Seeking to build out its pipeline-in-a-product Vyvgart, Argenx is returning to its roots with plans to pursue an expanded approval in the drug’s initial myasthenia gravis indication.
On Monday, Argenx reported that its chief drug Vyvgart (efgartigimod) met the mark in a phase 3 trial assessing the FcRn blocker in certain patients with generalized myasthenia gravis (gMG).
The late-stage study, dubbed ADAPT SERON, looked at Vyvgart’s safety and efficacy in the subset of gMG patients who are seronegative, meaning they do not have detectable antibodies against the proteins in their blood known as acetylcholine receptors (AChR), which help the body’s nerves and muscles communicate.
In the topline data announcement from the trial, which met its primary endpoint, Argenx noted that Vyvgart—currently approved in the roughly 80% of gMG patients who are seropositive—helped a wide pool of seronegative patients achieve “statistically significant and clinically meaningful” improvements to their scores on the Myasthenia Gravis Activities of Daily Living (MG-ADL) test, a common metric of gMG symptoms.
The drug appeared safe and well tolerated, too, with no new safety concerns cropping up during the trial, Argenx said in its press release.
In turn, the Dutch drugmaker says it plans to submit Vyvgart for approval to the FDA by the end of the year across all three subtypes of seronegative gMG, which are known as MuSK-positive, LRP4-positive and triple seronegative. Argenx added that it plans to unveil detailed results from the ADAPT SERON trial at an upcoming medical conference.
If Argenx wins the seronegative gMG label it’s hoping for, Vyvgart would boast the “broadest label of all FcRn antagonists approved in gMG,” analysts at William Blair wrote in a Monday note to clients. The seronegative nod could add around 11,000 new patients to Vyvgart’s current U.S. prescribing pool, the analysts added.
Argenx won its first-ever approval when the FDA signed off on Vyvgart in adult gMG patients who test positive for AChR antibodies back in December of 2021. The green light also marked the first FDA nod for a neonatal Fc receptor (FcRn) inhibitor.
From the jump, the company has touted Vyvgart’s potential to tackle a wide range of autoimmune diseases, while continuing to prioritize its gMG niche in parallel.
In the base gMG indication, Argenx in June of 2023 won an FDA nod for a subcutaneous formulation of the drug known as Vyvgart Hytrulo. The medicine is now also approved in the U.S. to treat the rare peripheral nervous system disease, chronic inflammatory demyelinating polyneuropathy (CIDP).
The ADAPT SERON trial in seronegative patients specifically assessed intravenous Vyvgart.
Although myasthenia gravis is a rare disease, affecting an estimated 75,000 to 100,000 people in the U.S., the treatment space has become increasingly crowded in recent years.
Just a few months after Argenx’s flagship Vyvgart nod, AstraZeneca’s Soliris successor Ultomiris picked up an FDA approval in gMG. Subsequently, UCB’s Rystiggo (rozanolixizumab) landed a 2023 U.S. green light in gMG, both for AChR antibody- and MuSK antibody-positive patients.
As of late April, Johnson & Johnson has joined the fray, too, thanks to FDA sign off on nipocalimab, now marketed under the brand name Imaavy. That drug's approval covers its use in patients ages 12 and older who have detectable antibodies against AChR or MuSK. At the time of the nod, J&J touted Imaavy’s label as covering the “broadest population of people living with gMG.”