The therapeutic efficacy of M2000 as a novel immunosuppressive and anti-inflammatory agent in T cell-mediated autoimmune disease was tested. The influence of M2000 on myelin basic protein (MBP)-induced experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis was assessed. The onset and symptoms of EAE in Lewis rats could be suppressed by intraperitoneally administration of M- 2000 during the induction phase of disease. Disease suppression was associated with a marked suppression of MBP-specific T cell reactivity in vitro, without any evidence for a generalized impairment of T cell activity. Collectively, our data suggest that M2000 may provide a novel therapeutic option for T cell-mediated autoimmune diseases in animal models and possibly in man.