Serum Autoantibody Lowering by the Anti-FcRn Monoclonal Antibody, Nipocalimab, Correlates With Clinical Improvement in Generalized Myasthenia Gravis Patients

Objective To evaluate the relationship between clinical improvement in Myasthenia Gravis-Activities of Daily Living (MG-ADL) scores and pharmacodynamic effects IgG autoantibody lowering induced by nipocalimab Vivacity MG Phase 2 study. Background Nipocalimab is a fully human, aglycosylated, effectorless IgG1 anti-FcRn monoclonal antibody that targets neonatal Fc receptor (FcRn) with high affinity, thereby pathogenic antibodies autoimmune disease. Design/Methods The reduction acetylcholine-receptor (AChR)- Muscle-Specific-Tyrosine-Kinase (MuSK)- autoantibodies MG-ADL were explored across four dose arms Study generalized myasthenia gravis (gMG) patients. Results Of 68 patients enrolled, 54 randomized to one dosing arms. 51 (94%) seropositive for anti-AChR, 3 (6%) anti-MuSK. was well-tolerated achieved substantial, dose-dependent rapid reductions serum total IgG, including all subtypes anti-AChR autoantibodies. These associated dose-dependent, durable responses nipocalimab-treated groups. A similar trend IgG4 noted, though sample size MuSK positive small. Conclusions results support rapid, predictable effect inducing gMG. In addition, close correlation response suggest potential using serial levels as biomarker management gMG treated nipocalimab; this will be tested ongoing trial.