CMPD101 hydrochloride is a novel membrane-permeable, small-molecule inhibitor of both GRK2 and GRK3 with IC 50 s of 18 nM and 5.4 nM, respectively. CMPD101 hydrochloride also inhibits Rho-associated kinase 2 ( ROCK-2 ) and PKCα ( IC 50 s =1.4 μM and 8.1 μM, respectively).