Case Name: Actelion Pharms. Ltd. v. Mylan Pharms. Inc., No. 2022-1889, 2023 WL 7289417 (Fed. Cir. Nov. 6, 2023) (Circuit Judges Reyna, Stoll, and Stark presiding; Opinion by Stoll, J.) (Appeal from N.D.W.V., Bailey, J.) 

Drug Product and Patent(s)-in-Suit: Veletri® (epoprostenol); U.S. Patents Nos. 8,318,802 (“the ’802 patent”) and 8,598,227 (“the ’227 patent”)

Nature of the Case and Issue(s) Presented: Epoprostenol is a naturally occurring substance useful for treating cardiovascular diseases that Plaintiffs sell under the tradename Veletri. The patents-in-suit claim improved epoprostenol formulations that “can be reconstituted with commercially available IV fluids and do not require refrigeration after reconstitution until use.” Mylan filed an ANDA seeking approval to make and sell a generic version of Veletri and Plaintiffs sued. The parties disputed the meaning of the claim term “a pH of 13 or higher.” Plaintiffs posited the definition, “a value of acidity that is given as an order of magnitude that is subject to rounding,” which would allow a pH of 12.5, rounding up to 13, to read on the claim limitation. Mylan argued that the proper construction cannot cover any pH values less than 13. Actelion took issue with Mylan’s proposed construction, relying, in part, on three textbooks. The textbooks explain how to calculate pH and identify significant figures for pH values.

The district court did not address this extrinsic evidence, adopting Plaintiffs’ construction based on the intrinsic record alone. The parties stipulated to final judgment of infringement in favor of Plaintiffs. Mylan appealed, and the Federal Circuit vacated and remanded.

Why Mylan Prevailed: The sole issue before the Federal Circuit is the meaning of “a pH of 13 or higher.” While the claim language appears to be a range with a specified lower limit, “there is no blanket rule that ranges, or specifically open-ended ranges, must foreclose rounding. This is especially true in this case where, though not expressly specified, there is in fact an upper limit in the claim because, as a matter of science, pH values are often said to range from 0 to 14.” Moreover, the absence of approximation language might suggest no approximation, but that the nature of measuring a pH value might nonetheless reasonably require a margin of error. The parties submitted extrinsic evidence on this issue that the District Court ignored.

The Federal Circuit next turned to the specification, which revealed that the inventor inconsistently described the level of specificity for a pH of 13. In one instance, the specification states, “[t]he pH of the bulk solution is preferably adjusted to about 12.5-13.5, most preferably 13.” Mylan argued that this shows that the inventor knew how to use approximation language when it wanted and chose not to for a pH of 13; distinguished a pH value of “12.5” from that of “13”; and distinguished a range from a definite value. Relying on the same disclosure, Plaintiffs argued that the inventor clearly shows that “13” should allow rounding or else a preferred embodiment of the invention, meaning a pH of about 12.5 to 13.5, would be excluded from the claim scope.

The Federal Circuit then found that the prosecution history also did not provide clarity. The inventor amended the claim language at issue several times, including: “a pH of greater than 11,” “a pH of greater than 12,” and “a pH of at least 12.” The prosecution history shows that the Examiner drew a distinction between the stability of a composition with a pH of 13 and that of 12. But that did not resolve the narrower issue before the court.

“We find that this case is one where the proper claim construction cannot be reached without the aid of extrinsic evidence, and that the district court should have considered, at minimum, the textbook excerpts offered and addressed by the parties. … It is not for this court to make those findings in the first instance.”