HZ-52 is a potent, reversible inhibitor of 5-lipoxygenase, blocking leukotriene synthesis with an IC50 value of 0.7 μM in intact human polymorphonuclear leukocytes. HZ-52 also attenuates leukotriene B4 synthesis, prevents carrageenan-induced pleurisy, and protects against platelet-activating factor-induced shock in mice when given intraperitoneally (10 mg/kg).