Underscoring functional relationships as limitations in patent claims and the importance of claim construction, the US Court of Appeals for the Federal Circuit affirmed in part, vacated in part, and remanded a Patent Trial & Appeal Board decision that found claims of a patent unpatentable notwithstanding a functional relationship recitation. Bayer Pharma Aktiengesellschaft v. Mylan Pharmaceuticals Inc., et al., Case No. 23-2434 (Fed. Cir. Sept. 23, 2025) (Moore, Cunningham, Scarsi, JJ.)
Bayer owns a patent that describes the results of a phase III clinical trial that evaluated the efficacy and safety of administering rivaroxaban with and without aspirin for the prevention of major adverse cardiac events. Certain claims require “administering to the human patient rivaroxaban and aspirin in amounts that are clinically proven effective in reducing the risk of myocardial infarction, stroke or cardiovascular death[,] wherein rivaroxaban is administered in an amount of 2.5 mg twice daily and aspirin is administered in an amount of 75 – 100 mg daily.” Other claims are directed to a once daily administration of “a first product comprising rivaroxaban and aspirin” and “a second product comprising rivaroxaban.”
Mylan challenged the patent in inter partes review (IPR), arguing that certain claims were anticipated by the Foley reference and others were obvious over Foley alone or in combination with Plosker. The Board agreed, finding all challenged claims unpatentable. Bayer appealed.
Bayer argued that the Board erred in:
- Construing “clinically proven effective” as non-limiting and finding, in the alternative, that it was inherently anticipated
- Construing “first product comprising rivaroxaban and aspirin” to encompass administration of rivaroxaban and aspirin as separate dosage forms
- Failing to articulate why a skilled artisan would have combined Foley and Plosker with a reasonable expectation of success
- Failing to analyze whether clinical proof of efficacy was an unexpected result
The Federal Circuit declined to resolve whether “clinically proven effective” is a limiting claim element, concluding that even if it were, it would not render the claims patentable. The Court explained that the phrase does not create a “new and unobvious functional relationship” with the known method of treatment. Analogizing to a hypothetical claim for a known drug method modified by a post-dated accolade (e.g., “Best Drug of 2026”), the Court emphasized that requiring clinical proof of efficacy does not transform the underlying treatment process.
Bayer relied on the Federal Circuit’s 2019 decision in Allergan Sales v. Sandoz, in which the Court found “wherein” clauses specifying safety and efficacy to be material to patentability. The Federal Circuit distinguished Allergan, noting that the claims there were written in open format and the “wherein” clauses modified the overall composition. In contrast, the claims of Bayer’s patent already specified exact dosages, and “clinically proven effective” did not modify any particular component. The Court therefore affirmed the Board’s finding of unpatentability for these claims.
However, the Federal Circuit agreed with Bayer on the construction of claims requiring a “first product comprising rivaroxaban and aspirin.” Bayer argued that this language required a single dosage form containing both drugs. The Court explained that the plain language of the claims supported Bayer’s interpretation, and that the Board’s broader construction, which allowed for separate dosage forms, was incorrect.
As a result, the Federal Circuit vacated the Board’s obviousness determination for the single dosage claims and remanded for further analysis under the correct construction.
