Effective treatment of relapsed/refractory CD19‐positive B/T‐type mixed‐phenotype acute leukemia with blinatumomab: A case report

Abstract

AbstractA 26‐year‐old man was diagnosed with B/T‐type mixed‐phenotype acute leukemia (MPAL‐B/T) based on blasts being positive for CD19, cytoplasmic CD3, and cyCD79a, but negative for myeloperoxidase. Acute lymphoblastic leukemia‐based chemotherapy was started, but the leukemia was refractory. He underwent cord blood transplantation with the conditioning regimen of total body irradiation plus cyclophosphamide and cytarabine with granulocyte‐colony stimulating factor priming. Prophylaxis for graft versus host disease was performed with short‐term methotrexate and cyclosporin. The leukemia relapsed in bone marrow 20 months later. At that time, he was treated with inotuzumab ozogamicin because the blasts expressed CD22 (75.4%), but this was ineffective. He was next administered blinatumomab with dexamethasone pretreatment, resulting in a complete remission (CR). He subsequently underwent human leukocyte antigen‐haploidentical peripheral blood stem cell transplantation. He has still maintained a CR for 12 months. Blinatumomab might be a promising treatment and a bridge to stem cell transplantation even in relapsed/refractory CD19‐expressing MPAL‐B/T.