Pyrido[3',2':4,5]thieno[3,2-d]-N-triazines: a new series of orally active antiallergic agents.

A new series of orally active mediator release inhibitors, pyrido[3',2':4,5]thieno[3,2-d]-N-triazines, was synthesized and evaluated for antiallergic activity. Several products showed high activity as inhibitors or wheal information in the rat passive cutaneous anaphylaxis screen and as inhibitors of histamine release from passively sensitized rat mast cells. Many compounds were orally active in the PCA test. The most potent compound, 7-phenylpyrido-[3',2':4,5]thieno[3,2-d]-1,2,3-triazin-4(3H)- one (10) with an I50 value of 0.05 microM, was 60 times more potent than disodium cromoglycate (DSCG) in the RMC assay.