It appears that another round of Amgen (Nasdaq: AMGN) and Roche's anemia-drug wars is over. Yesterday, Roche gave in to a judge's recommendation that it pay a higher royalty to Amgen on sales of its anemia drug Mircera -- if it's allowed on the market at all.

Roche and Amgen have been feuding about whether Roche's Mircera violates the patents on Amgen's $6 billion-a-year anemia drug franchise, comprising Epogen and Aranesp. The FDA approved Mircera last November, as a treatment for chronic kidney disease, but because of a patent-lawsuit loss against Amgen, Roche has not been able to sell the drug in the U.S.

In February, a judge presiding over the patent case proposed several conditions under which Roche might be able to release Mircera. Most importantly, the judge requested that Roche pay Amgen a 22.5% royalty on sales of Mircera. Roche balked at the size of the royalty rate, proposing 20% instead. But apparently, Roche decided to give in yesterday -- as if the court had given the company any choice -- and accept the higher rate.

The arguments continue
Yet Roche's decision doesn't end the dispute. Amgen has argued to the judge that Mircera should be barred from the market outright, since Roche lost the patent-infringement lawsuit. Past results in cases like this have been mixed, but I'm inclined to believe that this particular judge will give his blessing to Mircera, now that Roche has agreed to his terms. Nevertheless, a final decision on whether Mircera will be allowed on the market remains pending.

The stakes are high for Amgen. The U.S. is one of Amgen and partner Johnson & Johnson's (NYSE: JNJ) last major bastions of monopoly control over the erythropoiesis-stimulating-agent anemia-drug market, via Aranesp, Epogen, and J&J's Procrit. In the European Union, Amgen faces many more competitors. Since it's likely that the royalty Roche pays Amgen on Mircera sales will be lower than Amgen's margins on Aranesp or Epogen, it's understandable why Amgen is in no hurry to open the U.S. anemia-drug market any wider. 

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. Johnson & Johnson is an active Income Investor pick. The Fool has an A+ disclosure policy.