Efgartigimod alfa

Myasthenia gravis (MG) is an autoimmune disorder affecting the neuromuscular junction of the skeletal muscles. While the pathophysiologic mechanisms of MG differ depending on the subtype in question, all forms involve the production of IgG autoantibodies to some endogenous protein. One of the most commonly implicated proteins against which autoantibodies are produced are acetylcholine receptors (AChRs), which undergo degradation via the membrane attack complex (MAC) secondary to their interaction with AChR-specific autoantibodies. The destruction of AChRs prevents regular transmission of electrical impulses across the neuromuscular junction, which ultimately leads to the characteristic muscular weakness - especially of the eyes, throat, and extremities - observed in patients with MG.

Immunoglobulin G, as opposed to other immunoglobulins, undergoes a recycling phase in the vascular endothelium that dramatically extends its half-life. In the case of pathogenic IgGs causing MG, this may facilitate an increased ability to impair neuromuscular transmission. This recycling involves IgG binding to the neonatal Fc receptor (FcRn), which rescues IgG from lysosomal degradation.

Efgartigimod alfa is a human IgG1 antibody fragment that binds to FcRn, thus preventing IgG recycling and subsequently reducing the amount of circulating IgG, including the autoantibodies responsible for MG.