New York, Jan 5, 2026, 15:30 EST — Regular session
- U.S.-listed ARGX shares slid after argenx mapped out a CEO transition tied to a May shareholder vote.
- COO Karen Massey is set to take over as CEO; co-founder Tim Van Hauwermeiren is slated to become board chair.
- Investors are looking ahead to a Jan. 12 preliminary fourth-quarter update and the Feb. 26 full-year report.
Shares of argenx fell about 5% on Monday after the immunology drugmaker said Chief Operating Officer Karen Massey will succeed co-founder Tim Van Hauwermeiren as CEO, with Van Hauwermeiren set to become board chairman pending a shareholder vote on May 6. The stock was down 5% at $797.94 in afternoon trading. 1
The CEO handover matters because argenx is priced like a growth company that still has to prove it can widen its flagship franchise while keeping a costly pipeline on track. Any hint of a change in risk appetite can move a stock that has become a bellwether for large-cap biotech momentum.
The next near-term catalysts are close. Argenx has scheduled a preliminary key fourth-quarter 2025 financial update for Jan. 12, followed by full-year and fourth-quarter 2025 results on Feb. 26. 2
The leadership plan keeps the top two executives in place through a transition period. Massey would move from COO to CEO and executive director, while Van Hauwermeiren shifts to a non-executive role as chairman, succeeding outgoing chair Peter Verhaeghe.
Investors have linked argenx’s valuation to Vyvgart, its antibody-targeting therapy used in autoimmune diseases. The drug is part of a class designed to lower levels of IgG antibodies — proteins that can drive disease when the immune system turns on the body.
In a note cited by BioPharma Dive, Stifel analyst Alex Thompson said argenx “is in a position of strength,” with Vyvgart on track for more than $4 billion in 2025 revenue and “sustainable profitability and a strong balance sheet.” 3
The company also lodged the announcement with U.S. regulators on Monday in a Form 6-K filing. 4
For traders, the immediate question is whether management uses the Jan. 12 update to steady expectations on Vyvgart demand and spending as the company moves toward its next strategic phase. Any new detail on commercial execution, pricing and pipeline timelines could reset the tone into February’s report.
But the succession plan also introduces a clear risk: leadership changes can rattle investors even when they are planned, particularly in drug developers where growth depends on flawless execution and clinical readouts. If Vyvgart growth slows or late-stage programs stumble, the stock’s premium multiple could come under sharper pressure.
