UPDATE 1-Apotex to appeal court ruling on Plavix patent

(Adds Apotex, patent lawyer comments, details, background)

By Bill Berkrot

NEW YORK, June 19 (Reuters) - Canadian generic drugmaker Apotex Corp. said on Tuesday it would immediately appeal a U.S. court decision that found the patent on Plavix -- the widely-used blood clot preventer sold by Bristol-Myers Squibb Co. and Sanofi-Aventis -- was valid and enforceable.

If the federal appeals court should reverse the decision by U.S. District Judge Sidney Stein in Manhattan, Apotex said it would be able to resume selling generic Plavix, known as clopidogrel, at that time. It was ordered to stop shipping the generic Plavix by Stein last August, pending his decision.

Apotex expressed confidence in its chances of prevailing on appeal, saying that the issues in the Plavix case were "extremely similar" to those in its challenge of the patent on Pfizer Inc.'s (PFE.N) blood pressure medicine Norvasc, in which Apotex lost at the circuit court level but won on appeal.

"We are unwavering in our belief that the '265' (Plavix) patent will ultimately be held invalid," Apotex Chief Executive Barry Sherman said in a statement, in which he promised to "pursue the Plavix case full bore and work relentlessly to invalidate the patent."

However, in the two most prominent recent drug patent disputes -- involving generic challenges to Eli Lilly and Co.'s (LLY.N) schizophrenia drug Zyprexa and Pfizer's cholesterol medicine Lipitor -- the big drug makers prevailed.

Apotex also cited a recent U.S. Supreme Court ruling in a technology patent case that it felt could lead the federal appeals court to look favorably on its Plavix case.

In that case brought by Canadian manufacturer KSR International, the Supreme Court said the courts should be more flexible in interpreting standards governing whether patents are valid or merely "obvious" combinations of previous inventions.

"Apotex is right that it's an easier job now to invalidate a patent after that ruling than it was before," said attorney Bruce Sunstein, a patent expert with the Boston-based firm of Bromberg & Sunstein.

When an apparent deal between Bristol-Myers and Apotex designed to keep generic Plavix off the market collapsed last year, a loophole allowed Apotex to briefly flood the market with several months' supply of cheaper copies of the medicine before an injunction halted generic sales.

In striking that deal, Bristol-Myers had agreed to a short period of time before it would seek any injunction halting generic sales, giving Apotex its window to ship massive amounts of the pills.

"That was an enormous blunder by Bristol," said Tom Carey, another attorney with Bromberg & Sunstein, who believes Apotex will fail to get Tuesday's ruling reversed on appeal.

Bristol-Myers has said that when all is said and done, the generic supply will have cost it roughly $2 billion in lost Plavix sales. The drug posted $6 billion in annual global sales -- $4 billion in U.S. sales -- before the Apotex generic was launched.

The companies maintain that their patent protection runs until November 2011.

Generally, when a company launches a generic that is later found to have infringed branded product patents, the generic drug producer risks having to pay damages triple the amount of the branded product's lost sales.