argenx released its first-quarter 2026 financial results and provided a business update today, which is a clear same-day event that can drive trading in the shares. The company disclosed $1.3 billion in Q1 global product net sales, representing 63% year-over-year growth, and highlighted near-term regulatory timing for its lead franchise.

The update pointed to an upcoming FDA decision with a PDUFA target action date of May 10, 2026 for VYVGART in anti-AChR antibody negative (seronegative) generalized myasthenia gravis. With the decision date close, shares can trade on positioning and perceived approval risk even if quarterly results are strong.

With no separate same-day litigation, M&A, or safety headline identified in the search results, the most concrete explanation for a -3% move is investors reacting to the earnings release contents and outlook details (including what was or wasn’t said on guidance and commercial momentum) and short-term de-risking ahead of the May 10 regulatory event.