Efgartigimod Effective in Treating Juvenile Myasthenia Gravis

Juvenile myasthenia gravis (MG) may be treated with efgartigimod, which demonstrated efficacy through 4 weeks in a new study published in Muscle & Nerve.¹ The study provides an extra option for young patients to reduce their symptoms of MG, although future studies will need to confirm these results.

MG is a condition that primarily affects the neuromuscular signals in the body but that can also affect muscle function in the face and limbs, among other areas. Those who have onset of MG before the age of 18 most commonly have juvenile MG,² which makes up about 45% of all cases in China.¹ Conventional immunosuppressants that are used in adults with MG may not always work with those diagnosed with juvenile MG, which makes finding alternatives important. This study looks to evaluate the safety and efficacy of efgartigimod in patients with juvenile MG due to its previous efficacy in adults with MG.

The study was conducted between September 2023 and May 2024 at 12 centers throughout China. Patients were included if they had fluctuating muscle weakness and fatigability with at least 1 of the following: abnormal neuromuscular transmission, a positive neostigmine test, or the presence or absence of anti–acetylcholine receptor (AChR) antibodies. Patients were excluded if they had Kearns-Sayre syndrome, congenital myasthenic syndromes, transient neonatal myasthenia, or atypical Graves disease.

Patients were given a weekly dose of efgartigimod at 10 mg/kg. The patients received this treatment for 4 weeks for the purposes of this study. Standard immunosuppressive therapies were also still given to the patients. Demographic data were collected from all patients, including their age at onset of MG, disease duration, initial symptoms, and timing of efgartigimod administration.

Treatment efficacy was assessed with the MG Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores. A reduction of at least 2 points in MG-ADL compared with baseline was defined as clinically meaningful improvement (CMI). A score of 0 or 1 on the MG-ADL scale was considered minimal symptom expression (MSE). The proportion of patients achieving CMI at week 4 was the primary end point of the study. Mean changes in MG-ADL and QMG scores acted as the secondary end points.

There were 17 patients included in this study, of which 82.4% were women. Most patients had moderate to severe disease at baseline and positive for AChR antibodies. Patients primarily took efgartigimod because of acute exacerbation (16/17), and 1 patient switched to efgartigimod due to insufficient clinical response.

CMI was achieved by 70.6% of the patients at week 1; 91.7% of the 12 patients who were evaluated at week 4 had achieved CMI. MSE criteria were met by 66.7% of the 12 patients at week 4. There were 6 patients who did not complete a full cycle of treatment due to economic considerations or due to symptom relief, of whom 4 achieved CMI at week 1.

The researchers found that efgartigimod was effective in juvenile MG regardless of disease duration, onset of symptoms, or treatment resistance to prior medications. Adverse events related to the medication were not reported by the patients.

There were some limitations to this study. The sample size was small and could have been affected by other disease states. The standardization of clinical examinations was difficult due to the multicenter retrospective design. The patients were mostly refractory cases, as efgartigimod is often used when other immunosuppressants are not effective. Infants and toddlers were not included in the i. Long-term efficacy and safety could not be determined due to short follow-up. Repeat AChR antibody testing was not done by most patients at week 4.

The authors concluded that “efgartigimod has a favorable safety profile and potential clinical efficacy in patients with [juvenile MG], including those with refractory disease.” Larger studies will be needed to assess whether efgartigimod is an effective treatment for juvenile MG.

References

1. Lin J, Qi G, Luo S, et al. Experience using efgartigimod to treat juvenile myasthenia gravis in China: a multicenter retrospective study. Muscle Nerve. Published online March 7, 2026. doi:10.1002/mus.70202
2. Myasthenia gravis. Children’s Hospital of Philadelphia. Accessed March 9, 2026. https://www.chop.edu/conditions-diseases/myasthenia-gravis