Abivax slides on phase 3 data in ulcerative colitis

Shares in French biotech Abivax tumbled more than 30% today, after it announced phase 3 data with ulcerative colitis (UC) candidate obefazimod that showed strong efficacy, but also cases of cancer that unnerved investors.

The Paris-based company – which has been the subject of speculation about a rumoured $17.5 billion takeover bid from Eli Lilly – revealed that obefazimod achieved a 40% improvement in clinical remission rates compared to placebo at 44 weeks when used as maintenance therapy in the ABTECT trial involving people living with moderately to severely active UC.

The trial enrolled patients from Abivax's ABTECT-1 and ABTECT-2 trials of obefazimod as induction therapy for UC in this hard-to-treat patient population, which showed an impressive placebo-adjusted remission rate of 19.3% after eight weeks, and the results have been highly anticipated as it has been anticipated that patients would require longer treatment to achieve optimal results.

The strong efficacy result for the potentially first-in-class oral miR-124 enhancer has been undermined, however, by the finding that there were cases of prostate, breast, and skin cancers among patients taking obefazimod, as well as a case of colonic dysplasia, abnormal-looking cells that can be a precursor to cancer.

Abivax has said it believes the cancer cases were unrelated to the treatment and do not represent a safety signal – one of the skin cancer cases was in a patient with a history of the disease, and colonic dysplasia is also seen as a consequence of inflammatory bowel disease, for example – but that assertion did not appear to reassure investors who seem to have been banking on a clean safety profile.

Analysts at Leerink Partners were impressed with the data, with calling it a "best-case" outcome with the best remission rates ever reported in a placebo-controlled pivotal UC study, while Citizens JMP Securities' Jason Butler said the result had exceeded his expectations, combining strong efficacy with a compelling safety profile. Jefferies was a little more cautious, calling the cancer cases an "overhang" that could weigh on the stock.

ABTECT met all key secondary endpoints, including endoscopic improvement, endoscopic remission, corticosteroid-free clinical remission and sustained clinical remission, and was "generally well tolerated," according to Abivax, which now plans to file obefazimod for approval towards the end of this year. Meanwhile, topline results from a phase 2b induction trial in Crohn’s disease are expected mid-year 2027.

The company has previously said it wants to secure a partner to bring obefazimod to international markets, and the readout has reignited chatter about the possibility of a takeover play, with AstraZeneca another potential suitor mentioned in dispatches.

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