Trader consensus implies an 85% probability of FDA approval for argenx's Vyvgart (efgartigimod alfa-fcab) in acetylcholine receptor antibody (AChR-Ab) seronegative generalized myasthenia gravis (gMG), driven by robust Phase 3 ADAPT SERON trial data showing a statistically significant 3.35-point mean improvement in MG-ADL scores at week 4 (p=0.0068) across MuSK+, LRP4+, and triple seronegative subtypes, with sustained benefits and a safety profile consistent with prior indications. Recent presentations at the AAN 2026 meeting (April 18) highlighted rapid symptom control in open-label extensions, reinforcing efficacy in this underserved population comprising 15-20% of gMG patients lacking targeted therapies. The FDA granted priority review to the sBLA in January, setting a PDUFA target action date of May 10; while small trial size (n=119) introduces modest uncertainty around labeling scope, no advisory flags have emerged. Watch for the FDA decision next week.