Efgartigimod Effective in Broad Subsets of Patients With gMG

An expanded trial built off the results of the ADAPT trial (NCT06298552), showing that efgartigimod was effective for use in a broad range of patients with generalized myasthenia gravis (gMG). This finding, published in the Journal of Neurology,¹ expanded on the previous finding showing that patients with acetylcholine receptor antibody–positive (AChR-AB) gMG exclusively saw efficacy in treatment when using efgartigimod.

As an autoimmune disease, gMG can cause muscle weakness throughout the body, as well as issues with speaking or swallowing due to the weakened skeletal muscle. The condition affects patients in different ways, ranging from droopy eyes or double vision to potential respiratory failure in severe cases.² However, despite the differences in presentation, approximately 85% of patients with gMG have immunoglobulin G (IgG) autoantibodies against the skeletal AChR. Efgartigimod aims to reduce IgG subtypes without affecting the production of IgG overall.³ The ADAPT trial aimed to assess the efficacy of this treatment in patients with AChR Ab-positive or -negative gMG. This report presented the findings of smaller subgroups of patients who had previously had nonsteroidal immunosuppressive treatment (NSIST), were using other gMG treatments throughout the study, and had different baseline characteristics.¹

This current analysis used the data from the ADAPT study, with patients aged 18 years and older with gMG, with or without AChR-Abs, and a Myasthenia Gravis Activities of Daily Living (MG-ADL) score of 5 or more included in the study. Participants for this analysis also needed to be receiving a stable dose of at least 1 treatment for gMG.

The proportion of AChR-Ab participants who were responders in the MG-ADL in the first treatment cycle acted as the primary end point of the study. The secondary end point was the proportion of participants who responded to the Quantitative Myasthenia Gravis (QMG) score.

There were 167 participants included in the ADAPT trial, of whom 77.2% were AChR-Ab; these patients were split evenly between efgartigimod (n = 65) and placebo (n = 64). The efgartigimod group had a higher number of patients who had undergone thymectomy (69.2% vs 46.9%) or were receiving only AChE inhibitors (20.0% vs 9.4%). The median (IQR) baseline scores for MG-ADL and QMG were 9.0 (2.0) and 16.0 (6.0) in those using efgartigimod and 8.0 (3.0) and 15.5 (6.0) in those using placebo.

Significantly higher responder rates were found across both MG-ADL and QMG in those treated with efgartigimod. Responder rates were 63.8% in the efgartigimod group vs 30.2% in the placebo group in those who had used any prior NSIST. Responder rates were greater in cycle 2 in those who used efgartigimod compared with placbo.

Participants using efgartigimod had higher MG-ADL and QMG responder rates regardless of age, sex, or body mass index (BMI) at baseline. Those aged less than 65 years had a difference in response of 29.4% between efgartigimod and placebo. The difference was 32.5% and 51.7% between efgartigimod and placebo in those with a BMI of less than 30 and 30 or higher, respectively. Women had a difference of 34.9% between the groups, whereas men had a difference of 43.4% between the groups.

Rates of treatment-emergent adverse events were similar across both the efgartigimod and placebo groups. A total of 44.6% of the efgartigimod group experienced at least 1 treatment-emergent adverse event of special interest compared with 33.3% of the placebo group.

There were some limitations to this study. There was a smaller sample size, especially in some subgroups, which could have affected the results and ultimately makes them exploratory rather than definitive. Generalizability of the findings could be limited due to the controlled design of the study. The study duration was also shorter at 26 weeks.

“These results build on the findings from the overall population described in the pivotal publication [for the ADAPT trial]. Efgartigimod 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 authors concluded.

References

1. Howard JF, Saccà F, Hoffmann S, et al; The ADAPT Study Group. 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). J Neurol. 2026;273:363. doi:10.1007/s00415-026-13877-z
2. Myasthenia gravis. Cleveland Clinic. Updated November 10, 2023. Accessed June 4, 2026. https://my.clevelandclinic.org/health/diseases/17252-myasthenia-gravis-mg
3. Efgartigimod. Argenx. Accessed June 4, 2026. https://argenx.com/pipeline/efgartigimod