Bottom line: In Biofer S.p.A. v. Vifor (International) AG, No. 2025‑1005 (Fed. Cir. Sept. 3, 2026) (nonprecedential), the Federal Circuit affirmed a judgment of non‑infringement after construing “reacting a sugar … with bromine in a solution at a pH between 7.0 and 9.0” to mean the pH is maintained within that range during the reaction step. The patentee's theory — that briefly reaching the range was enough — failed.
What happened?
Biofer sued Vifor in the Eastern District of New York alleging that Vifor's manufacturing process for iron‑sugar complexes (used to treat iron deficiency) infringed U.S. Patent No. 8,759,320, a process patent for preparing “activated” sugars by bromine oxidation. The district court construed the claim that required an oxidation reaction in the process to occur “at a pH between 7.0 and 9.0” to mean “pH is maintained in the interval separating 7.0 and 9.0.” Testing showed Vifor's process stayed in the 7.0–9.0 range for roughly 90% of the oxidation reaction. After the district court adopted the “maintained” construction, Biofer stipulated to noninfringement and appealed.
The panel (Judges Dyk, Linn and Reyna; opinion by Judge Reyna) affirmed, relying on:
- Claim language — the pH range modifies the reacting step, so it defines the reaction environment for the duration of that step.
- Specification — the patent repeatedly describes the pH as “controlled and maintained,” and the examples describe maintaining it.
- Prosecution history — the inventor's declaration stressed the criticality of the pH range to secure allowance.
The court also held Biofer forfeited a new “brief excursions” argument it raised for the first time at oral argument.
Why does it matter for chemical and pharma companies?
Numerical process parameters — pH, temperature, pressure, concentration — are often where infringement cases are won or lost. How the specification describes a parameter (“maintained,” “controlled,” “about”) can decide whether a competitor's process infringes.
Key takeaways
- Drafting: If you intend a parameter to be satisfied at any point, say so expressly; describing it as “maintained” invites a duration requirement.
- FTO: Process data logs showing time spent outside a claimed range can be valuable non‑infringement evidence.
- Litigation: Pick your claim‑construction theory early — new theories raised on appeal are likely forfeited.
Frequently Asked Questions
Q: Does a pH range in a process claim have to be met for the whole reaction?
A: In Biofer v. Vifor, the Federal Circuit read “at a pH between 7.0 and 9.0” in the reaction step to mean the pH is maintained in that range during the step, relying on claim wording, the specification and the prosecution history.
Q: Why does this matter for freedom to operate?
A: If your process drifts outside a claimed range for meaningful portions of a step, a “maintained” construction may support a non‑infringement position — but the answer depends on each patent's claims, specification and file history.
Questions about how this decision affects your process patents or freedom to operate?
Contact Green, Griffith & Associates LLP for chemical and pharmaceutical patent strategy.