Holding: The typical meaning of the phrase “consisting essentially of” can be modified by limiting statements made during patent prosecution which demonstrate how the inventor understood the invention.
Eye Therapies owns US Patent No. 8,293,742 which teaches a method of reducing eye redness using brimonidine. The preamble for the independent claims of the ‘742 Patent each use the phrase “consisting essentially of” when describing the administration of brimonidine or the administration of a composition consisting essentially of brimonidine. Initially, the claims of the ‘742 Patent used “comprising” in the preamble rather than “consisting essentially of.” However, during prosecution, the examiner found these claims to be anticipated by Dean, a prior art reference that disclosed the administration of brimonidine and brinzolamide to treat ocular diseases. In response to this rejection, the claims were amended to include the “consisting essentially of” language, since Dean only disclosed the use of brimonidine in combination with brinzolamide.
Slayback challenged the patentability of the ‘742 Patent in an IPR, and the PTAB held all claims of the ‘742 Patent to be unpatentable. In the IPR, the PTAB construed the phrase “consisting essentially of” to have its normal meaning that the invention necessarily includes the listed ingredients but is open to unlisted ingredients that do not materially affect the basic and novel properties of the invention. Using this construction, the PTAB reasoned that since the specification of the ‘742 Patent stated that low-dose brimonidine can reduce eye redness on its own, additional agents included in a composition for treatment would not materially affect the basic and novel characteristics of the invention. Therefore, the phrase “consisting essentially of” did not preclude the use of additional active agents in the composition.
Eye Therapies argued that the prosecution history of the ‘742 Patent demonstrated that “consisting essentially of” should have a special meaning in this case to require that brimonidine be the sole active ingredient in a composition used for treating eye redness. The Federal Circuit reversed the PTAB’s claim construction and agreed with Eye Therapies, finding that a patentee can alter the typical meaning of the phrase “consisting essentially of” by making this alternative meaning clear in the specification or disclaiming an alternative meaning in the prosecution history. In the prosecution history of the ‘742 Patent, the applicant stated that the innovation was that the claimed method did not require the use of any other active ingredients other than brimonidine. Additionally, the examiner repeated this distinction as one of the reasons for allowance in the notice of allowance.
The Federal Circuit recognized that these statements may not reach the level of unmistakable disavowal, but the statements may still be used to inform the claim construction. Amendments and arguments that are made during prosecution can be used to limit claim interpretation. In this case, the ‘742 Patent was allowed because claimed methods did not require the use of any active ingredients other than brimonidine. This promotes a more restrictive interpretation of the phrase “consisting essentially of” in comparison to its standard meaning. Additionally, the more restrictive interpretation applies even though some embodiments described in the specification of the ‘742 Patent would not fit within this construction. A claim construction does not have to encompass all alternative embodiments in the application, particularly when there is compelling support for the more restrictive claim construction in the prosecution history.
Federal Circuit Precedential 
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