Marlborough, Mass. — Sumitomo Pharma America Inc. said it presented new clinical and translational research at the European Hematology Association 2026 Congress, including preliminary data for an investigational combination therapy in relapsed or refractory myelofibrosis and new findings on menin inhibition in leukemia.
The congress was held June 11-14 in Stockholm.
The company said the data included the first disclosure of preliminary clinical results for nuvisertib, an investigational PIM1 inhibitor, in combination with momelotinib for patients with myelofibrosis. Sumitomo Pharma America also presented translational research on the potential mechanism behind hemoglobin improvement observed in patients with myelofibrosis in an ongoing Phase 1/2 study of nuvisertib.
The company also shared new data on acquired resistance patterns observed with enzomenib in acute leukemia.
“We are excited to present the preliminary data for our investigational combination of nuvisertib and momelotinib at EHA 2026, while also sharing learnings from our ongoing translational research of nuvisertib and enzomenib,” said Tsutomu Nakagawa, Ph.D., President and Chief Executive Officer of SMPA. “We appreciate this opportunity to share the latest data for these two programs with the oncology community, and these results reinforce our commitment to developing multi-faceted therapeutic approaches that address the most persistent challenges in treating hematologic malignancies.”
James McCloskey, M.D., Interim Chief of the Division of Leukemia at John Theurer Cancer Center, presented preliminary clinical data from an ongoing global Phase 1/2 study evaluating nuvisertib and momelotinib in patients with relapsed or refractory myelofibrosis and anemia.
As of Dec. 6, 2025, 26 patients had been enrolled across four dose levels of nuvisertib in combination with the approved myelofibrosis dose of momelotinib. All patients had previously received at least one approved Janus kinase inhibitor, and 41% had high molecular risk mutations.
Sumitomo Pharma America said the combination appeared well tolerated, with no dose-limiting toxicities observed. The most common treatment-related adverse events occurring in at least 20% of patients were diarrhea, nausea and thrombocytopenia. The most frequent treatment-related Grade 3 adverse event was thrombocytopenia without bleeding, which occurred in three patients.
Mean hemoglobin and platelet count levels remained stable throughout the 24-week treatment period, the company said.
Among 15 efficacy-evaluable patients who completed at least 12 weeks of treatment, the combination showed evidence of clinical activity. Spleen volume reduction of at least 25% was achieved by 73% of patients at Week 12 and 100% at Week 24 among five patients. A total symptom score reduction of at least 50% was achieved by 53% of patients at Week 12 and 60% at Week 24 among five patients.
Anemia response by IWG ELN2024 criteria was observed in 50% of patients at any time. The company said 60% of patients achieved a triple response at Week 24, meeting criteria for symptom reduction, spleen volume reduction and anemia improvement.
The development of the nuvisertib and momelotinib combination is intended to address multiple pathways involved in myelofibrosis progression. Sumitomo Pharma America said that while standard treatments focus on inhibiting the JAK signaling pathway, PIM1 expression is often elevated in myelofibrosis and can be driven by JAK-independent compensatory pathways.
The company said combining nuvisertib with momelotinib, a JAK and ACVR1 inhibitor, may help target pathways that allow the disease to progress during JAK inhibitor therapy.
Joseph M. Scandura, M.D., Ph.D., of the Division of Hematology and Medical Oncology at Weill Cornell Medicine, presented translational research on nuvisertib’s proposed mechanism of action.
In addition to nuvisertib’s primary activity as a PIM1 inhibitor, in vitro and biochemical data showed that the drug also binds to and inhibits ACVR1, leading to reduced hepcidin mRNA expression. Hepcidin is a central regulator of iron homeostasis.
Sumitomo Pharma America said preliminary clinical data from a Phase 1/2 study of nuvisertib monotherapy showed reduced hepcidin levels in patients with relapsed or refractory myelofibrosis, potentially explaining the hemoglobin stability and improvement observed in patients treated with the drug.
“Preliminary clinical data suggests that the combination of nuvisertib and momelotinib may provide a more comprehensive suppression of the disease pathways driving myelofibrosis,” said Raajit Rampal, M.D. Ph.D., Director of the Myeloproliferative Neoplasms Program at the Memorial Sloan Kettering Cancer Centre, New York, USA. “The promising symptom, spleen and anemia responses, coupled with the new nonclinical data on potential dual PIM1 and ACVR1 inhibitory activity by nuvisertib, suggest that this combination therapy may potentially offer meaningful clinical benefits for patients with myelofibrosis.”
The company also presented translational research in leukemia and menin inhibition. Jevon Cutler, PhD, Assistant Professor of Cell, Developmental and Cancer Biology at Oregon Health Sciences University School of Medicine, shared findings identifying distinct MEN1 mutational signatures associated with acquired resistance to the menin inhibitor enzomenib in patients with acute leukemia.
Serial molecular profiling showed that the E368K mutation was the predominant resistance signature at relapse, appearing in 53% of patients who relapsed after an initial response. Sumitomo Pharma America said preclinical work predicted E368K as the primary resistance mutation and suggested that the mutation may not affect other menin inhibitors.
The company said the findings support further exploration of rational, sequential menin inhibitor therapy to improve outcomes for patients with acute leukemia.
