Phase 3 Clinical Trial to Evaluate Imetelstat in Patients with Intermediate-2 of High-Risk Myelofibrosis That Are Refractory to a Janus Kinase (JAK) Inhibitor


trial Design

IMpactMF is an ongoing Phase 3 clinical trial in refractory myelofibrosis (MF) and is designed with registrational intent as an open label 2:1 randomized, controlled study to evaluate imetelstat compared to best available therapy (BAT) in approximately 320 patients with Intermediate-2 or High-risk MF. Patients eligible for the trial will be required to be non-responsive, or refractory, to a janus kinase (JAK) inhibitor. The primary efficacy endpoint for the trial is overall survival (OS). Secondary endpoints include symptom response, spleen response, progression free survival, duration of response, safety, pharmacokinetics, and patient reported outcomes.

The final analysis for OS is planned to be conducted after more than 50% of the total enrolled patients have died. An interim analysis of OS is planned to be conducted after approximately 70% of the total projected number of events, or deaths, for the final analysis have occurred. At the interim analysis, if the pre-specified statistical OS criterion is met, then Geron expects such data may support registration of imetelstat in refractory MF. If the prespecified OS criterion is not met at interim analysis, the trial will continue to the final analysis. Both the planned interim and final analyses are event driven and could occur on different timelines than currently expected.


IMpactMF opened for patient screening and enrollment in December 2020, and the first patient was dosed in April 2021. We expect to engage over 180 sites to participate in IMpactMF across North America, South America, Europe, Australia and Asia.

To learn more about this trial, including enrollment criteria, locations and current status, visit

Imetelstat, a telomerase inhibitor, is an investigational treatment for cancer and has not been approved by the FDA or any other regulatory agency.