Cleavable Linker

Cleavable linkers are critical structural components of antibody-drug conjugates (ADCs) that control intracellular payload release while maintaining systemic stability during circulation^[1][2]. Mechanistically, cleavable linker systems exploit tumor-associated biochemical triggers, including lysosomal proteases, acidic intracellular compartments, and reducing cytosolic environments, to enable selective drug release within target cells^[1][2][3]. Enzyme-sensitive peptide linkers, particularly valine-citrulline (Val-Cit) motifs, are extensively used because cathepsin-mediated cleavage efficiently liberates cytotoxic payloads after ADC internalization and lysosomal trafficking^[2][3][4]. Disulfide-based cleavable linkers instead respond to elevated intracellular glutathione concentrations and redox imbalance in malignant cells, providing an alternative release mechanism for targeted drug delivery^[1][2]. In cancer models, linker design directly influences pharmacokinetic stability, payload exposure, bystander activity, and therapeutic index, making linker selection a major determinant of ADC performance^[1][2]. Compared with non-cleavable linkers, cleavable linkers can generate membrane-permeable payload species that extend cytotoxic activity beyond antigen-positive cells, although stability optimization remains essential to minimize premature release and off-target toxicity^[2][3]. For experimental applications, ongoing linker engineering focuses on improving plasma stability while preserving efficient intracellular cleavage, supporting the development of next-generation targeted oncology therapeutics^[1][4].