The same claim term (e.g., “substantially”) can have different constructions depending upon the context of how the term is used within the claims and specification.
Background / Facts: This case concerns the processes used to make various piperidine derivatives, which are commonly used as active ingredients in antihistamines. The lone asserted independent claim recites a process of preparing a piperidine derivative using a cyclopropylketone (“CPK”) intermediate and a piperidine intermediate, and refers to a “substantially pure regioisomer” of a specific formula as a precursor. However, the term “substantially pure” is not defined anywhere in the specification or otherwise associated with any numeric value. The district court determined that because the term “substantially pure” is used indiscriminately with regards to the CPK intermediate and the piperidine derivative end product throughout the specification, “substantially pure” should have only one construction throughout the patent. That construction was found to be 98% purity based on interference proceedings in a related application where the inventor was discussing the purity of pharmaceutical-grade end products.
Issue(s): Whether “substantially pure” as describing regioisomeric purity should be given the same construction as when it is used to describe overall chemical purity.
Holding(s): No. The “one construction throughout the patent” rule adopted by the district court is incorrect. “We have previously held that the same claim term can have different constructions depending upon the context of how the term is used within the claims and specification.” While “substantially pure” refers to both the CPK intermediate and the piperidine derivative end product in the specification, the term “substantially pure” is used only in reference to the CPK intermediate in relevant claims. The lack of any “substantially pure” limitation on the piperidine derivative end products in the claims obviates any explicit requirement to apply a construction of “substantially pure” that is consistent for both the CPK intermediate and the piperidine derivative end product. Further, a person of ordinary skill in the art would recognize that an intermediate of the claimed chemical reaction would not be required to have the same purity as the end product.