Swiss biotech company Roche Holding AG has received approval from U.S. regulators for its anemia drug Mircera, a drug that has been found to violate patents held by competing biotech firm Amgen Inc.

Mircera was approved last Thursday by the U.S. Food and Drug Administration for patients with anemia caused by kidney failure. It was found by a jury late last month to infringe on 11 patents used in Amgen's best-selling Aranesp and Epogen drugs, which had combined sales of more than $6 billion last year.

Roche said it is considering an appeal, but Thousand Oaks-based Amgen has already moved to bar the company from launching the drug and has already asked the judge hearing the case to issue an injunction to stop U.S. sales.

With an injunction in place, Roche wouldn't be able to sell its version of the drug in the U.S. until at least 2012, when the first patents on Amgen's anemia drugs expire.

Shares in Amgen gained 2 percent to $55.92 in afternoon trading Friday on the Nasdaq. Shares are down more than 22 percent for the year.

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