Jefferies downgraded the French biotech to Hold and cut its price target nearly in half, warning the cancer overhang won't resolve quickly

Abivax said its experimental treatment for ulcerative colitis showed significant efficacy in a closely watched trial, but shares of the company tanked on safety concerns.

A handful of cancer cases reported among treatment recipients overshadowed efficacy results analysts described as “best-in-disease” and sent shares down more than 30%.