On December 19, 2013, Hanmi Pharmaceuticals received good news in the form of a decision by the U.S. Court of Appeals for the Federal Circuit (CAFC). Invoking 35 U.S.C. §271(e)(2), AstraZeneca had alleged that a drug Hanmi proposed to market falls within claims of U.S. Patent Nos. 5,714,504 and 5,877,192. After the district court construed the claim terms “alkaline salt” in the ’504 patent and “pharmaceutically acceptable salt” in the ’192 patent, the parties consented to the entry of a final judgment of non-infringement based on the constructions. This case is of particular interest to the industry because omeprazole is the active ingredient in the popular over-the-counter heartburn medication know as Prilosec.
Creating a salt out of omeprazole can enhance stability during storage and transportation, a useful property in pharmaceutical compounds. AstraZeneca discovered that certain salts of an omeprazole enantiomer have improved pharmacokinetic and metabolic properties which will give an improved therapeutic profile such as a lower degree of interindividual variation. During prosecution, AstraZeneca conducted experiments that led it to conclude that one of the two enantiomers gave particularly good results. The preferred enantiomer became known as “esomeprazole.”
In response to the Examiner’s rejection of original claims, AstraZeneca filed amended claims to focus on esomeprazole. The new claims, which were the ones at issue in the Federal Circuit decision, were all limited to pharmaceutical compounds that contain certain esomeprazole salts as an active ingredient; but the independent claims no longer expressly refer to the originally identified six specific salts, instead claiming an “alkaline salt” or “pharmaceutically acceptable salt.”
On December 12, 2012, the district court construed the term “alkaline salt” in the ’504 patent and “pharmaceutically acceptable salt” in the ’192 patent. AstraZeneca argued that both terms have the same broad meaning: any “basic” salt of esomeprazole that is suitable for use in a pharmaceutical formulation. Hanmi argued that both terms are limited to the disclosed “Na+, Mg2+, Li+, K+, Ca2+ or N+(R)4 salts of the single enantiomers of omeprazole.” The district court agreed with Hanmi, concluding that the written description defines the invention as limited to the disclosed salts.
The Federal Circuit explained that the appeal presented but a single issue: Whether the written description limits “alkaline salt” in the ’504 patent to certain specifically named salts. The Federal Circuit held that it does.
The Federal Circuit went on to explain that the written description described the invention clearly and narrowly as including only those salts that were expressly disclosed. The Federal Circuit (per Judge Taranto with Judges Dyk and Moore) summarized its findings as follows: “The written description of the ’504 patent contains a clear disclaimer of claim scope, and no other aspect of the intrinsic record clearly points the other way. We therefore conclude that the district court’s construction of ‘alkaline salt’ was correct, and we affirm the judgment of noninfringement based on that construction.”
The judgment removes a major hurdle for Amneal Pharmaceuticals LLC, a U.S.-based manufacturer of generic pharmaceuticals, which is marketing the product in the U.S. under an exclusive license and distribution agreement with Hanmi. Amneal launched branded Esomeprazole strontium delayed-release capsules 49.3 mg, a 505(b)(2) NDA drug, on December 17, 2013.
“The appellate court adopted the position that Hanmi and Amneal advocated from the outset – specifically, that the Hanmi esomeprazole strontium capsule product does not infringe the patents asserted by AstraZeneca. Moreover, Amneal’s recent launch will proceed free from the legal uncertainty that may have been perceived before last week’s favorable decision,” said Kenneth M. Cappel, Amneal’s Vice-President of Global Intellectual Property.