Phase 3 IMpactMF Trial of Imetelstat Discontinued After Unfavorable Overall Survival Assessment
Clinical Summary:
- Design/Population: The phase 3 IMpactMF trial evaluated imetelstat versus best available therapy in patients with intermediate-2 or high-risk myelofibrosis who had relapsed after or were refractory to JAK inhibitor treatment.
- Key Outcomes: The trial was discontinued following a recommendation from the independent Data Monitoring Committee, which determined that the trial was unlikely to meet its primary overall survival end point. No new safety signals were observed that would change the known safety profile or require additional monitoring.
- Clinical Relevance: The discontinuation represents a setback for imetelstat development. Further analysis needs to characterize the study outcomes and identify potential insights for future treatment strategies.
Geron has announced the discontinuation of the phase 3 IMpactMF trial evaluating imetelstat in patients with JAK inhibitor-relapsed or refractory myelofibrosis following a recommendation from an independent Data Monitoring Committee that the study was unlikely to meet its primary overall survival (OS) end point.
The October 28, 2026, decision was based on the Data Monitoring Committee’s assessment of the trial, which evaluated whether imetelstat could improve survival compared with best available therapy in patients with intermediate-2 or high-risk myelofibrosis following JAK inhibitor treatment.
In this open-label, controlled trial, 327 patients with intermediate-2 or high-risk myelofibrosis who had relapsed after or become refractory to JAK inhibitor therapy were randomized 2:1 to receive either 9.4 mg/kg of imetelstat every 3 weeks or best available therapy. The primary end point was OS, with the trial designed to evaluate whether imetelstat could provide a survival benefit compared with best available therapy in this previously treated population.
Following its assessment, the independent Data Monitoring Committee recommended discontinuation because the trial was unlikely to meet its primary OS end point. Detailed efficacy findings including median OS, hazard ratios, and statistical comparisons between treatment groups were not provided in the announcement.
No new safety signals were identified that would change the known safety profile of imetelstat or require additional safety monitoring.
Geron stated that a detailed analysis of the trial data will be conducted, with findings to be shared with the scientific community at a future date.
The discontinuation of IMpactMF limits the current development path for imetelstat in JAK inhibitor-relapsed or refractory myelofibrosis, although further analysis may provide insights into treatment outcomes and inform future research.
The company concluded that it remains committed to evaluating the IMpactMF data and sharing findings that may contribute to future research in hematologic malignancies.
Source:
Geron. Geron corporation provides update on phase 3 IMpactMF clinical trial of imetelstat in relapsed/refractory myelofibrosis. Accessed on October 30, 2026. https://ir.geron.com/news-releases/news-release-details/geron-corporation-provides-update-phase-3-impactmf-clinical
