Duostatin 5 is a cytotoxin designed based on dolastatin, can meet the requirement of serving as an effective cytotoxin in ADC , but has the advantages of fewer synthesis steps, easy operation, less difficulty in quality control and more stable chemical synthesis process. Duostatin 5 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.