Identifying Drug Combination Strategies for Fusion Positive Leukemia.

Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions (MLN-TK) are a class of fusion protein-driven, poor prognosis leukemias. Leukemias harboring FGFR1 fusions have previously been referred to as 8p11.2 myeloproliferative syndrome (EMS) or stem cell leukemia/lymphoma (SCLL) and are currently referred to as Myeloid/lymphoid neoplasms with FGFR1 rearrangement based on the most recent WHO classification system. To identify new therapeutic options for MLN-TK patients, we evaluated clinical and drug response data from a -positive patient who was successfully treated with FGFR kinase-targeting inhibitors. After initially responding to ponatinib, the patient was switched to pemigatinib which eventually transitioned them to a successful transplant. Leukemia cells isolated from the patient exhibited ex vivo sensitivity to ponatinib, bortezomib and axitinib. ZMYM2:FGFR1-transformed Ba/F3 cells were exquisitely sensitive to next generation FGFR inhibitors, and combinations of FGFRi plus trametinib or midostaurin were found to be synergistic, suggesting novel therapeutic options for FGFR1-fusion positive patients.