[Anti-allergic effects of 1-(2-ethoxyethyl)-2-(4-methyl-1-homopiperazinyl)benzimidazole fumarate (KB-2413)].

The effects of KB-2413 on four types of allergic reactions classified by Coombs and Gell were investigated. KB-2413 inhibited homologous passive cutaneous anaphylaxis and passive anaphylactic bronchoconstriction in guinea pigs mediated by IgE-like antibody, and ED50 values were 0.0017 mg/kg, p.o., and 0.022 mg/kg, p.o., respectively. KB-2413 also inhibited IgG-mediated anaphylactic bronchoconstriction in guinea pigs actively sensitized with egg albumin. Both complement-dependent immune hemolysis and complement-independent hypotonic hemolysis were inhibited by KB-2413 in a concentration-dependent manner. KB-2413 had no effect on the Forssman systemic reaction. The passive Arthus reaction in guinea pigs sensitized with anti-egg albumin rabbit serum was unaffected by KB-2413. However, the early stage of the active Arthus reaction in rabbits sensitized with egg albumin was inhibited. KB-2413 had an inhibitory effect on the efferent phase of delayed-type hypersensitivity induced by picryl chloride (PC-DTH) in mice. On the other hand, the afferent phase of PC-DTH in mice was unaffected. These results suggest that KB-2413 strongly suppresses type I allergic reactions, and it slightly suppresses type II, III and IV allergic reactions.