ABIVAX

Legal Proceedings Report • May 8, 2024

Abivax announces presentation of four abstracts for obefazimod in ulcerative colitis and preclinical colon cancer model at Digestive Disease Week 2024

PARIS, France, May 8, 2024, 8:30 a.m. CEST – Abivax SA (Euronext Paris & 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 four scientific abstracts on its lead drug candidate, obefazimod, for the treatment of moderately to severely active ulcerative colitis (UC) and in a preclinical model on colon cancer, will be presented at Digestive Disease Week (DDW) as part of scientific exchange, taking place May 18-21, 2024, in Washington D.C., U.S.

"With four abstracts accepted for presentation at DDW 2024, we look forward to our continued exchange with the IBD community around the emerging clinical profile of obefazimod," said Sheldon Sloan, M.D., M. Bioethics, Chief Medical Officer of Abivax. "We are excited to share new preclinical data showing obefazimod's impact in reducing the number of tumors in the azoxymethane (AOM)/dextran sodium sulfate (DSS) mouse model of colitis-associated cancer—data in support of obefazimod's novel mechanism of action."

For more information, visit the Abivax booth at the DDW exhibitor hall (booth #529) or see congress details on the DDW website.

Presentation Title	Session	Presenter	Presentation/	Session	Date and
			Session Number	Hall	Time (EDT)
Oral Presentation
Efficacy and safety of obefazimod in UC patients at weeks 48 and 96 of an open-label maintenance study among clinical responders at week 8 of the Phase 2b induction trial	IBD Controlled Trials II	Prof. Bruce E. Sands, M.D., M.S. Dr. Burrill B. Crohn Professor of Medicine and Chief, Dr. Henry D. Janowitz Division of Gastroenterology, Icahn School of Medicine at Mount Sinai, NY			May 21, 2024 8:00-9:30 a.m.
Poster Presentations
Obefazimod and its active metabolites ABX 464-N-Glu act by stabilizing protein protein interaction among key RNA biogenesis partners, CBC and ARS2	Cell and Molecular Biology of Gastrointestinal Disorders	Didier Scherrer, Ph.D. Chief Scientific Officer, Abivax			May 18, 2024 12:30-1:30 p.m.
Obefazimod reduces total number of tumors and high-grade adenomas in a murine colitis associated colorectal cancer model	GI Cancer Research Models: Organoids' Engineered Cell and Tissue Platforms' and Animal Models	Didier Scherrer, Ph.D. Chief Scientific Officer, Abivax			May 18, 2024 12:30-1:30 p.m.

Obefazimod data to be presented:

Efficacy of once-daily,	IBD: Controlled	Prof. Bruce E. Sands,		May 19, 2024
orally administered	Clinical Trials in	M.D., M.S.		12:30-1:30 p.m.
obefazimod in patients	Humans
with moderately to		Dr. Burrill B. Crohn
severely active UC at		Professor of Medicine
weeks 8, 48, and 96		and Chief, Dr. Henry D.
broken down by		Janowitz Division of
induction treatment dose		Gastroenterology, Icahn
		School of Medicine at
		Mount Sinai, NY

Abivax has also sponsored a Product Theater presentation titled, "An Investigational New MOA that Can Stabilize the Inflammatory Response in Ulcerative Colitis," taking place on May 20, 2024, at 2:30-3:15 p.m. EDT in room "DDW Theater 1," featuring Prof. Parambir S. Dulai, M.D., Associate Professor of Medicine in the Division of Gastroenterology and Hepatology at Northwestern University, Evanston, Illinois, U.S.

About Obefazimod

Obefazimod, Abivax's lead investigational drug candidate, is an orally administered small molecule that was demonstrated to potentially enhance the expression of a single microRNA, miR-124. Phase 2 clinical trials in patients with UC have generated positive data, resulting in the initiation of a pivotal global Phase 3 clinical trial program (ABTECT Program), with first patients enrolled in the United States in October 2022. Initiation of a Phase 2b clinical trial in Crohn's disease is expected in Q3 2024, and exploration of potential combination therapy opportunities in UC is ongoing.

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. More information on the Company is available at www.abivax.com. Follow us on LinkedIn and on X, formerly Twitter, @Abivax.

Contact:

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

Abivax Communications communications@abivax.com

FORWARD-LOOKING STATEMENTS

This press release contains forward-looking statements, forecasts and estimates, including those relating to the Company's business and financial objectives. Words such as "design," "expect," "forward," "future," "potential," "plan," "project" and variations of such words and similar expressions are intended to identify forward-looking statements. Although Abivax's management believes that the expectations reflected in such forward-looking statements are reasonable, investors are cautioned that forward-looking information and statements are subject to various risks, contingencies and uncertainties, many of which are difficult to predict and generally beyond the control of Abivax, that could cause actual results and developments to differ materially from those expressed in, or implied or projected by, the forward-looking information and statements. A description of these risks, contingencies and uncertainties can be found in the documents filed by the Company with the French Autorité des Marchés Financiers pursuant to its legal obligations including its universal registration document (Document d'Enregistrement Universel) and in our Annual Report on Form 20-F filed with the U.S. Securities and Exchange Commission on April 5, 2024 under the caption "Risk Factors." These risks, contingencies and uncertainties include, among other things, the uncertainties inherent in research and development, future clinical data

and analysis, decisions by regulatory authorities, such as the FDA or the EMA, regarding whether and when to approve any drug candidate, as well as their decisions regarding labelling and other matters that could affect the availability or commercial potential of such product candidates. Special consideration should be given to the potential hurdles of clinical and pharmaceutical development including further assessment by the company and regulatory agencies and IRBs/ethics committees following the assessment of preclinical, pharmacokinetic, carcinogenicity, toxicity, CMC and clinical data. Furthermore, these forward-looking statements, forecasts and estimates are only as of the date of this press release. Readers are cautioned not to place undue reliance on these forward-looking statements. Abivax disclaims any obligation to update these forward-looking statements, forecasts or estimates to reflect any subsequent changes that the Company becomes aware of, except as required by law. Information about pharmaceutical products (including products currently in development) that is included in this press release is not intended to constitute an advertisement. This press release is for information purposes only, and the information contained herein does not constitute either an offer to sell, or the solicitation of an offer to purchase or subscribe securities of the Company in any jurisdiction. Similarly, it does not give and should not be treated as giving investment advice. It has no connection with the investment objectives, financial situation or specific needs of any recipient. It should not be regarded by recipients as a substitute for exercise of their own judgment. All opinions expressed herein are subject to change without notice. The distribution of this document may be restricted by law in certain jurisdictions. Persons into whose possession this document comes are required to inform themselves about and to observe any such restrictions.