A Bitter pH-Ill to Swallow: Federal Circuit Affirms Mylan’s Win Over Actelion’s Epoprostenol Drug Patents

Why It Matters

By confirming the standard‑temperature reading and barring equivalents, the decision clears a major regulatory hurdle for generic entry, potentially lowering costs for pulmonary arterial hypertension treatment. The ruling also signals tighter limits on how patent owners can rely on the doctrine of equivalents.

Key Takeaways

• USP standard sets pH measurement at 25 ± 2 °C by default
• Amending claim to pH 13 created prosecution‑history estoppel
• Disclosure of sub‑13 pH ranges dedicates them to the public
• Mylan can launch generic epoprostenol without infringement risk
• Patentees must explicitly state non‑standard conditions in claims

Pulse Analysis

Epoprostenol, sold as Veletri®, is a life‑saving vasodilator for pulmonary arterial hypertension, but its instability in aqueous environments has driven costly formulation patents. The drug’s lyophilized form, stabilized by a highly basic bulk solution, has been protected by Actelion’s ’802 and ’227 patents. When Mylan filed an ANDA, the central question was whether its manufacturing process, which uses a bulk solution measured at standard laboratory temperature, fell within the patented pH threshold. The Federal Circuit’s decision clarifies that, absent explicit claim language, industry‑standard measurement conditions—here defined by the United States Pharmacopeia—govern claim construction, reinforcing predictability for generic developers.

The appellate panel’s analysis hinged on three legal doctrines. First, intrinsic and extrinsic evidence confirmed that the patents implicitly assumed a 25 ± 2 °C pH reading, making the “pH of 13 or higher” limitation a standard‑temperature metric. Second, the court applied prosecution‑history estoppel: Actelion’s amendment from “pH > 12” to “pH 13 or higher” during prosecution surrendered the intervening range, precluding a doctrine‑of‑equivalents argument for lower pH values. Third, the disclosure‑dedication rule barred recapturing sub‑13 pH ranges that the specification had openly disclosed but not claimed. Together, these doctrines tighten the fence around patent scope, limiting post‑grant claim expansion.

For the broader pharmaceutical landscape, the ruling sends a clear signal to patentees: any reliance on non‑standard conditions must be expressly captured in the claim language and supported by the specification. Generic manufacturers gain confidence that adherence to USP‑defined parameters can defeat infringement claims, accelerating market entry and potentially reducing drug prices for patients with severe cardiovascular disease. Simultaneously, the decision may prompt patent drafters to craft more precise claim limitations, balancing protection with the risk of forfeiting equivalents under estoppel and dedication doctrines.