The U.S. Court of Appeals for the Federal Circuit has reversed a Patent Trial and Appeal Board decision that invalidated Eye Therapies' patent claims for treating eye redness, finding that the Board misinterpreted key claim language in light of the patent's prosecution history.
Court Overturns Obviousness Ruling
In a precedential ruling issued Monday in Eye Therapies, LLC v. Slayback Pharma, LLC, the Federal Circuit vacated the PTAB's obviousness determination regarding U.S. Patent No. 8,293,742, which covers methods of treating conjunctival hyperemia using brimonidine, a vasoconstrictor. The patent claims methods of treating eye redness "consisting essentially of" administering brimonidine to patients with ocular conditions.
The inter partes review proceedings were initiated by Slayback Pharma to challenge the validity of Eye Therapies' patent. The PTAB had ruled that the claims were obvious over prior art references teaching the use of brimonidine alongside other active ingredients, interpreting "consisting essentially of" to permit inclusion of additional components that don't materially affect the invention's basic properties.
Prosecution History Reveals Narrower Interpretation
The Federal Circuit's analysis focused heavily on the patent's prosecution history at the USPTO. During original prosecution, Eye Therapies had initially claimed methods and compositions "comprising" brimonidine, but faced examiner rejection based on prior art claiming administration of brimonidine with brinzolamide, a separate active ingredient.
To overcome this rejection, Eye Therapies amended the claims to replace "comprising" with "consisting essentially of." In accompanying remarks, the applicant distinguished the prior art by explaining that the 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)."
The Federal Circuit found this prosecution history "strongly evinces a restrictive meaning of 'consists essentially of.'" The court noted that the applicant's use of "i.e." indicated "an intent to define the claimed 'methods consisting essentially of brimonidine' as 'methods which do not include administering other active agents.'"
Distinguishing Prior Precedent
The PTAB had relied on the Federal Circuit's 2009 ruling in Ecolab v. FMC Corp., where the court found that a patentee had not clearly disclaimed additional antimicrobial agents when using "consists essentially of." However, the Federal Circuit distinguished the current case, noting that unlike in Ecolab, where the specification disclosed compositions inconsistent with a restrictive interpretation, the intrinsic evidence here supported the narrower meaning.
The court acknowledged that some embodiments in the patent specification describe compositions containing active ingredients other than brimonidine, but found this "hardly surprising" given the narrowing amendments during prosecution. The Federal Circuit stated that such 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."
Implications for Patent Protection
Slayback Pharma had argued that Eye Therapies only contended its claims do not require additional active agents, not that they preclude their use. The Federal Circuit rejected this argument, applying reasoning analogous to its holding in Aylus Networks v. Apple (2017), where prosecution history estoppel was applied to dismiss similar contentions.
The court concluded that the Board's erroneous construction infected its obviousness ruling. While cautioning that proper claim construction could potentially lead to the same obviousness conclusion, the Federal Circuit found that the PTAB's analysis relied on a construction inconsistent with the prosecution history.
Remand for Further Proceedings
Having reversed the PTAB's claim construction and vacated its final written decision, the Federal Circuit remanded the case for further proceedings consistent with the corrected construction. The court did not prejudge whether the correct claim construction would permit the same factual findings or obviousness conclusion, leaving that determination for the Board on remand.
The ruling establishes important precedent for how prosecution history can narrow the typical meaning of transitional claim phrases, particularly when applicants make specific arguments to distinguish prior art during patent prosecution.
