Belgian biotech firm Argenx SE (ARGX.US) saw its shares plummet to their lowest level in seven months after announcing the termination of late-stage trials for its experimental drug targeting an autoimmune eye disorder. The company stated that Efgartigimod (branded as Vyvgart), which was being evaluated for moderate-to-severe thyroid eye disease in adults, would be discontinued based on recommendations from an independent data monitoring committee.
Argenx shares tumbled as much as 9.7% in Brussels trading, marking the steepest decline since May 8. In pre-market U.S. trading, the stock was down 5.31% at the time of reporting. The trial halt deals a blow to the company’s goal of treating 50,000 patients by 2030.
Argenx expects to release results from four other late-stage clinical trials next year for various autoimmune diseases, three of which involve Vyvgart. Analyst Michael Shah noted that the termination of the thyroid eye disease trial was "unexpected," effectively excluding a potential U.S. patient pool of around 100,000. He added that this places additional pressure on the "critical data readouts" expected in 2026 for ocular myasthenia gravis, myositis, and primary immune thrombocytopenia.
The independent data monitoring committee conducted a futility analysis based on unblinded data from patients who completed 24 weeks of treatment in the late-stage study. Argenx plans to share the study data at future medical conferences. According to a Monday statement, the drug demonstrated a favorable safety and tolerability profile, with no new safety signals identified.
Since its Brussels listing in July 2014, Argenx shares have surged over 8,000%, with the company’s fortunes closely tied to Vyvgart—its only approved drug. The blockbuster therapy is currently authorized for generalized myasthenia gravis and chronic inflammatory demyelinating polyneuropathy, with additional approval in Japan for primary immune thrombocytopenia.
Other analysts remain optimistic about Argenx’s long-term prospects. Sebastian Vanderschelden, an analyst at Van Lanschot Kempen, wrote, "While thyroid eye disease could have added $800 million to our current peak sales estimate of $11 billion, this represents only a small portion of Vyvgart’s valuation. We view the oversold sentiment as a buying opportunity for one of Europe’s must-own biotech stocks."
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