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Federal Circuit Affirms No Infringement in Pharmaceutical Patent Dispute Over pH Measurement Conditions For Epoprostenol Composition
06/09/2026On May 13, 2026, the U.S. Court of Appeals for the Federal Circuit (Judges Reyna, Taranto, and Stoll) affirmed a decision of the U.S. District Court for the Northern District of West Virginia finding that defendant does not infringe U.S. Patent Nos. 8,318,802 and 8,598,227 (collectively, the “’802” and “’227” patents), either literally or under the doctrine of equivalents. Actelion Pharmaceuticals Ltd v. Mylan Pharmaceuticals Inc., No. 2024-1641 (Fed. Cir. May 13, 2026). The decision addresses how pH measurements recited in pharmaceutical patent claims should be interpreted, and the application of prosecution history estoppel and the disclosure-dedication rule to bar equivalents-based infringement theories.
Plaintiff’s patents are directed to lyophilized pharmaceutical compositions of epoprostenol, the active ingredient in its hypertension drug Veletri®. Epoprostenol is unstable in water, and the patents describe processes for creating highly basic bulk solutions (with pH of 13 or higher) that yield freeze-dried powders with improved stability when reconstituted for intravenous administration. Representative claim 1 of the ’802 patent recites a lyophilized composition “formed from a bulk solution having a pH of 13 or higher.” Defendant submitted an abbreviated new drug application (ANDA) seeking FDA approval to market a generic epoprostenol product, and plaintiff sued for infringement under 35 U.S.C. § 271(e)(2).
The central dispute at trial was whether the pH of defendant’s bulk solution meets the “pH of 13 or higher” claim limitation. It was undisputed that defendant’s bulk solution, when measured at the standard temperature of 25±2°C, has a pH well below 12.98 (the district court’s construed threshold). Plaintiff argued that pH should instead be measured at the actual refrigerated “operating temperature” of defendant’s solution during manufacture, at which temperature the pH would exceed 13. The district court rejected this argument, and the Federal Circuit affirmed.
The Federal Circuit analyzed the intrinsic and extrinsic record to determine the proper construction of “a pH of 13 or higher.” The Court found the claim language alone did not resolve the question, as neither the phrase nor the remainder of the claims specifies the conditions under which pH should be measured. Turning to the specification, the Court noted that the patent defines “an alkaline environment” as one with “pH>7,” a definition that is accurate only at standard temperature and that the specification’s many experimental comparisons of pH values are most reasonably understood as reflecting a uniform, standard-temperature measurement approach. The Court also credited extrinsic evidence, including the United States Pharmacopeia (USP), which prescribes that, “unless otherwise specified,” pH measurements are made at 25±2°C, as well as expert testimony confirming that every reference to a pH 13 bulk solution in the specification’s experimental results notes measurement at standard temperature.
Having affirmed the standard-temperature claim construction, the Court found no literal infringement because defendant’s bulk solution undisputedly does not have a pH of 13 or higher at 25±2°C. The court then turned to plaintiff’s alternative theory of infringement under the doctrine of equivalents and found it independently barred on two grounds.
First, the Court held that prosecution history estoppel precluded plaintiff from recapturing pH values below 13 as equivalents. During prosecution, the examiner rejected the claims on obviousness grounds because no unexpected results had been demonstrated for bulk solutions with a pH of 12 or greater, and the examiner indicated that claims limited to pH 13 or higher would be allowable. Plaintiff then narrowed the pH limitation from “greater than 12” to “13 or higher.” The Court found this was a narrowing amendment made for a reason of patentability.
Second, the Court held that the disclosure-dedication rule independently barred plaintiff’s equivalents theory. The specification discloses preferred pH ranges for bulk solutions including values below 13 (e.g., “about 12.5–13.5” and “greater than 12”), but the claims are limited to pH 13 or higher. The Court found these disclosures sufficiently specific to identify the unclaimed subject matter and that they were expressly identified as alternatives to the claim limitation. Accordingly, plaintiff had dedicated those unclaimed pH ranges to the public and could not recapture them through the doctrine of equivalents.
This decision underscores the importance of clearly specifying the conditions under which key claim parameters are measured. It also highlights the risks of disclosing broad ranges in the specification while claiming only a narrow subset, and of making narrowing amendments during prosecution that may foreclose equivalents-based infringement theories in litigation.
