Issue 202 | May 21, 2004
Housey Pharmaceuticals, Inc.,
v. AstraZeneca UK Ltd.

On May 7, 2004, the Federal Circuit issued a ruling in Housey Pharmaceuticals, Inc., v. AstraZeneca UK Ltd., 2004 U.S. App. LEXIS 9011 (Fed. Cir., May 7, 2004) that has broad impact for the pharmaceutical industry and highlights the ongoing dispute within the Federal Circuit regarding the proper use of dictionaries and treatises in claim construction.

Housey sued a number of the leading pharmaceutical companies (including AstraZeneca, Aventis Pharmaceuticals, Bristol-Meyers Squibb, Merck, Roche, and Wyeth) for infringement of four patents relating to a method of identifying an inhibitor or activator of a protein, which is useful for identifying drug candidates. Claim 1 of U.S. 4,980,281 is representative:

  1. A method of determining whether a substance is an inhibitor or activator of a protein whose production by a cell evokes a responsive change in a phenotypic characteristic other than the level of said protein in said cell per se, which comprises:
    (a) providing a first cell line which produces said protein and exhibits said phenotypic response to the protein;

    (b) providing a second cell line which produces the protein at a lower level than the first cell line, or does not produce[] the protein at all, and which exhibits said phenotypic response to the protein to a lesser degree or not at all;

    (c) incubating the substance with the first and second cell lines; and

    (d) comparing the phenotypic response of the first cell line to the substance with the phenotypic response of the second cell line to the substance.

As can be appreciated from this claim and evidenced by the list of defendants, the patents had broad reach. At issue was the meaning of the highlighted phrase, "an inhibitor or activator of a protein." Housey conceded that if the district court construction were upheld on appeal, the claims would be invalid and not infringed. The district court had construed the claims to encompass compounds that inhibit or activate a protein by both binding directly to it and by an indirect mechanism (e.g., by altering the biological pathway the produces the protein). Housey argued and maintained on appeal that the phrase should be construed to be limited to compounds that bind directly to the protein.

The Federal Circuit (Clevenger and Chief Judge Mayer) upheld the district court's construction. The Court found that while the definition of activators and inhibitors of enzymes (a class of proteins) in certain technical treatises required direct binding, other sources supported a broader interpretation requiring only that the compound have an effect on the biological activity. The Court found that the intrinsic evidence did not clearly disavow this broad plain meaning and, further, that it was consistent with this broad meaning. Accordingly, the Federal Circuit affirmed the lower court's ruling, thereby rendering the claims invalid, as Housey had stipulated.

In a strongly worded dissent, Judge Newman chastised the majority's primary reliance on dictionaries and treatises, arguing that precedent demanded that the construction of claim terms be sought not in these sources but in the patent specification. Judge Newman noted conflicting evidence as to the meaning of the disputed term and would have remanded the case to the district court for re-determination of the meaning of the term under the principle of claim construction that places primacy on the specification rather than dictionaries and treatises. Importantly, Judge Newman noted conflict in recent Federal Circuit case law, complaining, "My colleagues' approach to construction is based on confusing recent pronouncements of panels of this court, contravening earlier statements of precedent, thus adding to the confusion." Practitioners will be observing with interest how this conflict is resolved.

For more information on this topic, please contact Michael S. Greenfield, who is a partner at the law firm of McDonnell Boehnen Hulbert & Berghoff.

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