(Adds company comments, background, share prices)
By Andrew Chung and Bill Berkrot
NEW YORK, July 21 (Reuters) - Novartis AG must wait until Sept. 2 to sell the first biosimilar drug to be approved in the United States, a copycat version of Amgen Inc's $1.2 billion-a-year Neupogen, a U.S. appeals court said on Tuesday.
The ruling stemmed from a lawsuit Amgen filed last October in federal court in San Francisco in which it accused Novartis' generic drugs unit Sandoz of infringing on a patent for Neupogen, which boosts white blood cell counts to fight infections in cancer patients.
In a 2-1 decision, the U.S. Court of Appeals for the Federal Circuit, the nation's top patent court, said that federal law governing close copies of biologic drugs required Sandoz to wait six months after the Food and Drug Administration approved the drug to begin to market it. FDA approval for the drug to be sold under the name Zarxio came in March.
"Sandoz, therefore, may not market Zarxio before 180 days from March 6, 2015, i.e., September 2, 2015," the appeals court said.
The court said it would maintain the injunction it imposed on marketing Zarxio until that date.
"We look forward to launching Zarxio on September 2 as the first U.S. biosimilar," Novartis spokesman Eric Althoff said in an emailed statement.
Amgen declined to comment on whether it planned to appeal the ruling or take further action on its patent infringement case.
While biosimilars aim to copy biologic products, which are made inside living cells, they are not considered exact duplicates, such as generic versions of more traditional pills. Insurers hope biosimilars will cost the public 40 percent to 50 percent less than the original brands.
Biosimilars, including a version of Neupogen, have been available in Europe since 2006. U.S. health insurers have said biotech drugs with expired patents should also face lower-cost competition in the United States.
Numerous drugmakers, including Amgen, are developing biosimilar versions of several multibillion-dollar medicines for rheumatoid arthritis and cancer, with some of those expected to reach the U.S. market by 2017.
The appeals court on Tuesday sent the case back down to the district court to consider Amgen's patent infringement allegations against Sandoz.
Evercore ISI analyst Mark Schoenebaum said in a note that he believes "that this ruling could be appealed to the U.S. Supreme Court."
Amgen shares were off nearly 1 percent at $162.90 on the Nasdaq, while Novartis shares were down about 2 percent at 100.20 Swiss francs in Zurich.
(Additional reporting by Bill Berkrot and Josh Franklin; Editing by Chizu Nomiyama, Alexia Garamfalvi and Paul Simao)