Some Myasthenia Gravis Patients Take Longer to Benefit from New Treatment
Patients with generalized myasthenia gravis who lack detectable anti-AChR antibodies show a delayed response to intravenous efgartigimod, often requiring two or three treatment cycles before noticeable improvement. This finding highlights the need for longer observation periods before discontinuing therapy in this subgroup. The results offer hope for a previously underserved patient population.
Intravenous efgartigimod (Vyvgart), a treatment for generalized myasthenia gravis, demonstrated continued efficacy and safety in patients lacking detectable anti-acetylcholine receptor (AChR) antibodies, according to open-label data from the ADAPT SERON trial presented at the American Association of Neuromuscular & Electrodiagnostic Medicine annual meeting in October 2026. These patients—often referred to as seronegative or triple seronegative, meaning they lack detectable antibodies against AChR, MuSK, or LRP4—represent approximately 10% of the myasthenia gravis population and have historically been underserved by newer targeted therapies. While most patients in prior trials responded within the first treatment cycle, those without AChR antibodies showed a delayed response, often requiring two to three cycles—potentially up to six months—before meaningful improvement was observed. This finding challenges previous clinical practice, which might have led clinicians to discontinue treatment after two cycles if no benefit was seen, potentially depriving these patients of effective therapy. James F. Howard Jr., MD, of the University of North Carolina at Chapel Hill, emphasized that this delay necessitates longer observation periods before concluding a treatment is ineffective. The safety profile remained consistent across subgroups, with no new adverse signals identified, reinforcing efgartigimod’s potential as a viable option for this historically neglected group.
The broader c
The findings could significantly impact care pathways for a small but vulnerable patient group, potentially reducing treatment abandonment and improving long-term outcomes for those previously excluded from effective therapies. Clinicians may need to revise guidelines to allow for extended observation periods before discontinuing efgartigimod in seronegative patients, which could influence insurance coverage decisions and payer policies. This shift may also encourage pharmaceutical companies to prioritize inclusive trial designs, potentially expanding access to novel treatments for other rare or poorly understood autoimmune subtypes. A comparable precedent exists with the development of rituximab for neuromyelitis optica spectrum disorder, where initial trials focused on antibody-positive patients, but subsequent research revealed benefit in seronegative cases, leading to broader approval. Moving forward, monitoring real-world treatment patterns and long-term outcomes will be critical.