Design Strategy of Antibody Pairs for Biepitopic Antigen‐Templated Chemical Reaction Depending on the Tertiary Structure of the Antigen

Template reactions are site‐specific, rapid chemical reactions driven by high‐affinity biomolecular interactions. Recently, our group reported a reaction triggered by antigen–antibody interactions, named the biepitopic antigen‐templated chemical reaction (BATER). In BATER, reactive groups are conjugated to two antibodies recognizing different epitopes of the same antigen. Upon antigen binding, these groups are brought into proximity, enabling rapid reaction. However, the report was limited to tumor necrosis factor receptor 2, and its applicability to other targets remained unclear. In this study, we report strategies to expand BATER to antigens with diverse structural characteristics. Three distinct approaches were applied: (1) epitope selection leveraging structural flexibility of the antigen; (2) the use of protein domains as spacers; and (3) the use of small engineered antibodies. These strategies enabled BATER with CD30 and human epidermal growth factor receptor 2, demonstrating its broad applicability. The expanded range of antigens targeted by BATER will pave the way for potential applications in chemical biology, diagnosis, and therapy.