Federal Circuit's Decision in In re Entresto: A Landmark Ruling on After-Arising Technology and Patent Validity
Introduction
This case presents a pivotal dispute concerning the intersection of patent law and "after-arising technology”, a concept that challenges fundamental assumptions about what patentees must disclose to obtain valid patent protection. The Federal Circuit's decision in In re Entresto (Sacubitril/Valsartan) is a significant patent ruling of 2025, with implications extending far beyond the pharmaceutical industry. The case involves Novartis's blockbuster heart failure drug, Entresto. It raises profound questions about whether patents should be able to capture later-invented technologies without describing them, creating what critics call a dangerous "loophole" in the patent system.
Patent at Issue
The litigation centers on U.S. Patent 8,101,659 (the "'659 patent"), which was filed on January 17, 2002, and expired on January 15, 2025 (due to Patent Term Extension (PTE)). This patent was listed in the U.S. Food and Drug Administration’s Orange Book for Entresto, Novartis's heart failure medication that generated over $3 billion in U.S. sales in 2023 alone.
The '659 patent generally relates to pharmaceutical compositions comprising valsartan (an angiotensin receptor blocker or "ARB") and sacubitril (a neutral endopeptidase or "NEP" inhibitor) for treating hypertension and heart failure. Significantly, this patent was filed years before scientists discovered how to create "complexes" of these two compounds.
Technology
The technology at the heart of this dispute involves two critical cardiovascular drugs and their relationship:
Valsartan is an angiotensin receptor blocker (ARB) that prevents angiotensin II from binding to its receptor, thereby reducing blood vessel constriction effects of this naturally occurring hormone. Sacubitril is a neutral endopeptidase (NEP) inhibitor that also reduces blood vessel constriction, but through a different mechanism, not involving angiotensin.
The '659 patent describes combining these compounds as a "physical combination" or mixture. However, four years after the patent was filed, scientists discovered they could create "complexes" of valsartan and sacubitril—single molecular entities formed through weak, non-covalent bonds that yield superior therapeutic effects. This complex technology became the basis for Entresto, which combines the two drugs into a single unit-dose form and has proven highly effective for treating heart failure with reduced ejection fraction.
This later-discovered complex represents what patent law calls "after-arising technology”, innovations that emerge after a patent's filing but potentially fall within the patent's claimed scope.
Representative Claims
The case focuses on claims 1-4 of the '659 patent, with claim 1 as the sole independent claim:
"1. A pharmaceutical composition comprising:
(i) the AT 1-antagonist valsartan or a pharmaceutically acceptable salt thereof;
(ii) the NEP inhibitor [sacubitril] or [sacubitrilat] or a pharmaceutically acceptable salt thereof; and
(iii) a pharmaceutically acceptable carrier;
wherein said (i) AT 1-antagonist valsartan or pharmaceutically acceptable salt thereof and said (ii) NEP inhibitor [sacubitril] or [sacubitrilat] or a pharmaceutically acceptable salt thereof, are administered in combination in about a 1:1 ratio."
Claim 2 adds that the valsartan and NEP inhibitor "are administered in amounts effective to treat hypertension or heart failure".
Claim 3 specifies that "the NEP inhibitor is sacubitril".
Claim 4 depends from claim 3 and recites "the composition is in the form of a capsule or tablet".
The critical dispute centered on the phrase "administered in combination" and whether this language was broad enough to encompass the later-discovered complex form or was limited to physical mixtures of separate compounds.
Procedural History
The district court proceedings unfolded in several key phases:
Claim Construction Phase (2021): The parties disputed only one term: "wherein said [valsartan and sacubitril] are administered in combination." MSN argued that this limited the claims to "two separate components”. At the same time, Novartis sought the plain and ordinary meaning: “wherein said [valsartan and sacubitril] are administered in combination”. The district court adopted Novartis's construction, finding the intrinsic record was "silent on whether sacubitril and valsartan must be separate (and not complexed)". It explained that “the absence of any indication in the written description that the patentee limited its invention solely to separate compounds means, in context, that a person of ordinary skill in the art [ ] would not read the claims as so limited”. The court was influenced by Novartis's representations to the USPTO during PTE proceedings, in which Novartis stated that the '659 patent claims covered Entresto—a drug containing complexed valsartan and sacubitril. Specifically, Novartis told the Patent Office that the claims of the ‘659 patent recite compositions that enclosed Entresto, a drug that includes “non-separate, complexed valsartan and sacubitril”.
Stipulation and Trial: Following the broad claim construction, MSN stipulated to infringement. The case proceeded to a three-day bench trial on validity issues, including obviousness, written description, and enablement.
District Court Decision (July 2023): Judge Richard G. Andrews found the claims were not invalid for obviousness or lack of enablement, but were invalid for lack of written description. The court applied the principle that patents must describe the full scope of their claims. Since the '659 patent never described complexes (which were unknown in 2002), it could not support claims construed to cover such complexes.
