Bayer AG said it's “determined to enforce intellectual property” after losing a bid to demand royalties from Abbott Laboratories over U.S. sales of the arthritis drug Humira.

Europe's largest drug and chemical maker, which sued Abbott in 2008 for violating its intellectual-property rights, conceded in a court filing yesterday that Humira doesn't infringe its patent under an interpretation by a judge in the case. Bayer's lawsuit can be revived if an appeals court overturns the judge's definition of the phrase “human monoclonal antibodies.”