In Shire, the Federal Circuit entered judgment of non-infringement upon a finding that Watson’s accused drug composition did not satisfy the Markush group requirements of Shire’s claims. Shire’s had used the “closed” transition phrase “consists of” in drafting claim limitations related to an outer hydrophilic matrix. Watson’s composition contained additional matrix components that were not among those recited in the claim, and therefore did not infringe the patent.
Shire’s patent to a controlled release oral composition of mesalamine, marketed as LIALDA®, having an inner lipophilic matrix that “consists of” substances selected from a specific recitation of lipophilic chemicals, an outer hydrophilic matrix that “consists of” substances selected from a specific recitation of hydrophilic chemicals and optionally other excipients. Watson’s allegedly infringing product contained substances from both groups of claimed matrices, but differed from the claim by the additional presence of magnesium stearate, a lipophilic lubricant, in the outer matrix.
The use of the transitional phrase “consists of” in a claim creates a strong presumption that the claim excludes any elements, steps or ingredients not specified in the claim. It is referred to as a closed transition, in contrast to open transitions such as the phrase “comprising,” which covers products having additional unclaimed elements so long as the claim limitations are met.
The district court found Watson’s product infringed Shire’s patent. With respect to the added magnesium stearate, the court discounted that compound by relying on a rare exception to the presumption for closed transitions that excludes additional elements that are unrelated to, or outside the scope of, the claimed invention. For example, in an earlier case, the Federal Circuit held that the addition of a spatula to a claimed chemical kit for repairing teeth did not avoid infringement because the spatula had no interaction with, and was irrelevant to, the function of the chemicals themselves. Here, the district court found that any lipophilic properties of the magnesium stearate were overwhelmed by hydrophilic compounds in the outer matrix, and thus it had no effect on the hydrophilic nature of the outer matrix making it functionally unrelated to the limitation.
Watson appealed the decision to the Federal Circuit, which reversed. It held that the district court’s explanation concedes that the lipophilic magnesium stearate interacts with, and is related to, the claimed outer matrix. To interpret “unrelated” to mean “anything that doesn’t advance the group’s inventive properties” would mean to equate “consisting of” with “consisting essentially of” (which does allow for components that do not materially affect the basic and novel properties of the invention).
Key Takeaway: Where a Markush group is introduced with the transition phase, “consisting of,” there is a strong presumption that the claim does not permit the addition of elements not listed in the Markush group. A narrow exception exists for additional elements that are unrelated to the invention, but that exception only covers additional elements that have no functional or structural relationship to the claimed invention.