Argenx halts Vyvgart trial in Sjögren's, shares fall 14%

Argenx makes Vyvgart, an approved treatment for a handful of autoimmune diseases. On Thursday, the company said it was stopping a late-stage trial testing Vyvgart in a new one. The target was Sjögren's disease, which damages the glands that make tears and saliva. An independent panel reviewing early data found the drug was unlikely to beat a placebo. Argenx shares fell more than 14% on the news.

Sjögren's disease was supposed to be Vyvgart's next big expansion. It was a chance to sell the drug to a whole new group of patients. Losing that chance removes what analysts had called the drug's next blockbuster opportunity. Argenx didn't release full data, so nobody outside the company knows exactly how close Vyvgart came to working. The same announcement included a bright spot. A different Argenx drug, acquired through its $2.2 billion purchase of Forte Biosciences, succeeded in a mid-stage celiac disease trial.

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Does one failed trial change how doctors and investors see Vyvgart's future? Probably not by itself. Vyvgart still works for the diseases it's approved to treat, and Argenx has other drugs in its pipeline. But the setback is a reminder. A drug approved for one autoimmune disease doesn't automatically work for another. That's true even when the underlying biology looks similar on paper.