Omeprazole, the generic name for the popular anti-heartburn drug PRILOSEC®, operates in a unique manner by transforming into its active ingredients in the acid-producing cells of the stomach lining and then inhibiting gastric acid production. Because omeprazole degrades in acidic and neutral environments, it must be protected while traveling to the acid-producing cells in the stomach by an enteric layer. AstraZenica's U.S. Patent No. 6,013,281 (the "'281 patent") claims a method for making an omeprazole formulation composed of a core containing the active, acid-inhibiting ingredient, a protective, enteric coating surrounding the core, and a water-soluble separating layer between the core and protective layer. Specifically, the patent recites a process for creating the separating layer by causing an in situ reaction involving the enteric-coating material and the core, producing an omeprazole formulation having three distinct layers.
In 2001, AstraZeneca filed suit for infringement of the '281 patent claims against several pharmaceutical companies seeking permission from the Food and Drug Administration to market generic versions of PRILOSEC®. The district court found that, while the '281 patent claims were infringed, the claims were invalid in view of a prior Korean patent application that recited or anticipated all of AstraZenica's claim limitations, either explicitly or inherently. In a 2-1 decision (Judge Rader filing the majority opinion with Judge Bryson concurring), the Court of Appeals for the Federal Circuit affirmed the district court decision holding that the in situ separation layer was formed when practicing the invention disclosed in the prior art. Therefore it was the natural result of practicing the invention and was inherent to the disclosure even though it was not explicitly disclosed in the Korean patent application.
Judge Rader's majority opinion and Judge Newman's concurring-in-part, dissenting-in-part opinion do differ in what is to be considered "inherent" in a disclosure and in how to evaluate and weigh the proof required to support such a finding. In the present case, questions arose as to whether following the process disclosed in the Korean patent application resulted in the formation of an in situ layer under all conditions or only under limited conditions. While this decision appears to have settled the issues present in this case, it certainly leaves room for further discussion of "inherent anticipation."
Vol. 53, June 2010