Boehringer Ingelheim has sued Amneal Pharmaceuticals over its bid to make a generic version of the brand manufacturer’s anti-stroke drug Aggrenox.

Amneal notified the German manufacturer of its Paragraph IV ANDA against Aggrenox (aspirin/extended-release dipyridamol) in a June 26 letter, BI said in its patent infringement lawsuit filed in the U.S. District Court for the District of New Jersey.

Aggrenox has faced several generic bids against the drug’s ’577 patent, which is set to expire in 2017, BI said in its complaint. In this case, the drugmaker took the unusual step of identifying the grounds on which Amneal is challenging the patent: obviousness. The complaint also specified why that challenge should fail, listing a variety of characteristics it argues are unique to Aggrenox.

Past legal battles over Aggrenox have focused on alleged efforts by BI to delay generic competition, including an alleged payoff to Teva subsidiary Barr Labs to keep its generic off the market. Barr is the only company listed in the Orange Book as holding an approved version of generic Aggrenox.

Amneal declined to comment. — Bryan Koenig

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