Covalent Stabilization of Antibody Recruitment Enhances Immune Recognition of Cancer Targets.

ABSTRACT

Antibody recruiting molecules (ARMs) represent an important class of "proximity-inducing" chemical tools with therapeutic potential. ARMs function by simultaneously binding to a hapten-specific serum antibody (Ab) (e.g., anti-dinitrophenyl (DNP)) and a cancer cell surface protein, enforcing their proximity. ARM anticancer efficacy depends on the formation of ARMAb complexes on the cancer cell surface, which activate immune cell recognition and elimination of the cancer cell. Problematically, ARM function in human patients may be limited by conditions that drive the dissociation of ARMAb complexes, namely, intrinsically low binding affinity and/or low concentrations of anti-hapten antibodies in human serum. To address this potential limitation, we previously developed a covalent ARM (cARM) chemical tool that eliminates the ARMantibody equilibrium through a covalent linkage. In the current study, we set out to determine to what extent maximizing the stability of ARMantibody complexes via cARMs enhances target immune recognition. We observe cARMs significantly increase target immune recognition relative to ARMs across a range of therapeutically relevant antibody concentrations. These results demonstrate that ARM therapeutic function can be dramatically enhanced by increasing the kinetic stability of ARMantibody complexes localized on cancer cells. Our findings suggest that a) high titres/concentrations of target antibody in human serum are not neccessary and b) saturative antibody recruitment to cancer cells not sufficient, to achieve maximal ARM therapeutic function.