Federal Circuit Rules Chemical Properties Measured At Standard Conditions

In Actelion Pharmaceuticals Ltd. v. Mylan Pharmaceuticals Inc., No. 2024-1641 (Fed. Cir. May 13, 2026), the Federal Circuit held that a claimed chemical property or characteristic is construed as being determined under standard conditions, e.g., standard temperature, where the specification does not otherwise specify the measurement conditions.

Actelion owns U.S. Patent Nos. 8,318,802 and 8,598,227, directed to its hypertension drug Veletri®. After Mylan filed an Abbreviated New Drug Application for a generic version, Actelion sued for infringement. The asserted claims require that the pharmaceutical composition be formed from “a bulk solution having a pH of 13 or higher,” and Mylan contended that its generic is made from a bulk solution with a pH outside the claimed range. The district court initially construed “pH of 13 or higher” under ordinary rounding rules, which would have reached pH values as low as 12.5. The Federal Circuit vacated and remanded, holding that proper construction could not be reached without the aid of extrinsic evidence. On remand, the district court considered the intrinsic and extrinsic evidence and construed “a pH of 13 or higher” to mean “a pH of 12.98 or higher,” measured at standard temperature (25 ± 2°C), and found that Mylan does not infringe either literally or under the doctrine of equivalents.

On appeal, Actelion argued that the term “having” implied the actual pH during manufacturing, which is well below standard temperature, rather than the pH as measured by the device. Finding no clear answer in the claim language, the Federal Circuit turned to the intrinsic and extrinsic evidence. Although the specification’s examples never state the measurement conditions, the Federal Circuit observed that the specification identifies an “alkaline environment” as one with “pH > 7,” a characterization accurate only at standard temperature, which the Federal Circuit found implicitly conveyed an assumption that pH was measured at standard temperature. The absence of any indication that the examples were measured at differing temperatures further suggested a uniform measurement approach. The Federal Circuit also found that the examiner’s reasons for allowance focused on the pH of the solution, as opposed to the specific temperatures at which pH was measured. As to the extrinsic evidence, the Federal Circuit affirmed that a person of ordinary skill in the art would understand pH, absent contrary indication, to be measured at standard temperature under industry standards reflected in the U.S. Pharmacopeia and general chemistry texts, a point on which both parties’ experts agreed. The Federal Circuit therefore affirmed the district court’s construction and its finding of no infringement.

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