The definition of a claim term can be affected through “repeated and definitive remarks” in the prosecution history. In particular, a patentee will usually be bound by any characterizations of the “invention” as a whole.
Background / Facts: The patents here are directed to pharmaceutical compositions of the single-enantiomer drug eszopiclone, the active ingredient in the chiral drug marketed as a sleep medication under the brand name Lunesta. The claims require that each composition be “in the form of its dextrorotatory isomer and essentially free of its levorotatory isomer.” It is undisputed that neither the claims nor the written description defines what degree of enantiomeric purity of the dextrorotatory isomer is “essentially free” of the levorotatory isomer.
Issue(s): Whether the patentee is bound by its own definition, through a declaration submitted by a co-inventor and through amendments and arguments made during prosecution, of the invention as containing less than 0.25% of the levorotatory enantiomer.
Holding(s): Yes. The applicants’ “repeated and consistent attribution” of the purity level of less than 0.25% levorotatory isomer to “the invention” and “the instant invention” gives meaning to the term “essentially free.” For example, at one point, the applicants relied on the disclosure of Example 1 as “evidence of the fact that the material of the instant invention consists essentially of the [dextrorotatory]-isomer of zopiclone.” To make their meaning clear, the applicants also submitted a declaration by a named co-inventor, which stated that the data of Example 1, i.e., less than 0.25% levorotatory isomer content, “demonstrate the purity of the [dextrorotatory]-isomer of the invention and show[] that the instant invention consists essentially of the [dextrorotatory]-isomer of zopiclone.”