By Peter Loftus

Of Dow Jones NEWSWIRES

A federal judge has upheld the validity of a U.S. patent covering Merck & Co.'s (MRK) Vytorin cholesterol-lowering drug, which could stave off competing generic copies for several years.

In an opinion released Friday, U.S. District Judge Jose Linares in federal court in Newark, N.J., said a patent for Vytorin was valid and enforceable.

Merck, based in Whitehouse Station, N.J., said in a recent regulatory filing it expects its U.S. exclusivity for Vytorin and a related drug, Zetia, to expire in April 2017.

Mylan Inc. (MYL) had applied for U.S. Food and Drug Administration approval to sell a generic version of Vytorin before its patent protection expired, arguing that the patent was invalid and unenforceable.

Schering-Plough, which was acquired by Merck in 2009, filed a patent-infringement lawsuit against Mylan in late 2009, seeking to block Mylan's product. A trial was held in December 2011, leading to Judge Linares's opinion Friday.

On a conference call with analysts Friday morning, Merck Chief Executive Kenneth Frazier said he was anticipating a favorable decision. "We believe this is a patent that is valid and enforceable," he said.

A Mylan spokeswoman couldn't immediately be reached.

Earlier Friday, Merck reported first-quarter Vytorin sales of $444 million and Zetia sales of $614 million.

Merck previously reached a settlement of patent litigation for Zetia with generics manufacturer Glenmark Pharmaceuticals. The pact will allow Glenmark to sell generic Zetia in December 2016, subject to final regulatory approval.

-By Peter Loftus, Dow Jones Newswires; +1-215-982-5581; peter.loftus@dowjones.com