Real-world efficacy and safety of efgartigimod in patients with autoimmune encephalitis: a single-center retrospective analysiss

Objective This study was conducted to evaluate the efficacy and safety of efgartigimod (EFG), a neonatal Fc receptor (FcRn) antagonist, in the treatment of autoimmune encephalitis (AE) under real-world conditions and to provide clinical evidence for treating AE patients who respond poorly to first-line and/or second-line immunotherapy. Methods In this study, clinical data of 14 AE patients who were treated with EFG at the Department of Neurology, The Second Hospital of Hebei Medical University between November 2023 and November 2025 were retrospectively analyzed. Treatment efficacy, disease prognosis, and adverse reactions were assessed. Results In total, 14 AE patients were included, 11 with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, and one each with anti-metabotropic glutamate receptor 5 (mGluR5) antibody-associated encephalitis, anti-leucine-rich glioma-inactivated protein 1 (LGI1) antibody-associated encephalopathy, and anti-IgLON family protein 5 (IgLON5) antibody-associated encephalopathy. The baseline median Modified Rankin Scale (mRS) score was 3.00 (3.00, 4.00), and the baseline median Clinical Assessment Scale for Autoimmune Encephalitis (CASE) score was 5.00 (4.25, 12.75). After EFG treatment, both mRS and CASE scores decreased significantly at all follow-up time points (Friedman test, P< 0.05). By week 12, 92.86% of patients achieved a favorable functional outcome (mRS ≤ 2). Clinical Global Impressions (CGI) scores indicated that most patients experienced clinically meaningful overall improvement, consistent with the improvements observed in the above scores. The Anti-NMDAR Encephalitis One-Year Functional Status (NEOS) score suggested that the overall prognosis of patients was satisfactory, and no relapses occurred during follow-up. Regular monitoring of peripheral blood immunoglobulin G (IgG) levels in nine patients showed a marked reduction at one week and three weeks after EFG treatment compared to baseline levels. The levels were higher at 12 weeks compared to those in the third week, although the levels remained below baseline. No patient required treatment discontinuation due to severe adverse reactions throughout the course of treatment. Conclusion When AE patients with poor response to first-line and/or second-line immunotherapy were administered EFG treatment, they showed rapid and significant clinical improvement, favorable prognosis, and few adverse reactions. However, the long-term efficacy and safety of EFG require validation in multicenter, large-sample studies.