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. Around 10 to 15 percent of people with generalised myasthenia gravis—a chronic autoimmune disease that causes fluctuating muscle weakness—do not have the specific acetylcholine receptor antibodies that current treatments target. These seronegative patients are often excluded from clinical trials, leaving them with less evidence on which therapies work. This phase 3 study directly addresses that gap by testing efgartigimod, an intravenous drug that blocks antibody recycling, in this overlooked group. If the drug proves effective, seronegative patients could gain access to a treatment already shown to help seropositive patients, potentially reducing muscle weakness and improving daily function. The study also includes an open-label extension, allowing all participants to receive the drug long-term. For a condition that can affect breathing, swallowing, and mobility, even modest improvements can be life-changing.