FDA Approves New Myasthenia Gravis Drug

Megan Brooks

December 17, 2021

The US Food and Drug Administration (FDA) has approved efgartigimod (Vyvgart, argenx), a first-in-class, targeted therapy for adults with generalized myasthenia gravis (gMG) who test positive for the antiacetylcholine receptor (AChR) antibody.

"There are significant unmet medical needs for people living with myasthenia gravis, as with many other rare diseases," Billy Dunn, MD, director, Office of Neuroscience, FDA Center for Drug Evaluation and Research, said in a news release.

This approval represents "an important step in providing a novel therapy option for patients and underscores the agency's commitment to help make new treatment options available for people living with rare diseases," Dunn added.

Effective, Well-Tolerated

The rare and chronic autoimmune neuromuscular disorder of gMG causes debilitating and potentially life-threatening muscle weakness and significantly impaired independence and quality of life.

Most patients with gMG have immunoglobulin G (IgG) antibodies, which are most often directed against skeletal muscle nicotinic acetylcholine receptors.

Efgartigimod is an antibody fragment designed to reduce pathogenic IgG antibodies and block the IgG recycling process in patients with gMG.

The novel agent binds to the neonatal Fc receptor (FcRn), which is widely expressed throughout the body and plays a central role in rescuing IgG antibodies from degradation. Blocking FcRn reduces IgG antibody levels.

As reported by Medscape Medical News, efgartigimod was effective and well-tolerated in the phase 3, randomized, placebo-controlled ADAPT trial, which enrolled 187 adults with gMG regardless of acetylcholine receptor antibody status. All had a Myasthenia Gravis-Activities of Daily Living score of at least 5 (> 50% nonocular) on a background of a stable dose of at least one MG drug.

For 26 weeks, 84 patients were randomly assigned to receive efgartigimod 10 mg/kg and 83 to receive matching placebo. Both treatments were administered as four infusions per cycle at one infusion per week. The process was repeated as needed, depending on clinical response no sooner than 8 weeks after initiation of the previous cycle.

Treatment with efgartigimod reduced disease burden and improved strength and quality of life in patients with gMG across four MG-specific scales. In addition, these benefits were observed early and were reproducible and durable.

The results were published in June in Lancet Neurology .

"Important New Advance"

Efgartigimod is a "very rapidly acting drug relative to other treatments that may take 4, 6, sometimes 10 months before they start to work; and the side effect profile is much like placebo," principal investigator James Howard Jr, MD, Department of Neurology, University of North Carolina at Chapel Hill, told Medscape Medical News back in June.

The FDA granted efgartigimod fast track and orphan drug designation.

"People living with gMG have been in need of new treatment options that are targeted to the underlying pathogenesis of the disease and supported by clinical data," Howard said in a company news release issued upon approval. 

This approval "represents an important new advance for gMG patients and families affected by this debilitating disease. This therapy has the potential to reduce the disease burden of gMG and transform the way we treat this disease," Howard added.

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