Enhancement of Antibody Selectivity via Bicyclic Complex Formation

This study describes a strategy where antibody selectivity for high antigen-density surfaces is enhanced by forming a thermodynamically stable bicyclic complex. The bicyclic complex was formed via multivalent interactions of the antibody with a synthetic trivalent mimotope at a 3:2 molar ratio. Complex formation was analyzed using dynamic light scattering and analytical ultracentrifugation, showing a hydrodynamic radius of ?22 nm and a calculated molecular weight of 397 kDa, depicting a trimeric complex formation. The complex has high thermodynamic stability and results in a 10-fold higher binding affinity for the trivalent mimotope (Kd = 0.14 ?M) compared to the monovalent mimotope (Kd = 1.4 ?M). As bicyclic complexes, the antibodies showed ?18% binding of the monomeric form to low antigen-density surfaces. At high antigen-density, antibody binding was equal whether delivered as a complex or a monomer. These results establish bicyclic complex selectivity for high antigen-density surfaces and suggest a potential method to enhance therapeutic antibody selectivity for diseased cells.