In a recent press release, argenx announced the U.S. Food and Drug Administration (FDA) has accepted priority review for a supplemental Biologics License Application for efgartigimod alfa-fcab as a treatment for patients with acetylcholine receptor (AChR) antibody seronegative generalized myasthenia gravis (MG).
Efgartigimod alfa-fcab (marketed as Vyvgart) is a monoclonal antibody that is already FDA-approved for patients with generalized MG who are AChR-antibody positive. Approximately 80% of MG cases are AChR-antibody positive.
The remaining 20% of patients with MG are AChR-antibody seronegative, though some may have MuSK or LRP4 antibodies. These patients often often face a higher disease burden and may have fewer treatment options.
“Patients living with seronegative gMG continue to face limited treatment options and there remains a significant need to meaningfully improve their lives. The FDA’s acceptance of our sBLA with Priority Review status reflects the potential of VYVGART to address this need,” said Dr. Luc Truyen, chief medical officer at argenx.
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The FDA must respond to the application by May 10, 2026, its Prescription Drug User Fee Act target action date.
The application was based on data from the Phase 3 ADAPT SERON clinical trial. This study enrolled around 120 adults with confirmed AChR-seronegative MG. Participants received four once-weekly intravenous infusions of efgartigimod or placebo, with the primary endpoint being change in myasthenia gravis activities of daily living (MG-ADL) score from the start of the study to four weeks.
The study found that efgartigimod led to a statistically significant and clinically meaningful improvement in MG-ADL scores, and was well-tolerated.
“This development brings us closer to expanding the use of VYVGART in a broad spectrum of patients with myasthenia gravis. We look forward to continuing our dialogue with the FDA as they review our application,” noted Truyen.
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