Geron halts Phase 3 IMpactMF trial of imetelstat in myelofibrosis

Geron Corporation said on October 28, 2026 that it is discontinuing its Phase 3 IMpactMF trial testing imetelstat in patients with JAK inhibitor relapsed or refractory myelofibrosis. The company made the decision following a recommendation from the trial's independent Data Monitoring Committee.¹ The committee told Geron that the study was unlikely to reach its primary goal of showing an overall survival benefit.¹

Geron said the safety picture for imetelstat was unchanged by the trial's results, reporting no new concerns that would alter the drug's known risk profile or call for extra monitoring. The company said it plans to conduct a full review of the trial data and intends to present those findings to the scientific community at a later, unspecified date.

IMpactMF had enrolled 327 patients with intermediate-2 or high-risk myelofibrosis who had relapsed on or were refractory to JAK inhibitor therapy, randomized 2:1 in an open-label design comparing imetelstat, dosed at 9.4 mg/kg intravenously every three weeks, against best available therapy.¹

Chief Medical Officer Joseph E. Eid said the company believes discontinuing the trial is the right course of action given the DMC's recommendation, and thanked the patients, families and clinical teams involved in the research.¹ CEO Harout Semerjian said Geron remains focused on growing demand for RYTELO in the United States while expanding access for eligible lower-risk MDS patients outside the U.S. as the IMpactMF data are fully analyzed.¹

Geron described itself as a commercial-stage hematology company, noting that its marketed product, imetelstat, is sold under the brand name RYTELO and has regulatory clearance in the United States and the European Union for a specific group of lower-risk myelodysplastic syndrome patients.