Efgartigimod for generalized myasthenia gravis in the extreme elderly (≥80 years): a multicenter retrospective real-world study.

Background: Target-specific immunotherapies have been shown to effectively treat myasthenia gravis (MG) with less side effects. One such immunotherapy is efgartigimod, a neonatal Fc receptor antagonist, promotes degradation of pathogenic IgG antibodies. However, data specifically focusing on elderly, especially for those over 80 years, remain limited. Methods: This study included generalized MG patients over 80 years old from four neuromuscular centers who were treated with efgartigimod. Data regarding MG history, treatment regimens, and scores from the MG-ADL, QMG, and MGC scales, as well as adverse events, were prospectively recorded. Results: Twelve patients with mean age of 82.9 ± 2.5 years were included. Anti-AChR antibodies were positive in 11 patients and anti-MuSK antibodies were detected in 1 patient. All patients received at least one cycle of efgartigimod treatment, for the following indications: myasthenia gravis acute exacerbation (MGAE, n=8), mild/moderate disease (n=3), and myasthenic crisis (MC, n=1). At week 4 (1week after the final infusion), the study showed significant reductions in all efficacy measurements: MG-ADL scores decreased by 52.2% ± 30.8% (from 10.9 ± 2.7 to 3.6 ± 2.1), QMG scores by 36.6% ± 28.4% (from 18.2 ± 7.0 to 11.7 ± 8.3), MGC scores by 48.2% ± 33.4% (from 17.8 ± 7.5 to 9.0 ± 8.6). The greatest improvement was observed in the MGAE subgroup, with reductions of 69.8% ± 16.9% in MG-ADL, 51.8% ± 20.6% in QMG, 66.5% ± 20.2% in MGC. Clinically meaningful improvement (CMI) was rapidly achieved by 91.7% (11/12) of patients at 1.3 ± 0.5 weeks, with 8.3% (1/12) reaching minimal symptom expression (MSE) by week 4. However, two patients in the mild/moderate group failed to sustain CMI through week 4, resulting in nine responders overall (8 MGAE, 1mild/moderate). These responders maintained symptom control throughout the 24-week follow-up with subsequent therapies. Treatment-related adverse events were mild: two patients experienced transient minor headache and one patient had mild upper respiratory tract infection. Conclusions: This multicenter study demonstrated that efgartigimod was efficacious and safe in the elderly MG over 80 years of age. Elderly patients with MGAE presented to benefit the most from efgartigimod treatment.