The effect of FcRn inhibition on overlapping autoimmune comorbidity in AChR-seropositive generalized myasthenia gravis

Introduction Generalized Myasthenia gravis (gMG) is a rare autoimmune disorder of the neuromuscular junction caused by IgG autoantibodies against antigens in the postsynaptic cleft. This study aimed to assess the real-world effectiveness and safety of Efgartigimod (EFG) in AChR-positive gMG with overlapping autoimmune comorbidity. Methods EFG was administered as 4 consecutive weekly infusions or injections. Myasthenia Gravis Activity of Daily Living (MG-ADL) and Myasthenia Gravis quantitative (QMG) scales were administered at baseline and after 4 weeks. Clinical data on autoimmune comorbidities and prednisone use were collected. Results 35 patients (20 women, mean age 53.6 years) received EFG, with a significant and clinical improvement in both MG-ADL and QMG scores. MG-ADL responder rate (MG-ADL reduction≥2) was 79%, while 68% on QMG (QMG reduction≥3); Minimal symptoms expression was reached in 4 patients, with a mean reduction in daily prednisone dose of 8 mg. Overlapping autoimmune comorbidity was reported in 12 gMG patients (34%). gMG patients with Stiff-Person syndrome, type 1 Diabetes and Lambert-Eaton myasthenic syndrome benefited more from EFG with a higher reduction on MG-ADL. Conclusion Overlapping autoimmune comorbidity is not rare. EFG demonstrated a meaningful clinical benefit in patients with AChR-positive gMG with overlapping IgG-mediated disorders.