Balapiravir (Ro 4588161; R1626) is an orally active proagent of a nucleoside analogue inhibitor of the RNA-dependent RNA polymerase (RdRp) of HCV (R1479; 4′-Azidocytidine). Balapiravir has anti-HCV activity. Balapiravir 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.