ARGX-113-2308 - A Randomized, Double-Blinded, Placebo-Controlled, Phase 3, Parallel-Group Design Study Evaluating the Efficacy and Safety of Efgartigimod IV in Adult Participants With Acetylcholine Receptor Binding Antibody Seronegative Generalized Myasthenia Gravis

A drug already approved for one form of myasthenia gravis is now being tested in patients whose standard antibody test comes back negative. About one in ten people with generalised myasthenia gravis—a condition where the immune system attacks communication between nerves and muscles, causing fluctuating weakness—lack the specific acetylcholine receptor antibodies that current treatments target. These patients have been excluded from most major drug trials, leaving them with fewer proven options. This phase 3 study directly addresses that gap by testing efgartigimod, an intravenous drug that blocks antibody recycling, against a placebo in this overlooked group. If efgartigimod proves effective here, it would expand the treatment toolkit for a patient population that currently has no licensed therapy specifically tested in them. The study also includes an open-label extension, meaning all participants who complete the initial blinded phase can receive the drug long-term, providing data on sustained safety and benefit. For clinicians, this could mean a clearer, evidence-based choice for seronegative patients who today are often treated on a trial-and-error basis.