Abivax Shares Plunge 40% After Phase 3 Data Reveal Cancer Cases at 50 mg Dose
ABVX•Abivax’s Phase 3 ABTECT maintenance study in ulcerative colitis showed obefazimod achieved 50.8% and 51.3% remission rates versus 10.4% on placebo in 44 weeks. Scattered cancer cases in the 50 mg cohort—prostate, breast, colonic dysplasia and four non-melanoma skin cancers—sparked a 40% share plunge, erasing billions in market value.
1. Phase 3 ABTECT Study Results
The global 44-week ABTECT maintenance study evaluated obefazimod in moderately to severely active ulcerative colitis patients, many refractory to advanced biologics. Clinical remission rates reached 50.8% at 25 mg and 51.3% at 50 mg once daily, compared with 10.4% for placebo, yielding roughly a 40% placebo-adjusted benefit.
2. Safety Findings in High-Dose Arm
In the 50 mg cohort, investigators identified individual cases of prostate cancer, breast cancer and colonic dysplasia, plus four non-melanoma skin cancers. These findings, concentrated exclusively in the high-dose group, raised immediate safety concerns despite no apparent dose–response trend in the lower 25 mg arm.
3. Stock Market Reaction
Shares in Paris and New York tumbled as much as 40%, collapsing to €66.10 and wiping out billions in market capitalization. The selloff reversed a nearly 1,700% rally over the prior year driven by takeover speculation and positive early-stage data.
4. Company Response and Outlook
Abivax leadership and clinical heads stated no evidence links obefazimod to the malignancies, noting colonic dysplasia is a known ulcerative colitis risk and that skin cancer patients had prior histories and older ages. The company is reviewing the safety data and planning further analyses before discussing next steps.
