CP-481,715, a potent and selective CCR1 antagonist with potential therapeutic implications for inflammatory diseases

The chemokines CCL3 and CCL5, as well as their shared receptor CCR1, are believed to play a role in the pathogenesis of several inflammatory diseases including rheumatoid arthritis, multiple sclerosis, and transplant rejection. In this study we describe the pharmacological properties of a novel small molecular weight CCR1 antagonist, CP-481,715 (quinoxaline-2-carboxylic acid [4(R)-carbamoyl-1(S)-(3-fluorobenzyl)-2(S), 7-dihydroxy7- methyloctyl] amide). Radiolabeled binding studies indicate that CP-481,715 binds to human CCR1 with a K-d of 9.2 nM and displaces I-125-labeled CCL3 from CCR1-transfected cells with an IC50 of 74 nM. CP-481,715 lacks intrinsic agonist activity but fully blocks the ability of CCL3 and CCL5 to stimulate receptor signaling (guanosine 5'-O-(thiotriphosphate) incorporation; IC50 = 210 nM), calcium mobilization (IC50 = 71 nM), monocyte chemotaxis (IC50 = 55 nM), and matrix metalloproteinase 9 release (IC50 = 54 nM). CP- 481,715 retains activity in human whole blood, inhibiting CCL3-induced CD11b up-regulation and actin polymerization (IC50 = 165 and 57 nM, respectively) on monocytes. Furthermore, it behaves as a competitive and reversible antagonist. CP- 481,715 is > 100-fold selective for CCR1 as compared with a panel of G-protein-coupled receptors including related chemokine receptors. Evidence for its potential use in human disease is suggested by its ability to inhibit 90% of the monocyte chemotactic activity present in 11/15 rheumatoid arthritis synovial fluid samples. These data illustrate that CP- 481,715 is a potent and selective antagonist for CCR1 with therapeutic potential for rheumatoid arthritis and other inflammatory diseases.