Claim Construction Should Be Well-Grounded in Both Intrinsic and Extrinsic Evidence
| January 15, 2024
ACTELION PHARMACEUTICALS LTD v. MYLAN PHARMACEUTICALS INC.
Decided: November 6, 2023
Before REYNA, STOLL, and STARK, Circuit Judges.
Summary
The Federal Circuit ruled that the patent claim term “a pH of 13 or higher” could not be interpreted solely based on the patent’s intrinsic evidence. The court remanded the case to the district court, instructing it to consider extrinsic evidence to determine the proper construction of this claim limitation.
Background
The case of Actelion Pharmaceuticals Ltd v. Mylan Pharmaceuticals Inc. involves a dispute over patent infringement related to epoprostenol, a drug used for treating hypertension. Actelion Pharmaceuticals, the patent holder, owns two patents of the drug: U.S. Patent Nos. 8318802 and 8598227. These patents disclose a pharmaceutical breakthrough in stabilizing epoprostenol using a high pH solution, which is otherwise unstable and difficult to handle in medical applications.
Mylan Pharmaceuticals, aiming to enter the market with a generic version of epoprostenol, filed an Abbreviated New Drug Application (ANDA). In this process, Mylan certified under Paragraph IV that the patents held by Actelion were either invalid or would not be infringed by Mylan’s manufacture, use, or sale of the generic drug. In response, Actelion asserted these patents against Mylan, claiming infringement.
The key issue in the dispute revolves around the interpretation of the phrase “a pH of 13 or higher” in the patent claims. This particular claim is crucial because the stability of epoprostenol is significantly impacted by the pH level of its solution. Actelion’s patents suggest that the epoprostenol bulk solutions should preferably have a pH adjusted to about 12.5 to 13.5 to achieve the desired stability. However, in the claims, Actelion’s patents only set the limitation as “a pH 13 or higher” as shown in claim 11 of the ’802 patent, a representative of the asserted claims:
11. A lyophilisate formed from a bulk solution comprising:
(a) epoprostenol or a salt thereof;
(b) arginine;
(c) sodium hydroxide; and
(d) water,
wherein the bulk solution has a pH of 13 or higher, and wherein said lyophilisate is capable of being reconstituted for intravenous administration with an intravenous fluid.
The dispute centered on the interpretation of the pH value specified in the patent claims. Actelion contended that the claim should encompass pH values that effectively round up to 13, including values like 12.5. Conversely, Mylan argued for a narrower interpretation, asserting that the claim should only cover pH values strictly at 13 or higher, thus excluding anything below this threshold, such as 12.5.
This interpretation was critical in determining whether Mylan’s generic version of epoprostenol would infringe upon Actelion’s patents. The district court initially adopted Actelion’s interpretation, which led to a stipulated judgment of infringement against Mylan.
Discussion
The Federal Circuit’s analysis began with a de novo review of the district court’s decision. The central question was whether the district court’s adoption of Actelion’s interpretation, which included pH values that could round up to 13 (such as 12.5), was appropriate. This broader interpretation affected the scope of the patent and the potential infringement by Mylan’s generic version of the drug. In scientific and technical contexts, the practice of rounding pH levels, such as rounding 12.5 to 13, depends on the specific requirements of the situation and the level of precision needed. pH is a logarithmic scale used to specify the acidity or basicity of an aqueous solution, and even small changes can represent significant differences in acidity or basicity.
Mylan Pharmaceuticals argued for a narrower interpretation of the term. They insisted that “a pH of 13” sets a definitive lower limit, suggesting that any pH value below 13, even those marginally lower like 12.995, would not fall within the scope of the patent. Mylan suggested that if a margin of error was considered necessary for a pH of 13, it should be minimal, encompassing a range only from 12.995 to 13.004. This interpretation was grounded in the belief that precision was implicit in the claim term, as the absence of approximation language like “about” in the claim suggested an exact value.
In contrast, Actelion Pharmaceuticals argued for a broader interpretation. They argued that the term should include values that round up to 13, thus potentially including values such as 12.5. Actelion’s argument was based on the principle that a numerical value in a patent claim includes rounding, dictated by the inventor’s selection of significant figures, unless the intrinsic record explicitly indicates a different intention. Actelion maintained that rounding was a common practice in scientific measurements and that the absence of specific approximation language did not necessarily dictate a precise value.
One of the key findings of the Federal Circuit was the inadequacy of intrinsic evidence to resolve the dispute conclusively. Intrinsic evidence, which includes the original patent claim language, specification, and prosecution history, is generally the primary resource for interpreting patent claims. However, in this case, these sources did not clearly define the precision of the pH value in question. The specification stated that, “the pH of the bulk solution is preferably adjusted to about 12.5-13.5, most preferably 13.” This language suggested that while the inventor recognized a preferred range (about 12.5-13.5), they specifically highlighted a most preferred value (13). The Federal Circuit also noted that the specification uses both “13” and “13.0” and various degrees of precision for pH values generally throughout the specification. Moreover, the prosecution history shows that the Examiner drew a distinction between the stability of a composition with a pH of 13 and that of 12. However, such distinction does not clarify the narrower issue of whether a pH of 13 could encompass values that round to 13, in particular 12.5.
The specifications and prosecution history left ambiguous whether the term referred exclusively to a pH of 13.0 or could include values that round up to 13. Recognizing this ambiguity, the Federal Circuit emphasized the need for extrinsic evidence to properly interpret the term. This approach is aligned with the Supreme Court’s guidance in Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., which acknowledged the importance of considering such evidence in certain contexts of patent claim interpretation. The Federal Circuit decided to vacate the district court’s ruling and remand the case for further consideration of extrinsic evidence.
Takeaway
- Precise and specific wording in patent claims is crucial, especially in technical fields, as it defines the scope and protection of the invention.
- Although intrinsic evidence (claim language, specifications, and prosecution history) is primary in patent interpretation, it may not always be sufficient. In cases where intrinsic evidence is ambiguous or lacks clarity, extrinsic evidence such as expert testimonies, scientific literature, and other technical documents becomes crucial for a comprehensive understanding of the claim.
