The Beneficial Clinical Effects of Teriflunomide in Experimental Autoimmune Myasthenia Gravis and the Investigation of the Possible Immunological Mechanisms

Myasthenia gravis (MG) is an autoantibody-mediated autoimmune disease characterized by skeletal muscle weakness exacerbated with exercise. There is a need for novel drugs effective in refractory MG. We aimed to test the potential of teriflunomide, an immunomodulatory drug currently used in rheumatoid arthritis and multiple sclerosis treatment, in a murine experimental autoimmune myasthenia gravis (EAMG) model. EAMG was induced by immunizations with recombinant acetylcholine receptor (AChR). Teriflunomide treatment (10 mg/kg/day, intraperitoneal) was initiated to one group of mice (n = 21) following the third immunization and continued for 5 weeks. The disease control group (n = 19) did not receive medication. Naïve mice (n = 10) received only mock immunization. In addition to the clinical scorings, the numbers of B cells and T cells, and cytokine profiles of T cells were examined by flow cytometry. Anti-AChR-specific antibodies in the peripheral blood serum were quantified by ELISA. Teriflunomide significantly reduced clinical disease scores and the absolute numbers of CD4+ T cells and some of their cytokine-producing subgroups (IFN-γ, IL 2, IL22, IL-17A, GM-CSF) in the spleen and the lymph nodes. The thymic CD4+ T cells were also significantly reduced. Teriflunomide mostly spared CD8+ T cells' numbers and cytokine production, while reducing CD138+CD19+lambda+ plasma B cells' absolute numbers and CD138 mean fluorescent intensities, probably decreasing the number of IgG secreting more mature plasma cells. It also led to some selective changes in the measurements of anti-AChR-specific antibodies in the serum. Our results showed that teriflunomide may be beneficial in the treatment of MG in humans.