Abivax reported strong efficacy from its Phase 3 maintenance study of obefazimod (a daily oral therapy) in ulcerative colitis, but disclosed a small number of cancer cases among treated patients that fueled immediate market concern. In the trial of 580 participants, Abivax said 44–51% of patients achieved clinical remission at 44 weeks depending on dose versus 10.4% on placebo. Analyst commentary highlighted that placebo-adjusted remission rates were among the highest seen in long-term UC studies, reinforcing the drug’s efficacy signal. However, the cancer findings introduced a safety overhang that is likely to dominate subsequent discussions with regulators and clinicians. The data set underscores the clinical development risk profile in chronic inflammatory disease trials, where long follow-up and careful adjudication drive benefit-risk assessment. The story also captured the immediate stock reaction, reflecting how efficacy breakthroughs can still be undermined by serious adverse-event questions.