Abivax shares tumble after obefazimod trial over cancer reports

Abivax shares declined 31% after the company reported that obefazimod met the primary and all key secondary endpoints in a Phase 3 maintenance study for ulcerative colitis, and malignancy cases were reported in the 50 mg dose group.

The ABTECT trial tested once-daily 25 mg and 50 mg doses of obefazimod in patients with moderately to severely active ulcerative colitis who had responded to induction treatment. At week 44, clinical remission rates were 50.8% in the 25 mg arm and 51.3% in the 50 mg arm, compared with a 10.4% remission rate on placebo. Abivax reported placebo-adjusted differences of 39.3 and 40.3 percentage points for the 25 mg and 50 mg doses, respectively. The company said both doses met the U.S. Food and Drug Administration primary endpoint for clinical remission.

Abivax reported that the trial met all key secondary endpoints, including endoscopic improvement, endoscopic remission, corticosteroid-free clinical remission and sustained clinical remission through 44 weeks.

On safety, Abivax disclosed malignancy cases in the 50 mg arm, listing prostate, breast and colon cancers among those events. Investigators judged the cancer cases unrelated to treatment, and the company reported no new safety signals over the 44-week maintenance period.

Analysts responded to the data with a mix of enthusiasm and caution. Thomas Smith of Leerink Partners described the outcome as a ‘best-case’ scenario, noting the high placebo-adjusted remission rates and the low placebo response. Smith assigns an Outperform rating. Other firms maintain positive views: Citizens maintains a Market Outperform rating, and Guggenheim retains a Buy rating with a $175 price target.

Abivax plans to submit a New Drug Application to the U.S. Food and Drug Administration in late 2026. Regulators will review the full dataset, including efficacy measures and the reported malignancy cases, during the review process.

Current ulcerative colitis treatments include injectable biologics and other advanced therapies. An oral maintenance option that delivers sustained remission would add another treatment choice for clinicians and patients. The ABTECT results add to Abivax’s clinical dataset while the malignancy reports remain an item for investors and regulators to examine before any potential approval.