Abivax to be Added to Nasdaq Biotechnology Index

PARIS, France – December 18, 2025 – 10:05 pm CET – Abivax SA (PARIS:FR, NASDAQ:ABVX) ("Abivax" or the "Company"), 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, today announced that it will be added to the Nasdaq Biotechnology Index (NASDAQ:NBI), effective prior to market open on Monday, December 22, 2025.

Didier Blondel, Chief Financial Officer of Abivax commented: "Our inclusion in the Nasdaq Biotechnology Index marks a significant milestone for Abivax. It highlights the meaningful progress we've made as a company, particularly in advancing obefazimod through the successful Phase 3 ABTECT Induction trials for ulcerative colitis and reflects the increased visibility and perception of Abivax within the global biotechnology community."

The NBI is designed to track the performance of a set of securities listed on The Nasdaq Stock Market^® that are classified as either biotechnology or pharmaceutical companies according to the Industry Classification Benchmark. Companies in the Nasdaq Biotechnology Index must meet eligibility requirements, including minimum market capitalization, average daily trading volume and seasoning as a public company, among other criteria. The NBI is evaluated annually in December and is calculated under a modified capitalization-weighted methodology.

For more information about the NBI, visit: https://indexes.nasdaqomx.com/Index/Overview/NBI

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.

Contact:	Media Contact:
Patrick Malloy SVP, Investor Relations Abivax SA patrick.malloy@abivax.com +1 847 987 4878	LifeSci Communications Karissa Cross, Ph.D. Account Supervisor kcross@lifescicomms.com