2025 Federal Circuit IP Appeals: Bayer Pharma Aktiengesellschaft v. Mylan Pharmaceuticals Inc., 152 F.4th 1400 (Fed. Cir. 2025) (Moore, Cunningham, Scarsi¹)

Pharmaceutical companies developing a method of treatment often simultaneously seek patent protection and U.S. Food and Drug Administration (FDA) approval for the method. Balancing clinical trials with the timing of the initial patent application is crucial, as publications describing the clinical trial protocol risk becoming prior art and invalidating the claimed method. That is what happened with Bayer’s anticoagulant drug Xarelto (rivaroxaban).

Bayer’s ’310 patent described the results of a Phase III clinical trial evaluating the safety and efficacy of administering rivaroxaban with aspirin to prevent major adverse cardiovascular events among patients with cardiovascular disease. The clinical trial protocol and claimed regimen were published in an academic journal prior to conclusion of the study and filing of the patent application. The results of the study, however, were not in the prior art.

Mylan, Teva, and Invagen jointly challenged the ’310 patent in an inter partes review, relying in part on the prior art disclosure of the clinical trial protocol. The relevant claim recited a method of administering rivaroxaban and aspirin in amounts that are “clinically proven effective” for reducing the risk of adverse cardiac events and further specified a regimen of 2.5 mg rivaroxaban twice daily and 75–100 mg aspirin daily.

Bayer argued the “clinically proven effective” language distinguished the claims from the clinical trial protocol because the results of the study were not known in the prior art. The Patent Trial and Appeal Board (PTAB) disagreed, finding that the “clinically proven effective” element was nonlimiting and was, in any event, inherently disclosed by the prior art disclosure of the protocol.

The Federal Circuit affirmed on alternative grounds. The court declined to decide if the phrase “clinically proven effective” was limiting or inherently anticipated and instead held that it was “a functionally unrelated limitation that fail[ed] to make the claims patentable.” The court expressed concern that a contrary holding would create the potential for “indefinite patenting of known methods through the addition of novel, yet functionally unrelated limitations.” In reaching this conclusion, the court relied on King Pharmaceuticals, Inc. v. Eon Labs, Inc., 616 F.3d 1267 (Fed. Cir. 2010), which held that an otherwise anticipated method of treatment was not made patentable by the addition of an instructional limitation requiring informing the patient about the treatment. The “clinically proven effective” limitation, the court found — like the “informing” step in King — could not make the claims patentable because it lacked a new and nonobvious functional relationship with the remaining steps of the claimed method. In other words, the limitation in question “in no way transform[ed] the process of taking the drugs at the amounts and frequencies expressly recited in the claims.” The court also observed that the “clinically proven effective” limitation was no different in substance from a limitation specifying an accolade like “Best Drug of 2026.”

Given that conclusion, the court also rejected Bayer’s reliance on unexpected results as a secondary consideration of nonobviousness. Bayer had argued that the success of the clinical trial was unexpected. But, because the “clinically proven effective” limitation was not entitled to patentable weight, that evidence lacked any nexus to “the merits of the claimed invention.”

Related:

Top Brand LLC v. Cozy Comfort, 143 F.4th 1349 (Fed. Cir. 2025) (applying prosecution history disclaimer to narrow claims of design patent on an enlarged oversized garment with a marsupial pocket because applicant had focused on specific design features in response to examiner’s rejection and thereby clearly surrendered claim scope).

Maquet Cardiovascular LLC v. Abiomed Inc., 131 F.4th 1330 (Fed. Cir. 2025) (declining to find prosecution history disclaimer in construing claims related to positioning a lumen within an intravascular blood pump because, while the patentee had disclaimed claim scope when prosecuting the patent’s parent application, the claims at issue were not “sufficiently similar” to the parent claims “such that the prosecution history of the latter would be relevant when construing the former”).

In re Xencor, Inc., 130 F.4th 1350 (Fed. Cir. 2025) (holding that the preamble to a Jepson claim must be supported with adequate written description in the specification, and affirming the PTAB’s finding that the Jepson claim preamble at issue lacked written description support).

[1] Honorable Mark C. Scarsi, District Judge, United States District Court for the Central District of California, sitting by designation.

This article appeared in the 2025 Federal Circuit IP Appeals: Summaries of Key 2025 Decisions report.