Myasthenia gravis is a rare, heterogeneous, classical
autoimmune disease characterized by fatigable skeletal muscle weakness, which is directly mediated by
autoantibodies targeting various components of the neuromuscular junction, including the
acetylcholine receptor, muscle specific
tyrosine kinase, and
lipoprotein-related
protein 4. Subgrouping of
myasthenia gravis is dependent on the age of onset, pattern of clinical weakness,
autoantibody detected, type of thymic pathology, and response to
immunotherapy. Generalized immunosuppressive therapies are effective in all subgroups of
myasthenia gravis; however, approximately 15% remain refractory and more effective treatments with improved safety profiles are needed. In recent years, successful utilization of targeted B-cell
therapies in this disease has triggered renewed focus in unraveling the underlying immunopathology in attempts to identify newer therapeutic targets. While
myasthenia gravis is predominantly B-cell mediated, T cells, T cell-B cell interactions, and B-cell-related factors are increasingly recognized to play key roles in its immunopathology, particularly in
autoantibody production, and novel
therapies have focused on targeting these specific immune system components. This overview describes the current understanding of
myasthenia gravis immunopathology before discussing B-cell-related
therapies, their therapeutic targets, and the rationale and evidence for their use. Several prospective studies demonstrated efficacy of
rituximab in various
myasthenia gravis subtypes, particularly that characterized by
antibodies against muscle-specific
tyrosine kinase. However, a recent randomized control trial in patients with
acetylcholine receptor antibodies was negative.
Eculizumab, a
complement inhibitor, has recently gained regulatory approval for
myasthenia gravis based on a phase III trial that narrowly missed its primary endpoint while achieving robust results in all secondary endpoints.
Zilucoplan is a subcutaneously administered terminal
complement inhibitor that recently demonstrated significant improvements in functional outcome measures in a phase II trial.
Rozanolixizumab,
CFZ533,
belimumab, and
bortezomib are B-cell-related
therapies that are in the early stages of evaluation in treating
myasthenia gravis. The rarity of
myasthenia gravis, heterogeneity in its clinical manifestations, and variability in immunosuppressive regimens are challenges to conducting successful trials. Nonetheless, these are promising times for
myasthenia gravis, as renewed research efforts provide novel insights into its immunopathology, allowing for development of targeted
therapies with increased efficacy and safety.