Abivax to Present Data on Obefazimod at Digestive Disease Week^®

Presentations Highlight Comprehensive Efficacy, Safety, and Patient-Reported Outcomes from the Phase 3 ABTECT Program and Preclinical Anti-Fibrotic Models in Inflammatory Bowel Disease

PARIS, France – April 22, 2026 – 10:05 pm CEST – 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 nine scientific abstracts on obefazimod, its lead drug candidate for the treatment of moderately to severely active ulcerative colitis (UC), will be presented at the 2026 Digestive Disease Week (DDW) taking place May 2-5, 2026 in Chicago, IL. These presentations will highlight data from the Phase 3 ABTECT program, including efficacy, safety, and patient-reported outcomes, along with preclinical anti-fibrotic activity in two preclinical fibrosis models.

Fabio Cataldi, MD, Chief Medical Officer of Abivax, said: "The data being presented at this conference reinforce our confidence in obefazimod as a meaningful advancement for patients living with ulcerative colitis. From histologic and endoscopic outcomes to patient-reported improvements in fatigue and quality of life, these abstracts paint a comprehensive picture of a therapy with potential to address what matters most to patients and clinicians alike. We continue to be encouraged by the findings across the spectrum of disease severity and line of therapy."

Marc de Garidel, MBA, Chief Executive Officer of Abivax, added: "Our presence at DDW with nine abstracts highlights the depth and growing strength of the obefazimod dataset we are building in inflammatory bowel disease. These findings contribute to a more comprehensive understanding of its potential and support our ongoing efforts to bring meaningful innovation to patients."

Visit the publications page of our website to view the presentations after the conclusion of the meeting.

Obefazimod Data to be Presented:

Date & Time	Session	Abstract #	Title	Presenter
Oral Presentation
Mon, May 4 10:00-10:15	Controlled Clinical Trials 1	4470489	Impact of obefazimod treatment on histologic and combined histologic-endoscopic outcomes in patients with moderately to severely active UC: results from the ABTECT-1 and ABTECT-2 phase 3, double-blind, placebo-controlled induction trials	Prof. Fernando Magro, MD, PhD Head of the Department of Clinical Pharmacology and Professor of Pharmacology and Therapeutics at University Hospital São João in Porto, Portugal
Poster Presentation
Mon, May 4 12:30-1:30	Controlled Clinical Trials of IBD Treatment	Mo1513	Early symptomatic improvement with obefazimod in patients with moderately to severely active UC: pooled results from the ABTECT-1 and ABTECT-2 phase 3, double-blind, placebo-controlled induction trials	Prof. Marla Dubinsky, MD Professor of Pediatrics and Medicine, Chief, Division of Pediatric Gastroenterology and Nutrition
Mon, May 4 12:30-1:30	Controlled Clinical Trials of IBD Treatment	Mo1533	Efficacy and safety of obefazimod in an elderly population with moderately to severely active UC: week 8 results from the ABTECT-1 and ABTECT-2 phase 3, double-blind, placebo-controlled induction trials	Andres J Yarur, MD Associate Professor of Medicine, Cedars-Sinai Medical Center
Mon, May 4 12:30-1:30	Controlled Clinical Trials of IBD Treatment	Mo1522	Efficacy of obefazimod in patients with moderately to severely active ulcerative colitis: results in subgroups of prior inadequate response to advanced therapy (AT-IR) including or excluding patients with prior JAK-IR from ABTECT phase 3 induction trials	Prof. Bruce E Sands, MD, MS Professor of Medicine, Icahn School of Medicine at Mount Sinai
Mon, May 4 12:30-1:30	Controlled Clinical Trials of IBD Treatment	Mo1525	Integrated summary of safety of obefazimod in phase 3 ABTECT induction trials	Prof. Bruce E Sands, MD, MS Professor of Medicine, Icahn School of Medicine at Mount Sinai
Mon, May 4 12:30-1:30	Quality of Life and Psychosocial Outcomes	Mo1677	Improvements in patient-reported fatigue among patients with moderately to severely active UC treated with obefazimod: pooled results from the 8-week ABTECT-1 and ABTECT-2 phase 3 double-blind, placebo-controlled induction trials	Prof. Marla Dubinsky, MD Professor of Pediatrics and Medicine, Chief, Division of Pediatric Gastroenterology and Nutrition
Mon, May 4 12:30-1:30	Quality of Life and Psychosocial Outcomes	Mo1667	Improvements in patient-reported, disease-specific and overall quality-of-life among patients with moderately to severely active UC treated with obefazimod: pooled results from the 8-week ABTECT-1 and ABTECT-2 phase 3 induction trials	Prof. Bruce E Sands, MD, MS Professor of Medicine, Icahn School of Medicine at Mount Sinai
Tue, May 5 12:30-1:30	Mechanisms of IBD Therapeutics	Tu1433	Obefazimod shows first evidence of dual anti-inflammatory and anti-fibrotic activity in murine in vivo and human in vitro models	Prof. Silvio Danese, MD, PhD Director of Gastroenterology and Gastrointestinal Endoscopy Unit at IRCCS San. Raffaele Hospital
Tue, May 5 12:30-1:30	Mechanisms of IBD Therapeutics	Tu1449	Obefazimod enhances mir-124 expression in blood and colon tissue and reduces the key inflammatory cytokines IL-17A and IL-6 in serum of patients with moderate-to-severely active UC: results from the phase 3 ABTECT induction trials	Parambir S Dulai, MD Associate Professor, Feinberg School of Medicine at Northwestern University

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:

Patrick Malloy

SVP, Investor Relations

Abivax SA

patrick.malloy@abivax.com

+1 847 987 4878

Media Contact:

LifeSci Communications

Karissa Baltz, Ph.D.

Associate Director

LSC_ABIVAX@lifescicomms.com

FORWARD-LOOKING STATEMENTS

This press release contains forward-looking statements, forecasts and estimates, including those relating to the Company's business. Words such as "anticipate," "expect," "on track," "potential," "will" and variations of such words and similar expressions are intended to identify forward-looking statements. These forward-looking statements include statements concerning the potential therapeutic benefit of obefazimod and other statements that are not historical fact. 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 its Annual Report on Form 20-F for the fiscal year ended December 31, 2025 filed with the U.S. Securities and Exchange Commission on March 23, 2026 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, and the availability of funding sufficient for the Company's foreseeable and unforeseeable operating expenses and capital expenditure requirements. 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 made 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 for 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.

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260422_Abivax at DDW 2026

Abivax to Present Data on Obefazimod at Digestive Disease Week®