A newly reported case from Nanchang University suggests that efgartigimod, a neonatal Fc receptor (FcRn) blocker approved for generalized myasthenia gravis, may offer a promising treatment option for patients who develop immune checkpoint inhibitor (ICI)-related myasthenia gravis (MG)-myositis overlap syndrome, a rare but potentially serious complication of cancer immunotherapy.
Rare Neurological Toxicity of Immunotherapy
Immune checkpoint inhibitors targeting the PD-1/PD-L1 pathway have transformed cancer treatment but can also trigger immune-related adverse events affecting multiple organ systems. Among the most challenging neurological complications is ICI-related MG-myositis overlap syndrome, which may occur alone or in combination with myocarditis and is associated with significant morbidity and mortality.
Current treatment strategies generally include:
- High-dose corticosteroids
- Intravenous immunoglobulin (IVIG)
- Plasma exchange (PE)
However, evidence supporting newer targeted therapies remains limited.
Case Overview
The case involved a 69-year-old woman with cervical cancer who developed neuromuscular symptoms after treatment with tislelizumab, an anti-PD-1 monoclonal antibody.
Following immunotherapy, the patient experienced:
- Bilateral eyelid drooping (ptosis)
- Dysarthria (speech difficulty)
- Limb weakness
Neurological examination revealed:
- Asymmetric ptosis
- Weak eye closure
- Positive fatigability testing
Further diagnostic workup supported a diagnosis of ICI-related MG-myositis overlap syndrome:
- Elevated serum creatine kinase (CK) level of 553.82 U/L
- Electromyography showing myopathic changes and fibrillation potentials
- Positive neostigmine test
- Presence of anti-acetylcholine receptor antibodies
- Negative repetitive nerve stimulation study
Treatment With Efgartigimod
Given the overlap syndrome diagnosis, clinicians administered four infusions of efgartigimod at 10 mg/kg.
The patient’s response was notable:
| Outcome Measure | Before Treatment | After Treatment |
|---|---|---|
| Creatine kinase | 553.82 U/L | Normalized |
| MG Activities of Daily Living (ADL) score | 10 | 1 |
| Quantitative Myasthenia Gravis (QMG) score | 16 | 5 |
Clinical symptoms improved substantially following treatment, and laboratory markers returned to normal.
Sustained Benefit at Follow-Up
At five months of follow-up, the patient remained asymptomatic and did not require an additional cycle of efgartigimod therapy.
Importantly, investigators reported that treatment was well tolerated, with no adverse events observed during the treatment period.
Growing Evidence for FcRn Blockade
According to the authors, only four previously published cases have described the use of efgartigimod in ICI-related overlap syndromes involving myasthenia gravis and myositis, with or without accompanying myocarditis.
This latest report adds to a small but growing body of evidence suggesting that FcRn blockade may help rapidly reduce pathogenic IgG antibodies and improve outcomes in immune-mediated neuromuscular complications associated with checkpoint inhibitor therapy.
Clinical Implications
Although conclusions cannot be drawn from a single patient, the case highlights the potential role of efgartigimod as a targeted therapeutic option for patients with ICI-related MG-myositis overlap syndrome, particularly when conventional approaches are insufficient or when rapid symptom control is needed.
The authors emphasize that larger studies are required to establish the safety, efficacy, and optimal positioning of efgartigimod within treatment algorithms for these rare but serious immune-related neurological adverse events.
