(Adds Pfizer studying decision; updates shares)
WASHINGTON, March 7 (Reuters) - A U.S. federal appeals court upheld on Friday a lower court ruling that Teva Pharmaceutical Industries Ltd TEVA.O infringed two patents held by Pfizer Inc (PFE.N) on its popular Celebrex drug.
The U.S. Court of Appeals for the Federal Circuit rejected claims by Teva that the two Celebrex patents at issue in the case were invalid, although it agreed with Teva a third patent was invalid.
A U.S. district court in Newark ruled in favor of Pfizer, upholding its three main patents for Celebrex nearly a year ago. The decision barred Israel-based Teva from launching a competitor drug in the United States until December 2015.
Pfizer sued Teva in February 2004 after the generic drugmaker asked U.S. regulators for permission to sell a copycat version of Celebrex.
Celebrex, approved in 1998, is an anti-inflammatory drug used to treat osteoarthritis and rheumatoid arthritis. It is one of Pfizer’s biggest revenue producers with annual global sales of $2.3 billion.
A Pfizer spokesman said the company was still studying the decision and could not immediately comment on its significance.
Teva shares were down 0.8 percent at $47.35 at midday on the Nasdaq. Pfizer slipped 0.9 percent to $21.39 on the New York Stock Exchange, amid a moderate downturn for the drug sector. (Reporting by Peter Kaplan; additional reporting by Ransdell Pierson in New York; editing by Leslie Gevirtz/Andre Grenon)