, anagrelide and/or interferon-alpha). Platelet counts were reduced in all patients (a 100% hematologic response rate) and normalized in 13 out of 14 patients (a 92.9% complete response rate). The allelic burden of the JAK2 V617F gene mutation decreased over time in the seven patients who had such a mutation, with substantial reductions that qualified as partial molecular responses achieved in six out of seven (85.7%) patients within three to six months of treatment with imetelstat.

Imetelstat was initially administered weekly by intravenous infusion during an induction phase. After achieving a complete hematologic response, which occurred in a median time of approximately six weeks, a maintenance phase was begun in which dosing frequency was modified based on a patient's individual response profile. In 11 out of 13 (84.6%) patients who attained a complete hematologic response, the frequency with which imetelstat was administered to maintain the response was reduced to every two weeks or less, generally decreasing over time. Six out of seven (85.7%) eligible patients have chosen to remain on treatment beyond one year.

Safety Results
In the study, imetelstat was generally well tolerated. The majority of the non-hematologic adverse events were mild-to-moderate in severity, the most frequent being gastrointestinal events. No drug-related Grade 4 non-hematological adverse events were reported. Neutropenia was the most frequently reported hematologic abnormality. Two patients had Grade 4 neutropenia, but no cases of febrile neutropenia were reported. No thromboembolic events or bleeding events associated with thrombocytopenia were reported.

Imetelstat Development in Hematologic Malignancies
"The molecular responses observed in this study suggest that imetelstat had a selective inhibition of the malignant progenitor cells, which are believed to be responsible for the underlying disease," said Stephen Kelsey, M.D., Geron's Executive Vice President, Head of R&D, and Chief Medical Officer. "As a consequence, we believe that imetelstat may have applicability for the treatment of other progenitor cell-driven hematologic malignancies, including myelofibrosis."

Based on the results from the ET study, Dr. Ayalew Tefferi, M.D., at the Mayo Clinic has begun an investigator-sponsored pilot study to evaluate safety and efficacy of imetelstat in patients with myelofibrosis, a myeloproliferative neoplasm in the same spectrum of diseases as ET. For more information about this study, please refer to http://clinicaltrials.gov/ct2/show/NCT01731951. Geron is in the initial planning stages of a company-sponsored Phase 2 study in myelofibrosis, which will be informed, in part, by data from the Mayo Clinic study. In addition, Geron intends to expand its directed program of investigator-sponsored trials in 2013 to other hematologic myeloid indications, including acute myelogenous leukemias.

About Essential Thrombocythemia (ET)

ET is a chronic blood disorder characterized by increased numbers of platelets in the blood. These platelets may have abnormal function, which can lead to an increased risk of thrombotic or hemorrhagic complications. Currently used treatments, such as hydroxyurea and anagrelide, can be effective in reducing platelet counts in patients with ET, but do not alter the underlying biology of the disease, and clinical resistance or intolerance to these agents occurs in a proportion of patients. The utility of interferon-alpha, which can induce molecular responses in some patients, is limited by tolerability.

About Imetelstat

Imetelstat (GRN163L) is a potent and specific inhibitor of telomerase. This first-in-class compound is a specially designed and modified short oligonucleotide, which targets and binds directly and with high affinity to the active site of telomerase. Unique and proprietary oligonucleotide chemistry improves binding affinity and stability in plasma and tissues. A lipid modification enables cellular and tissue penetration and biodistribution. To date, clinical data from Phase 2 studies indicate that the compound has activity against hematologic malignancies and in solid tumors with short telomeres.

Update on Phase 2 Trial in Multiple Myeloma
A Phase 2 trial of imetelstat in patients with multiple myeloma was designed to measure the effect of imetelstat on the progenitor cells responsible for the disease. Preliminary data from this trial showed a rapid and significant decrease in myeloma progenitor cells that were detected in the blood over the course of imetelstat treatment in eight out of nine patients. In addition, several patients experienced delayed, but sustained, clinical responses as measured by standard criteria. The data have been published in an abstract in the journal, Blood (ASH Annual Meeting Abstracts) 2012 120: Abstract 4898, which is available online at http://abstracts.hematologylibrary.org/content/vol120/issue21. Geron expects that full clinical data from all patients enrolled in the multiple myeloma trial will be available in 2013.

About Geron

Geron is a biopharmaceutical company developing first-in-class therapies for cancer, including its telomerase inhibitor, imetelstat. For more information about Geron, visit www.geron.com.

Use of Forward-Looking Statements

Except for the historical information contained herein, this press release contains 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 Geron's plans or expectations for or of: dates to obtain or present data or other results from any clinical trials; and clinical development plans or success of imetelstat, including imetelstat possibly having applicability for the treatment of other progenitor cell-driven hematologic malignancies, including myelofibrosis, constitute forward-looking statements. These statements involve risks and uncertainties that can cause actual results to differ materially from those in such forward-looking statements. These risks and uncertainties, include, without limitation: (a) regarding dates for the availability of data or other results - delays in enrollment, delays caused by institutional review boards or regulatory agencies, shortage of supply, dependence on clinical trial collaborators and safety issues; and (b) regarding the development of imetelstat - those risks and uncertainties inherent in the development of potential therapeutic products, including without limitation, results from the ET trial may not mean that imetelstat has applicability for the treatment of other progenitor cell-driven hematologic malignancies, including myelofibrosis; successful clinical trial results and the protection of Geron's intellectual property rights. Additional information and factors that could cause actual results to differ materially from those in the forward-looking statements are contained in Geron's periodic reports filed with the Securities and Exchange Commission under the heading "Risk Factors," including Geron's quarterly report on Form 10-Q for the quarter ended September 30, 2012. Undue reliance should not be placed on forward-looking statements, which speak only as of the date they are made, and the facts and assumptions underlying the forward-looking statements may change. Except as required by law, Geron disclaims any obligation to update these forward-looking statements to reflect future information, events or circumstances.

CONTACT:

Anna Krassowska, Ph.D.
Investor and Media Relations
650-473-7765
investor@geron.com
media@geron.com

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