t-Boc-N-amido-PEG4-Val-Cit is a protease-cleavable ADC linker featuring a Boc-protected amine, a hydrophilic PEG spacer, and a Val-Cit dipeptide. The Val-Cit dipeptide is cleavable by cell proteases and features a carboxylic acid which is free for coupling reactions with amines to form amides. The Boc can be removed under acidic conditions to reveal a free primary amine, which may be used in a variety of reactions such as coupling or reductive amination.