Eye Therapies, LLC v. Slayback Pharma, LLC, No. 2023-2173 (Fed. Cir. (PTAB) June 30, 2025). Opinion by Scarsi, joined by Taranto and Stoll.
Eye Therapies owns a patent that claims a method for reducing eye redness “consisting essentially of” administering brimondine to a patient. Slayback Pharma petitioned for inter partes review of all of the claims of that patent. The Board construed the phrase “consisting essentially of” and, relying on that construction, determined that all claims were unpatentable as obvious. Eye Therapies appealed the Board’s construction and ultimate determination of obviousness.
The Federal Circuit reversed the Board’s construction of “consisting essentially of,” vacated its obviousness finding, and remanded for further proceedings.
The Federal Circuit acknowledged that—consistent with the Board’s claim construction—the transitional phrase “consisting essentially of” generally “has long been understood to permit inclusion of components not listed in the claim, provided that they do not ‘materially affect the basic and novel properties of the invention.’” The court explained, however, that limiting statements in the patent prosecution history can “inform the meaning of the claim language by demonstrating how the inventor understood the invention and whether the inventor limited the invention in the course of prosecution, making the claim scope narrower than it would otherwise be.”
The Federal Circuit determined that such a situation presented itself in this case. During prosecution of the patent at issue, the applicant amended the claims to replace “comprising” with the transitional phrase “consisting essentially of” to distinguish the claims from the prior art. The applicant explained that the innovation in the “claimed methods is that they do not require the use of any other active ingredients (emphasis added) in addition to brimonidine.” In differentiating the claims, the applicant further stated that the prior art teaches away from methods consisting essentially of administering brimonidine (i.e., methods which do not include administering other active agents). The court determined that the applicant’s use of “i.e.” here indicates an intent to define the claimed “methods consisting essentially of brimonidine” as “methods which do not include administering other active agents.” As such, the court determined that the standard meaning of “consisting essentially of”—which would have allowed an interpretation that included additional active agents in addition to brimonidine—is incompatible with the more restrictive meaning the applicant ascribed to the phrase.
Because the PTAB’s obviousness analysis was predicated on its erroneous claim construction, the Federal Circuit vacated the unpatentability determination and remanded for further proceedings under its construction of the term “consisting essentially of.”
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