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VYVGART Achieves Primary Endpoint in Phase 3 Trial for AChR-Ab Seronegative Myasthenia Gravis

5 hours ago4 min read

Key Insights

  • argenx's VYVGART met its primary endpoint in the ADAPT SERON study with a statistically significant improvement in MG-ADL scores (p-value=0.0068) for AChR-Ab seronegative generalized myasthenia gravis patients.

  • The study represents the first global Phase 3 trial to demonstrate clinically meaningful improvements across all three seronegative subtypes: MuSK+, LRP4+, and triple seronegative patients.

  • argenx plans to submit a supplemental Biologics License Application to the FDA by end of 2025 to expand VYVGART's label to include all AChR-Ab seronegative gMG patients.

argenx SE announced positive topline results from its pivotal ADAPT SERON Phase 3 study of VYVGART (efgartigimod alfa-fcab) in patients with AChR-Ab seronegative generalized myasthenia gravis (gMG). The study met its primary endpoint with a p-value of 0.0068, demonstrating statistically significant and clinically meaningful improvement in MG-ADL (Myasthenia Gravis Activities of Daily Living) total score compared to placebo.

Breakthrough for Underserved Patient Population

The ADAPT SERON study marks the first global Phase 3 trial to demonstrate clinically meaningful improvements in disease activity across all three AChR-Ab seronegative subtypes: MuSK+, LRP4+, and triple seronegative patients. This represents a significant advancement for a patient population that has historically been excluded from clinical studies and faces limited treatment options.
"The results of the ADAPT SERON study, the largest study to date of AChR-Ab seronegative gMG, confirm that VYVGART now has the potential to be a targeted, effective, safe, and necessary treatment for patients living with gMG, regardless of autoantibody status," said James F. Howard Jr., M.D., Professor of Neurology at The University of North Carolina at Chapel Hill School of Medicine and Principal Investigator for the ADAPT SERON trial.

Study Design and Patient Population

The Phase 3 ADAPT SERON study was a randomized, double-blind, placebo-controlled, multi-center trial evaluating 119 adults with AChR-Ab seronegative gMG across North America, Europe, China, and the Middle East. Part A randomized participants 1:1 to receive either four once-weekly infusions of efgartigimod IV or placebo, followed by a 5-week follow-up period for primary analysis.
The primary endpoint measured MG-ADL total score change from baseline to day 29 in Part A. Enrolled participants had confirmed MG diagnosis by an independent panel of experts and an MG-ADL total score of 5 or greater. All participants were on stable doses of at least one gMG treatment prior to randomization, including acetylcholinesterase inhibitors, corticosteroids, or nonsteroidal immunosuppressive drugs.

Addressing Significant Unmet Medical Need

AChR-Ab seronegative gMG affects approximately 20% of patients with generalized myasthenia gravis, a rare chronic neuromuscular autoimmune disease caused by pathogenic IgGs targeting the neuromuscular junction. Within this population, anti-MuSK antibodies are detected in approximately 1-10% of patients, while anti-LRP4 antibodies are found in approximately 1-5% of patients. About 10% of patients are triple seronegative, having no detectable autoantibodies against AChR, MuSK, or LRP4.
Triple seronegative patients have historically been excluded from studies and experience higher disease burden and unmet medical need compared to patients with detectable autoantibodies. Currently, no approved treatments are available for patients with anti-LRP4 antibodies or for triple seronegative patients.

Safety Profile Consistent with Previous Studies

VYVGART was well tolerated and safe across AChR-Ab seronegative subtypes, with a safety profile consistent with that established in patients with AChR-Ab seropositive gMG and other indications. No new safety concerns were identified in the study.

Regulatory Timeline and Next Steps

Based on these results, argenx plans to submit a supplemental Biologics License Application (sBLA) to the U.S. FDA by the end of 2025, seeking expansion of the VYVGART label to include adult AChR-Ab seronegative gMG patients across all three subtypes. Detailed results from the ADAPT SERON study will be presented at an upcoming medical meeting.
"The positive outcome of the ADAPT SERON study clearly shows VYVGART's ability to provide meaningful benefit across all AChR-ab seronegative gMG subtypes," said Luc Truyen, M.D. Ph.D., Chief Medical Officer at argenx.
VYVGART is currently the first approved FcRn blocker in the United States, EU, China, and Canada for treating adults with generalized myasthenia gravis who are anti-acetylcholine receptor antibody positive, and in Japan for adults with gMG who do not have sufficient response to steroids or non-steroidal immunosuppressive therapies.
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