Zafirlukast

Zafirlukast (ICI 204219) is a potent orally active leukotriene D₄ (LTD₄) receptor antagonist. Zafirlukast shows anti-asthmatic, anti-inflammatory and anti-bacterial effects. IC50 & Target: Leukotriene D4 receptor^[1] In Vivo: Zafirlukast is a peptidyl leukotriene antagonist and inhibitor of LTD₄. After 13 weeks of exposure, the yield of lung tumors is significantly decreased by both dose levels of Zafirlukast (270 and 540 mg/kg), the high dose of Zileuton (1200 mg/kg), and the combinations containing 600 mg/kg Zileuton with either Zafirlukast or MK-866. The efficacy of the combination containing Zileuton and Zafirlukast to prevent lung tumors is not significantly different from the efficacy of either inhibitor administered alone. Although when administered alone at the dose level in their combination, neither Zileuton or MK-886 prevents lung tumors; the combination containing them does significantly prevent tumors. In contrast, the combination containing Zafirlukast and MK-886 does not reduce the yield of tumors, whereas Zafirlukast administered alone does significantly reduce the yield of tumors^[2].