Amgen announced Friday it has filed a patent infringement lawsuit concerning its cholesterol drug in the United States District Court of Delaware against Sanofi and Regeneron Pharmaceuticals Inc.The lawsuit filed by the Thousand Oaks-based biotechnology company seeks an injunction to prevent the manufacture, use and sale of Sanofi and Regeneron's drug alirocumab, which has completed Phase 3 clinical trials, claiming it infringes on patents owned by Amgen..Amgen previously announced it had submitted a Biologics License Application to the U.S.