argenx (ARGX) stock falls after the Phase 3 UNITY trial of Vyvgart in Sjögren's disease is stopped for futility, October 8, 2026

argenx (Euronext Brussels and Nasdaq: ARGX) said on Thursday, October 8, 2026 that it is stopping UNITY, its Phase 3 trial of subcutaneous efgartigimod in adults with moderate-to-severe Sjögren's disease, after the independent data monitoring committee concluded at a planned interim analysis that the study could not meet its primary endpoint. The release reached the MoveSurge news feed at 05:00:00 UTC, two hours before the Brussels open, and the shares were down 15.7% at €707.40 in Brussels by mid-morning, according to Investing.com. On Tradegate in Germany they were 17.43% lower at €685.80 at 10:44 local time, dpa-AFX reported.

The same release window carried positive Phase 2 results for FB102 in celiac disease, the antibody argenx bought with Forte Biosciences in July. Vyvgart's approved uses are not affected, and argenx reported no new safety signals in UNITY.

How the shares traded on October 8

MoveSurge has no one-minute bars for the Brussels listing this morning, so the readings below are those published by the outlets named, at the times they gave.

What the monitoring committee found

UNITY measured the change from baseline in clinESSDAI, a clinician-scored index of systemic disease activity, after 48 weeks of treatment. The trial began on January 15, 2025, enrolled more than 500 patients with a clinESSDAI of at least 6, and argenx had told investors in January 2026 to expect topline results in the second half of 2027. A futility stop means the committee looked at the data gathered so far and judged that even a full run to week 48 would not produce a statistically significant result, so the answer has come about a year early. The company will close the study, lock the database and run the full analysis to guide any further work in Sjögren's.

Efgartigimod blocks the neonatal Fc receptor, which normally recycles IgG antibodies, so it lowers the level of all IgG in the blood, including the autoantibodies that drive disease. Its approvals so far are in diseases where autoantibodies do much of the damage, such as myasthenia gravis. Sjögren's patients carry autoantibodies too, but much of the damage to the tear and salivary glands comes from immune cells infiltrating them, which made it a harder test for a drug that works by lowering IgG. The Phase 2 RHO study had shown enough of a signal on a composite responder measure to justify the larger trial, and the FDA had granted Fast Track designation.

Why a low-probability bet still took a sixth off the price

Bernstein had given UNITY a 20% chance of success and said the result was not very surprising, dpa-AFX reported. Degroof Petercam's model used 41%, and after the news it doubled its assumed chance for FB102 to 60%; KBC Securities removed Sjögren's from its model and pointed to the next readout in multifocal motor neuropathy, De Aandeelhouder reported. A 15.7% fall on an outcome these models treated as unlikely suggests investors had given Sjögren's more weight than the published estimates did. It is also the second late-stage efgartigimod programme stopped for futility in ten months, after the thyroid eye disease studies in December 2025.

argenx's trial record, 2025 to 2026

1. January 15, 2025: UNITY begins enrolling.
2. December 15, 2025: the Phase 3 UplighTED studies in thyroid eye disease are stopped for futility at an interim analysis.
3. February 26, 2026: the Phase 3 ADAPT OCULUS trial in ocular myasthenia gravis meets its primary endpoint.
4. May 8, 2026: the US label for generalized myasthenia gravis is widened to adults of every antibody type, based on ADAPT SERON.
5. August 17, 2026: the Phase 3 ALKIVIA trial in myositis meets its primary endpoint.
6. October 8, 2026: UNITY is stopped for futility, and FB102 meets its Phase 2 endpoint in celiac disease.

FB102 in celiac disease

FB102 is an antibody against CD122, part of the receptor for interleukin-2 and interleukin-15, which drive the immune cells that damage the gut lining in celiac disease. The Phase 2 trial randomized 126 patients to one of two intravenous doses or placebo during an eight-week gluten challenge. It met its primary endpoint, the change in the ratio of villus height to crypt depth at day 78 compared with placebo (p=0.0176), and the gut-lining lymphocyte count, a composite histology score and symptoms moved the same way. argenx reported no new safety signals and plans a Phase 3 trial.

The sales base the stock rests on

Vyvgart is approved for generalized myasthenia gravis and chronic inflammatory demyelinating polyneuropathy, and for immune thrombocytopenia in Japan. Global net product sales were $1,516 million in the second quarter of 2026, including a $25 million one-off in Japan, against $949 million a year earlier, and $1,298 million in the first quarter against $790 million. None of that revenue depended on Sjögren's, which was a future indication.