Claim Construction That Differs from Intrinsic Evidence is Proper, in Right Context: Federal Circuit | Practical Law

Claim Construction That Differs from Intrinsic Evidence is Proper, in Right Context: Federal Circuit | Practical Law

In Aventis Pharmaceuticals Inc. v. Amino Chemicals Ltd., the US Court of Appeals for the Federal Circuit held that a patent claim term should not be construed in accordance with its use in the prosecution history because one of ordinary skill in the art would understand from the term's context that the term should be construed differently in the claim. Specifically, in this pharmaceutical case, the Federal Circuit held that the term "substantially pure" when used in the claim to describe an intermediate should be construed differently from its use in the prosecution history to describe an end product.

Claim Construction That Differs from Intrinsic Evidence is Proper, in Right Context: Federal Circuit

by PLC Intellectual Property & Technology
Published on 21 May 2013 • USA (National/Federal)
In Aventis Pharmaceuticals Inc. v. Amino Chemicals Ltd., the US Court of Appeals for the Federal Circuit held that a patent claim term should not be construed in accordance with its use in the prosecution history because one of ordinary skill in the art would understand from the term's context that the term should be construed differently in the claim. Specifically, in this pharmaceutical case, the Federal Circuit held that the term "substantially pure" when used in the claim to describe an intermediate should be construed differently from its use in the prosecution history to describe an end product.
On May 20, 2013, the US Court of Appeals for the Federal Circuit issued an opinion in Aventis Pharmaceuticals Inc. v. Amino Chemicals Ltd. holding that the US District Court for the District of New Jersey erred in construing the term "substantially pure" as used in claims 1, 6 and 7 of US Patent No. 5,750,703 (the '703 patent) and reversed and remanded the case to the district court.
Aventis Pharmaceuticals, Inc, and Albany Molecular Research, Inc. (appellants) are the assignee and exclusive licensee of the '703 patent, which concerns processes for synthesizing fexofenadine, the active ingredient in the antihistamines marketed under the brand name ALLEGRA. The appellees, including Amino Chemicals Ltd., are generic drug manufacturers.
This case arose when Amino Chemicals filed a Drug Master File that was referenced in Abbreviated New Drug Applications (ANDAs) of two former parties that sought FDA approval to market antihistamines containing fexofenadine. When the ANDAs were submitted to the FDA, the appellants sued the generic drug manufacturers for, among other things, infringement of the ’703 patent.
In its claim construction of the term "substantially pure" in connection with the intermediate in the '703 patent, the district court:
  • Found that the specification consistently used that term to describe both the intermediate and the end product.
  • Noted that the term is not defined anywhere in the specification.
  • Relied on statements from the prosecution history concerning the purity of an end product to conclude that the term "substantially pure" means at least 98% purity with respect to all impurities.
  • Extended this construction to describe the purity level of both the intermediate and the end product.
In light of this claim construction, the appellants stipulated that they could no longer prove infringement, and the district court entered final judgment in favor of the appellees. The appellants then appealed the district court's claim construction of the ’703 patent to the Federal Circuit.
The Federal Circuit agreed with the district court that the claims themselves were not sufficient to define "substantially pure," but found that the district court improperly conflated the purity required for the intermediate compound and end product.
The court noted that while the specification used "substantially pure" to refer to both the intermediate and end products, the relevant claims only referred to the intermediate. Therefore, it found no requirement to construe "substantially pure" consistently for both. The court was further persuaded because:
  • A person reasonably skilled in the art would recognize that it is not necessary for an intermediate in the claimed chemical reaction to have the same purity as the end product.
  • Giving the same meaning to both uses of "substantially pure" ignored the distinct contexts in which the term was used.
The Federal Circuit went on to construe "substantially pure" in the context of the intermediate to only apply to regioisomeric impurities, not all impurities.
Court document