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Enhanced tumor-targeting selectivity by modulating bispecific antibody binding affinity and format valence
Yariv Mazor1, Kris F Sachsenmeier2, Chunning Yang1
1Department of Antibody Discovery and Protein Engineering, MedImmune, Gaithersburg, MD, USA.
Abstract:
Bispecific antibodies are considered attractive bio-therapeutic agents owing to their ability to target two distinct disease mediators. Cross-arm avidity targeting of antigen double-positive cancer cells over single-positive normal tissue is believed to enhance the therapeutic efficacy, restrict major escape mechanisms and increase tumor-targeting selectivity, leading to reduced systemic toxicity and improved therapeutic index. However, the interplay of factors regulating target selectivity is not well understood and often overlooked when developing clinically relevant bispecific therapeutics. We show in vivo that dual targeting alone is not sufficient to endow selective tumor-targeting, and report the pivotal roles played by the affinity of the individual arms, overall avidity and format valence. Specifically, a series of monovalent and bivalent bispecific IgGs composed of the anti-HER2 trastuzumab moiety paired with affinity-modulated VH and VL regions of the anti-EGFR GA201 mAb were tested for selective targeting and eradication of double-positive human NCI-H358 non-small cell lung cancer target tumors over single-positive, non-target NCI-H358-HER2 CRISPR knock out tumors in nude mice bearing dual-flank tumor xenografts. Affinity-reduced monovalent bispecific variants, but not their bivalent bispecific counterparts, mediated a greater degree of tumor targeting selectivity, while the overall efficacy against the targeted tumor was not substantially affected.
Insights
Bispecific antibodies can target cancer cells, but selectivity depends on more than just dual targeting. Affinity and format are key for effective tumor targeting and reduced toxicity.
Area of Science:
- Immunology
- Biotechnology
- Oncology
Background:
- Bispecific antibodies offer dual-targeting capabilities for enhanced therapeutic efficacy.
- Selective targeting of cancer cells over normal tissues is crucial for reducing toxicity.
- Factors influencing bispecific antibody selectivity remain incompletely understood.
Purpose of the Study:
- To investigate the roles of individual arm affinity, overall avidity, and format valence in bispecific antibody tumor targeting selectivity.
- To determine if dual targeting alone is sufficient for selective tumor targeting.
- To evaluate bispecific antibody variants for targeting double-positive cancer cells over single-positive normal tissue.
Main Methods:
- Development of monovalent and bivalent bispecific IgGs combining anti-HER2 (trastuzumab) and anti-EGFR (GA201) moieties with modulated affinities.
- In vivo testing in nude mice bearing dual-flank tumor xenografts, with target tumors (NCI-H358) and non-target tumors (NCI-H358-HER2 CRISPR knockout).
- Assessment of tumor targeting selectivity and eradication efficacy.
Main Results:
- Dual targeting alone did not guarantee selective tumor targeting.
- Affinity-reduced monovalent bispecific variants demonstrated superior tumor targeting selectivity compared to bivalent counterparts.
- Overall therapeutic efficacy against the targeted tumor was not significantly impacted by affinity reduction.
Conclusions:
- Individual arm affinity, overall avidity, and format valence are critical determinants of bispecific antibody selectivity.
- Optimizing these factors, particularly affinity reduction in monovalent formats, can enhance tumor targeting selectivity.
- These findings provide crucial insights for the rational design of clinically relevant bispecific therapeutics.
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