Characterization of the anti‐CD22 targeted therapy, moxetumomab pasudotox, for B‐cell precursor acute lymphoblastic leukemia

Moxetumomab pasudotox is a second‐generation recombinant immunotoxin against CD22 on B‐cell lineages. Antileukemic activity has been demonstrated in children with chemotherapy‐refractory B‐cell precursor acute lymphoblastic leukemia (BCP‐ALL), with variable responses. Here, we report in vitro and in vivo evaluation of moxetumomab pasudotox treatment of human cell lines and patient‐derived cells as a preliminary study to understand characteristics of sensitivity to treatment. Binding, internalization, and apoptosis were evaluated using fluorescently tagged moxetumomab pasudotox. Studies in NOD‐scid IL2Rgnull mice showed a modest survival benefit in mice engrafted with 697 cells but not in NALM6 or the two patient‐derived xenograft models.