Design, synthesis, and X-ray structural studies of a series of highly potent, selective, and drug-like G protein-coupled receptor kinase 5 inhibitors.

G protein-coupled receptor kinase 5 (GRK5) has emerged as a potential drug development target against heart failure and cancer. A close homolog, GRK6 represents a therapeutic target for multiple myeloma. We have rationally designed a series of highly selective, potent, noncovalent, and drug-like GRK5 inhibitors. Several inhibitors exhibited low nanomolar GRK5 inhibition and high selectivity over GRK2, and, surprisingly, some were selective for GRK6. We determined high-resolution X-ray crystal structures of several inhibitors in complex with GRK5, which provide molecular insights into the ligand-binding site interactions responsible for GRK5 selectivity and potency.