On Friday, the Federal Circuit weighed in on the exception to the closed nature of the “consisting of” transition in patent claims, holding that the exception is more limited than perhaps previously thought.  In Shire Development, LLC v. Watson Pharmaceuticals, Inc., the Federal Circuit reversed the district court’s infringement finding, holding that a claimed Markush group was closed and did not permit the addition of components not falling within the Markush group.

The district court found that Watson’s ANDA product infringed Shire’s formulation patent covering Lialda® (mesalamine).   The claims at issue covered pharmaceutical compositions having an (1) inner, lipophilic matrix; (2) an outer, hydrophilic matrix, and (3) other optional excipients.    The outer, hydrophilic matrix, according to the claims, “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.”  The district court found infringement even though the outer matrix of Watson’s ANDA formulation contained magnesium stearate, a compound outside the claimed Markush group.  The court reached this conclusion because it found that magnesium stearate was “unrelated” to the invention.  The district court found that since magnesium stearate did not drive the water-affinity property of the outer matrix, its inclusion in Watson’s formulation did not preclude infringement.

The Federal Circuit acknowledged an exception to the closed nature of “consisting of” for aspects that are “unrelated to the invention.”  The Federal Circuit discussed Norian v Stryker, where it concluded that adding a spatula to a calcium phosphate chemical kit did not avoid infringement because “the spatula has no interaction with the chemicals, and is irrelevant to the invention.”

In this case, it was not really disputed that magnesium stearate fell outside of the the Markush group; the appeal centered on whether magnesium stearate was sufficiently “unrelated to the invention” for the Norian exception to apply.   The district court found that, because magnesium stearate is highly lipophilic, it did not contribute to the hydrophilic nature of the outer matrix, and therefore was not “related” to the claimed invention. The Federal Circuit reversed, concluding that “the magnesium stearate structurally and functionally relates to the invention, and its presence in the outer matrix violates the ‘consisting of’ requirement in [the claim].”   The Federal Circuit specifically declined to find that the Norian exception could restrict “related” components only to those that advance or are intended to advance a Markush group’s allegedly inventive elements.

Future ANDA filers should keep this holding in mind when faced with branded patents containing “consisting of” Markush groups.  Based on this case, if an ANDA filer can include excipients outside of the Markush group, it will be much harder for the branded company to prevail on infringement.