In vitro activity: GSK180736A was developed as a novel and potent Rho-associated, coiled-coil-containing protein kinase (ROCK) inhibitor which binds to GRK2 (G protein-coupled receptor kinase 2) with IC50 of 0.77 μM; G protein-coupled receptors (GPCRs) are central to many physiological processes. Regulation of this superfamily of receptors is controlled by GPCR kinases (GRKs), some of which have been implicated in heart failure. GSK180736A shows ≥400-fold selectivity for GRK2 over both GRK1 and GRK5. GSK180736A is structurally similar to paroxetine. ROCK1 is a potential therapeutic target in the treatment of cardiovascular diseases such as hypertension. GSK180736A is a weak inhibitor of PKA with an IC50 of 30 μM, but highly potent against ROCK1 with IC50 of 100 nM.

Kinase Assay: G protein-coupled receptors (GPCRs) are central to many physiological processes. Regulation of this superfamily of receptors is controlled by GPCR kinases (GRKs), some of which have been implicated in heart failure. GSK180736A, developed as a Rho-associated coiled-coil kinase 1 (ROCK1) inhibitor, was identified as an inhibitor of GRK2 and co-crystallized in the active site. Guided by its binding pose overlaid with the binding pose of a known potent GRK2 inhibitor, Takeda103A, a library of hybrid inhibitors was developed. This campaign produced several compounds possessing high potency and selectivity for GRK2 over other GRK subfamilies, PKA, and ROCK1. The most selective compound, 12n (CCG-224406), had an IC50 for GRK2 of 130 nM,>700-fold selectivity over other GRK subfamilies, and no detectable inhibition of ROCK1. Four of the new inhibitors were crystallized with GRK2 to give molecular insights into the binding and kinase selectivity of this class of inhibitors.

Cell Assay: Cardiac myocytes are isolated from LV free wall and septum of C57/Bl6 mice. Cells are treated with isoproterenol (0.5 μM) for 2 min for the recording of contraction, with pretreatment of either PBS as vehicle or paroxetine (10 μM), 215022 (0.1, 0.5, 1, 10 μM), 215023 (0.1, 0.5, 1, 10 μM), 224064 (0.1, 0.5, 1, 10 μM), and GSK180736A ( 0.5, 1 μM), for 10 min.