CYSLTR1 and asthma: Montelukast (MTK, 1-([(1(R)-(3-(2-(7-chloro-2-quinolinyl)-(E)-ethenyl)phenyl)-3-(2-(1-hydroxy-1-methylethyl)phenyl)propyl)thio]methyl) cyclopropylacetic acid, Figure 5), widely used in asthma management and allergic rhinitis, is a potent antagonist of CysLTR1, a receptor with high affinity for the leukotriene, LTD4.