Novel antiasthmatic agents with dual activities of thromboxane A2 synthetase inhibition and bronchodilation. V. Thienopyridazinone derivatives.

Synthesis and pharmacological evaluation of novel thienopyridazinones and related compounds are described. A thiophene ring was found to be able to replace the benzene ring of a phthalazinone without loss of biological activities. This observation supports our hypothesis that the benzene ring plays an important role in both thromboxane A2 (TXA2) synthetase-inhibitory and bronchodilatory activities. Further, it was shown that the carbonyl moiety of a phthalazinone is not necessary for these activities.