Potent and selective CXCR2 chemokine receptor antagonist (IC50 = 22 nM) that displays > 150-fold selectivity over CXCR1 receptors. Causes inhibition of IL-8 and GROα-mediated calcium mobilization in HL60 cells (IC50 values are 8 and 10 nM respectively). Prevents IL-8-induced neutrophil chemotaxis in vitro and sequestration in vivo. Inhibits HIV replication in lymphocytes and macrophages.