Exo‐Cleavable Linkers:Antibody Enhancing‐Drug StabilityConjugates and Therapeutic Efficacy in

Customized drug delivery systems are essential for precision medicine, with antibody‐drug conjugates (ADCs) representing a pivotal approach that integrates cytotoxic payloads with monoclonal antibodies (mAbs) through sophisticated chemical linkers. However, optimizing ADC stability while achieving controlled payload release remains challenging. The FDA‐approved valine‐citrulline (Val‐Cit) linker commonly used in ADCs, suffers from issues such as hydrophobicity‐induced aggregation, limited drug‐antibody ratio (DAR), and premature payload release. This study introduces an innovative exo‐linker approach strategy that positions a cleavable peptide linker at the exo position of the p‐aminobenzylcarbamate (PAB) moiety. This modification incorporates hydrophilic glutamic acid to address the drawbacks of the Val‐Cit platform, resulting in improved stability, efficacy, and pharmacokinetics of ADCs. In vitro and in vivo evaluations demonstrate that exo‐linker ADCs effectively reduce premature payload release, increase DAR, and minimize aggregation, particularly with hydrophobic payloads. The exo‐linker represents a significant advancement over traditional Val‐Cit ADCs, maintaining stable payload conjugation even under enzymatic conditions, thus enhancing safety and clinical utility. These findings underscore the potential of the exo‐linker in refining ADC design and functionality through precise molecular engineering. © 2024 Society of Synthetic Organic Chemistry. All rights reserved.