Europe's best-performing blue-chip stock in 2025 is widely expected to be bought by a larger peer, in a deal analysts say could be worth as much as $23 billion.Abivax, the French clinical-stage biotech company developing a treatment for ulcerative colitis and Crohn's disease, saw shares rocket 1,681% last year, far outpacing the Stoxx 600 index's second-best performing stock, mining company Fresnillo, which rose 453%.Now, the big question for analysts seems to be when, not if, Abivax announces a deal.The st ...