Design and development of masked therapeutic antibodies to limit off-target effects: Application to anti-EGFR antibodies

Abstract

Therapeutic antibodies frequently cause side effects by binding antigen in non-target tissues. Here we demonstrate a novel molecular design of antibodies that addresses this problem by reversibly  “masking” antibody complementarity determining regions until they reach diseased tissues containing disease-associated proteases. Specifically, two distinct single-chain Fv (scFv) fragments derived from antibodies against the epidermal growth factor receptor (cetuximab and 425) were fused with a protease susceptible linker to their epitopes engineered to encourage intermolecular association. Surface plasmon resonance and flow cytometry were used to confirm that the masked complex poorly recognizes native antigen whereas protease treatment restores antigen recognition. Minimally the "masked”scFvs posses an eight-fold lower association with the epitope compared with the individual scFvs unmasked by proteolytic cleavage. This molecular design may have general utility for targeted release of therapeutic antibodies at disease sites.