Phase 2 study of imetelstat for the treatment of essential thrombocythemia (ET)

Geron Corporation announced enrollment of the first patient in a Phase 2 clinical trial to evaluate imetelstat (GRN163L) in patients with essential thrombocythemia (ET). ET is a chronic disorder that arises in the hematopoietic (blood) stem cells in the bone marrow. The leukemic stem cells produce aberrant clones of platelet-forming cells (megakaryocytes), which results in increased numbers of circulating platelets. This trial is an open-label study of imetelstat as a single agent in patients with ET who have failed or are intolerant to at least one prior therapy or who refuse standard therapy, such as hydroxyurea, anagrelide or interferon-alpha. The primary efficacy endpoint is best overall hematologic response rate, determined by a normalization or reduction in platelet counts. Approximately half of patients with ET have a molecular mutation in the JAK2 or MPL genes. The rate of molecular response is a secondary endpoint in patients who have one or both of these mutations at baseline. A molecular response is determined by a reduction in the percentage of mutant JAK2 or MPL alleles detected in patients’ granulocytes.

Imetelstat is a lipidated short chain oligonucleotide that binds with high affinity and specificity to the catalytic site of telomerase, resulting in competitive inhibition of enzyme activity.

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