Promising Antigen-specific Immunotherapy for the Treatment of Myasthenia Gravis

Abstract

Myasthenia gravis (MG) is a T cell-dependent, antibody-mediated, autoimmune disorder with well-established antigenic targets at the neuromuscular junction. MG autoantibodies mainly target the nicotinic acetylcholine receptor (AChR) and especially epitopes located in the extracellular domain of the α1 subunit (α1-ECD). Today, most therapeutic regimens for MG are non-specific and not curative, requiring chronic treatments that are associated with significant side effects. We aim to develop an antigen-specific therapeutic approach, based on reestablishing tolerance towards the AChR, the dominant autoantigen in MG. To this end, we used a soluble mutated form of the human α1-ECD, which incorporates a major fraction of MG autoreactive T cell epitopes and examined the therapeutic efficiency of intravenous administration in a rat experimental autoimmune MG model. We found that repeated intravenous administration of α1-ECD for up to 12 days led to a robust amelioration of disease symptoms in a dose and time-dependent manner. The observed therapeutic effect of α1-ECD was significantly better than the effect of two current mainstay drugs for MG treatment. There were no signs of toxicity in α1-ECD-treated animals and further studies are underway to fully elucidate the immunological mechanism underlying the treatment effect. Taken together, our preclinical data strongly suggest that intravenous administration of α1-ECD may represent an efficacious and safe strategy to treat MG and thus α1-ECD represents a new drug candidate for clinical application in MG.