Federal Circuit Agrees That "pH of 13 or higher" Means When Measured at "Standard" Temperature, In the Absence of Any Contrary Evidence in the Patents
In a recent decision, the U.S. Court of Appeals for the Federal Circuit affirmed a district court’s judgment that Mylan Pharmaceuticals Inc. did not infringe, literally or under the doctrine of equivalents, two of Actelion Pharmaceutical Ltd.’s patents.[1] This decision provides additional clarity into the Federal Circuit’s interpretations for claim construction issues as well as when the doctrine of equivalents can apply as it relates to tangentiality and the rule of disclosure-dedication.
Actelion’s patents describe pharmaceutical compositions involving epoprostenol. Epoprostenol is known to be unstable in water where this instability is accelerated with increased acidity. pH is a measure of acidity with lower pH values corresponding to solutions that are more acidic.
Prior compositions including epoprostenol were stabilized by storing a freeze-dried powder containing epoprostenol and reconstituting the powder using a diluent that was less acidic (higher pH) than typical intravenous fluids and subsequently storing the reconstituted solution under refrigeration to maintain the solution.
Actelion’s patents describe a process for making a freeze-dried pharmaceutical composition containing epoprostenol that could be reconstituted using typical intravenous fluids and, upon reconstitution, could then be stored at room temperature while remaining stable. This process includes a condition, as claimed in Actelion’s patents, that the freeze-dried pharmaceutical composition be “formed from a bulk solution having a pH of 13 or higher.”
Mylan sought approval from the U.S. Food and Drug Administration (“FDA”) to market a generic epoprostenol drug before expiration of Actelion’s patents. Actelion sued Mylan for patent infringement alleging that Mylan’s proposed generic drug was covered (literally or under the doctrine of equivalents) by certain claims of Actelion’s patents.
In February 2024, the issue of infringement was tried to the district court (that is, without a jury) with the only dispute being whether the bulk solution used by Mylan to form their generic epoprostenol drug satisfied the claim limitation of “having a pH of 13 or higher.”
Regarding literal infringement, Actelion acknowledged that at a temperature of 25±2° C Mylan’s bulk solution has a pH below 13. However, Actelion pointed to Mylan’s application filed with the FDA that indicated that Mylan’s bulk solution is manufactured under refrigeration and argued that the pH of Mylan’s bulk solution should be measured at the refrigerated “operating temperature” where, at this temperature, the bulk solution has a pH that is higher than 13.
Actelion further argued that Mylan’s generic epoprostenol drug infringed under the doctrine of equivalents because Mylan’s manufacturing process performed the same function of improved manufacturing stability to achieve the same result of increased composition stability in the same way (high pH of the bulk solution) as claimed.
The district court rejected Actelion’s assertion of literal infringement by looking to both the intrinsic record and extrinsic evidence to interpret the key claim language. In particular, the district court noted that Actelion’s patents never define the term “pH” despite emphasizing the importance of pH thresholds to the invention. Further, the patents reported many experimental results that would not make sense if pH was measured at any temperature other than 25±2° C. In view of these facts the district court concluded that, because the patents did not specify another method for measuring pH values at temperatures other than 25±2° C, the claimed pH value would have been understood by a person of ordinary skill in the art (“POSITA”) to refer to a pH measurement taken at the “standard” temperature of 25±2° C. There being no dispute that Mylan’s bulk solution has a pH below 13 at this standard temperature, the district court found no literal infringement.
Similarly, the district court rejected Actelion’s allegation that Mylan infringed under the doctrine of equivalents. The court ruled that Actelion was barred by the disclosure-dedication rule because the patents disclose bulk solutions having pH values less than 13.
Further, the district court ruled that because Actelion, during prosecution of its patents, amended the contested pH limitation to the range of 13 or higher, Actelion was estopped from attempting to recapture as equivalents and bulk solutions having pH values lower than 13.
The Federal Circuit affirmed the district court’s construction of the claim term “pH of 13 or higher” to refer to a pH measurement made at 25±2° C citing essentially the same intrinsic and extrinsic evidence relied upon by the district court. The appellate court also affirmed the trial court’s determination that Actelion was barred from asserting infringement under the doctrine of equivalents, indicating that there was no discernible “error in the district court’s application of both the prosecution history estoppel and disclosure-dedication bars.”
A key rationale for this decision is that, when responding to an examiner’s rejection by narrowing claims, the applicant is estopped from later arguing that the subject matter covered by an original, broader claim was nonetheless an equivalent of the subject matter covered by the amended, narrowed claims. Under U.S. patent law, a narrowing amendment made for patentability purposes generally surrenders the scope between the original claim and the amended claim.
However, there is narrow exception to this principle, which arises if a patentee can show that the alleged equivalent’s departure from what the claim literally requires “is tangential to the discernible objective reason for the narrowing amendment.”[2]
Actelion relied on this tangentiality exception in their arguments against prosecution history estoppel and argued that the reason for arriving at the granted claims was not to surrender functional equivalence. For instance, Actelion noted that the pH of Mylan’s bulk solution was functionally equivalent and had the same benefits of Actelion’s composition (e.g., inhibition of epoprostenol degradation upon reconstitution). However, the final amendment achieving allowance of the claims involved narrowing the independent claim’s pH from “a pH of greater than 12” to “a pH of 13 or higher” to rebut an obviousness rejection issued by the Examiner as no “unexpected results” were demonstrated for the pH value of 12 or greater, but were considered present for the pH of 13 or higher.
The Federal Circuit found that the prosecution history clearly demonstrated that the examiner viewed pH 13 as the threshold for which unexpected results were shown, and that improved stability with a pH of 12 was not demonstrated. As such, the Federal Circuit’s opinion was that this rationale qualifies as a discernible objective reason for the narrowing amendment. However, the CAFC concluded that Actelion had failed to show that the claim amendment was only tangential to the differences between the alleged equivalent and the claim scope at issue.
This CAFC decision also highlighted that disclosure-dedication rule independently bars availability of the doctrine of equivalents in an infringement case. The U.S. disclosure-dedication rule dictates that when a patent drafter discloses in the written specification, but declines to claim, certain subject matter, that certain unclaimed subject matter is inevitably “dedicated” to the public. Consequently, the patentee cannot later recapture such subject matter as an equivalent after issuance of the patent. The caveat for this rule is that the disclosure of such matter needs to be of such specificity that a POSITA can identify the disclosed, but unclaimed, subject matter and that the unclaimed subject matter must have been identified by the patent drafter as an alternative to the claimed limitation in question.
Thus, because Actelion’s patents disclose that the pH can be adjusted to a range of 12.5–13.5 or 13, the CAFC found that the patents are specific enough such that a POSITA can identify certain ranges as alternatives. Importantly, this principle does not require that the alternatives be mutually exclusive, where overlapping alternatives can be considered disclosed but partially unclaimed.
The outcome of this case reminds applicants and practitioners alike of the mindfulness required for prosecution history estoppel when writing claims and when considering potential amendments during prosecution. The Federal Circuit’s decision further reiterates that unless otherwise stated in the specification, the ordinary and customary meaning of a claim term is the meaning that the term would have had to a person of ordinary skill in the art.
