Linker for Antibody-Drug-Conjugation (ADC). The Val-Cit will specifically be cleaved by catepsin B. As this enzyme is only present in the lysosome the ADC payload will be release only in the cell. The BCN group can react with azide-tagged biomolecules. The PFP ester is a better leaving group compared to a hydroxyl group and can be used to label the primary amines (-NH2) of proteins, amine-modified oligonucleotides, and other amine-containing molecules.