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 IL2Rg(null) mice showed a modest survival benefit in mice engrafted with 697 cells but not in NALM6 or the two patient-derived xenograft models.