In vitro activity: CCG215022 has nanomolar potency against both GRK2 and GRK5 and is at least 20-fold more potent than Paroxetine. In the course of a GRK2 structure-based drug design campaign, CCG215022 exhibits nanomolar IC50 values against both GRK2 and GRK5 and good selectivity against other closely related kinases such as GRK1 and PKA. Treatment of murine cardiomyocytes with CCG215022 results in significantly increases contractility at 20-fold lower concentrations than Paroxetine, an inhibitor with more modest selectivity for GRK2

Kinase Assay: GRK5 and urea-washed bovine rod outer segments (ROS) are mixed in the dark in buffer containing 20 mM HEPES, pH 7.5, 4 mM MgCl2, and 2 mM EDTA and incubated for 35 min at room temperature. The reaction mixtures are exposed to ambient fluorescent light for 1 min prior to initiation of the reaction by addition of ATP (with [γ-32P]ATP) to a final concentration of 1 mM. Final concentration of GRK5 is 100 nM and ROS is between 0.75 and 24 μM. Reactions are initiated at room temperature, and samples are taken at 2-5 min and then quenched with SDS-PAGE loading dye. Proteins are separated using SDS-PAGE, gel is dried, and the incorporation of γ-32P is detected using a phosphor storage screen. Rates at 0 min are plotted against the ROS concentration, and Vmax and Kmvalues are determined using the Michaelis-Menten equation. Vmax of each curve is normalized to the Vmax of GRK5561 run in parallel. Melting point determinations in response to 200 μM CCG215022 are performed in 20 mM HEPES, pH 7.0, 5 mM MgCl2, 2 mM DTT, 1 mM CHAPS at a final GRK5 concentration of 0.2 mg/mL and 100 μM anilinonaphthalene-8-sulfonic acid using a ThermoFluor plate reader. Melting points of GRK5 variants are assayed in a buffer containing 20 mM HEPES, pH 8.0, 200 mM NaCl, 2 mM DTT, 2.5 mM MgCl2, and 0.1 mM anilinonaphthalene-8-sulfonic acid with or without 5 mM ATP. Final GRK5 concentration for these assays is 0.1 mg/mL

Cell Assay: Treatment of murine cardiomyocytes with CCG215022 results in significantly increases contractility at 20-fold lower concentrations than Paroxetine, an inhibitor with more modest selectivity for GRK2.