argenx and Regeneron Log Phase 3 Wins in Myasthenia Gravis

argenx SE reported that its pivotal ADAPT SERON Phase 3 trial met its primary endpoint in adults with acetylcholine-receptor antibody (AChR-Ab) seronegative generalized myasthenia gravis. Vyvgart delivered a statistically significant improvement in Myasthenia Gravis Activities of Daily Living (MG-ADL) scores versus placebo (p = 0.0068) and showed benefit across all three seronegative subtypes—MuSK-positive, LRP4-positive and triple seronegative—without new safety concerns. The Dutch–Belgian biotech intends to submit a supplemental biologics license application to the U.S. Food and Drug Administration by year-end 2025, positioning the FcRn blocker for what analysts describe as the broadest potential label in the disease. A day later, Regeneron Pharmaceuticals said its NIMBLE Phase 3 study in AChR-positive gMG achieved its goals. Single-agent cemdisiran, an investigational small-interfering RNA dosed quarterly, produced a 2.3-point placebo-adjusted reduction in MG-ADL scores after 24 weeks, outperforming a combination regimen of cemdisiran and the C5 antibody pozelimab. No treatment discontinuations due to adverse events were reported. Regeneron plans to seek U.S. approval for cemdisiran monotherapy in the first quarter of 2026. The back-to-back readouts intensify competition in the fast-growing gMG market, where treatments from argenx, Johnson & Johnson and AstraZeneca are already approved. If cleared, argenx’s expanded indication would give Vyvgart access to roughly one-fifth of patients currently lacking targeted options, while Regeneron’s quarterly, subcutaneous siRNA could offer a differentiated mechanism against C5-mediated disease activity.