Tipelukast (KCA 757) is a sulfidopeptide leukotriene receptor antagonist, an orally bioavailable anti-inflammatory agent and used for the treatment of asthma. In Vitro Tipelukast inhibits the binding of [ 3 H] LTD4 to the LTD4 receptors on pul-monary cell membrane of guinea-pigs (IC 50 = 2.3 μmol). MCE has not independently confirmed the accuracy of these methods. They are for reference only. In Vivo Fiftheen min after an aerosolized antigen challenge, and UNDW inhaled 5 min later into the guinea pigs, Tipelukast significantly alters the UNDW-induced bronchoconstriction . Tipelukast (1 and 5 mg/kg) administered intravenously 15 min after antigen challenge reduces the propranolol-induced bronchoconstriction (PIB) in a dose-dependent manner in guinea-pigs. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:LTD 4 6.41 (pA2, In guinea-pigs) LTE 4 6.45 (pA2, In guinea-pigs)