Abivax’s Phase 3 ulcerative colitis maintenance readout showed strong efficacy, but the stock moved sharply lower after malignancy cases emerged among treatment recipients. In the Abtect trial, obefazimod met key endpoints including clinical remission at week 44, but investors focused on three cancer events outside non-melanoma skin cancer in the 50 mg cohort. Abivax reported that remission rates were substantially higher than placebo, and analysts noted the results as among the strongest long-term maintenance data in the UC space. Still, the malignancy signals shifted attention to the benefit-risk profile and potential impact on future regulatory discussions. The update adds to investor scrutiny that can follow “best-in-disease” efficacy claims when safety concerns surface late in clinical development.