Azide-C2-SS-C2-biotin is a cleavable ADC linker used in the synthesis of antibody-drug conjugates (ADCs) [1]. Azide-C2-SS-C2-biotin 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.