Abivax Reports Positive ABTECT Maintenance Part 2 Results for Obefazimod, Demonstrating Meaningful Clinical Benefit in Refractory Ulcerative Colitis Patients and Strengthening the Phase 3 Maintenance Safety Database

Abivax Reports Positive ABTECT Maintenance Part 2 Results for Obefazimod, Demonstrating Meaningful Clinical Benefit in Refractory Ulcerative Colitis Patients and Strengthening the Phase 3 Maintenance Safety Database

• Obefazimod delivered meaningful clinical benefit in a highly refractory ulcerative colitis (“UC”) population, with 37.2% of induction non-responders achieving clinical remission and 34.5% achieving endoscopic remission at Week 44 following continued 50 mg treatment
• Dose escalation to obefazimod 50 mg recaptured clinical remission in 45.5% of patients who relapsed during ABTECT Maintenance Part 1, supporting a practical dose-escalation strategy for regaining and sustaining disease control over time
• Across the integrated Phase 2 and Phase 3 UC program (1,704 patient-years of exposure), exposure-adjusted incidence rates (“EAIRs”) for malignancies excluding non-melanoma skin cancer (“NMSC”) were 0.35 and 0.64 events per 100 patient-years (“PYs”), and for NMSC were 0.59 and 0.64 events per 100 PYs in the all-active combined (50 mg + 25 mg) and 50 mg cohorts respectively, all consistent with expected UC background rates
• In ABTECT Maintenance Part 2, EAIRs for malignancies excluding NMSC were 0.48 and 0.69 events per 100 PYs, and for NMSC were 0.95 and 0.69 events per 100 PYs, in the all-active combined and 50 mg cohorts respectively, all consistent with expected UC background rates
• Abivax to host a conference call and webcast today at 4:30 p.m. EDT (10:30 p.m. CEST) to discuss the results

PARIS, France – June 29, 2026 – 10:05 pm CEST – Abivax SA (Euronext Paris: FR0012333284 – ABVX / 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 topline results from ABTECT Maintenance Part 2, the supplemental portion of its Phase 3 UC maintenance program evaluating obefazimod, its investigational oral miR-124 enhancer, in adults with moderately to severely active UC.

Part 2 of the Phase 3 Maintenance trial enrolled patients who either did not achieve clinical response following induction treatment or who experienced disease relapse during the re-randomized maintenance trial (Part 1), expanding both the efficacy and safety results in a more refractory patient population than the registrational maintenance cohort.

The additional safety results generated through Part 2 expand the Phase 3 maintenance database and provide important context for interpreting the safety findings reported following the Maintenance Part 1 readout. The integrated post-hoc analyses presented today include the new Part 2 results, the combined Phase 3 maintenance program, and the broader Phase 2 and Phase 3 clinical development program.

Marc de Garidel, MBA, Chief Executive Officer of Abivax, said: “The results from ABTECT Maintenance Part 2 represent an important milestone in the clinical development of obefazimod, demonstrating meaningful clinical benefit in patients with highly refractory ulcerative colitis while substantially expanding our long-term safety database. Together with the unprecedented efficacy results from the ABTECT Phase 3 program, these findings build a comprehensive body of evidence supporting the potential of obefazimod to address significant unmet needs across a broad spectrum of patients living with ulcerative colitis.

“The expanded cumulative safety data further strengthens our confidence in the long-term safety profile of obefazimod and reinforces the favorable benefit-risk profile for our program as we prepare for our planned NDA submission later this year. We believe this growing body of evidence positions obefazimod, if approved, to become a paradigm defining treatment option for patients living with ulcerative colitis.”

Clinically meaningful efficacy results observed in induction non-responders following additional obefazimod exposure

Among patients who failed to achieve clinical response after 8 weeks of induction, continued treatment with obefazimod resulted in clinically meaningful rates of clinical, endoscopic, and combined histologic-endoscopic endpoints at Week 44. Patients treated continuously with 50 mg obefazimod demonstrated the strongest outcomes across all endpoints, including clinical remission (37.2%), clinical response (61.5%), endoscopic improvement (48.0%), Histologic-Endoscopic Mucosal Improvement (“HEMI”) (44.6%), and endoscopic remission (34.5%). These findings suggest that a meaningful proportion of patients who do not initially respond may still derive substantial benefit from longer treatment exposure.

Learn more in the Abivax press release.