The Food and Drug Administration on Friday accepted paperwork for a biosimilar version of Amgen Inc.’s popular arthritis medication Enbrel. The copycat medication is made by Sandoz, a division of Swiss drug maker Novartis S.A. Just last month, Novartis launched a biosimilar version of Amgen’s Neupogen known as Zarxio, which was the first biosimilar drug to hit the U.S. market. Amgen, in Thousand Oaks, reported sales revenue of $4.7 billion from Enbrel last year. Outside of North America, Pfizer distributes the drug and had sales of about $4.3 billion last year. Biosimilars aim to copy established bioengineered medications, but because they are made in living cells, they cannot be exact replicas of the original. Yet, to be approved by the FDA, they must be “highly similar” to the drug they are aiming to copy, meaning there must be no meaningful differences in safety and effectiveness. Amgen’s shares closed up $2.24 or 1.6 percent to $142.47 on the Nasdaq.