Anemia drugs sold by Amgen Inc. took another hit Thursday when government regulators said two new studies indicated that the drugs may increase the risk of death in some patients, the Los Angeles Times reports.


Based on the studies, the Food and Drug Administration may further restrict the use of the drugs, which already carry the agency's strictest "black box" warning.


"This new information further underscores the safety concerns," said Janet Woodcock, acting director of the FDA's Center for Drug Evaluation and Research. She said the agency "is reviewing these data and may take additional action."


In recent years, six studies have found that the drugs -- all manufactured by Amgen and marketed by Amgen as Aranesp and Epogen and by Johnson & Johnson as Procrit -- can lead to an increased risk of heart attack, stroke, heart failure and cancer tumor growth in some patients.


Amgen, based in Thousand Oaks, until recently enjoyed an unusually charmed life in the often treacherous biotech industry, with profit and a market value higher than many top-shelf pharmaceutical companies. A large share of the company's fortunes came from Aranesp and Epogen, which accounted for more than half of its net income.


Since the summer, Amgen's stock has fallen to a five-year low and has lost $17 billion in value. The company laid off 14% of its employees late last year.


Known as erythropoietin-stimulating agents or ESAs, the anemia drugs are bioengineered versions of a natural protein made in the kidney that stimulates bone marrow to produce more red blood cells. Cancer and dialysis patients use injectable ESAs to treat anemia and boost energy.

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