Halogen substitution at the isoxazole ring enhances the activity of N-(isoxazolyl)sulfonamide endothelin antagonists

Replacement of the 4-methyl group in a series of N-(3,4-dimethylisoxazolyl)benzenesulfonamide endothelin antagonists with a bromine or chlorine atom resulted in a three- to ten-fold increase in the binding affinity for both the ETA and ETB receptors. This potentiation in activities was also observed for naphthalene and biphenylsulfonamide endothelin antagonists.