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Clinical trials necessary to determine invention works for intended purpose

August 27, 2008
Post by Blog Staff

In a recent decision, the Federal Circuit affirmed a district court's ruling in favor of AstraZeneca, holding that the generic drug manufacturers Apotex and Impax Laboratories infringed patents for the popular heartburn medication Prilosec® (generic form omeprazole) in filing abbreviated new drug applications (ANDAs). The Federal Circuit previously addressed these patents in the context of other defendants in a decision blogged about here.The major issue in this appeal was whether the clinical trials of omeprazole constituted an invalidating public use under § 102(b). The district court held the clinical trials were experimental use, and the formulation was not ready for patenting at the time of the trials. Accordingly, the district court held the public use bar of § 102(b) did not apply. The Federal Circuit affirmed the district court's holding on the basis that the invention was not ready for patenting at the time, as the clinical trials were necessary for the inventors to know that the invention would work for its intended purpose, a necessary predicate to a finding of public use.The court also addressed a potpourri of other issues, including anticipation, obviousness and the permissible extension of a patent term due to prolonged delay for FDA testing and approval. The Federal Circuit affirmed the district court's finding on these issues, ending a decade long series of litigation over the popular heartburn medication.More on In re Omeprazole Patent Litig. after the jump.The appeal stems from a case brought by AstraZeneca against several defendants for patent infringement. The complex litigation was split into four phases; two addressing product patents and two addressing method patents. The Federal Circuit decided another appeal in the related cases this spring; a summary of that decision can be found in this post. The patents at issue involve the addition of an inert subcoating that rapidly disintegrates in water in order to prolong the storage life of the omeprazole product and allow for gastric acid resistance to prevent the drug from degrading in the stomach, and allowing it to reach the small intestine before the drug is released. U.S. Patent No. 4,786,505 claims in part "an inert subcoating which is soluble or rapidly disintegrating in water disposed on said core region"; U.S. Patent No. 4,853,230 claims more broadly a preparation containing "an acid-labile pharmaceutically active substance." The lawsuit began after Impax and Apotex requested Food and Drug Administration generic approval for 10, 20, and 40 mg tablets of generic omeprazole. AstraZeneca responded by filing an infringement lawsuit against both drug manufacturers. The Federal Circuit addressed the appeal of each drug manufacturer individually. During the litigation procedure leading to a trial between Impax and AstraZeneca, the patent term for the patents at issue expired. At that point Impax filed a motion to dismiss on the grounds of mootness. However, the court continued with the bench trial and granted a verdict because AstraZeneca had been granted a six month period of market exclusivity following the expiration of the patents by the FDA. Then the district court issued its decision holding AstraZeneca's patents to be valid, enforceable, and infringed by Impax. Impax first argued the district court had no jurisdiction over the case as soon as the patents had expired. The Federal Circuit affirmed the decision of the district court finding that jurisdiction was valid for the district court to render its decision that patents were valid, enforceable and also infringed by Impax, due to the extended six month period of market exclusivity granted to AstraZeneca. Such extension of the patent right was a result of AstraZeneca's adherence to the FDA's request that additional pediatric testing be performed for the product in exchange for additional life of the patent term. The court agreed that AstraZeneca properly sought relief under § 271(e)(4)(A). Impax also challenged the sufficiency of the evidence that its formulations infringed the claims of the patents at issue. Specifically, Impax argued that its formulation does not have "an effective amount" of omeprazole and an alkaline reacting compound nor an inert subcoating. The Federal Circuit agreed with the district court's decision finding that Impax patent claims did have a basic compound that created a "micro-pH" in the drug core with a pH not less than 7. The court found this to be the same limitation as an "alkaline reacting compound" in the patents at issue. The Federal Circuit further noted that the limitation of "enhanced stability" was found as a result of Impax's products having an inert subcoating and a drug core with a micro-pH of not less than 7 of which results in increased stability. The Federal Circuit again agreed with the district court stating that the finder of fact made a factual determination based on evidence presented at trial showing that Impax's inert subcoating increased the stability of its formulation of the generic Prilosec. The Federal Circuit again agreed with the district court and rejected Impax's arguments that the court needed to identify the process by which the subcoatings were produced in order to find infringement.Impax also challenged the district court's finding relating to the public use bar under § 102(b). The critical date of the patents was April 20, 1986. Impax alleged that AstraZeneca's large clinical studies performed before this date constituted a public use of the claimed formulation, thereby invalidating the patent. Here, the Federal Circuit in part agreed with Impax, holding AstraZeneca did not meet the experimental use exception because the formulation had previously been reduced to practice before the initiation of the clinical studies. However, the Federal Circuit affirmed the district court's conclusion that the claims were not invalid under § 102(b), holding the claimed formulation was not ready for patenting until after the clinical studies were completed. In order for an invention to be in public use, it must be ready for patenting at the time of the use. Under the Supreme Court's Pfaff decision, an invention can be shown to be ready for patenting either by showing it has been reduced to practice or that "the inventor had prepared drawings or other descriptions of the invention that were sufficiently specific to enable a person skilled in the art to practice the invention." Here, Impax argued the invention had been reduced to practice before the phase 3 trials, and was therefore ready for patenting. In order to show an invention is reduced to practice, two conditions must be met: the inventor must (1) construct an embodiment or perform a process that met all the claim limitations, and (2) determine that it would work for its intended purpose.The court examined the second requirement of reduction to practice. Examining the experimentation conducted during the clinical trials, the court noted the gastric acid resistance and the improved shelf life stability were changed throughout phase 1, 2 and 3 clinical drug studies. The court held "the Phase 3 formulation still required extensive clinical testing and real-time stability testing to determine whether it could treat gastric acid diseases safely and effectively." As a result, the court held the inventors did not yet know that it would work for its intended purpose, and as a result had not been reduced to practice. Given that the invention was not reduced to practice, it could not have been in public use as required by § 102(b). Accordingly, the court affirmed the district court's decision as to Impax.The Federal Circuit then turned to Apotex's appeal. Apotex also argued that its formulation did not infringe the patents at issue, namely that it did not have a subcoating within a core region or a continuous subcoat that is water soluble, and that it was merely practicing the manufacturing process of the prior art. The court quickly discounted Apotex's arguments and found infringement, stating that infringement is measured according to the patents at issue and not the prior art, and finding the district court's decision supported by substantial evidence. Apotex also argued that the patents at issue were anticipated by two U.S. patents and one European patent based on the district court's claim construction of "acid labile" and "alkaline salt." The Federal Circuit


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