Addressing infringement under the doctrine of equivalents, the U.S. Court of Appeals for the Federal Circuit vacated and remanded a grant of summary judgment that the guaifenesin product described by Perrigo’s Abbreviated New Drug Application (ANDA) would not infringe the asserted claims. Adams Respiratory Therapeutics, Inc. v. Perrigo Co., Case No. 10-1246 (Fed. Cir., Aug. 5, 2010) (Moore, J).

Perrigo filed an Abbreviated New Drug Application (ANDA) with the Food and Drug Administration (FDA) to market 600 mg guaifenesin extended-release tablets. During reexamination of its U.S. patent directed to extended release formulations of guaifenesin, the U.S. Patent and Trademark Office (USPTO) rejected a claim directed to an extended release product having a Cmax “equivalent” to the Cmax of an immediate release product when dosed as recited in the claim. The USPTO indicated that the claim term “equivalent” was not sufficiently defined under 35 U.S.C. § 112, paragraph 1. Adams indicated in a statement and a declaration that the claim term “equivalent” referred to the FDA’s bioequivalence guidelines.

Relying on Adams’ statements during the reexamination, the district court construed “equivalent” as “within 80% to 125% of the value with which it is being compared, at a 90% confidence interval” (emphasis added), and granted summary judgment of non-infringement to Perrigo. On appeal, the Federal Circuit addressed whether the lower court’s interpretation of the word “equivalent” was correct in encompassing both the FDA’s bioequivalence guidelines and the “confidence interval” that generics must demonstrate to secure FDA approval.

In vacating the district court’s summary judgment of non-infringement, the Federal Circuit construed “equivalent” to require a Cmax that is 80% to 125% of the value to which it is being compared. The panel noted that the range and the confidence interval are independent concepts, explaining that the range reflects a medical decision that a difference in the concentration of the active ingredient in blood will not be clinically significant, while the confidence interval reflects the FDA’s concern that a generic drug consistently match the performance of the branded drug.

The Federal Circuit held that patent infringement does not require bioequivalence and concluded that Adams did not import the 90% confidence interval into its claim. The Court explained that requiring a 90% confidence interval would inappropriately raise the bar for establishing infringement. Instead, Adams must show that it is more likely than not that Perrigo’s ANDA product will have a Cmax within the 80-125% range.

The Court also examined how availability of the doctrine of equivalents is affected by inclusion of the term “at least” in the claim element that the product has an AUCinf of “at least 3500 hr*ng/mL.” The Court noted that it is bound by precedential decisions holding that the doctrine of equivalents can apply to a range, i.e., a numerical limitation in a claim. The Court added that the mere existence of a numerical value or range in a claim, absent more limiting language in the intrinsic record, does not preclude application of the doctrine of equivalents.