Synthesis and pharmacological properties of N-[4-[4-(1H-indol-3-yl) piperidinoalkyl]-2-thiazolyl]alkanesulfonamides as novel antiallergic agents.

A number of N-[4-[4-(1H-indol-3-yl)piperidinoalkyl]-2- thiazolyl]alkanesulfonamides (8--21) were synthesized and evaluated for their preventive effects on systemic anaphylaxis in guinea pigs. Structure-activity analysis revealed that methane- and ethanesulfonamide derivatives having a one to three methylene tether between the piperidine and thiazole rings exhibited potent activity but the introduction of a substituent on the indole part reduced the activity. Administration (100 mg/kg p.o.) of the four compounds 8, 9, 12, 13, together with ketotifen, oxatomide, terfenadine and azelastine as reference compounds, to mice revealed that only compound 8 caused no significant increase of the sleeping time induced by hexobarbital. In addition, compound 8 (10 mg/kg i.v.) did not change the electroencephalogram in conscious rabbits. These results led to the selection of N-[4-[4-(1H-indol-3-yl)piperidinomethyl]-2-thiazolyl]methanesulfon amide (8, FK613) for further development as a novel antiallergic agent. Clinical evaluation of FK613 is now in progress.