Abivax's stock plunged in early European trading, falling over 32% by 07:34 GMT, after the company reported late-stage data for obefazimod, an investigational oral treatment for ulcerative colitis. The clinical readout delivered remission rates that outperformed expectations but was clouded by a handful of malignancy events noted in the trial report.
The randomised 44-week study showed approximately half of patients treated with obefazimod achieved clinical remission. Specifically, 50.8% of patients on the 25 milligram dose and 51.3% of those on the 50 milligram dose reached remission, compared with 10.4% in the placebo arm. These headline efficacy figures came in well above what analysts had anticipated and were described as exceeding the performance of currently available therapies.
Overall tolerability across the trial was described as broad, with obefazimod generally well tolerated during the course of the study. Nevertheless, the trial safety appendix contained several malignancy events. Those cases were characterised in the report as rare and scattered and were assessed as unrelated to the investigational treatment. Despite those determinations, the presence of the events contributed to investor concern and a marked drop in the company's share price.
Analysts from Stifel, led by Damien Choplain, said the results were "clearly above expectations and outperforming current therapies, confirming the differentiated profile of obefazimod." At the same time, they noted the malignancy events had "introduced uncertainty and put the share price under pressure." The analysts further wrote that, while the malignancy signal "cannot be ignored," they viewed it as "a potential labelling overhang rather than evidence of a clear causal safety risk."
The market reaction highlighted the sensitivity of biotech equities to safety signals, even when efficacy data are strong and adverse events are considered unrelated to treatment. In this case, the coexistence of markedly positive efficacy outcomes and isolated safety concerns produced a sharp reassessment by investors that materially affected the company's trading levels in early European hours.
What the data showed
- Study duration: 44 weeks.
- Obefazimod remission rates: 50.8% (25 mg) and 51.3% (50 mg).
- Placebo remission rate: 10.4%.
- Safety: broadly well tolerated; a small number of malignancy events reported and judged unrelated to treatment.
Market impact
- Paris-listed shares fell more than 32% by 07:34 GMT in early European trading.
The information presented in this article is drawn directly from the reported clinical results and market reaction. Where statements from analysts are included, they reflect the quotes provided in the trial commentary and follow-up analyst note.