Abstract
Antibody-drug conjugates （ADCs） combine cytotoxic payloads with monoclonal antibodies via chemical linkers. While the number of ADCs approved by the FDA continues to increase, the conventional Val-Cit linker still presents several challenges, including increased aggregation due to hydrophobicity, limitations in drug-to-antibody ratio （DAR）, and instability of the linker moiety during blood circulation. In this study, we incorporated hydrophilic amino acid residues into the cathepsin-cleavable Val-Cit linker and introduced the cleavable linker at the “Exo” position—i.e., the branch position of the linear connection between the antibody and payload—to enhance the masking effect by shortening the distance between the antibody and payload. This design addresses the limitations of the Val-Cit platform and improves the ADC in vivo profiles. In vitro and in vivo evaluations showed that Exo-linker ADCs reduced premature payload release, increased DAR, and avoided significant aggregation, even with hydrophobic payloads. Furthermore, the payload remained stably attached to the ADC even in the presence of enzymes like carboxylesterases and human neutrophil elastase, indicating the potential for a favorable safety profile.
