Abivax $ABVX drops 30% as cancer cases cloud Phase 3 UC data

Abivax $ABVX fell more than 30% after Phase 3 ulcerative-colitis data created a split between efficacy and safety interpretation. The company release reported placebo-adjusted clinical remission rates at Week 44 of 39.3% for 25 mg obefazimod and 40.3% for 50 mg, both with p<0.0001.

The market reaction centered on safety details rather than the primary endpoint. The ABTECT maintenance trial enrolled 580 responders from induction studies. Any treatment-emergent adverse event was reported in 50.0% of placebo patients, 58.0% of 25 mg patients, and 71.8% of 50 mg patients. Serious treatment-emergent adverse events were 4.2%, 2.6%, and 5.6%, respectively.

Cancer-case disclosures drove the selloff reported by CNBC. Abivax listed one prostate cancer case, one breast cancer case, and one colonic dysplasia case in the 50 mg arm, which investigators considered unrelated to treatment. Non-melanoma skin cancer cases included basal cell carcinoma and squamous cell carcinoma across placebo, 25 mg, and 50 mg groups; Abivax said two of the four 50 mg patients were deemed not or unlikely related to drug.

The regulatory clock remains explicit. Abivax said it plans to submit a New Drug Application to the FDA for obefazimod in ulcerative colitis in late Q4 2026, with Crohn's disease Phase 2b induction topline results expected in mid-2027. Investors will watch whether future congress presentations and FDA interactions change the safety debate before the NDA filing.

Not investment advice. Verify all figures with primary sources before acting.