A recent U.S. Court of Appeals for the Federal Circuit ruling on Amgen Inc.‘s lucrative patents relating to the production of the protein erythropoietin upheld a permanent injunction barring Roche, F. Hoffman-La Roche Ltd.’s Swiss parent, from selling Mircera in the United States. But in making rulings that place some of Amgen’s patent claims at risk, the decision highlights how careful patent filers must be when filing nearly identical claims.

The panel issued several rulings in the Sept. 15 decision, Amgen Inc. v. F. Hoffman-La Roche Ltd., including a number upholding jury findings that concluded that Roche’s renal anemia treatment drug Mircera would infringe on Amgen patents if imported into the United States. The Federal Circuit also reversed a noninfringement ruling of the lower court, the District of Massachusetts, on a fifth patent and ordered a new trial.