Use of “consisting of” Creates a Strong Presumption that is Difficult to Overcome

By: Anthony Amert


In an appeal of a district court ruling on a patent infringement suit, the U.S. Federal Circuit in Shire v. Watson reminded patentees that claim language can create presumptions regarding claim scope that impact the boundaries of the claimed subject matter that are difficult to overcome and may preclude a finding of infringement.

In the litigation, Shire Development, LLC sued Watson Pharmaceuticals, Inc. for infringement of claims 1 and 3 of U.S. Patent No. 6,773,720 (“’720”).  Claim 1 of the ‘720 patent was directed toward an oral pharmaceutical composition.  The district court held that Watson’s product infringed claim 1 of the ‘720 patent.

The claimed pharmaceutical composition required an outer hydrophilic matrix that consists of compounds defined by a Markush group.  Typically, to infringe such a claim a product must include an outer hydrophilic matrix that only includes compounds defined by the Markush group.  The use of consisting of creates a presumption that the hydrophilic matrix contains only those compounds expressly set forth in the closed group, as opposed to the use of comprising which would create a presumption that the hydrophilic matrix contains includes both compounds expressly set forth in the closed group and others not set forth in the closed group.

However, while consisting of limits the claimed invention, it does not limit aspects that are unrelated to the invention.  In claim 1 of the ‘720 patent, inclusion of compounds in a hydrophilic matrix that are not defined by the Markush group and that do not impact the chemical activity of the claimed matrix, i.e., impact whether the matrix is hydrophilic, are unrelated to the invention.

The district court found that the Watson product accused of infringing the ‘720 patent had a hydrophilic matrix that included compounds not defined by the Markush group, which typically renders the accused product to be non-infringing.  However, the district court held that the accused product still infringed the ‘720 patent because the compounds not defined by the Markush group were unrelated to the invention.  In other words, the district court held that Watson’s product, even though it failed to explicitly meet all of the claim limitations, still infringed the ‘720 patent because the inclusion of the compounds not defined by the Markush group did not change the chemical activity of the claimed hydrophilic matrix.

When reviewing the district court holding, the court of appeals found that the district court had erred by finding that the compounds not defined by the Markush group included in the hydrophilic matrix of the accused product were unrelated to the invention.  To reach this conclusion, the court of appeals looked to the chemical activity of the compounds not defined by the Markush group included in the hydrophilic matrix and found that inclusion of the compounds impacted the chemical activity of the hydrophilic matrix.  Due to the change of chemical activity imparted by the inclusion of the compounds, the court of appeals concluded that the inclusion of these compounds was related to the invention because the compounds made the hydrophilic matrix less hydrophilic.

The holding by the court of appeals reminds patent applicants that using extremely limiting language such as consisting of can make designing around a patent a much easier task.  Had the patentee here used less limiting language such as consisting essentially of, which allows infringement to be found when a product includes components not explicitly listed in the claim so long as they do not materially affect the basic and novel properties of the invention, the outcome of the appeal would likely have ended more favorably for Shire Development.