Epertinib (S-22611) hydrochloride is a potent, orally active, reversible, and selective tyrosine kinase inhibitor of EGFR , HER4 and HER2 , with IC 50 s of 1.48 nM, 2.49 nM and 7.15 nM, respectively. Epertinib hydrochloride shows potent antitumor activity . Epertinib (hydrochloride) is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups.