Enhanced tumor-targeting selectivity by modulating bispecific antibody binding affinity and format valence

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.