Anti-CD22 (C-terminal) polyclonal antibody

The past decade has witnessed tremendous progress in the treatment of acute lymphoblastic leukaemia (ALL), primarily due to the development of targeted therapies, including tyrosine kinase inhibitors targeting BCR-ABL1 tyrosine kinase, monoclonal antibodies targeting cell surface antigens (CD19, CD20 and CD22), bispecific antibodies and chimeric antigen receptor T- cell therapy. A number of new therapies have been approved by the US Food and Drug Administration in the past 5 years, including blinatumomab in 2014, inotuzumab ozagamicin in 2017 and tisagenlecleucel in 2017 for relapsed/refractory ALL. This has led to tremendous improvement in long-term survival, of more than 50% in patients with precursor B-ALL [50-70% in patients with Philadelphia chromosome (Ph)-positive ALL)], 50-60% in T-ALL and 80% in mature B-ALL. Research is ongoing to optimize the benefit of targeted therapeutics with the goal of decreasing the use of cytotoxic therapies.

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.