Bristol-Myers Squibb Co. shares rose nearly 8 percent Monday after a media report said the U.S. company could be bought by French drugmaker Sanofi-Aventis SA.
A pre-merger memorandum was signed last week and the deal could be finalized by September, weekly La Lettre de l'Expansion reported, though it did not cite sources.
Sanofi-Aventis and Bristol-Myers both declined to comment.
Shares of Bristol-Myers Squibb traded in Frankfurt jumped 7.6 percent to euro21.68 (US$28.01), and nearly 5 percent to US$27.50 (euro21.30) in pre-market U.S. trading. Shares of Sanofi Aventis slipped 1.1 percent to euro69.15 (US$89.35) in Paris.
Sanofi and Bristol-Myers already cooperate on selling branded Plavix, a blood thinner that is the world's second best-selling drug.
But Dresdner Kleinwort said it sees limited strategic rationale in a merger between the companies, suggesting that it would be seen as an admission that neither company has the strength to grow organically.
Bristol-Myers Squibb reported a loss of US$134 million for the fourth-quarter last week as sales of Plavix sank and it took a hefty charge to settle government probes.
Last August, generic drug manufacturer Apotex Inc. began selling a cheaper version of Plavix after an agreement to settle a patent dispute fell apart. A judge issued an injunction forcing Apotex to stop selling the generic drug but it wasn't required to recall what was already in the market.