BCN-PEG1-Val-Cit-PABC-OH is a cleavable 1 unit PEG ADC linker used in the synthesis of antibody-drug conjugates (ADCs). BCN-PEG1-Val-Cit-PABC-OH is a click chemistry reagent, it contains a BCN group that can undergo strain-promoted alkyne-azide cycloaddition (SPAAC) with molecules containing Azide groups.