2,2-Diethylsuccinanilic acid substituted at a meta- position by an (E)-2-(4-cyclobutyl-1,3-thiazol-2-yl)ethenyl group. It selectively antagonizes leukotriene D4 at the cysteinyl leukotriene receptor, in the human airway, preventing airway edema, smooth muscle contraction, and enhanced secretion of thick, viscous mucus. It is used in the treatment of asthma.