Abstract
Leukemia is well suited for monoclonal antibody therapy due to the accessible, differentiation antigens that characterize stages of maturation. In this paper, we describe the use of radio-labeled M195, a murine IgG2a, anti-CD33 monoclonal antibody, that can be used to effectively cytoreduce AML cells in relapsed patients when tumor burden is high; or to eliminate minimal residual disease and lengthen disease-free survival in patients with APL in remission. To decrease the likelihood of immunogenicity, a humanized IgG1 version of M195 was constructed that demonstrated a higher avidity and improved effector function than the parent murine antibody. Preliminary results of the first trial in AML using a humanized antibody showed specific bone marrow targeting without an immunogenic response.