Chimeric antigen receptor T‐cell therapy for marrow and extramedullary relapse of infant acute lymphoblastic leukemia

Chimeric antigen receptor (CAR) T‐cells, engineered autologous T‐cells that target antigens found in leukemia, have shown durable remissions in relapsed acute lymphoblastic leukemia (ALL). Infant ALL with KMT2A rearrangements ( KMT2A r) is a rare, aggressive form of leukemia associated with extramedullary disease both at diagnosis and at relapse, and overall outcomes for these patients are dismal. Here we report the successful use of tisagenlecleucel, a CAR T‐cell product approved for relapsed/refractory ALL, in a patient with KMT2A r infant ALL who was treated for combined marrow and extramedullary (renal) relapse.