Endo Says Zydus’ Rival Chantix Copy Infringes Key New Patent

Endo International Plc accused Zydus Lifesciences Ltd. of making its generic version of Pfizer Inc.'s recalled Chantix using a process that infringes a new patent covering what for two years had been the only approved version of the blockbuster smoking-cessation tablets.

Chantix, whose active ingredient is varenicline tartrate, was approved in 2006 by the US Food and Drug Administration. “At its height,” according to a complaint filed Tuesday by Endo’s Par Pharmaceutical Inc. in the US District Court for the District of Delaware, “Pfizer’s revenues from its sales of Chantix were in excess of $1 billion per year.”

But in ...