LONGMONT - The U.S. Supreme Court has ruled that a class-action lawsuit can go forward against Amgen Inc. The suit alleges that the biotech company downplayed safety concerns about two anemia drugs.

Thousand Oaks, California,-based Amgen (Nasdaq: AMGN) makes one of the anemia drugs - Epogen - at its Longmont plant. The lawsuit brought by a Connecticut pension fund alleges that Amgen repeatedly reassured investors about the safety of Epogen and the anemia drug Aranesp, even as clinical data showed that the drug might be harmful to cancer patients. Aranesp is made in Puerto Rico.

Epogen stimulates red blood cells in patients with cancer and chronic kidney disease. The Supreme Court ruled 6-3 in its decision, which was written by Justice Ruth Bader Ginsburg and announced Wednesday. The Supreme Court ruling affirmed a lower court's ruling that allowed the lawsuit to proceed as a class-action lawsuit.

Amgen spokeswoman Kristen Davis said Thursday that the Supreme Court ruling was solely procedural, and the company will defend itself vigorously in the case once it is remanded back to the district court where it was filed.

Amgen said in August that it would stop making Epogen at the Longmont plant within 12 to 15 months, causing an unspecified number of job cuts. The building where Epogen is manufactured will be idled, the company has said, although the plant will remain open.

In all, Amgen employs about 700 people in Longmont and Boulder. Nplate, the trade name for a drug used to treat a bleeding disorder, is made in Boulder, as well as drug product candidates currently in clinical development, Davis said.

Workers at the plant in Boulder also made amounts of Amgen's newest drug - denosumab - as it went through the process to receive approval for sale from the U.S. Food and Drug Administration. That approval was granted in 2010. Denosumab can be used to treat osteoporosis in post-menopausal women, and is sold under the trade names Prolia and Xgeva.