CCG273441 is a covalent inhibitor of G protein-coupled receptor ( GPCR ) kinase 5 ( GRK5 ) with an IC 50 value of 3.8 nM. CCG273441 is highly selective to GRK5 over GRK2 (IC 50 =4.8 μM) by binding Cys474, a GRK5 subfamily-specific residue, as a covalent handle In Vitro Human GRKs (GRK1−GRK7) are classified into three subfamilies: GRK1 (GRK1 and GRK7), GRK2 (GRK2 and GRK3), and GRK4 (GRK4, GRK5, and GRK6). CCG273441 (compound 9j) shows moderate potency (GRK5 IC 50 =3.8 nM) but 1000-fold selectivity over GRK2 (IC 50 =4.8 μM). MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:IC50: 3.8 nM (human GRK5), 19 nM (GRK5-C474S), 4.8 μM (bovine GRK2)