Gilteritinib Combined with Azacitidine as Salvage Therapy for B/Myeloid Mixed Phenotype Acute Leukemia

Mixed phenotype acute leukemia (MPAL) is a rare group of acute leukemias with blasts that co-express antigens of more than one lineage or separate populations of blasts of different lineages. Though treatment guidelines are not well established, the standard of care in treating MPAL remains the acute lymphoblastic leukemia (ALL)-derived chemotherapeutic regimen of hyper-cyclophosphamide, vincristine, doxorubicin (also known by its trade name, Adriamycin), and dexamethasone (CVAD) followed by allogeneic stem-cell transplant (ASCT). Beyond induction chemotherapy, evidence-based treatments remain to be investigated, especially regarding patients who relapse prior to ASCT. This case report illustrates a patient with relapsed MPAL following induction hyper-CVAD who was not immediately eligible for ASCT. After brief treatment with gilteritinib alone, the patient was started on gilteritinib and azacitidine as salvage therapy and achieved and maintained complete remission with incomplete count recovery (CRi) for eight months. Targeted therapy is a novel approach to improve survival rate, but unfortunately, there have been very few studies in the context of MPAL. We report a patient with relapsed FLT3-mutant MPAL who achieved remission using a combination approach with targeted therapy.