Euronext:ABVX

Abivax Plunges 43% Despite Strong Phase 3 Success as Cancer Concerns Rattle Investors

Shares of Abivax (NASDAQ: ABVX) plunged 43% despite reporting highly successful Phase 3 results for obefazimod in ulcerative colitis, as investors focused on several cancer cases reported in the higher-dose treatment group.

The Phase 3 ABTECT maintenance trial delivered impressive efficacy results. Both the 25 mg and 50 mg doses met the primary endpoint, with clinical remission rates of 50.8% and 51.3%, respectively, compared with 10.4% for placebo. The drug also met all key secondary endpoints, including endoscopic remission and sustained clinical remission.

However, investors appeared concerned about malignancies reported in the 50 mg treatment arm. These included individual cases of prostate cancer, breast cancer, and colonic dysplasia, along with several non-melanoma skin cancer cases. Abivax noted that investigators did not consider the cancers treatment-related, and no clustering around a specific cancer type was observed (Quartz).

The concerns prompted Jefferies to downgrade the stock to Hold from Buy and reduce its price target, citing uncertainty surrounding the cancer findings. At the same time, several analysts defended the results, arguing that the strong efficacy profile and lack of evidence linking the cancers to the drug suggest the issue may ultimately represent a labeling consideration rather than a major safety problem (Quartz).

Despite the selloff, Abivax remains on track to submit a New Drug Application to the FDA in late 2026. Management highlighted the drug's favorable overall safety profile and believes obefazimod has the potential to become an important new treatment option for ulcerative colitis.

The sharp decline reflects how sensitive biotech investors can be to potential safety concerns, even when clinical efficacy results significantly exceed expectations. Full trial data are expected later this year and will likely play a key role in determining the market's longer-term view of obefazimod.
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Author
European Investor 06-02-26