argenx NV ADR (NASDAQ: ARGX) shares rose about 3% in premarket trading Monday after the U.S. Food and Drug Administration expanded the approved use of VYVGART and VYVGART Hytrulo. The broadened indication now covers all adult patients living with generalized myasthenia gravis - including those who test positive for anti-AChR, anti-MuSK, anti-LRP4 antibodies, and triple seronegative patients.
The supplemental Biologics License Application approval rests on findings from the Phase 3 ADAPT SERON study. That trial enrolled 119 patients with generalized myasthenia gravis who do not have detectable anti-acetylcholine receptor antibodies across three serotypes. The study met its primary endpoint: patients treated with VYVGART achieved a statistically significant improvement in Myasthenia Gravis Activities of Daily Living (MG-ADL) total score compared with placebo at week 4. In the overall trial population, the treatment effect corresponded to a clinically meaningful 3.35-point improvement in MG-ADL total score at week 4.
Clinicians and health systems have faced challenges diagnosing and managing gMG when standard assays do not detect AChR antibodies. Approximately 20% of patients with generalized myasthenia gravis fall into that seronegative category, according to the information supporting the approval. With this expanded indication, healthcare providers can prescribe VYVGART and VYVGART Hytrulo upon clinical diagnosis of gMG, without restriction by serotype.
Safety data reported from the trial indicate that VYVGART was generally well tolerated across the serotypes studied, with a safety profile consistent with prior experience in patients who are anti-AChR-Ab positive. The company reported improvements on both MG-ADL and Quantitative Myasthenia Gravis measures across subsequent treatment cycles in the overall population and within each serotype evaluated.
Separately, the company disclosed positive results from the ADAPT OCULUS study evaluating VYVGART Hytrulo in ocular myasthenia gravis and continues pediatric development through the ADAPT Jr study for younger patients with generalized myasthenia gravis. VYVGART is offered in three administration options, one of which is VYVGART Hytrulo self-injection delivered via a prefilled syringe.
Market reaction and context
The stock movement in premarket trading reflected investor response to the expanded label, which positions VYVGART and its subcutaneous Hytrulo formulation as the first therapies approved for all adult gMG serotypes. The regulatory change affects stakeholders across the biotech and healthcare sectors, including specialty pharmacies, clinicians treating neuromuscular diseases, and investors tracking commercial uptake of novel therapies for rare autoimmune conditions.
What remains under development
The company continues to evaluate additional indications and age groups. ADAPT OCULUS results for ocular myasthenia gravis were reported as positive, and pediatric development continues in the ADAPT Jr study. These ongoing programs represent the next phases of clinical assessment beyond the adult generalized myasthenia gravis expansion that secured the recent approval.