Transkaryotic Therapies Inc. and Hoechst Marion Roussel are about to begin late-stage human trials on a rival version of Amgen Inc.'s top-selling drug, the anemia treatment Epogen, Transkaryotic's chief executive said. The two companies will start the last of three trials needed to apply for Food and Drug Administration approval "within a matter of days," said Richard Selden. They're taking the move after a U.S. District Court in April gave them permission to test the drug after a 1997 patent infringement suit filed by Thousand Oaks-based Amgen, the world's largest biotech company. The judge who issued that ruling didn't rule on whether Cambridge, Mass.-based Transkaryotic can sell its version of the drug. About half of Amgen's 1997 revenue of $2.4 billion came from Epogen, which spurs the growth of red blood cells. Selden declined to discuss specifics of the trials, saying the companies will soon issue a statement detailing them. Hoechst Marion Roussel is a unit of Germany's Hoechst. While the April ruling in the patent case allows Transkaryotic and Hoechst to complete human trials on their version of the drug, both sides have said further litigation will be required to determine whether Epogen's would-be competitor will make it to market. Amgen shares fell $2.50 to close at $75.50, and Transkaryotic shares fell 75 cents to $27.50. Both trade on Nasdaq.
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