Phase II FRACTION trial: Fedratinib + nivolumab in MF

Results from the single-arm, open-label, phase II FRACTION trial (NCT05393674), evaluating fedratinib + nivolumab in 30 patients with myelofibrosis (MF) who have had a suboptimal or no response to Janus kinase inhibitor (JAKi) therapy, were presented by Isfort at the European Hematology Association (EHA) 2026 Congress, June 11–14, 2026, Stockholm, SE. The primary endpoint was best response rate within 12 treatment cycles according to the International Working Group-Myeloproliferative Neoplasms Research and Treatment (IWG-MRT) criteria and red blood cell (RBC) transfusion independence (TI).  

Key data: At a median follow-up of 16.5 months, 46.7% of patients had completed ≥12 cycles of therapy. The estimated median overall survival (OS) was 31.8 months. A response was achieved in 40% of patients, while progression occurred in 1 patient. Greater responses were observed in patients with JAK2 vs CALR mutations (50% vs 29%) and in patients with RBC-transfusion dependency (TD) vs RBC-TI at baseline (67% vs 29%). The most common treatment-emergent adverse events (TEAEs) were nausea, anemia, diarrhea, fatigue, and alanine aminotransferase (ALT) increase.  

Key learning: Fedratinib + nivolumab demonstrated promising clinical efficacy, particularly in patients with RBC-TD at baseline, with a well-tolerated safety profile that is consistent with prior experience.