Merck just lost some patent protection on its Zetia cholesterol drug. A federal judge in Newark, New Jersey, invalidated several items that were added in 2002, when Schering-Plough (now owned by Merck) obtained a reissued patent. But US District Court Judge Jose Linares ruled the patent shouldn’t have been reissued because a valid and enforceable one already exists, The New Jersey Law Journal reports.

The ruling is a boost to Glenmark Pharmaceuticals, which is fighting a patent infringement lawsuit and wants FDA permission to sell a generic version of Zetia, which is one of Merck’s biggest-selling pills. As the legal newspaper points out, the financial stakes are high. Combined sales last year for Zetia and Vytorin, which includes Zetia and simvastatin, reached $4.3 billion. And Merck would like to sell a pill that combines Zetia and a generic version of Pfizer’s Lipitor.

Glenmark still faces allegations that it infringed the earlier patent, which contains claims broader than those added in 2002. The Zetia patent is set to expire in 2017 and if Glenmark becomes the first company approved to market a generic equivalent, it will get the benefit of an 180-day exclusivity period. The disputed patent items involve ezetimibe, the active ingredient in Zetia.