Identification of potent, selective non-peptide CC chemokine receptor-3 antagonist that inhibits eotaxin-, eotaxin-2-, and monocyte chemotactic protein-4-induced eosinophil migration

Eosinophils have been implicated in the pathogenesis of asthma and other al lergic diseases. Several CC chemokines including eotaxin (CCL-11), eotaxin- 2 (CCL-24), RANTES (CCL-5), and monocyte chemotactic protein-3 (MCP-3, CCL- 7) and 4 (MCP-4 CCL-13) are potent eosinophil chemotactic and activating pe ptides acting through CC chemokine receptor-3 (CCR3). Thus, antagonism of C CR3 could have a therapeutic role in asthma and other eosinophil-mediated d iseases. A high throughput, cellular functional screen was configured using RBL-2H3 cells stably expressing CCR3 (RBL-2H3-CCR3) to identify non-peptid e receptor antagonists. A small molecule CCR3 antagonist was identified, SK &F 45523, and chemical optimization led to the generation of a number of hi ghly potent, selective CCR3 antagonists including SB-297006 and SB-328437, These compounds were further characterized in vitro and demonstrated high a ffinity, competitive inhibition of I-125-eotaxin and I-125-MCP-4 binding to human eosinophils. The compounds were potent inhibitors of eotaxin- and MC P-P induced Ca2+ mobilization in RBL-2H3-CCR3 cells and eosinophils. Additi onally, SB-328437 inhibited eosinophil chemotaxis induced by three ligands that activate CCR3 with similar potencies. Selectivity was affirmed using a panel of 10 seven-transmembrane receptors. This is the first description o f a non-peptide CCR3 antagonist, which should be useful in further elucidat ing the pathophysioiogical role of CCR3 in allergic inflammatory diseases.