Abivax (NASDAQ:ABVX) experienced a significant surge in its American Depositary Shares (ADS) during after-hours trading on Tuesday, jumping 29.49% to $124.50 as of 7 p.m. ET. The move came after the company released expanded safety data from its ABTECT maintenance study for obefazimod, its lead candidate for ulcerative colitis. This late-breaking news is set to influence trading on Euronext Paris when the market opens Wednesday.
The after-hours rally added approximately $2.26 billion to Abivax's equity value, based on 79.78 million shares outstanding. In contrast, the company's ordinary shares on Euronext Paris closed Tuesday at €83.30, down 1.42%, before the data release. The Paris session ended at 5:30 p.m. local time, and the company issued its press release at 10:05 p.m. CEST, after both European and U.S. markets had closed.
The safety data addressed previous investor concerns about potential cancer risks associated with obefazimod. Abivax reported that the integrated safety set from Phase 2 and Phase 3 ulcerative colitis trials included 1,704 patient-years of exposure. Malignancy rates were in line with expected background rates for ulcerative colitis, with 0.35 events per 100 patient-years for all-active arms (excluding non-melanoma skin cancer), compared to a background range of 0.30-0.70. Non-melanoma skin cancer rates were 0.59 events per 100 patient-years, versus background rates of 0.70-1.40.
CEO Marc de Garidel stated that the broader safety data "strengthens our confidence" in obefazimod's long-term outlook. Dr. Remo Pannacione, a professor of medicine and IBD Clinic director at the University of Calgary, noted that the observed cancer and skin-cancer rates matched expected background rates. Additionally, Keith Fournier, Abivax's head of regulatory affairs, told Reuters that four independent former senior FDA leaders deemed it "highly unlikely" the agency would impose its strictest boxed warning, a key factor for investors concerned about label restrictions.
The stock had been under pressure since June 1, when top-line maintenance data showed strong remission rates—50.8% on 25 mg and 51.3% on 50 mg by week 44, versus 10.4% for placebo—but three cancer-linked cases in the 50 mg group weighed on shares. Jefferies called those cases a break in their investment thesis, while Yale Jen at Laidlaw & Company labeled the market reaction an "overreaction" and described the data as a "homerun."
Abivax's balance sheet remains a focus. As of March 31, the company reported €491.6 million in cash, cash equivalents, and short-term investments, sufficient to fund operations into the fourth quarter of 2027. Research and development costs for the first quarter were €49.5 million, with 94.5% allocated to obefazimod. In May, Abivax bought back all outstanding royalty certificates for $90 million, using half cash and half ADSs, resulting in a roughly 0.5% dilution.
Looking ahead, Chief Medical Officer Fabio Cataldi confirmed the company remains "on track" for a New Drug Application (NDA) filing. The half-year report is due on September 21, followed by a planned U.S. filing for obefazimod in the fourth quarter. Phase 2b topline data for Crohn's disease are expected by mid-2027. The after-hours surge positions Abivax for a potential gap-up in Paris trading, with the ADS still 16.3% below its 52-week high of $148.83 but 11.6% above the $111.57 per ADS price used in May's royalty-certificate deal.
