A phase 3 trial shows efgartigimod works across all forms of generalized myasthenia gravis (gMG), including patients who lack detectable antibodies — a group historically excluded from clinical research. Benefits deepened with repeated treatment cycles, with more patients achieving near-symptom-free status over time. The FDA has already expanded efgartigimod's indication to cover all gMG patients, regardless of antibody status.
For years, patients with generalized myasthenia gravis (gMG) who lack detectable anti-acetylcholine receptor (AChR) antibodies have been largely overlooked — misdiagnosed, underserved, and excluded from clinical trials. New phase 3 data from the ADAPT SERON trial suggest that efgartigimod, a first-in-class neonatal Fc receptor (FcRn) antagonist, can meaningfully help these patients too. The drug works by reducing circulating IgG autoantibodies — the underlying drivers of gMG — regardless of which specific antibodies a patient has.
In the trial's double-blind phase, efgartigimod significantly improved daily functioning scores (MG-ADL) compared to placebo at 4 weeks. Benefits continued to deepen over subsequent open-label treatment cycles, with more patients achieving minimal symptom expression (MG-ADL score of 0 or 1) with each additional cycle. Investigators recommend trying at least 3–4 cycles before concluding the therapy isn't working.
By the Numbers:
Why it matters: The FDA expanded efgartigimod's indication in May 2026 to cover all gMG patients regardless of antibody status — a landmark shift for a condition where treatment options were previously tied to specific antibody profiles. For the roughly 10–20% of gMG patients with no detectable autoantibodies, this represents a significant therapeutic advancement.
