ABIVAX / FR0012333284

PARIS, France, July 24, 2025 – 07:30 a.m. (CEST) – Abivax SA (Euronext Paris: FR0012333284 – ABVX) (“Abivax” or the “Company”), a clinical-stage biotechnology company focused on developing therapeutics that harness the body’s natural regulatory mechanisms to modulate the immune response in patients with chronic inflammatory diseases, announced today that trading of its ordinary shares on the regulated market of Euronext Paris (“Euronext Paris”) will be temporarily halted, at the Company’s request, from the opening of the market at 9:00 a.m. CEST. This trading halt takes place in the context of the previously announced public offering by the Company of its American Depositary Shares, each representing one ordinary share, €0.01 nominal value per share, of the Company, in the United States (the “Offering”), in order to allow for the confirmation of allocations to investors and the announcement of the pricing of the Offering. This suspension will be effective until a new communication is released by the Company. Trading on Euronext Paris is expected to resume today, July 24, 2025, at approximately 3:30 p.m. (CEST). *** About Abivax Abivax is a clinical-stage biotechnology company focused on developing therapeutics that harness the body’s natural regulatory mechanisms to stabilize the immune response in patients with chronic inflammatory diseases. Based in France and the United States, Abivax’s lead drug candidate, obefazimod (ABX464), is in Phase 3 clinical trials for the treatment of moderately to severely active ulcerative colitis. Contacts:

Abivax Investor Relations Patrick Malloy patrick.malloy@abivax.com +1 847 987 4878

*** Disclaimers This press release does not constitute an offer to sell or the solicitation of an offer to buy any securities of the Company, nor shall there be any sale of such securities, in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.