Treatment Maintains Benefits for Antibody-Negative Myasthenia Gravis Patients

Efgartigimod demonstrated sustained effectiveness in patients with generalized myasthenia gravis who lack detectable acetylcholine receptor antibodies, maintaining an average improvement of approximately 5 points in activity-of-daily-living scores at 52 weeks. The medication, which works by reducing circulating autoantibodies, showed no new safety concerns during the extended observation period. The FDA approved the expanded indication in May 2026 to include all people with generalized myasthenia gravis, regardless of serum antibody status.

Myasthenia gravis encompasses several distinct biological subtypes distinguished by which proteins trigger the autoimmune response. While roughly one-fifth of patients lack antibodies against the acetylcholine receptor, some instead develop antibodies targeting alternative neuromuscular junction proteins like MuSK or LRP4, while others display no detectable antibodies across all three categories. This heterogeneity has historically complicated treatment decisions.

The trial data suggests a unifying mechanism: circulating immunoglobulin G antibodies appear central to disease progression across antibody subtypes. By targeting the neonatal Fc receptor, efgartigimod reduces these pathogenic antibodies regardless of their specific target. Importantly, the study found that additional treatment cycles yielded incremental gains, with more patients approaching minimal symptom expression as they received successive doses, suggesting a cumulative benefit pattern distinct from previous drug observations in AChR-positive populations.