Background
Biofer owns U.S. Patent No. 8,759,320, which describes a process for making iron-and-sugar complexes used to treat iron deficiency. The patent seeks to avoid unstable or toxic products by controlling how a sugar is oxidized before it is combined with iron.
Claim 1 requires reacting a sugar with bromine “in a solution at a pH between 7.0 and 9.0.” Biofer accused Vifor of infringement, but the district court construed that language to require the pH to remain within the claimed interval throughout the oxidation step. Testing showed that Vifor’s process stayed within the range for about 90% of the reaction, not all of it. Biofer therefore stipulated to noninfringement under the court’s construction and appealed.
The Court’s Holding
The Federal Circuit affirmed. Judge Reyna’s opinion explained that the grammar of claim 1 makes the pH limitation apply to the entire “step of reacting a sugar.” Because that step is the oxidation reaction as a whole, the claimed range describes the reaction environment for its duration—not merely a value the process must reach at some point.
The specification reinforced that reading. It repeatedly says that pH is “maintained” or “controlled and maintained” during activation, and all three relevant examples describe maintaining pH within the range. The prosecution history pointed the same way: an inventor declaration used experiments conducted while maintaining specified pH ranges to show why the narrower range was critical, and Biofer relied on that evidence to obtain allowance.
The court rejected Biofer’s contention that this construction improperly imported a preferred embodiment. Although the specification also discusses a broader range, claim 1 expressly chose the narrower 7.0-to-9.0 interval. Biofer’s new suggestion at oral argument that brief excursions outside the interval should be allowed was forfeited because it had not presented that position below. The court also declined to address a second claim-construction dispute because the stipulated judgment did not depend on that term.
Key Takeaways
- A process parameter may have to remain within a claimed range for an entire step when the claim grammar, specification, and prosecution history consistently describe it that way.
- Operating inside a numerical range for most—but not all—of a reaction did not establish infringement under this construction.
- A stipulated judgment should identify every claim construction a party wants reviewed; an unrelated construction may fall outside the appeal.
- Claim-construction positions should be preserved in the district court, because a materially different interpretation raised for the first time on appeal can be forfeited.
Why It Matters
The nonprecedential ruling illustrates how a seemingly simple numerical limitation can carry a temporal requirement. For chemical and manufacturing patents, words surrounding a range—and repeated statements about maintaining process conditions—can determine whether a competitor that spends nearly all of a reaction within the range infringes.
The decision also offers a drafting lesson. If an inventor intends to cover temporary deviations, the claims and specification should say so. Conversely, repeated descriptions of a condition as continuously maintained may narrow the practical reach of the patent even when the claim does not expressly use words such as “throughout.”