Background
Biofer S.p.A. sued Vifor (International) AG for infringing U.S. Patent No. 8,759,320, which claims a process for preparing iron-sugar complexes used to treat iron deficiency. Claim 1 covers the activation of dextrin or dextran through oxidation in a solution “at a pH between 7.0 and 9.0.”
The Eastern District of New York construed that phrase to mean that the pH must be maintained between 7.0 and 9.0 throughout the oxidation reaction. Discovery showed that Vifor’s process remained within that range for approximately 90% of the reaction, but not for its entirety. Biofer therefore stipulated to noninfringement under the district court’s construction while preserving its right to appeal, and the court entered judgment for Vifor.
The Court’s Holding
The Federal Circuit affirmed the construction of “pH between 7.0 and 9.0” as requiring the pH to be maintained within that interval throughout the oxidation step. The claim’s grammar made the specified pH the solution environment for the entire reacting step, while the specification repeatedly described controlling and maintaining pH during the reaction to avoid depolymerization.
The prosecution history reinforced that interpretation because Biofer had relied on experiments comparing reactions conducted while maintaining different pH ranges to establish the criticality of the claimed range. The court held that Biofer forfeited its appellate argument that the claim permits brief excursions outside the range because Biofer had not advanced that position below. It also declined to review the construction of a separate limitation concerning stoichiometric quantities because that term was not implicated by the parties’ stipulation or the resulting judgment. Given Biofer’s concession that Vifor did not infringe under the affirmed construction, the court upheld the noninfringement judgment.
Key Takeaways
- A claimed process performed “at a pH between 7.0 and 9.0” required maintaining that pH range throughout the identified reaction step.
- Repeated descriptions in the specification and representations made during prosecution supported imposing a continuous pH-range requirement.
- A stipulated judgment must implicate each claim-construction issue a party seeks to appeal, and new construction theories generally cannot be introduced for the first time on appeal.
Why It Matters
The nonprecedential decision illustrates how process parameters can operate as requirements lasting for an entire claimed step, even when the claim does not expressly use the word “throughout.” Patent litigants should evaluate claim grammar together with consistent descriptions in the specification and statements made to secure allowance.
It also highlights the need to preserve appellate issues carefully. Both the arguments presented to the district court and the terms expressly tied to a stipulated judgment can determine which claim-construction disputes the Federal Circuit will review.