Based on new data, argenx expects to file for the expansion of Vyvgart’s label into patients with generalized myasthenia gravis who are negative for antibodies against the AChR marker—an indication William Blair analysts called the broadest option in this disease space.
Argenx’s Vyvgart significantly improved disease activity and daily life in certain patients with generalized myasthenia gravis in a Phase III study, setting the FcRn inhibitor up for a potential label expansion.
Writing to investors on Monday, William Blair analysts said that with these new data, Vyvgart “represents the first FcRN inhibitor to demonstrate statistically significant clinical efficacy in AChR seronegative gMG [generalized myasthenia gravis] patients”—the specific population that the Phase III ADAPT SERON trial focused on. If cleared for this specific indication, Vyvgart would have “the broadest label of all FcRn antagonists approved in gMG,” they added.
Argenx did not reveal specific data in its news release on Monday, noting only that Vyvgart elicited a “statistically significant and clinically meaningful improvement” in disease activity in patients with gMG who are seronegative for antibodies against the AChR marker. According to the biotech, this particular subpopulation represents about 20% of all gMG patients, a group that often experiences a heavier disease burden.
With these findings, argenx is gearing up for a supplemental application to expand Vyvgart into patients negative for antibodies against AChR, covering all three subtypes: MuSK-positive, LRP4-positive and triple seronegative patients, as per its Monday release. The company expects to make its submission by the end of the year.
If approved, Vyvgart would gain access to roughly 11,000 additional gMG patients beyond its current market, according to William Blair. Breaking into this patient population would also give Vyvgart an edge over its current competitors, including Johnson & Johnson’s Imaavy and UCB’s Rystiggo, both of which “are approved only in gMG patients with AChR-positive or MuSK-positive” disease, according to the analysts.
Infused intravenously, Vyvgart is a human IgG1 antibody fragment that treats gMG by lowering the circulating levels of IgG. The therapy was first approved in 2021 but is currently only indicated for patients who are positive for antibodies against AChR. In June 2023, argenx secured an approval for a subcutaneous formulation of Vyvgart, called Vyvgart Hytrulo, for gMG. The under-the-skin injection has also been approved for chronic inflammatory demyelinating polyneuropathy.
Last year, argenx reached more than 10,000 patients and brought in nearly $2.2 billion in sales from its Vygart line alone.
