argenx Announces FDA Acceptance of Supplemental Biologics License Application with Priority Review for VYVGART in AChR-Ab Seronegative gMG

January 13, 2026, 7:00 AM CET 

Amsterdam, the Netherlands – argenx SE (Euronext & Nasdaq: ARGX), a global immunology company committed to improving the lives of people suffering from severe autoimmune diseases, today announced that the U.S. Food and Drug Administration (FDA) has accepted for priority review a supplemental Biologics License Application (sBLA) for VYVGART (IV: efgartigimod alfa-fcab) for the treatment of adults with acetylcholine receptor antibody (AChR-Ab) seronegative generalized myasthenia gravis (gMG). The application has been granted a Prescription Drug User Fee Act (PDUFA) target action date of May 10, 2026.

“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 Luc Truyen, M.D., Ph.D., Chief Medical Officer, argenx. “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.”

The sBLA is supported by data from the Phase 3 ADAPT SERON study, which evaluated the efficacy and safety of VYVGART in adults with AChR-Ab seronegative gMG across all three subtypes – MuSK+, LRP4+, and triple seronegative gMG. The study met its primary endpoint (p-value=0.0068), demonstrating a statistically significant improvement in Myasthenia Gravis Activities of Daily Living (MG-ADL) total score compared to placebo after four weeks.

In the overall population, mean change from baseline in patients treated with VYVGART was a clinically meaningful 3.35 point improvement in MG-ADL total score at week 4. Improvements in MG-ADL and Quantitative Myasthenia Gravis (QMG) scores were observed across subsequent treatment cycles in the overall population and in all patient subgroups, including MuSK+, LRP4+, and triple seronegative gMG.

VYVGART was well-tolerated with a safety profile consistent with the established profile of VYVGART in patients with AChR-Ab seropositive gMG and other indications. No new safety concerns were identified.

ADAPT SERON Study Design
The Phase 3 ADAPT SERON study is a randomized, double-blind, placebo-controlled, multi-center study evaluating the safety and efficacy of efgartigimod in adults with AChR-Ab seronegative gMG (n=119) across North America, Europe, China, and the Middle East. Part A randomized participants (1:1) received 4 once-weekly infusions of efgartigimod IV or placebo, followed by a 5-week follow-up and primary analysis. Part B is an open-label extension: participants receive 2 fixed cycles of 4 once-weekly efgartigimod infusions (4-week interval between cycles); from cycle 3 onward, additional cycles could be started ≥1 week after the last administration of the previous cycle, based on clinical status. The primary endpoint is the MG-ADL total score change from baseline to day 29 in part A. Other scales of evaluation include QMG, MG-QoL 15r, MGC, and EQ-5D-5L VAS. Enrolled participants had a confirmed MG diagnosis by an independent panel of experts, and an MG-ADL total score of 5 or greater. Participants were on a stable dose of at least one gMG treatment prior to randomization, including acetylcholinesterase inhibitors, corticosteroids or nonsteroidal immunosuppressive drugs. Participants were eligible to enroll in ADAPT SERON if they were AChR-Ab seronegative, which included participants who are MuSK-Ab seropositive, LRP4-Ab seropositive, or triple seronegative.