The US Court of Appeals for the Federal Circuit reversed a district court’s judgment of infringement, finding that the accused product contained an excipient not within the asserted claim’s closed Markush group. Shire Dev., LLC v. Watson Pharm., Inc., Case No. 16-1785 (Fed. Cir., Feb. 10, 2017) (Hughes, J).

The patent at issue is directed to a controlled-release oral pharmaceutical composition of mesalamine used to treat certain inflammatory bowel diseases. The claimed composition includes the mesalamine active ingredient, an inner lipophilic matrix, an outer hydrophilic matrix and other optional excipients. A lipophilic matrix has an affinity for lipids and resists dissolving in water, while a hydrophilic matrix has an affinity for water and readily dissolves in water. 

In a previous appeal, the Federal Circuit found that the claimed matrix compositions were limited by the Markush groups added during prosecution to overcome the examiner’s obviousness rejection (IP Update, Vol. 18, No. 7). In that prior appeal, the Court also found that the correct construction of the claims required that the inner volume contain substances from the group described for the inner lipophilic matrix, and that the outer volume separately contain substances from the group described for the outer hydrophilic matrix.

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 language of a Markush claim is generally presumed to exclude any elements, steps or ingredients not specified in the claim, unless this presumption is overcome by the specification and prosecution history. Specifically, at issue in this case, the Markush group is recited as follows:

[A]n 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. (emphasis added)

On remand, the district court found that Watson’s abbreviated new drug application (ANDA) product satisfied the Markush limitations despite containing an excipient falling outside of the Markush group, i.e., magnesium stearate. Relying on the Federal Circuit’s 2004 decision in Norian Corp., the district court concluded that the magnesium stearate was “unrelated” to the invention because it did not drive the water-affinity property of the respective matrix, and thus the inclusion of this excipient did not avoid infringement. Watson appealed.

The Federal Circuit reversed. The Court found that Watson’s ANDA product did not literally infringe the recited Markush group because the product included an excipient not within the Markush group. Disagreeing with the district court’s interpretation of Norian, the Federal Circuit explained that Norian did not restrict “related” components to only those that advance or are intended to advance a Markush group’s allegedly inventive elements. The Court thus rejected Shire’s argument that, notwithstanding the addition of magnesium stearate, the accused product satisfied the Markush group because the excipient is “overwhelmed” by the hydrophilic properties of the sodium starch glycolate in the extragranular space. The Court found that the magnesium stearate structurally and functionally relates to the invention because it retains its lipophilic character in the extragranular space. Concluding that magnesium stearate’s presence in the outer matrix is inconsistent with the “consisting of” requirement in claim 1(b), the Court found that Watson’s ANDA product did not satisfy the Markush group requirement and therefore did not infringe.

Practice Note: The Federal Circuit explained that the Markush group “consisting of” was different from one recited as “comprising” or “consisting essentially of,” which might admit components not explicitly recited in the claim.