The CysLTs, LTC4 and LTD4, are potent mediators of asthma and hypersensitivity. They induce bronchoconstriction, increase microvascular permeability, and are vasoconstrictors of coronary arteries. Their biological effects are transduced by a pair of GPCRs, CysLT1 and CysLT2. Zafirlukast is a potent, selective CysLT1 receptor antagonist sold under the trade name Accolate for the treatment of asthma as well as for the symptoms associated with allergic rhinitis. It binds to the human CysLT1 and CysLT2 receptors with IC50 values of approximately 5 and 7,400 nM, respectively.