The Appellants in HZNP Medicines v. Actavis Laboratories saw their hopes for rehearing dashed on February 25, 2020, when the Federal Circuit issued an order denying their petitions for panel rehearing and en banc rehearing. The decision leaves intact an order finding that claims reciting “consisting essentially of” could be found indefinite based on ambiguities in the basic and novel properties of the claimed compound—even if not recited in the claims.

The petitions stem from an appeal of a district court decision in which HZNP Medicines’ patents were found to be invalid. In the appeal to the Federal Circuit, the Court was tasked with deciding, among other issues, whether the phrase “consisting essentially of,” as used in the claims of the patents at issue, was indefinite. The patents at issue generally related to methods and compositions for treating osteoarthritis. The composition patents incorporated the “consisting essentially of” language and claim 49 of US Patent No. 8,252,838 (the ‘838 patent) provides an illustrative example of the way this language was used in the claims:

49. A topical formulation consisting essentially of:
1–2% w/w diclofenac sodium;
40–50% w/w DMSO;
23–29% w/w ethanol;
10–12% w/w propylene glycol;
hydroxypropyl cellulose; and
water to make 100% w/w, wherein the topical formulation has a viscosity of 500–5000 centipoise.

The Federal Circuit’s 1998 decision in PPG Indus. v. Guardian Indus. Corp., 156 F.3d 1351, established the principle that “consisting essentially of,” despite its apparent indefiniteness, has definite meaning when used in composition patents. In particular, use of this phrase indicates that the composition includes the listed ingredients that follow the phrase, as well as any unlisted ingredients that do not materially affect the basic and novel properties of the composition.

This principle was applied by the district court here in its August 17, 2016 Claim Construction Order and a subsequent ruling on a motion for reconsideration. The district court found that the definiteness of the claims turned on an identification of the basic and novel properties of the claimed composition. In this respect, the district court identified 5 different basic and novel properties of the claimed compound, including better drying time. The district court concluded that the property of better drying time was indefinite because of inconsistent drying time results presented in the specification. Due to the inconsistencies in the meaning of “better drying time,” the claims that recited the phrase “consisting essentially of,” under the district court’s reasoning, were also found to be indefinite. Essentially, the district court concluded that a person of skill in the art would not be able to understand the scope of the claimed phrase “consisting essentially of” based on the identified inconsistencies in the basic and novel property of “better drying time.”

In its October 2019 decision affirming the district court, the Federal Circuit reasoned, based on the definiteness standard from Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898 (2014), that use of the phrase “consisting essentially of” in a composition claim invites an evaluation of the basic and novel properties of the claimed composition. Thus, the Federal Circuit concluded, claims that use this phrase are definite as long as the basic and novel properties are definite as well.

The Federal Circuit thus turned to the assessment of the definiteness of the basic and novel properties. The Court concluded that a person of skill in the art would not be able to ascertain what constitutes a material effect to the basic and novel properties of the composition. The Federal Circuit agreed with the district court’s finding that the specification presented inconsistent results for the basic and novel property of better drying time. In particular, the specification described two different tests of drying time where, at 30 minutes after application of the inventive compound, some results showed better drying compared to a comparative compound while at least one test did not show improved drying at the 30 minute mark. The ambiguity in this basic and novel property arose, according to the Court, due to an absence in the prosecution history of the appropriate time frame for evaluating drying of the claimed composition. Therefore, the Federal Circuit reasoned that the claims that recited the “consisting essentially of” language were indefinite because of indefiniteness in the basic and novel properties of the claimed compound created by the specification.

The order denying rehearing was based on an 8-4 vote of the Federal Circuit judges, with the 4 judges who voted in favor of granting the rehearing issuing a dissenting opinion. The dissenting opinion expressed concern that the Court’s decision may lead to unintended consequences, and agreed with the Appellants that the Court erred in holding that the claims reciting “consisting essentially of” are indefinite because the basic and novel properties that the specification indicates the clamed composition process are indefinite. While the majority, in denying the petitions for rehearing, concluded that the claim was indefinite because of inconsistencies in the meaning of “better drying time,” the dissenting judges noted that better drying time is not recited in the claim. Rather, claim 49 recites diclofenac sodium, DMSO, ethanol, and propylene glycol, with all having definite quantity ranges. Claim 49 also recites hydroxypropyl cellulose with no range, and that the remainder of the formulation consists of water.

The dissenting opinion reasoned that the specification describes “better drying time” as one of the advantages of the claimed formulation, and that this disclosure may serve to satisfy other requirements of §112 and the utility requirement of §101. Hence, the dissenting opinion believed that the description of “better drying time” may be relevant to showing that the invention has utility and may assist in showing non-obviousness; however, it is the language of the claims that must be definite, rather than the clarity of an advantage of the invention. The dissenting opinion therefore concluded that the advantages of an invention are not to be incorporated into the claims for purposes of evaluating indefiniteness, and that such a holding could have unintended potential effects beyond the case at hand.

Ultimately, this decision highlights the importance of a well-drafted specification, particularly in the context of compound-related patents that utilize the “consisting essentially of” language in connection with reciting the ingredients of the claimed compound. While the phrase “consisting essentially of” is recognized as being definite in these types of patents, the Court’s decision illustrates that the phrase can be supplied with meaning from the specification. Namely, a court may look to the specification for the identification, meaning, and manner of evaluating the basic and novel properties of a compound claimed with “consisting essentially of” language. If the specification does not clearly articulate these points, or creates ambiguity in them, a compound patent claimed with “consisting essentially of” language may be invalidated for indefiniteness under this decision.