Argenx's Vyvgart Shows Promise in Expanded Myasthenia Gravis Population

Argenx, a Dutch pharmaceutical company, has announced positive results from a late-stage clinical trial for its drug Vyvgart (efgartigimod) in treating a broader population of patients with generalized myasthenia gravis (gMG). This development could significantly expand the drug's reach and solidify its position in an increasingly competitive market.

Phase 3 Trial Success in Seronegative gMG Patients

The ADAPT SERON phase 3 trial evaluated Vyvgart's efficacy and safety in gMG patients who are seronegative, meaning they lack detectable antibodies against acetylcholine receptors (AChR). This group represents approximately 20% of all gMG patients and has been historically underserved in treatment options.

Key findings from the trial include:

• Vyvgart met the primary endpoint, demonstrating statistically significant and clinically meaningful improvements in patients' Myasthenia Gravis Activities of Daily Living (MG-ADL) scores.
• The drug's safety profile remained consistent with previous studies, with no new safety concerns identified.
• Argenx plans to submit a regulatory filing to the FDA by the end of the year, seeking approval for Vyvgart across all three subtypes of seronegative gMG: MuSK-positive, LRP4-positive, and triple seronegative.

Expanding Vyvgart's Market Reach

Vyvgart, an FcRn blocker, received its initial FDA approval in December 2021 for adult gMG patients who test positive for AChR antibodies. Since then, Argenx has been actively working to broaden the drug's applications:

• In June 2023, the FDA approved Vyvgart Hytrulo, a subcutaneous formulation of the drug for gMG.
• The drug also gained approval for treating chronic inflammatory demyelinating polyneuropathy (CIDP), a rare peripheral nervous system disease.

If approved for seronegative gMG, Vyvgart could potentially add around 11,000 new patients to its current U.S. prescribing pool, according to analysts at William Blair. This expansion would give Vyvgart the "broadest label of all FcRn antagonists approved in gMG," potentially strengthening its market position.

Competitive Landscape in gMG Treatment

The gMG treatment space has become increasingly crowded in recent years, with several pharmaceutical companies vying for market share:

• AstraZeneca's Ultomiris, a successor to Soliris, received FDA approval for gMG shortly after Vyvgart's initial approval.
• UCB's Rystiggo (rozanolixizumab) gained U.S. approval in 2023 for both AChR antibody- and MuSK antibody-positive gMG patients.
• Johnson & Johnson recently entered the market with Imaavy (nipocalimab), approved for patients ages 12 and older with detectable AChR or MuSK antibodies.

As Argenx prepares to submit its regulatory filing for the expanded gMG indication, the company aims to differentiate Vyvgart in this competitive landscape by potentially offering the most comprehensive coverage for gMG patients, including those who are seronegative.