Pranlukast (ONO-1078) is a potent, selective and orally active CysLT1 receptor antagonist.{14104} Sold under the trade name Ultair, it was the first cysteinyl (peptidyl) leukotriene receptor antagonist (LTRA) marketed for the treatment of asthma.{14103} Clinical studies in Japan, Europe, and North America all show that pranlukast significantly attenuates bronchoconstriction in response to a variety of allergen challenges as well as to inhaled LTD4.{14103} Pranlukast binds to the human CysLT1 and CysLT2 receptors with IC50 values of approximately 4-7 nM and 3,600 nM, respectively.{7174,8519,14081}