Eye Therapies, LLC v. Slayback Pharma, LLC
Authored by: Jeremy J. Gustrowsky
In a significant decision for patent claim interpretation, the Federal Circuit recently reversed a Patent Trial and Appeal Board (PTAB) ruling in Eye Therapies, LLC v. Slayback Pharma, LLC, clarifying how the phrase “consisting essentially of” should be understood in patent claims. The case centered on U.S. Patent No. 8,293,742, which covers methods for reducing eye redness by administering low concentrations of brimonidine. The key dispute was whether the patent claims allowed for the use of other active ingredients alongside brimonidine.
During the original patent prosecution, the applicant changed the claim language from “comprising” (an open-ended term) to “consisting essentially of” to overcome prior art that involved brimonidine used with other drugs. The applicant specifically argued that their invention did not require any other active ingredients besides brimonidine. However, the PTAB interpreted “consisting essentially of” in its usual, broader sense, which can allow for unlisted ingredients as long as they don’t change the invention’s main features. Based on this, the PTAB found the claims unpatentable over the prior art.
The Federal Circuit disagreed, finding that the prosecution history—especially the applicant’s clear statements and use of “i.e.” to define the claim scope—showed an intent to exclude other active ingredients entirely. The court emphasized that while “consisting essentially of” is typically somewhat open-ended, patent applicants can limit its meaning through statements made during prosecution. Because the PTAB relied on the broader interpretation, its analysis of obviousness was flawed.
As a result, the Federal Circuit reversed the PTAB’s claim construction, vacated its obviousness finding, and sent the case back for further proceedings under the narrower interpretation. This decision highlights potential issues with using the term “consisting essentially of” rather than “comprising”, and the importance of clear statements during patent prosecution. It further demonstrates how prosecution history can shape the meaning of claim terms.