The Federal Circuit recently affirmed a district court’s determination, holding a group of patents invalid for indefiniteness.

In December 2014, HZNP Medicines LLC (“Horizon”) brought suit against Actavis Laboratories UT, Inc. (“Actavis”) in the District of New Jersey, alleging infringement of a group of its patents relating to the formulation and method-of-use of a drug for treating osteoarthritis. This suit was in response to Actavis having previously filed an ANDA with a Paragraph IV certification, stating that Horizon’s patents-at-issue were invalid and that they would not be infringed by Actavis’ generic product. The district court issued its Markman order on August 17, 2016, finding three terms in Horizon’s asserted claims indefinite and thus ruling in summary judgment that the formulation patents were invalid.

On appeal, the Federal Circuit affirmed.

The Federal Circuit addressed whether three key terms met the definiteness requirement under 35 U.S.C. 112 (b). For the first term, “impurity A,” Actavis successfully argued at the district court that the term “impurity A” is indefinite because neither the claims nor intrinsic evidence defined it. Horizon argued that a person of ordinary skill in the art (POSITA) would recognize “impurity A” as “USP Related Diclofenac Compound A” based on extrinsic evidence, including available pharmacopeias. The Court disagreed with Horizon for several reasons. The Court concluded that the term’s usage within the challenged claims does not make clear that it refers to any particular compound. Nor does the specification provide a clue as to the impurity’s identity. Also, the Court noted that the specification and claims referred to “impurity A” in quotes, indicating that its actual composition was not known. Therefore, the term “impurity A” is indefinite.

Second, the Court held a set of claims invalid for indefiniteness because they regarded the degradation of “impurity A” through the term “degrades at less than 1% over 6 months.” The Court reasoned that because “impurity A” itself was unidentified and therefore indefinite, it followed that any claim regarding its degradation would also be invalid as indefinite.

Third, the Court addressed the effect of the transitional phrase “consisting essentially of” on indefiniteness. The transitional phrase “consisting essentially of” serves a middle ground between closed-ended claims using the phrase “consisting of” and open-ended claims using the phrase “comprising.” The Court states that here it means that the invention necessarily includes the listed ingredients within the claims, but could include unlisted ingredients that do not materially affect the basic and novel properties of the invention. Characterizing the patents’ basic and novel property as superior drying time of the compositions of the invention, the Court applied the Nautilus test for indefiniteness (i.e. failing to inform a POSITA, with reasonable certainty, the scope of the invention) to the drying time. Though Horizon argued that the indefiniteness test should apply only to the claims and not to the basic and novel property of the invention, the court reasoned that because the claim language used the phrase “consisting essentially of,” evaluating definiteness of the claim language inherently necessitated an analysis of the basic and novel property as well. Because the patent provided for two different methods of evaluating drying time and the two methods provided inconsistent results, the court held that the underlying basic and novel property of the invention was indefinite, hence making the claims indefinite and invalid as well.

HZNP Medicines LLC, Horizon Pharma USA, Inc. v. Actavis Laboratories UT, Inc., 2017-2149, 2017-2152, 2017-2153, 2017-2202, 2017-2203, 2017-2206 (Fed. Cir. Oct. 10, 2019)

Practice Tip: When a claim refers to an impurity, the remainder of the claim or specification should provide reference to a specific, identifiable compound. Further, when using the transition phrase “consisting essentially of” to list a set of elements, an indefiniteness analysis can extend to the specification and the basic and novel properties of the invention described therein. Thus, patent applicants should make sure to clearly delineate such properties in the written description.

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