 Several changes to the structure can be made without the loss of activity.Among these changes are reducing the quinoline ring, replacing the chlorine with fluorine, inserting an ether linkage in between the two aromatic rings instead of the double bound and adding an amide group for the sulfur.Replacement of the quinoline by benzothiazole, dichlorothienopyridines or alkyl-substituted thiazoles is possible but none of these is superior.Zafirlukast is an indole derivative that satisfies the pharmacophore need for an ionizable moiety with a sulfonamide group.