Abivax reported positive Phase 3 maintenance efficacy for obefazimod in ulcerative colitis, but said a small number of malignancies in the higher-dose cohort triggered major market fallout. In the Abtect maintenance trial, obefazimod achieved clinical remission in 50.8% of patients in the 25-mg group and 51.3% in the 50-mg group versus 10.4% on placebo at week 44. The company framed the results as “landmark” for long-term disease control. However, investors focused on three cancer cases other than non-melanoma skin cancer reported in the 50-mg cohort—one prostate cancer noted during the induction period, one breast cancer, and one instance of colonic dysplasia—while no cases were reported in the 25-mg or placebo groups. Abivax’s share price fell sharply following the disclosure.