Eisai Prevails in Aciphex Suit

A federal appeals court has affirmed a ruling in favor of Eisai in a patent infringement case over proposed generic versions of its proton pump inhibitor Aciphex, a treatment for gastroesophageal reflux disease.

Japan-based Eisai filed the lawsuit in November 2003 in the U.S. District Court for the Southern District of New York after Teva Pharmaceuticals and Dr. Reddy’s Laboratories submitted separate ANDAs with Paragraph IV certifications to market generic Aciphex (rabeprazole sodium) before the May 2013 expiration of the ’552 patent. 

Although Dr. Reddy’s stipulated the validity of the patent, both defendants took the position that the patent should be found unenforceable because Eisai committed inequitable conduct in applying for it. They alleged that Eisai misled the examiner reviewing the ’552 patent by not disclosing the existence of a pending application for an ’013 patent, which claimed the ethyl homolog of rabeprazole.

Because the compounds in the applications for the two patents were substantially similar, the defendants held Eisai should have told the examiner about the ’013 application to avoid double-patenting, according to court documents.

In October 2006, the district court granted partial summary judgment to Eisai. The following May, the court ruled that Eisai had established that the defendants had infringed on the patent, a ruling they appealed to the U.S. Court of Appeals for the Federal Circuit.

In the appeal, Teva and Dr. Reddy’s reiterated their claim that Eisai had committed inequitable conduct. The court disagreed, finding that while the disclosure of the ’013 patent application “would have been prudent,” Eisai’s failure to do so was “by no means fatal.”