The safety update for Vyvgart rattled argenx’s shares on Monday, a reaction that analysts at William Blair said was “overdone.”
The FDA is currently “evaluating the need for regulatory action” on argenx’s Vyvgart Hytrulo after detecting a “severe” safety signal.
The agency on Monday issued its quarterly update to the Adverse Event Reporting System, flagging the risk of severe worsening of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with Vyvgart Hytrulo. The drug, a neonatal Fc receptor blocker delivered via an injection under the skin, is approved to treat that disease as well as generalized myasthenia gravis (gMG).
The safety update triggered share volatility for argenx, which was down by as much as 8% intraday on Monday, according to analysts from William Blair. The analysts called the stock reaction “overdone” in a note to clients issued the same day. Safety considerations for Vyvgart Hytrulo, they added, are not new in the prescribing community.
“Yes, there is perceived risk of potential labeling language changes pending FDA review,” William Blair noted, “but we believe the more important aspect is clinician education on switching”—something that the company is already doing, according to the analysts.
The Vyvgart franchise—which includes Vyvgart Hytrulo and Vyvgart, the original formulation of the same drug that is infused intravenously—is argenx’s only commercial presence, but one that analysts have high hopes for. In its note on Monday, William Blair said that despite the safety flags from the FDA, Vyvgart still has “multiblockbuster potential” in CIDP and gMG.
In 2024, Vyvgart products brought in $2.2 billion. Argenx is continuing to develop its Vyvgart line with studies in other indications, such as thyroid eye disease, Sjogren’s disease, lupus nephropathy and myositis. This last indication, in particular, could open “significant opportunity” for the franchise, according to William Blair.
Still, Vyvgart’s earnings could be put at risk in coming years as the drug approaches its loss of exclusivity, which could come as early as 2033. In preparation, the biotech is advancing a pipeline of investigational therapies, anchored by the antibody empasiprubart for dermatomyositis, multifocal motor neuropathy (MMN), delayed graft function and CIDP.
William Blair sees “billion-dollar opportunities” for argenx’s pipeline, particularly for empasiprubart in MMN, the firm’s analysts wrote on Monday.
On Tuesday, argenx further deepened its pipeline, betting $1.5 billion on a partnership with Unnatural Products to develop oral macrocyclic peptides for “undruggable”—but not yet specified—disease targets.
