CCG-271423 is a potent and selective GRK5 inhibitor with IC 50 values of 0.0021 μM and 44 μM for GRK5 and GRK2, respectively. CCG-271423 inhibits cardiomyocyte contractility and decreases in Ca 2+ transience. CCG-271423 is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups.