A non-competitive allosteric inhibitor of IL-8/CXCL8 activation of CXCR1 and CXCR2 chemokine receptors (IC50s = 1 and 100 nM, respectively); blocks IL-8-induced leukocyte recruitment (IC50 = 1 nM) and other inflammatory responses, without affecting receptor activation induced by other CXCR1 and CXCR2 agonists; at 100 nM, depletes a cancer stem cell population in human breast cancer cell lines in vitro