Purity >98%. Antagonists of the chemotactic and inflammatory lipoxygenase product leukotriene B4 (LTB4 ) have been potential drug development targets for several years. The tetrazole LY255283 is a competitive antagonist of the BLT2 receptor. It displaces radiolabeled LTB4 from guinea pig lung membrane, with an IC50 of about 100 nM. LY255283 exhibits IC50 values of ~950 nM and >10 μM at human recombinant BLT2 and BLT1 receptors, respectively. LY255283 inhibits eosinophil chemotaxis by 80% at a concentration of 10 μM, and inhibits the binding of radiolabeled LTB4 to eosinophil membranes with an IC50 of 260 nM.