The “Consisting Essentially Of” Transition Phrase, if not Adequately Supported, May Render Claims Indefinite

by Joshua B. Goldberg (Nath, Goldberg & Meyer – U.S.A.)

It has long been the case in the U.S. that the patent claim transition phrase “consisting essentially of” is well understood to the ordinary practitioner to clearly limit the claims to those recited elements plus any other elements that “do not materially affect the basic and novel properties of the invention.” Now, however, the US Court of Appeals for the Federal Circuit (CAFC) has decided that that the phrase “consisting essentially of” was indefinite based on inadequate support for the “basic and novel” feature of “better drying time”, calling into question the value of this transition phrase moving forward.

In the recent case of HZNP Medicines LLC v. Actavis Laboratories UT, Inc. (Fed. Cir. 2019),, the CAFC held most but not all of the claims at issue as invalid for a variety of reasons. Of particular importance, the CAFC held some of the involved claims were invalid as indefinite based on construction of the claim term “consisting essentially of”. Specifically, this claim term was held indefinite because “the parties disputed what were ‘basic and essential’ properties of the claimed formulations and thus the scope of what additional components could be added in excess of the recited elements was indefinite.”

In the original decision, the District Court recognized five “basic and essential” properties of the claimed formulations: “(1) better drying time; (2) higher viscosity; (3) increased transdermal flux; (4) greater pharmacokinetic absorption; and (5) favorable stability.” The District Court limited its determination to the “better drying time” property, finding it to be indefinite because the two methods set forth in the specification for measuring this property gave inconsistent results. This persuaded the District Court that the skilled worker would not know which measurement method to use, which precluded the skilled artisan from having the “reasonable certainty” required under Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898, 910 (2014), for the “consisting essentially of” term to be definite.

This part of the decision was affirmed by the CAFC. Despite the clear, distinct meaning of “consisting essentially of”, the CAFC agreed with the District Court that the indefiniteness question involves the nature of the “basic and novel” properties of the formulation “consisting essentially of” the expressly recited components. Ultimately, the CAFC disagreed with HZNP’s contention that the standard meaning of “consisting essentially of” should apply only to the elements recited in the claims. In reaching this decision, the CAFC indicated:

By using the phrase “consisting essentially of” in the claims, the inventor in this case incorporated into the scope of the claims an evaluation of the basic and novel properties.  The use of “consisting essentially of” implicates not only the items listed after the phrase, but also those steps (in a process claim) or ingredients (in a composition claim) that do not materially affect the basic and novel properties of the invention.  Having used the phrase “consisting essentially of,” and thereby incorporated unlisted ingredients or steps that do not materially affect the basic and novel properties of the invention, a drafter cannot later escape the definiteness requirement by arguing that the basic and novel properties of the invention are in the specification, not the claims.  Indeed, this contravenes the legal meaning associated with the phrase “consisting essentially of.”  And a holding to the contrary would promote the innovation-discouraging “zone of uncertainty” that the Supreme Court has warned against.

Accordingly, the majority held that the District Court properly applied these rubrics in concluding that the term “consisting essentially of” was indefinite based on the “basic and novel” feature of better drying time.

In her dissent, Judge Newman faulted the majority for incorporating method steps (better drying time) or properties (increased stability) into indefiniteness determinations of composition of matter claims.  But Judge Newman’s principal concern was that the majority’s decision will “cast countless patents into uncertainty.”

It remains to be seen whether this decision is an anomaly, or whether the ability to use the “consisting essentially of” claim language in the US will be drastically limited.