AstraZeneca went back to court on Wednesday to defend the U.S. patent on its multibillion-dollar cholesterol fighter Crestor in the face of an appeal by generic drugmakers.
Industry analysts believe the British company is likely to win the case, protecting exclusivity on its top-selling product in the world's biggest market until 2016, and a defeat would be a major upset.
The U.S. District Court in Delaware ruled in June 2010 that generic drugmakers who challenged the main patent on Crestor had failed to prove it was invalid because it was an obvious invention. The generic firms are appealing that decision.
The hearing is expected to last one day but the Federal Circuit's decision in the appeal case could take three to six months, according to brokerage Jefferies, which sees a 75 percent chance of AstraZeneca prevailing.
Crestor had sales of $5.7 billion in 2010, of which $2.6 billion was generated in the United States, and the medicine is forecast to reach global sales of more than $7 billion in 2015, according to estimates compiled by Thomson Reuters.
It faces increased competition from late next month, when cheap generic copies of Pfizer's Lipitor are expected to hit the U.S. market, but it remains a key driver for AstraZeneca's sales and profits.
"AstraZeneca is confident in the patents protecting Crestor and will aggressively defend the intellectual property protecting the product," a spokeswoman for the company said.
AstraZeneca has been fighting several companies seeking to sell cheap versions of Crestor. They include Mylan, Teva, Sun, Aurobindo, Par, Watson, Sandoz -- the generic division of Novartis -- and Toronto-based privately held Apotex.
The patent on Crestor, or rosuvastatin, was originally obtained by Japan's Shionogi. The generic drugmakers argued that Shionogi's legal team withheld documents from the U.S. Patent and Trademark Office in order to obtain the patent through deception, but the judge in the case last year did not buy that argument.
(Reporting by Ben Hirschler; Editing by David Jones)