Antiallergic properties of an orally effective agent, [[3-(1H-tetrazol-5-yl)-phenyl] amino] oxoacetic acid n-butyl ester

A newly synthesized compound, [[3-(1H-tetrazol-5-yl)-phenyl] amino]oxoacetic acid n-butyl ester (MTB) has been demonstrated to be an orally active antiallergic agent. This compound inhibited the 48-hr passive cutaneous anaphylaxis (48-hr PCA) induced by IgE in rats. In guinea pigs, MTB also inhibited the 8-day passive cutaneous anaphylaxis (8-day PCA) and the 8-day passive systemic anaphylaxis induced by IgE. The compound partially inhibited the IgG-mediated 3-hr PCA in rats and guinea pigs, but failed to have any effect on the rabbit IgG-mediated 3-hr PCA in these animals. In the rat, MTB was not an antagonist of histamine or serotonin. The antiallergic effect of MTB was not mediated via any adrenergic mechanisms. MTB significantly inhibited histamine release from rat peritoneal cells induced by rat IgE in vitro.