In Shire Development. LLC v. Watson Pharmaceuticals, Inc., [2016-1785] (February 10, 2017), the Federal Circuit reversed a finding of infringement because the accused product did not meet the Markush claim element, and remanded for entry of an order of non-infringement.

The claims of U.S. Patent No. 6,773,720 required:

an outer hydrophilic matrix wherein the lipophilic matrix is dispersed, and said outer hydrophilic matrix consists of compounds selected from the group consisting of polymers or copolymers of acrylic or methacrylic acid, alkylvinyl polymers, hydroxyalkyl celluloses, carboxyalkyl celluloses,

polysaccharides, dextrins, pectins,

starches and derivatives, alginic acid, and natural or synthetic gums

After noting that a Markush claim is a particular kind of patent claim that lists alternative species or elements that can be selected as part of the claimed invention, the Federal Circuit pointed out that the Markush elements used the language “consisting of” which is presumed to be closed to additional elements.  Though the “consisting of” presumption is very strong, there have been rare exception for “aspects unrelated to the invention.”

The Federal Circuit found that magnesium stearate, an excipient not within the claim 1(b) Markush group, was present in the outer hydrophilic matrix, and thus the claim 1(b) limitation was literally violated.  The district court nonetheless found infringement because the component outside of the Markush group — i.e., the lipophilic magnesium stearate in the hydrophilic outer matrix — was unrelated to the invention.  The Federal Circuit disagreed with the district court’s interpretation of what constitutes a component unrelated to the invention.  The Federal Circuit found that the magnesium stearate structurally and functionally relates to the invention, and its presence in the outer matrix violates the “consisting of” requirement in claim 1(b).

While the magnesium stearate was included as a lubricant, rather than for its lipophilic properties, this was not sufficient to overcome the strong presumption of the closed nature of the claim.  Even the fact that examples in the patent included magnesium stearate was insufficient to overcome this strong presumption.