2025 Federal Circuit IP Appeals: In re Entresto, 125 F.4th 1090 (Fed. Cir. 2024) (Lourie, Prost, Reyna)

Novartis markets and sells Entresto, a combination therapy of valsartan and sacubitril for treating heart failure. After MSN Pharmaceuticals and others sought U.S. Food and Drug Administration (FDA) approval to sell generic versions of the drug, Novartis sued them for infringement of a patent directed to a pharmaceutical composition of valsartan and sacubitril administered “in combination.”

MSN initially sought a construction of the phrase “in combination” excluding a valsartan-sacubitril “complex” — i.e., a noncovalently bonded form of the two compounds, which had not been discovered until four years after the patent’s priority date (and which was covered by Novartis’ later-filed patents). The district court rejected that construction, holding that “in combination” should receive its plain and ordinary meaning. Based on that construction, MSN stipulated to infringement since its generic drug comprised a valsartan-sacubitril complex. Following a bench trial, the district court held that the patent claims were invalid for lack of written description since the specification does not describe a complex. But the district court rejected MSN’s enablement challenge, reasoning that valsartan-sacubitril complexes were not known as of the priority date and that patentees need not enable after-arising technology.

The Federal Circuit reversed the district court’s written-description ruling and affirmed its enablement ruling. As to written description, the court noted that Novartis need only show written description of that which is claimed, not that which the claims “cover” for purposes of infringement. The claims recite a “combination,” not a “complex,” and so valsartan-sacubitril complexes “need not have been described” in the patent. By holding otherwise, the district court “erroneously conflated the distinct issues of patentability and infringement, which led it astray in evaluating written description.”

The Federal Circuit then determined that Novartis’ patent adequately discloses a “combination” of valsartan and sacubitril since the patent describes both compounds and explains that they can be combined in a “composition.” The court thus found that the “patent has an adequate written description of what is claimed.”

As to enablement, the Federal Circuit employed a similar analysis, noting that “a specification must only enable the claimed invention,” which, here, is simply a “combination” of valsartan and sacubitril. The court also agreed with the district court that valsartan-sacubitril complexes constitute after-arising technology that need not have been enabled in Novartis’ patent. Thus, regardless of whether such complexes are covered by the claims, they “cannot be used to ‘reach back’ and invalidate the asserted claims.” Accordingly, because the patent “does not expressly claim complexes, and because the parties did not otherwise dispute that the … patent enables that which it does claim,” the Federal Circuit concluded that MSN failed to show lack of enablement.

Related:

Regeneron Pharms., Inc. v. Mylan Pharms. Inc., 127 F.4th 896 (Fed. Cir. 2025) (affirming that claims directed to a protein formulation with an upper bound range of stability had adequate written description, citing expert testimony indicating that a skilled artisan would have understood the stability to be limited by what was understood to be workable).

Duke University v. Sandoz Inc., 160 F.4th 1305 (Fed. Cir. 2025) (reversing after finding a patent’s written description (1) failed to describe a representative number of species of a subgenus of prostaglandin analogs recited in a method, and (2) failed to provide sufficient blaze marks or structural features common to the subgenus because the specification did not identify how the disclosed features were unique to the claimed subgenus, as opposed to the entire genus).

Seagen Inc. v. Daiichi Sankyo Co., 2023-2424, 160 F.4th 1322 (Fed. Cir. 2025) (reversing a jury verdict of willful infringement after finding an earlier patent application failed to provide written description, e.g., blaze marks, for an 81-member subgenus of peptide linkers recited in an antibody-drug conjugate claim based on disclosure of a broad genus encompassing over 47 million peptides, and finding the application failed to enable a broad functional limitation of cleaving a drug from an antibody).

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