[Successful treatment with sequential blinatumomab/ponatinib in a patient with chronic myeloid leukemia presenting...

Mixed-phenotype acute leukemia is extremely rare as the initial presentation of chronic myeloid leukemia (CML) in the blast phase (CML-BP). No treatment has been established, and differentiation from de novo BCR::ABL1-positive mixed phenotype acute leukemia is challenging. A 53-year-old woman was diagnosed as having CML-BP with mixed-phenotype acute leukemia (B/myeloid) onset, based on the clinical course and treatment response in addition to findings supporting CML. Treatment with ponatinib resulted in a major molecular response, and a deep molecular response was achieved by 2 cycles of sequential blinatumomab and ponatinib. Blinatumomab was later given again due to CD19 expression on blasts. HLA-matched allogeneic stem cell transplantation was performed during the deep molecular response, and the patient has maintained the deep molecular response with ponatinib. This case suggests that alternating treatment with blinatumomab and ponatinib may be an effective bridge to allogenic stem cell transplantation for CD19-positive mixed-phenotype CML-BP.