Immunopharmacological studies of new 3-benzoyl-4-mercaptobutyric acids. Immunomodulating effects.

A number of D-penicillamine (PA) derivatives (3-benzoyl-4-mercaptobutyric acids) having acetylthio groups on an alpha or beta position of a carboxylic acid, were synthesized and examined for their immunological effects compared with PA. New PA derivatives suppressed adjuvant-induced arthritis (AA) in SD rats and enhanced AA in Lewis rats like PA. Suppressive effects of 2-acetylthiomethyl-3-(4-methyl-benzoyl)propionic acid (compound II-3) on AA in SD rats was most potent among PA derivatives and PA. II-3 enhanced type II collagen-induced arthritis in rats more effectively than PA, and it slightly prolonged the survival time of NZBXNZW hybrid (BWF1) mice. Hemolytic plaque forming cells in the spleen cells of BDF1 and aged Balb/c mice were potentiated but those of BWF1 were suppressed by both compounds. In in vitro experiments, both compounds enhanced lymphocyte transformation. On the contrary, II-3 had no effect on the acute inflammatory response, delayed type hypersensitivity and IgE antibody response. The abnormal release of lysosomal enzymes from the peritoneal macrophages of aged MRL/l mice were suppressed by both compounds. These results suggest that II-3 is an immunomodulator like PA but more effective than PA. II-3 may be clinically effective for rheumatoid arthritis.