By Brendan Pierson

Dec 5 (Reuters) - The top U.S. patent appeals court has upheld the dismissal of a lawsuit brought by Sandoz Inc that sought to shield its planned version of Amgen Inc's psoriasis and arthritis drug Enbrel from patent lawsuits.

The ruling, handed down Friday by Judge Richard Taranto of the U.S. Court of Appeals for the Federal Circuit, does not stop Sandoz from developing its drug. Taranto only ruled that the lawsuit against Amgen was premature because Sandoz had not yet sought approval for the drug from the U.S. Food and Drug Administration (FDA).

Sandoz, the generics arm of Novartis AG, sued Amgen in June 2013 seeking a judgment that its planned "biosimilar" version of Enbrel, a so-called biologic drug, would not infringe two of Amgen's patents. At the same time, Sandoz announced it was launching a late-stage clinical trial of the drug.

A U.S. District judge in Northern California dismissed the case in November 2013, and Sandoz appealed.

Biologic drugs such as Enbrel are complex substances derived from living organisms. Unlike traditional chemical drugs, they are difficult to replicate.

The 2009 federal Biologics Price Competition and Innovation Act allows drugmakers to introduce biosimilar versions of existing biologics that need not be identical to the original.

The law around biologics is largely untested. The FDA accepted its first biosimilar application only this year. In Friday's opinion, Taranto declined to address whether Sandoz's suit was barred by the federal biologics law.

Amgen spokeswoman Kristen Davis said the company was pleased with the outcome. Sandoz did not immediately return a request for comment.

Judges Timothy Dyk and Raymond Chen joined in Friday's decision.

The case is Sandoz Inc v. Amgen Inc et al, U.S. Court of Appeals for the Federal Circuit, No. 2014-1693.

(Editing by Ted Botha and Peter Galloway)