Eye Therapies, LLC v. Slayback Pharma, LLC, Appeal No. 2023-2173 (Fed. Cir. June 30, 2025)

In its only precedential patent opinion last week, the Federal Circuit reviewed construction of the transitional claim phrase “consisting essentially of” in a patent for eyedrops owned by Eye Therapies, LLC.   Following an inter partes review in which the Patent Trial and Appeal Board found all claims of U.S. Patent No. 8,293,742 unpatentable as obvious, the Court found that the Board had erred by applying the typically open-ended meaning of “consisting essentially of” in view of the patent’s prosecution history, vacated the Board’s obviousness finding, and remanded for further proceedings.

The ’742 patent claims methods of treating conjunctival hyperemia—or eye redness—using a low-concentration dose of brimonidine, a vasoconstrictor.  As relevant to the appeal, its claims recite compositions “consisting essentially of” brimonidine and methods of treating redness “consisting essentially of” administering brimonidine.  In the underlying proceedings, the Board relied on Federal Circuit precedent to the effect that the transition “consisting generally of” “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.”  AK Steel Corp. v. Sollac, 344 F.3d 1234, 1239 (Fed. Cir. 2003) (citation and internal quote marks omitted).  Finding that the ’742 patent thus did “not preclude the use of additional active agents that may also cause vasoconstriction and reduction of hyperemia,” the Board found its claims obvious over prior art references teaching the use of brimonidine alongside other active ingredients.

Based on its prosecution history, however, the Federal Circuit disagreed.  Prior to issuance, the ’742 patent’s claims had initially recited methods and compositions “comprising” brimonidine, with “comprising” traditionally being a completely open-ended transition.  Those claims were rejected over the prior art, and the applicant had amended them to replace “comprising” with the transition “consisting essentially of.”  In its remarks accompanying the amendments, the applicant distinguished the prior art by explaining, e.g., that its claimed methods “do not require the use of any other active ingredients in addition to brimonidine,” and that the prior art does not teach “methods consisting essentially of administering brimonidine (i.e. methods which do not include administering other active agents).”  On such a record, the Federal Circuit found that the applicant had narrowed the typical meaning of “consisting essentially of” in this case to preclude the coverage of methods or compositions using any other active ingredients.  The Court particularly noted the applicant’s use of “i.e.” at points, which it held “indicates an intent to define the claimed ‘methods consisting essentially of brimonidine’ as ‘methods which do not include administering other active agents.’”  (Original emphasis.)  Against this intrinsic record, the Court gave little weight to the fact that its construction excluded certain of the ’742 patent’s disclosed embodiments, noting that an applicant’s narrowing amendments “post-dating the filing of the specification, naturally can and often do result in claims that do not cover all embodiments in the specification.”

Accordingly, the Federal Circuit reversed the Board’s construction of “consisting essentially of,” but did not purport to “prejudge whether the correct claim construction permits the same factual findings or obviousness conclusion.”  Instead, the Court vacated the Board’s obviousness determination and remanded for further proceedings consistent with its corrected construction.

The full opinion can be found here.

By Jason A. Wrubleski

This article summarizes aspects of the law and does not constitute legal advice. For legal advice with regard to your situation, you should contact an attorney.