Patent attorneys learn at an early age that "consisting of" is one of the most narrowly construed terms in patent claims, not allowing for any additional elements than those recited in the claim. Contrast this construction with other more liberal transitional terms such as "comprising," which allows for the presence of additional components or steps, and "consisting essentially of," which allows for additional components or steps as long as they do not affect the basic and novel characetristics of the claimed element. However, there are exceptions to every legal rule, and this rule is no exception. Under Norian Corp. v. Stryker Corp., 363 F.3d 1321, 1331 (Fed Cir. 2004), there is a limited exception that allows for additional elements not recited in the claim when those elements are not related to the invention.
The patent holder in this case pushed the Norian exception to the limit, arguing that an accused formulation satisfied the "inner lipophilic matrix" limitation in U.S. Patent No. 6,773,720, even though "consisting of" was used to define the elements of the "inner lipophilic matrix," and the alleged infringer's inner lipophilic matrix also included magnesium stearate, . The claim term recited:
an inner lipophilic matrix consisting of substances selected from the group consisting of unsaturated and/or hydrogenated fatty acid, salts, esters or amides thereof, fatty acid mono-, di- or triglycerids, waxes, ceramides, and cholesterol derivatives with melting points below 90° C.
The trial court agreed with the patent owner, and held that the alleged infringer's formulation did in fact satisfy this limitation, but the Federal Circuit reversed, holding that the trial court's decision would allow the exception to swallow the rule. According to the Federal Circuit:
Shire argues, and the district court held, that the magnesium stearate in Watson's product-which Watson includes as a lubricant rather than for its lipophilic properties- is unrelated to the invention because it is not sufficiently lipophilic to render the outer matrix lipophilic. But Norian did not restrict "related" components to only those that advance or are intended to advance a Markush group's allegedly inventive elements. And we decline to impose such a requirement, which would in effect equate the scope of a Markush group's "consisting of" language with either "comprising" or "consisting essentially of" language.
The court could not figure out how to distinguish the patent owner's construction of "consisting of" with the normally accepted construction of "consisting essentially of."
It's nice to see good creative lawyering pushing the envelope of our firmly held dogmas once in a while, and this case was no exception. For more reading, go to Shire Dev. v. Watson Pharms., 2017 U.S. App. Lexis 2393.