Used in the development of antibody-drug conjugates (ADCs) as a linker-payload system. The Val-Cit-PABC segment acts as a cleavable peptide linker that is stable in circulation but releases the drug inside target cells, typically through lysosomal enzymes like cathepsin B. Mal (maleimide) allows conjugation to cysteine residues on antibodies. PEG1 improves solubility and may modulate the pharmacokinetics of the conjugate. This construct is particularly valuable for delivering cytotoxic agents selectively to cancer cells, minimizing damage to healthy tissues.