NH2-PEG6-Val-Cit-PAB-OH is a cleavable ADC linker composed of a primary amine, a hydrophilic PEG spacer, a Val-Cit dipeptide, and a PAB group. The benzyl alcohol on PAB is suitable for coupling with reactive groups (such as PNP) to facilitate binding with drug payloads. The primary amine enables versatile reactions, including coupling with carboxylic acids, reductive amination with ketones or aldehydes, and more specialized applications like SNAr reactions or heterocyclic chemistry. The Val-Cit dipeptide undergoes cleavage by intracellular proteases, allowing efficient payload delivery via an elimination mechanism within the PAB structure.