BCN-PEG3-Biotin is a non-cleavable 3 unit PEG ADC linker used in the synthesis of antibody-drug conjugates (ADCs) [1]. BCN-PEG3-Biotin is a click chemistry reagent, it contains a BCN group that can undergo strain-promoted alkyne-azide cycloaddition (SPAAC) with molecules containing Azide groups.