Federal Circuit Reverses PTAB on “Consisting Essentially Of”: Eye Therapies v. Slayback Pharma and the Power of Prosecution History

Introduction
The Federal Circuit’s recent decision in Eye Therapies, LLC v. Slayback Pharma, LLC offers a significant reminder of the interpretive weight prosecution history can carry in claim construction, especially for transitional phrases like “consisting essentially of.” The case centers on the patentability of methods for reducing eye redness using low concentrations of brimonidine, highlighting the nuanced interplay between claim language, prosecution history, and obviousness in pharmaceutical patent litigation.

Patent at Issue
The sole patent at issue is U.S. Patent No. 8,293,742 (“the ’742 patent”), owned by Eye Therapies, LLC. All claims of the ’742 patent were challenged and ultimately held unpatentable by the Patent Trial and Appeal Board (PTAB) in an inter partes review (IPR) initiated by Slayback Pharma, LLC.

What is the Technology?
The ’742 patent relates to methods for reducing ocular redness (conjunctival hyperemia) by administering low concentrations of brimonidine, an alpha-adrenergic receptor agonist known for its vasoconstrictive properties. Vasoconstriction counteracts vasodilation, which can cause undesirable clinical effects such as eye redness, surface hemorrhage, and hyperemia, particularly following procedures like LASIK surgery. The claimed methods focus on topical administration of brimonidine at concentrations between about 0.001% and 0.05% weight by volume, with specific claims specifying a pH range for the formulation and the use of ocular drops.

Representative Claims
The representative claims were independent claims 1 and 3 of the ’742 patent, both of which use the transitional phrase “consisting essentially of”:

• Claim 1: “A method for reducing eye redness consisting essentially of administering brimonidine to a patient having an ocular condition, wherein brimonidine is present at a concentration between about 0.001% weight by volume and about 0.05% weight by volume.”

• Claim 3:  “A method for reducing eye redness consisting essentially of topically administering to a patient having an ocular condition a composition consisting essentially of brimonidine into ocular tissue, wherein pH of said composition is between about 5.5 and about 6.5, wherein said brimonidine concentration is between about 0.001% and about 0.025% weight by volume and wherein said composition is formulated as an ocular drop.”

Prosecution History

During prosecution, the Examiner rejected prior versions of claims 1 and 3 that used the transitional phrase “comprising” instead of “consisting essentially of”.  The Examiner found that the claims reciting “comprising” were anticipated by U.S. Patent No. 6,242,442 (“Dean”), which disclosed the administration of brimonidine and brinzolamide to treat ocular diseases.  In response, the Applicant replaced “comprising” with “consisting essentially of”, among other amendments.  The Applicant argued that Dean only disclosed the use of brimonidine in combination with brinzolamide.  While Dean required brinzolamide as “an active ingredient” in addition ot brimonidine, the Applicant argued that the revised claims “do not require the use of any other active ingredients” (emphasis added) in addition to brimonidine.  The Examiner allowed the amended claims citing to Applicant’s argument that “the presently claimed methods do not require the use of any other active ingredients (emphasis added) in addition to brimonidine”. 

Decision of the PTAB
The PTAB instituted IPR and ultimately held all challenged claims unpatentable. The PTAB’s analysis turned on two key points:

1.       Claim Construction: The PTAB construed “consisting essentially of” according to its typical meaning, allowing for the presence of unlisted ingredients so long as those ingredients do not materially affect the basic and novel properties of the invention. The PTAB rejected Eye Therapies’ argument that the prosecution history required a narrower construction that would exclude any active ingredient other than brimonidine. The PTAB reasoned that such a reading would collapse “consisting essentially of” into the closed term “consisting of,” contrary to established Federal Circuit precedent.  Instead, the PTAB concluded that “under the proper scope of the claims and consistent with the prosecution history, the claimed methods cannot include additional active ingredients that are required to perform the method”.   Applying the decision in Ecolab, Inc. v. FMC Corp., 569 F.3d 1335 (Fed. Cir. 2009), the PTAB reasoned that “because the Specification states that low-dose brimonidine alone can significantly reduce hyperemia, if there are additional agents beyond low-dose brimonidine administered to a patient that may also reduce eye redness … those additional agents would not materially affect the basic and novel characteristics of the invention”.  Thus, the PTAB held that “the transitional phrase ‘consisting essentially of’ does not preclude the use of additional active agents that may also cause vasoconstriction and reduction of hyperemia along with low-dose brimonidine”.

2. Obviousness: Applying its broader construction, the PTAB found the prior art (including Dean, Norden, and Gil) taught or suggested all claim limitations, and that a person of ordinary skill would have been motivated to combine references with a reasonable expectation of success. The PTAB concluded that the claims were obvious, noting that additional agents administered with brimonidine (even those with similar vasoconstrictive effects) would not “materially affect” the invention’s basic and novel characteristics.

Issues on Appeal
Eye Therapies appealed on two grounds:

1.      Claim Construction:  Whether the PTAB erred in construing “consisting essentially of” to allow for the co-administration of other active ingredients, despite the prosecution history suggesting a narrower scope.

2. Obviousness: Whether the PTAB’s obviousness determination, which relied on its claim construction, could stand if the claims were properly construed to exclude other active ingredients.

Decision by the Federal Circuit
The Federal Circuit reversed the PTAB’s claim construction, vacated the obviousness finding, and remanded for further proceedings:

1.       Claim Construction: The Federal Circuit stated that the term “comprising” is an open-ended transitional term that allows for additional steps, whereas the 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.”  However, the Federal Circuit noted that as discussed in Ecolab, a patentee can alter the meaning of “consisting essentially of” by making the intended meaning clear in the specification or disclaim an alternative meaning in the prosecution history.  Citing Phillips v. AWH Corp., 415 F.3d 1303, 1317 (Fed. Cir. 2005), the Court stated 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 Court found that the prosecution history demonstrated a clear intent to give “consisting essentially of” a narrower meaning than its typical usage. During prosecution, the applicant amended the claims to overcome prior art (Dean) by replacing “comprising” with “consisting essentially of” and explicitly argued that the invention did not require any active ingredients other than brimonidine. The Examiner’s allowance was expressly based on this representation. The Court held that, in this context, “consisting essentially of” must be construed to exclude any active ingredient other than brimonidine.

2. Obviousness:  Because the PTAB’s obviousness analysis was predicated on its broader claim construction, the Federal Circuit vacated the unpatentability determination. The Court emphasized that the PTAB had not considered whether the prior art would have rendered obvious the narrower claims—i.e., methods excluding all other active ingredients. The case was remanded for the PTAB to reassess obviousness under the correct construction.

Key Takeaways

• Prosecution History Can Override Typical Claim Term Meanings: Even well-established transitional phrases, such as “consisting essentially of,” can be limited by statements made during prosecution. Here, the Applicant’s explicit and repeated representations to the Examiner narrowed the claim scope, and the Federal Circuit gave those statements decisive weight.

• Claim Construction Drives Obviousness Analysis: The scope of the claims as construed determines the relevant prior art and the obviousness analysis. A broader construction may sweep in more prior art, while a narrower construction, especially one supported by prosecution history, can significantly alter the outcome.

• PTAB and Parties Must Heed the Prosecution History: Both the PTAB and litigants should carefully consider the entire prosecution record. Overlooking or minimizing prosecution history can lead to reversible error, as seen here.

This decision is an important reminder for patent prosecutors and litigators alike: the words you choose and the arguments you make during prosecution can often define your claims for years to come.

This post was written by Lisa Mueller