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District Court Upholds Validity of Pfizer's Accupril Patent, Rejecting Teva's Nonenablement Argument

By Aaron Barkoff

Warner-Lambert v. Teva Pharms. USA, No. 99-922 (D.N.J. 2007)

Warner-Lambert (part of Pfizer) and Teva have been in patent litigation over Teva's ANDA for generic Accupril (quinapril hydrochloride) since 1999, when Warner-Lambert sued Teva for filing its ANDA with a paragraph IV certification to U.S. Patent No. 4,743,450.  According to Teva's 2002 approval letter, Teva also filed its ANDA with a paragraph III certification to U.S. Patent No. 4,344,949, which expired on October 3, 2002, and section viii statements to U.S. Patent Nos. 5,684,016 and 5,747,504.

The '450 patent broadly claims pharmaceutical compositions containing an ACE inhibitor, "an alkali or alkaline earth metal carbonate to inhibit cyclization and discoloration," and "a saccharide to inhibit hydrolysis."  The '450 patent did not expire until February 24, 2007, with pediatric exclusivity extending until August 24, 2007.

In October 2003, the district court granted Warner-Lambert's motion for summary judgment of infringement of claims 1, 4-10 and 12 of the '450 patent.  The court also granted Warner-Lambert's motion for summary judgment of validity of the same claims.  Following a trial in May 2004, the district court ruled that claims 16 and 17 are valid, and that the '450 patent is not unenforceable due to inequitable conduct.  Teva appealed the findings of infringement, no invalidity for lack of enablement, and no inequitable conduct, and in August 2005, the Federal Circuit reversed the district court's rulings on infringement and enablement and remanded the case for further proceedings.  In January 2006, the district court granted Warner-Lambert's motion for summary judgment of infringement, leaving the issue of enablement for trial.

The district court held a trial on the question of enablement on May 2 and 3, 2007, and released an opinion last week finding the claims enabled.  The court applied the standard test:  whether the specification provides "sufficient teaching such that one skilled in the art could make and use the full scope of the invention without undue experimentation."  Teva argued that the claims of the '450 patent are extremely broad and the specification provides insufficient guidance to develop the full range of pharmaceutical formulations encompassed by the claims.  In addition, Teva argued that numerous failures to arrive at operative embodiments of the claims proved nonenablement.  The court, however, found the testimony of Warner-Lambert's expert witness (who "wrote the book on stability of pharmaceutical formulations") to be more persuasive than the testimony of Teva's expert.  The court was convinced by Warner-Lambert's expert that one skilled in the art could readily practice the full scope of the claimed invention through routine experimentation.  In addition, the court found that none of the purported "failures" proffered by Teva were evidence of lack of enablement.

Last week's court decision could impact other cases in which the '450 patent has been asserted.  For instance, Warner-Lambert filed suit against Teva and Ranbaxy in January 2005, after Teva announced that it began shipping generic quinapril HCl tablets in partnership with Ranbaxy.  In addition, Schwarz Pharma AG, an exclusive licensee of the '450 patent, has asserted the patent against in litigation concerning generic versions of Univasc (moexipril).

Full post as published by Orange Book Blog: At the Intersection of Patent Law and FDA Law on December 05, 2007 (boomark / email).