MC-Val-Cit-PAB-MMAF is a cleavable ADC linker featuring a maleimide, a Val-Cit dipeptide, a PAB group, and an MMAF toxin. Maleimide is a thiol-specific covalent linker which is used to label cysteine residues in proteins while the Val-Cit dipeptide is a protease-cleavable motif which releases the MMAF warhead into cells via an elimination mechanism within the PAB structure.