Potent and selective CCR3 antagonist (IC50 = 39 nM). Displays 250-fold selectivity for CCR3 over other chemokine receptors, including CXCR1, CXCR2, CCR1 and CCR7 (IC50 >27 μM). Inhibits calcium mobilization induced by MCP-4, eotaxin-2 and eotaxin in RBL-2H3 cells transfected with CCR3 (IC50 values are 80, 90 and 210 nM respectively). Purity 99%. MW (observed): 342.35