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Engineered humanized dimeric forms of IgG are more effective antibodies
1Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
The Journal of Experimental Medicine
|October 1, 1992
Summary
Engineered homodimeric antibodies targeting CD33 antigens show enhanced leukemia cell internalization and retention of radioisotopes. These multimeric constructs demonstrate superior potency in leukemia cell killing via complement-mediated and cellular cytotoxicity mechanisms.
Area of Science:
- Immunology
- Oncology
- Biotechnology
Background:
- Humanized IgG1 M195 (HuG1-M195) is a recombinant monoclonal antibody targeting CD33, an antigen on myelogenous leukemia cells, currently in clinical trials for acute myelogenous leukemia therapy.
- The biological activity of immunoglobulin G (IgG) may be influenced by multimeric clustering of its Fab and Fc regions.
Purpose of the Study:
- To investigate the impact of IgG homodimerization on the therapeutic efficacy of HuG1-M195 against leukemia cells.
- To explore the potential advantages of genetically engineered multimeric antibody constructs over naturally occurring forms.
Main Methods:
- Construction of homodimeric HuG1-M195 by introducing a CH3 region mutation (serine to cysteine) for interchain disulfide bond formation.
- Comparison of homodimeric and non-multimeric HuG1-M195 in terms of radioisotope internalization, retention in leukemia cells, complement-mediated cytotoxicity, and antibody-dependent cellular cytotoxicity.
Main Results:
- Homodimeric HuG1-M195 exhibited significantly improved internalization and radioisotope retention in target leukemia cells compared to its non-multimeric counterpart, despite similar avidity.
- Homodimers demonstrated a 100-fold increase in potency for complement-mediated leukemia cell killing and antibody-dependent cellular cytotoxicity using human effectors.
Conclusions:
- Genetically engineered homodimeric IgG constructs, such as HuG1-M195, offer enhanced therapeutic potential compared to naturally occurring monomeric forms.
- Multimeric IgG engineering represents a promising strategy for improving antibody-based cancer therapies, particularly for acute myelogenous leukemia.