ZURICH (Reuters) - The Novartis (>> Novartis AG) copy of Amgen's (>> Amgen, Inc.) blockbuster psoriasis drug Enbrel will not go on sale before 2018 at the earliest because of the U.S. company's patent protection challenge, the Swiss drugmaker's head of generics told Reuters.

Though the U.S. Food and Drug Administration has approved the biosimilar copy of Enbrel, called Erelzi, for rheumatoid arthritis, plaque psoriasis, ankylosing spondylitis and other diseases, Amgen is arguing in U.S. federal court that its $4.7 billion a year drug has patent protection until 2029.

Richard Francis, head of Novartis's Sandoz generics business, said it will be at least another year before the legal fight plays out.

"That won't really reach a conclusion until 2018," Francis said on Wednesday. "That's the frustration sometimes of the legal situation, but the way I look at that, we're carving the landscape out as we go."

Novartis and Amgen are also embroiled in a separate legal battle over how quickly companies can begin sales of biosimilar copies.

The U.S. Supreme Court this month agreed to hear that case, hinging on whether companies must wait 180 days after FDA approval before beginning sales of their biosimilar copies.

(Reporting by John Miller; Editing by David Goodman)

Stocks treated in this article : Amgen, Inc., Novartis AG