Extrinsic Evidence Needed to Construe Numerical Limitation in the Claims

Actelion Pharmaceuticals Ltd, v. Mylan Pharmaceuticals Inc., [2022-1889] (November 6, 2023), the Federal Circuit vacated the district court’s claim construction order with respect to the term “a pH of 13 or higher” in U.S. Patent Nos. 8,318,802 and 8,598,227 and the judgment of infringement, and remand for the district court to consider the extrinsic evidence and its impact on claim construction.  The patents in suit were directed to improved epoprostenol formulations.

The claim required “the bulk solution has a pH of 13 or higher.”  Both parties proposed the plain and ordinary meaning of the term but disagreed on what that means.  Actelion argued that “a pH of 13” in the context of the asserted claims is “a value of acidity that is given as an order of magnitude that is subject to rounding.”  More specifically, Actelion’s proposal would allow a pH of 12.5, which rounds to 13, to read on the claim limitation of “a pH of 13 or higher.” By contrast, Mylan argued that the proper construction cannot cover any pH values less than 13.

The Federal Circuit said that there was no blanket rule that ranges, or specifically open-ended ranges, must foreclose rounding.  Unlike other claim terms, the disputed claim term lacks approximation language like “about.”  Mylan argued, “13” and “about 13” would both imply rounding, making the approximation language superfluous.  Actelion argued that rounding is required because approximation language like “about” signals different variations than those of rounding. Actelion also argued that “it is not practically possible to measure exact pH values” because to get an “exact” measurement “one would have to count every hydrogen ion in solution, which is not scientifically possible.”  Ultimately, the Federal Circuit did not find the absence of approximation language dispositive here, and rejected any invitation to create a bright-line rule.

The specification revealed that the inventor inconsistently described the level of specificity for a pH of 13.  The specification explains that “[t]he pH of the bulk solution is preferably adjusted to about 12.5-13.5, most preferably 13.”  Mylan argues that this shows that the inventor (1) knew how to use approximation language when it wanted (“about 12.5-13.5”) and chose not to for a pH of 13; (2) distinguished a pH value of “12.5” from that of “13”; and (3) distinguished a range (“12.5-13.5”) from a definite value (“13”).  Actelion countered that “13” should allow rounding or else a preferred embodiment of the invention, meaning a pH of about 12.5 to 13.5, would be excluded from the claim scope.

The specification seems to equate a pH of “13.0” to that of “13.” Example 4 describes screening several “formulations with the pH of bulk solution . . . adjusted between 10.5 and 13.0.” ’802 patent col. 10 ll. 63–64. Tables 8 and 9 show the resulting stability data and display a bulk solution pH as “13” with no decimal point. Mylan argues that this shows that the inventor equated a pH of “13” with “13.0.”  The Federal Circuit noted that the specification uses both “13” and “13.0”—and various degrees of precision for pH values generally—throughout. In other words, the specification supplies the same clarity as to the desired level of precision as muddied water.

Turning to the prosecution history, the Federal Circuit note that the inventor amended the claim language at issue several times, and that the Examiner said that the inventor had demonstrated that for a pH of 13 “there is a significant difference.”

The Federal Circuit said that this case was one where the proper claim construction cannot be reached without the aid of extrinsic evidence, and that the district court should have considered, at minimum, the textbook excerpts offered and addressed by the parties. The Supreme Court has made clear that there are cases where the district court must “look beyond the patent’s intrinsic evidence and . . . consult extrinsic evidence in order to understand, for example, the background science or the meaning of a term in the relevant art during the relevant time period.” The Federal Circuit vacated the district court’s judgment of infringement, and remand for the district court to consider the extrinsic evidence and its impact on claim construction.