Preliminary observations on the efficacy of efgartigimod in anti-LGI1-associated autoimmune encephalitis

Background: Leucine-rich glioma-inactivated 1 (LGI-1) antibodies are the second most common cause of autoimmune encephalitis, which is characterized by frequent seizures, memory loss, and psychiatric symptoms. Although most patients respond well to immunotherapy, treatment is often delayed or insufficient, resulting in a 14%−35% relapse rate and persistent neurological deficits. Therefore, exploring fast-acting and targeted therapies is crucial. Objectives: To present a series of cases involving anti-LGI1 encephalitis treated with efgartigimod, and to assess the efficacy and safety of this therapeutic approach in managing this condition. Design: A prospective, multicenter, and observational study. Methods: This study prospectively enrolled patients with anti-LGI1 encephalitis treated with efgartigimod and conducted a systematic review of the literature on the use of efgartigimod for anti-LGI1 encephalitis. The clinical outcomes before and 2 weeks after treatment were then compared. Results: A total of eight patients and two additional cases from the literature were included in the study, with a mean age of 55.6 ± 15.88 years and a male-to-female ratio of 6:4. The predominant clinical manifestations among the patients included seizures, psychiatric and behavioral abnormalities, and memory decline. Following treatment with efgartigimod, the modified Rankin scale ( p = 0.006; 95% confidence interval (CI) 2–2.5), Clinical Assessment Scale in Autoimmune Encephalitis ( p = 0.008; 95% CI 2.5–9.5), and Mini-Mental State Examination scores ( p = 0.042; 95% CI 0–14) significantly improved. In addition, a significant reduction was observed in both serum IgG levels ( p < 0.001; 95% CI 4.66–6.81) and antibody titers ( p = 0.004) post-treatment, indicating that the degree of antibody decline is negatively correlated with clinical severity. No adverse events were reported for any of the patients in this study. Conclusion: This study suggests that efgartigimod may offer promising efficacy and safety for patients with anti-LGI1 encephalitis. Further randomized controlled trials involving larger cohorts and extended follow-up periods are required to validate these findings.