The long wait for Sanofi-Aventis and Bristol-Myers Squibb to find out the fate of Plavix is over as a US court has finally upheld its patent on the blockbuster blood-thinner, a move which has restarted merger rumours.

A judge in the Southern District of New York has upheld the validity and enforceability of the firms’ US patent covering Plavix (clopidogrel), ensuring protection for the product until November 2011. Judge Sidney Stein said that the other key player in the case, the Canadian generic drugmaker Apotex, “has failed to prove by clear and convincing evidence that the Plavix patent is invalid or unenforceable'' and he issued a permanent injunction prohibiting Apotex from further infringement.

Problems initially rose when a deal between B-MS and Apotex, which was designed to keep generic Plavix off the market, collapsed last year and the latter firm sent out several months' supply of cheaper copies of clopidogrel before an injunction was issued. The fall-out cost the jobs of senior B-MS management, including the chief executive Peter Dolan.

Apotex insists it will immediately appeal this latest decision and is confident of winning. Chief executive Barry Sherman said “we are unwavering in our belief” that the Plavix patent “will ultimately be held invalid" and he promised to "pursue the Plavix case full bore and work relentlessly to invalidate” it. The Canadian firm feels the case is similar to its challenge of the patent on Pfizer’s blood pressure drug Norvasc (amlodipine), in which Apotex lost at court level but won on appeal.

However, Apotex’ confidence is not shared by analysts who are already looking to see what the consequences of the Plavix decision are and whether they will lead to Sanofi and B-MS tying the knot permanently. Such a deal seemed on the cards a few months ago but the attractiveness of such a link-up is less clear now.

The trans-Atlantic takeover would boost Paris-based Sanofi's weakened new drug pipeline and allow significant cost savings. But serious obstacles remain to any deal, analysts said, such as differences between top executives at the firms.

In March, Sanofi denied that there was a rift at the top with chairman Jean-Francois Dehecq backing a bid for B-MS, while chief executive Gerard Le Fur was thought to prefer organic growth, though this latter position may have shifted somewhat after a US Food and Drug Administration panel refused to recommend the obesity drug Acomplia (rimonabant) for approval. Regardless of the management line, investors may baulk at the asking price, thought to be in the region of $60 million.

B-MS may think independence is bliss

It is also highly debatable as to whether B-MS would welcome any takeover bid, as new drugs are performing well, notably the antipsychotic Abilify (aripiprazole), Sprycel (dasatanib) for leukaemia and Orencia (abatacept) for rheumatoid arthritis. The New York-based firm has also signed some interesting late-stage deals recently, with Pfizer for the anticoagulant apixaban and a diabetes link-up with AstraZeneca.

Viren Mehta, at healthcare investment firm Mehta Partners noted that “the 10% risk that Sanofi and B-MS might have lost this case has now dried to dust, and now strengthens the opportunity for management at B-MS to reassess an independent future". That said, even if Sanofi does not make a bid, other firms may well do, and GlaxoSmithKline and Pfizer have been mentioned as prospective buyers.

Ixabepilone gets priority review

B-MS' day just kept getting better as the firm announced that the FDA has granted priority review to the company's experimental breast cancer drug, ixabepilone.

The drugmaker is seeking approval for the compound, which is an epothilone B analogue, as a monotherapy to treat patients with metastatic or locally advanced breast cancer who have failed other chemotherapies, including an anthracycline, a taxane or Roche's Xeloda (capecitabine), and in combination with Xeloda. B-MS said it is also testing ixabepilone for lung cancer and for tumours of the pancreas, kidney, lymph system, ovaries and prostate.