Abivax’s Phase 3 Abtect maintenance trial of obefazimod (miR-124 enhancer) in ulcerative colitis reported strong efficacy, but a small number of cancer cases led to a sharp stock drop and intensified scrutiny of the benefit–risk profile. In the maintenance study of 580 patients, the primary endpoint of clinical remission at week 44 was met with 25 mg and 50 mg doses. The reported remission rates were 50.8% and 51.3% respectively versus 10.4% with placebo, alongside key secondary endpoint improvements. However, Wall Street reaction focused on three malignancy events outside non-melanoma skin cancer in the 50 mg cohort—reported as one prostate cancer, one breast cancer, and one case of colonic dysplasia—while none were observed in the 25 mg or placebo groups. The mixed response illustrates how oncology-adjacent safety signals can overwhelm even “best-in-disease” efficacy readouts, particularly when long-term monitoring questions remain for novel immunomodulatory mechanisms.