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Intrinsic Evidence Binds Patentee to Narrower Claim Construction

September 30, 2004

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Last Month at the Federal Circuit - October 2004

Judges: Michel (author), Archer, and Bryson

In Astrazeneca AB v. Mutual Pharmaceutical Co., No. 04-1100 (Fed. Cir. Sept. 30, 2004), the Federal Circuit reversed the district court’s judgment of infringement of a patent covering extended-release dosage forms of the antihypertension drug, felodipine.

Astrazeneca AB et al. (collectively “Astrazeneca”) asserted U.S. Patent No. 4,803,081 (“the ‘081 patent”), which is generally directed to a class of extended-release formulations of low-solubility drugs, against Mutual Pharmaceutical Company (“Mutual”) after Mutual filed an ANDA with the FDA seeking to market a generic version of Astrazeneca’s extended-release felodipine before the expiration date of the ‘081 patent.

The claims of the ‘081 patent all recite that the drug is dispersed or dissolved in “a semi-solid or liquid non-ionic solubilizer.” The parties agreed that, as a general matter, persons of ordinary skill in the art understand the term “solubilizer” to embrace three kinds of materials, including surfactants, cosolvents, and complexing agents. The central dispute in the case concerned whether the term “solubilizer” as used in the ‘081 patent claims should be construed to encompass this broad definition. Mutual’s drug formulation undisputedly contained cosolvents but not surfactants. Astrazeneca argued that the term should be construed broadly to encompass Mutual’s formulation, because the intrinsic record did not limit the ordinary meaning of the term “solubilizer.” The district court agreed with Astrazeneca.

On appeal, Mutual argued that the intrinsic evidence in the ‘081 patent showed that the term “solubilizer,” as used in the claims of the ‘081 patent, only covered surfactants, not cosolvents, and that, therefore, Mutual did not infringe Astrazeneca’s claims. The Federal Circuit agreed with Mutual that the intrinsic evidence of record supported a narrow construction of “solubilizer.” The Court noted that the ‘081 patent specification points to surfactants as a central feature of the invention, and indeed criticizes other types of solvents—and cosolvents inparticular— as leading to undesirable properties. The Court further observed that the specification explicitly states that “[t]he solubilizers suitable according to the invention are defined below,” and that all of the solubilizers and working examples listed thereafter in the specification include only surfactant solubilizers.

The Court found additional support for its narrow claim construction in the prosecution history of the ‘081 patent. For example, the Court noted that Astrazeneca had distinguished its invention over a cited prior art reference by pointing to the “definition” of that term in the specification as encompassing only surfactant-based compositions.

Accordingly, the Federal Circuit held that, notwithstanding the generally broader understanding of the term to those of ordinary skill in the art, the intrinsic evidence clearly bound Astrazeneca to a narrow construction of “solubilizer” that did not literally encompass Mutual’s cosolvent-based formulation. The Court further held that Astrazeneca’s statements in the ‘081 patent and prosecution history constituted a clear disavowal of nonsurfactant solubilizers, and that, therefore, no remand was necessary for a determination of infringement under the DOE. Finally, because Mutual conceded that the ‘081 patent is not invalid under a narrow construction of “solubilizer” that does not include cosolvents, the Federal Circuit affirmed the district court’s judgment in favor of Astrazeneca on validity.