AstraZeneca has sued India-based generics firm Zydus Cadila to block its bid for a version of the brand manufacturer’s acid-reflux drug Nexium.

The lawsuit, filed July 31 in the U.S. District Court for the District of New Jersey, claims Zydus’s Paragraph IV ANDA against Nexium’s (esomeprazole magnesium) infringes on the ’085, ’070 and ’175 patents, which run until 2018. Nexium’s main patent, however, runs out later this year.

Zydus seeks to market a generic Nexium in 20 mg and 40 mg doses, according to AstraZeneca.

Indian rival Ranbaxy claims first-to-file generic exclusivity status against Nexium. However, a citizen petition now under review by the FDA seeks to remove that status based on Ranbaxy’s history of manufacturing problems.

Nexium earned AstraZeneca $2.3 billion in 2012.

Zydus Cadila declined to comment. — Bryan Koenig

Originally appeared in Drug Industry Daily, the pharmaceutical industry’s number one source for regulatory news and information. Click here for more information.