Bottom line: In Actelion Pharmaceuticals Ltd. v. Mylan Pharmaceuticals Inc., No. 2024‑1641 (Fed. Cir. May 13, 2026), the Federal Circuit affirmed that Mylan's generic epoprostenol (Veletri®) did not infringe Actelion's formulation patents. A claim requiring a bulk solution “having a pH of 13 or higher” was measured at standard temperature, defeating literal infringement, and Actelion could not reach Mylan's product through the doctrine of equivalents.
What happened?
Actelion asserted U.S. Patent Nos. 8,318,802 and 8,598,227 against Mylan's ANDA in the Northern District of West Virginia. After an earlier appeal (85 F.4th 1167 (Fed. Cir. 2023)) sent the case back for extrinsic evidence, the district court construed the pH term to mean a pH of 12.98 or higher measured at standard temperature and found no infringement. The panel (Judges Reyna, Taranto and Stoll; opinion by Judge Taranto) affirmed:
- Measurement temperature. Relying on the USP default that pH is measured at standard temperature “unless otherwise specified,” textbooks and expert agreement, the court held no literal infringement.
- Prosecution history estoppel. Actelion had narrowed “greater than 12” to “13 or higher” to overcome an obviousness rejection; its tangentiality argument failed.
- Disclosure‑dedication. The specification disclosed but did not claim lower pH ranges, which independently barred the equivalents theory.
Why does it matter for pharma and chemical companies?
For brand companies, every numerical formulation limit should specify measurement conditions. For generic and biosimilar filers, file histories and unclaimed disclosed ranges can be powerful design‑around and non‑infringement tools.
Key takeaways
- State measurement conditions (temperature, method, standard) for pH, particle size, viscosity and similar limits.
- Narrowing amendments have a price — expect estoppel over the surrendered range.
- Disclosed but unclaimed alternatives may be dedicated to the public; claim what you disclose, or file continuations.
Frequently Asked Questions
Q: At what temperature is a claimed pH measured?
A: In Actelion v. Mylan (Fed. Cir. May 13, 2026), the court held that “pH of 13 or higher” refers to pH measured at standard temperature (25±2°C), consistent with the USP default.
Q: Can a narrowing amendment block the doctrine of equivalents?
A: Yes. Narrowing a claim to overcome a prior‑art rejection can create prosecution history estoppel that bars equivalents covering the surrendered range.
Facing a Paragraph IV challenge or evaluating a design‑around?
Contact Green, Griffith & Associates LLP for Hatch-Waxman litigation and pharmaceutical patent counsel.