Vyvgart improves daily living for wide range of gMG patients

Vyvgart (efgartigimod alfa-fcab) improves muscle strength and daily functioning in adults with generalized myasthenia gravis (gMG) who are positive for self-reactive antibodies against the acetylcholine receptor (AChR) protein, regardless of patient and disease features or simultaneous treatments.

Those are the main findings of a subgroup analysis of data from the global Phase 3 ADAPT clinical trial (NCT03669588), top-line results of which helped support Vyvgart’s initial approval for adults with gMG and anti-AChR antibodies, the most common type of MG-driving antibody. The therapy is now approved in the U.S. for all adults with gMG, regardless of antibody status.

Vyvgart “offers improvements to [quality of life] through relief of disease and treatment burdens, presenting an opportunity to shift the treatment paradigm toward the use of specific therapies earlier in the disease course and across a broad range of patients,” the researchers wrote.

The results were described in the study “Clinical effectiveness of efgartigimod in a broad population of patients with generalized myasthenia gravis: subgroup analyses from a randomized, double‑blind, placebo‑controlled, phase 3 trial (ADAPT),” which was published in the Journal of Neurology. It was funded by Argenx, the company that sells Vyvgart, and several of its authors are affiliated with the company.

gMG occurs when the immune system mistakenly attacks proteins involved in nerve-muscle communication, resulting in muscle weakness and fatigue. This attack is typically driven by self-reactive antibodies that most commonly target the AChR protein.

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Antibodies play a role

Vyvgart is designed to block the neonatal Fc receptor (FcRn), a protein that normally stabilizes and prevents the breakdown of circulating antibodies, including those driving MG. By suppressing FcRn, the therapy, administered directly into the bloodstream in four-week cycles, is expected to increase the rate at which these antibodies are destroyed, lowering their levels in the blood and easing MG symptoms.

ADAPT involved 167 adults with gMG, 77.2% of whom had anti-AChR antibodies, who were randomly assigned to receive either Vyvgart or a placebo, in addition to standard MG treatments.

Top-line results showed that significantly more AChR antibody-positive participants treated with Vyvgart experienced meaningful reductions in disease severity, as assessed with the standard measures MG Activities of Daily Living (MG-ADL) and the Quantitative MG (QMG), after the first treatment cycle.

MG-ADL assesses the impact of the disease on daily life activities, while QMG measures muscle strength. Meaningful reductions in disease severity were reflected by an MG-ADL score drop of at least two points and/or QMG score reduction of at least three points, each sustained for at least one month.

The researchers looked at whether Vyvgart worked well in relevant subgroups of ADAPT participants who were positive for anti-AChR antibodies, based on the proportion of MG-ADL and QMG responders (those experiencing meaningful score reductions in the respective scales).

Data showed that the treatment’s benefits were consistent across different patient and disease characteristics at the study’s start (baseline). Significantly higher proportions of MG-ADL and QMG responders were seen with the first cycle of Vyvgart treatment relative to the placebo regardless of:

• age (younger than 65 vs. 65 or older)
• sex
• presence of obesity
• time since diagnosis (less than three years vs. three or more years)
• disease severity at study’s start (moderate vs. severe)
• history of thymectomy, a surgery to remove the thymus gland (thymus abnormalities are thought to contribute to gMG)

Similar trends were seen across subgroups based on previous and simultaneous treatments. Participants on Vyvgart were significantly more likely than those on the placebo to be classified as MG-ADL and QMG responders, regardless of previous nonsteroidal immunosuppressive therapies (NSISTs) and simultaneous treatments during the study with:

• corticosteroids, a type of anti-inflammatory and immunosuppressive treatment
• NSISTs, or immunosuppressants that are not corticosteroids
• acetylcholinesterase (AChE) inhibitors, such as pyridostigmine bromide (sold as Mestinon, with generics available)
• any gMG treatment

Vyvgart’s superiority was also generally maintained across all subgroups during the second treatment cycle.

The rates of adverse events, serious adverse events, and treatment discontinuations due to adverse events were similar between the Vyvgart and placebo groups, regardless of which gMG treatments participants were also receiving during the study.

“We have demonstrated the efficacy and safety of [Vyvgart] in a variety of clinically relevant subgroups, including those early and later in their disease course, which indicates that [Vyvgart] could be considered as a potential therapy for gMG regardless of the treatments received and baseline patient and disease characteristics,” the researchers wrote.