Multivalent Antibody‐Recruiting Molecules for Targeted Immune‐Killing of Carbonic Anhydrase IX‐Expressing Cancer Cells

Antibody clustering on the surface of cells enables recognition by Fc receptors on innate immune cells and activation of the complement cascade, resulting in elimination. This effect can be leveraged for cancer therapy by monoclonal antibodies that recognize a cell surface antigen, but can also be achieved by synthetic bivalent molecules that mediate ternary complex formation between a cancer cell and endogenous, that is, non‐externally administered, antibodies. We report on antibody‐recruiting molecules (ARMs) targeting carbonic anhydrase IX (CAIX)‐expressing cancer cells. CAIX, a marker overexpressed in many hypoxic tumors, was targeted using acetazolamide (AAZ) analogs, while dinitrophenol (DNP) analogs were used to recruit endogenous anti‐DNP antibodies. We synthesized both single‐ligand ARMs (SL‐ARMs) and multivalent dextran‐templated ARMs (dex‐ARMs). Our results showed that dex‐ARMs significantly outperformed SL‐ARMs in recruiting anti‐DNP antibodies to the cell surface of CAIX‐expressing cells. The multivalent dex‐ARMs demonstrated robust antibody recruitment even in the presence of competing ligands, suggesting the recruitment of multiple antibodies per dextran. Furthermore, dex‐ARMs effectively recruited endogenous antibodies from serum, inducing cancer cell killing by macrophages. This study establishes the foundational efficacy of dex‐ARMs and suggests their utility in enhancing immune responses against hypoxia‐associated tumor markers, providing a novel strategy for cancer immunotherapy.