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Mere Disclosure of Potentially Material Art Does Not Automatically Limit Claims

02-1400
July 03, 2003

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Last Month at the Federal Circuit - August 2003

Judges: Rader (author), Gajarsa, and Dyk

In Abbott Laboratories v. Baxter Pharmaceutical Products, Inc., No. 02-1400 (Fed. Cir. July 3, 2003), the Federal Circuit vacated the district court’s grant of Defendants’ Baxter Pharmaceutical Products, Inc. and Baxter Health Care Corporation (collectively “Baxter”) motion for SJ of noninfringement because the district court erred in construing the asserted claims. The case was remanded for further adjudication.

Abbott Laboratories and Central Glass Company, Ltd. (collectively “Abbott”) own U.S. Patent No. 5,990,176 (“the ‘176 patent”), which claims compositions and methods for preventing degradation of sevoflurane anesthetic that combine sevoflurane with an effective amount of certain Lewis acid inhibitors, including water. Baxter filed an ANDA with the FDA proposing to market a generic sevoflurane with no more than 130 ppm of water. Baxter certified under paragraph IV that its proposed generic sevoflurane product does not infringe the ‘176 patent. Abbott then filed suit alleging infringement of the ‘176 patent. The district court construed the claims to require more than 130 ppm of water in order to preserve their validity in view of a sale described in an IDS that Abbott submitted to the PTO in the ‘176 patent and granted Baxter’s motion for SJ of noninfringement.

The district court’s decision hinged on its construction of the phrase “amount effective to prevent degradation [of the sevoflurane] by a Lewis acid.” The district court acknowledged that neither the plain language of the claims nor the specification of the ‘176 patent—which disclosed amounts of Lewis acid inhibitors that “can be used” and amounts “believed to be” effective—required a specific amount of Lewis acid inhibitor. Nevertheless, the district court construed the term “amount effective” as requiring more than 131 ppm of Lewis acid inhibitor.

In support of this conclusion, the district court pointed to Abbott’s submission of an IDS that referenced a sale of a sevoflurane with no more than 130 ppm water that occurred more than one year before the effective filing date of the ‘176 patent. According to the district court, the referenced sale constituted admitted prior art and a surrender of the subject matter of the sale. Thus, in order to preserve the validity of the claims in view of the assumed invalidating sale, the district court construed the term “effective amount” to mean an amount of inhibitor more than 131 ppm. Because the district court limited the claims of the ‘176 patent to compositions comprising more than 131 ppm of inhibitor, it concluded that the proposed generic product, which would have less than 130 ppm of water, did not infringe the claims of the ‘176 patent and granted SJ of noninfringement to Baxter.

On appeal, the Federal Circuit first construed the term “effective amount” of inhibitor and determined that it is not limited to concentrations of inhibitors greater than 131 ppm. The Federal Circuit concluded that the district court improperly construed the term “effective amount” by deviating from the customary usage of the term and importing the “more than 131 ppm” of inhibitor limitation into the claims. More specifically, the Federal Circuit determined that, under its customary usage, the term “effective amount,” as used in the ‘176 patent, means “the amount of Lewis acid inhibitor that will prevent the degradation of sevoflurane by a Lewis acid.” The Federal Circuit then noted that the specification of the ‘176 patent broadly defines the term “effective amount” as “an amount that prevents the degradation of the fluoroether compound by a Lewis acid” and teaches that the degradation of sevoflurane varies depending on environmental factors, such as the chemical composition of the container. The Federal Circuit further concluded that the reference to the previous sale in the IDS was not an admission of material prior art or a disavowal of claim scope. In sum, the Federal Circuit concluded that the specification and the prosecution history of the ‘176 patent (including the IDS) did not support a meaning different from the customary meaning, and, therefore, the district court improperly imported the more than 131 ppm limitation into the claims.

The Federal Circuit also determined that the effective amount of the Lewis acid inhibitor should be measured by reference to a single species of the inhibitors recited in the Markush group. Abbott had argued that the recitation of “a” Lewis acid inhibitor in the Markush group should be understood to mean that a composition that comprises an effective amount derived from “more than one inhibitor would still fall within the claim boundaries.” The Federal Circuit disagreed. According to the Court, although the word “a” indicates “one or more” in claims containing the transitional phrase “comprising,” the combination of the word “a” with the phrase “consisting of” in a Markush group indicates only one member of the group. Hence, because the applicant did not expressly indicate the selection of multiple members of the Markush group (e.g., by claiming “and mixtures thereof” or “at least one member of the group”), the claims of the ‘176 patent are limited to compositions in which a single inhibitor selected from the recited Markush group contributes an effective amount of an inhibitor. Thus, to prove literal infringement on remand Abbott must prove that a single species from the Markush group is present in Baxter’s proposed generic product in an amount effective to prevent degradation of the sevoflurane.