“Consisting of” Markush Claim Excludes Components Unrelated to the Invention

The Federal Circuit reversed a district court’s finding that Watson infringed Shire’s patent directed to a controlled-release oral pharmaceutical composition containing mesalamine, used to treat inflammatory bowel diseases.¹

Shire’s claims recited that the pharmaceutical composition contained an inner lipophilic matrix and an outer hydrophilic matrix. The opinion focused on the claim’s recitation regarding the outer hydrophilic matrix:

an outer hydrophilic matrix wherein the lipophilic matrix is dispersed, and said outer hydrophilic matrix consists of compounds selected from the group consisting of . . .²

The court focused on the recitation of “consists of compounds selected from the group consisting of” in finding that Watson’s product did not infringe the claim. Watson’s product contained a hydrophilic portion that contained a lipophilic component, magnesium stearate. Magnesium stearate was not included in the Markush group. The court explained that the terms in the claim of “consists of” to characterize the matrix and the term “consisting of” to define the groups creates “a very strong presumption” that the claim element is closed and excludes any elements not specified in the claim.³ A rare exception to the presumption exists for “aspects unrelated to the invention.”⁴

The district court reasoned that Watson infringed because the component outside of the Markush group, i.e., the lipophilic magnesium stearate, is unrelated to the invention because it is overwhelmed by the hydrophilic components. The Federal Circuit rejected this interpretation, disagreeing with Shire’s argument that magnesium stearate is unrelated to the invention because it is not sufficiently lipophilic to render the hydrophilic portion lipophilic. Thus, the Federal Circuit found that “related” components are not restricted only to those components that advance or are intended to advance a Markush group’s inventive elements. Doing so, the court argued, would in effect equate the scope of a Markush group’s “consisting of” language with either “comprising” or “consisting essentially of” language.