An independent committee recommended halting the Phase 3 UNITY study of subcutaneous efgartigimod in Sjögren's disease after an interim look. A separate celiac trial of FB102 met its primary endpoint.
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Argenx issued two trial results within minutes of each other on Thursday. Investors priced only one of them.
The biotech, whose shares trade in Brussels and New York, said it will discontinue its Phase 3 UNITY study of subcutaneous efgartigimod in adults with moderate-to-severe Sjögren's disease. An independent data monitoring committee recommended stopping the trial for futility after an interim analysis, concluding that it is unable to meet its primary endpoint, a change in disease activity measured at week 48. Safety was consistent with the drug's established profile.
"We are disappointed by this outcome, most of all for people living with Sjögren's disease," said Chief Medical Officer Luc Truyen.
The market's verdict
Argenx shares fell about 18.3% to €684.80 in Brussels. Its U.S.-listed shares were indicated about 17.7% lower in thin premarket trading, against a Wednesday close of $928.44 that valued the company at about $57.7 billion. A decline of that size implies roughly $10 billion of market value erased.
The company did not release the interim efficacy data, enrollment figures or any change to its financial outlook.
Why Sjögren's mattered
Efgartigimod is approved in generalized myasthenia gravis and chronic inflammatory demyelinating polyneuropathy, and in immune thrombocytopenia in Japan. Sjögren's, an autoimmune disease that attacks moisture-producing glands, was one of the larger new indications the company was pursuing. The size of the share-price move suggests investors had assigned meaningful value to it.
The other result
The second release concerned FB102, a CD122 inhibitor argenx gained through its August acquisition of Forte. A Phase 2 trial in celiac disease met its primary endpoint, with a p-value of 0.0176, and the company plans a Phase 3 study. The drug works on a different mechanism from efgartigimod, so its result says nothing about Sjögren's. It is, however, the first clinical readout from the August deal.
Franchise Strength Versus Pipeline Risk
One reading is that the futility stop removes a large expected market from the company's growth story and raises questions about how far efgartigimod can expand beyond its approved diseases, which the share price is now reflecting.
Another reading is that the core franchise is untouched. Approved uses are unaffected, the safety profile held, and a positive Phase 2 in a new disease area adds a pipeline asset on the same day, so a fifth of the company's value may overstate what was lost.
The questions now
Any release of the interim data, and whether argenx changes guidance or commentary on other planned indications, will show how much of the Sjögren's opportunity was in expectations. The U.S. regular session will give the first full-volume read on the move.