Abivax stock fell as much as 40% on Tuesday after the French biotech released late-stage trial data for its ulcerative colitis drug that showed strong efficacy results alongside cancer cases in the higher-dose group, rattling investors and prompting an analyst downgrade.
In the 44-week maintenance study, patients on either the 25 mg or 50 mg dose of obefazimod reached clinical remission at rates just above 51%, against a placebo rate of 10.4% — putting the placebo-adjusted remission figure at roughly 40% across both doses, the company said.
All of the notable malignancies appeared in patients taking the higher dose. Among them were individual cases of prostate cancer, breast cancer, and colonic dysplasia — none of which investigators linked to the treatment. The 50 mg group also produced four skin cancer diagnoses; Abivax said two of those patients had a pre-existing history of skin cancer, while the remaining two cases were characterized as not or unlikely related to the drug.
Citing the cancer signal as something that "complicates matters," Jefferies analyst Faisal Khurshid moved his rating on Abivax to Hold from Buy and reduced his price target to $90 from $160, according to Yahoo Finance. With no significant data readouts anticipated in the coming year, Khurshid cautioned that the uncertainty surrounding the malignancies was unlikely to fade quickly from investors' minds, according to Bloomberg.
Several other analysts pushed back on the bearish read. Stifel's Damien Choplain argued in a note that strong efficacy results put the malignancy concern in context, calling it "a potential labelling overhang rather than evidence of a clear causal safety risk," according to CNBC. At Van Lanschot Kempen, analysts framed the cancer cases as "more as noise than a true malignancy risk," according to Bloomberg, while Citizens lifted its price target to $187 from $131 and kept an Outperform rating on the stock, according to Yahoo Finance.
Before Tuesday's selloff, Abivax shares had surged nearly 1,700% over 2025, fueled by deal speculation and confidence in the drug's prospects. Van Lanschot Kempen analysts had flagged Eli Lilly $LLY, AstraZeneca $AZN, Takeda Pharmaceutical, and Pfizer $PFE as companies that might pursue the biotech, Bloomberg reported.
The company confirmed it still plans to seek FDA approval later this year and aims to launch the drug commercially in 2027. Full trial results are expected in October, and analysts believe potential buyers will wait for this data before starting deal talks.
The rate of cancer cases seen in the trial falls squarely within what one would anticipate given the underlying patient population, according to David Rubin, who leads the inflammatory bowel disease center at the University of Chicago Medicine, per Fierce Biotech.