Argenx (ARGX) Rises 1.82% as FDA Priority Review Looms Despite 399th-Ranked $310M Trading Volume

Market Snapshot

On January 13, 2026, Argenx (ARGX) closed with a 1.82% increase, despite a 21.12% decline in trading volume to $0.31 billion, ranking the stock 399th in market activity. The mixed performance reflects investor sentiment ahead of the FDA’s decision on the company’s expanded indication for Vyvgart. The stock’s modest gains contrast with its recent volatility, including a 3.5% intraday surge earlier in the week following the FDA’s priority review announcement.

Key Drivers

The U.S. Food and Drug Administration’s (FDA) acceptance of Argenx’s supplemental Biologics License Application (sBLA) for Vyvgart to treat acetylcholine receptor antibody-seronegative generalized myasthenia gravis (gMG) has emerged as the primary catalyst. This development grants the application priority review status, with a Prescription Drug User Fee Act (PDUFA) target action date of May 10, 2026. The sBLA, supported by data from the Phase 3 ADAPT SERON study, demonstrated statistically significant improvements in the Myasthenia Gravis Activities of Daily Living (MG-ADL) score for all seronegative subgroups, including MuSK-positive, LRP4-positive, and triple-seronegative patients. The study’s primary endpoint was met with a p-value of 0.0068, underscoring the drug’s efficacy in a patient population historically excluded from clinical trials.

The FDA’s decision builds on Vyvgart’s existing approvals for AChR-positive gMG, chronic inflammatory demyelinating polyneuropathy (CIDP), and primary immune thrombocytopenia (ITP). By expanding its label to seronegative gMG, Argenx could access an estimated 20% of the gMG patient population, a significant unmet medical need. Seronegative patients, who lack detectable anti-AChR antibodies, have limited treatment options and often face diagnostic challenges. The ADAPT SERON study’s success in this cohort—showing a 3.35-point improvement in MG-ADL scores at week four—positions Vyvgart as the first targeted therapy for these subtypes, potentially differentiating it in a competitive autoimmune disease market.

Vyvgart’s commercial performance further amplifies the significance of this regulatory milestone. In 2024, the drug generated $2.2 billion in global net sales, and preliminary 2025 figures reached $4.15 billion, a 90% year-over-year increase. The expansion into seronegative gMG could drive additional revenue, particularly as the drug’s safety profile remains consistent with its established use. The ADAPT SERON study reported no new safety concerns, with adverse events aligning with Vyvgart’s known profile, including infections and infusion-related reactions. This consistency reduces the risk of post-approval setbacks, a critical factor for investors evaluating long-term growth prospects.

The stock’s recent performance also reflects broader market dynamics. While trading volume dipped sharply on January 13, the 1.82% gain suggests sustained optimism about the FDA’s decision timeline. Priority review typically accelerates regulatory outcomes, with the PDUFA date providing a clear catalyst for investor activity. Analysts and institutional investors are likely factoring in the potential for a May 2026 approval, which could unlock new partnerships or pricing flexibility. Additionally, the study’s global enrollment—spanning North America, Europe, China, and the Middle East—highlights Vyvgart’s international appeal, a strategic advantage in scaling the drug’s market penetration.

In conclusion, Argenx’s stock movement is closely tied to the FDA’s regulatory trajectory for Vyvgart. The acceptance of the sBLA, robust clinical data, and the drug’s commercial momentum collectively underpin investor confidence. As the PDUFA date approaches, the company’s ability to secure approval for seronegative gMG will be pivotal in determining its next phase of growth.