N3-VC-PAB-PNP is the intermediate of bicyclic peptide ligand STING conjugates. N3-VC-PAB-PNP is a click chemistry reagent, it contains an Azide group and can undergo copper-catalyzed azide-alkyne cycloaddition reaction (CuAAc) with molecules containing Alkyne groups. It can also undergo strain-promoted alkyne-azide cycloaddition (SPAAC) reactions with molecules containing DBCO or BCN groups.