Efgartigimod as a salvage therapy for anti-NMDAR encephalitis patients after first-line treatment failure: a case series.
In a retrospective case series of five patients with anti-NMDAR encephalitis after first-line treatment failure, intravenous efgartigimod was associated with reduced disability scores and serum IgG, CSF antibody negativity in four patients, improvement in MRI or EEG abnormalities, and no reported serious adverse effects.
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In a retrospective case series of five patients with anti-NMDAR encephalitis after first-line treatment failure, intravenous efgartigimod was associated with reduced disability scores and serum IgG, CSF antibody negativity in four patients, improvement in MRI or EEG abnormalities, and no reported serious adverse effects.
Research significance
The reported clinical and biomarker changes support investigating FcRn inhibition as salvage therapy for refractory anti-NMDAR encephalitis; it is inferred, but not established by this uncontrolled series, that depletion of pathogenic IgG caused the neurological improvement or that the approach would benefit pediatric-oncology patients.
Source abstract
BACKGROUND: As an Fc receptor inhibitor, efgartigimod (EFG) could reduce serum IgG level, which might have a positive effect in the treatment of anti-N-methyl-D-aspartate-receptor (NMDAR) encephalitis (NMDARE). This study aimed to evaluate the treatment effects and safety of EFG on NMDARE patients following a first-line treatment failure. METHODS: We retrospectively reviewed five NMDARE patients who failed in first-line treatment. All patients received intravenous EFG (10 mg/kg/week). We conducted neurological function evaluation, cerebrospinal fluid (CSF) and hematological examination, magnetic resonance imaging (MRI), and electroencephalogram (EEG) in all patients to evaluate the treatment effects of EFG. RESULTS: After EFG treatment, the mean modified Rankin Scale (mRS) score decreased from 4.00 ± 0.70 at baseline to 1.60 ± 0.89, and the mean Clinical Assessment Scale in Autoimmune Encephalitis (CASE) score decreased from 14.6 ± 6.58 to 2.80 ± 2.95. The average period from EFG treatment to significant nerve function recovery (defined as mRS reduction ≥2) was 2.40 ± 2.19 weeks. Moreover, following a week after EFG treatment, the average serum IgG level decreased from 16.13 ± 7.47 g/L at baseline to 7.75 ± 5.17 g/L. Additionally, at 4 weeks post-EFG treatment, the IgG level decreased to 4.97 ± 2.30 g/L. Meanwhile, the anti-NMDAR antibody in CSF turned negative after EFG treatment in four out of five patients. The EFG helped in alleviating the abnormalities identified by MRI or EEG evaluations. CONCLUSION: The EFG can rapidly improve neurological function and enhance prognosis in NMDARE patients after first-line treatment failure. Meanwhile, no serious adverse effects were identified. The EFG treatment mechanism might be associated with the elimination of IgG, which contains anti-NMDAR antibodies.