Key Issues on Appeal
The Federal Circuit considered three primary validity challenges:
Written Description: Whether the '659 patent adequately described what it claimed, specifically focusing on whether it needed to describe valsartan-sacubitril complexes that were unknown at the time of filing.
Enablement: Whether the patent enabled the full scope of its claims, including the later-discovered complex technology.
Obviousness: Whether a person of ordinary skill would have been motivated to combine valsartan and sacubitril with a reasonable expectation of success, given the prior art as of 2002.
The central legal question underlying all these issues was whether "after-arising technology" should be considered in patent validity analysis—a question that has divided Federal Circuit panels for decades.
Federal Circuit Holdings
In a decision authored by Judge Lourie, the Federal Circuit reversed the district court's written description holding and affirmed the determinations of obviousness and enablement.
Written Description Reversal
The Federal Circuit fundamentally reframed the written description analysis. Rather than asking whether the patent described complexes, the Court held that "the issue on appeal is whether the '659 patent describes what is claimed, viz., a pharmaceutical composition comprising valsartan and sacubitril administered 'in combination’”. The issue is not whether the '659 patent describes valsartan-sacubitril complexes.
The Court found adequate written description support throughout the specification, noting the opening sentence stated, "the present invention relates to pharmaceutical combinations comprising valsartan... and a NEP inhibitor... and pharmaceutical compositions comprising them". The patent further specified that sacubitril could be used in combination with valsartan and taught that the components "may be administered simultaneously or sequentially in any order". According to the Federal Circuit, these disclosures (and more) plainly showed that the inventors had possession of a pharmaceutical composition comprising valsartan and sacubitril administered “in combination”. In fact, MSN’s expert conceded that the ‘659 patent adequately disclosed administration of valsartan and sacubitril in combination as a physical mixture.
The Court made it clear that the fact that the ‘659 patent did not describe a complexed form of valsartan and sacubitril did not affect the validity of the patent, because the complex was not what was claimed. The Court stated that by stating that the claims were “construed to cover complexes of valsartan and sacubitril”, the district court erroneously conflated patentability and infringement, which led it “astray” in evaluating written description. Therefore, because the '659 patent does not “claim valsartan-sacubitril complexes, those complexes need not have been described".
Enablement Affirmance
The Federal Circuit affirmed the district court's enablement holding, emphasizing that "a specification must only enable the claimed invention". Critically, the court held that "later-existing state of the art... may not be properly considered in the enablement analysis" and that "later-discovered valsartan-sacubitril complexes... cannot be used to 'reach back' and invalidate the asserted claims".
The court quoted extensively from In re Hogan, 559 F.2d 595, 606 (CCPA 1977), explaining:
“The use of a subsequently-existing improvement to show lack of enablement in an earlier-filed application on the basic invention would preclude issuance of a patent to the inventor of the thing improved, and in the case of issued patents, would invalidate all claims (even some ‘picture claims’) therein. Patents are and should be granted to later inventors upon unobvious improvements. Indeed, encouragement of improvements on prior inventions is a major contribution of the patent system and the vast majority of patents are issued on improvements. It is quite another thing, however, to utilize the patenting or publication of later existing improvements to ‘reach back’ and preclude or invalidate a patent on the underlying invention.”
The Court stated that the later-discovered valsartan-sacubitril complexes, which “arguably may have improved upon the ‘basic’ or ‘underlying invention claimed in the ‘659 patent, cannot be used to ‘reach back’ and invalidate the asserted claims”.
Obviousness Affirmance
The Federal Circuit found no clear error in the district court's obviousness analysis. While acknowledging that a person of ordinary skill might have been motivated to pursue ARB-NEP inhibitor combinations generally, the court agreed there was no motivation in the relied-upon prior art to combine valsartan and sacubitril, let alone with any reasonable expectation of success. Key factors included: sacubitril was one of over 100 NEP inhibitors known in 2002, it had never been administered to humans or animals, and the clinical results of other NEP inhibitors had been “discouraging".
Supreme Court Petition for Certiorari
On August 22, 2025, MSN filed a petition for writ of certiorari presenting the question: "[W]hether, in a patent-infringement suit, a court may consider after-arising technology to hold that the patent is invalid under § 112(a) of the Patent Act".
MSN's Arguments for Certiorari
MSN characterizes the Federal Circuit's decision as perpetuating "doctrinal chaos" in patent law regarding after-arising technology that conflicts with the Supreme Court’s decision in The Incandescent Lamp Patent, 159 U.S. 465 (1895). The petition identifies four conflicting doctrinal lines:
The Idenix Line: Holdings that after-arising technology is relevant to validity analysis and can invalidate patents that fail to describe or enable such technology. Idenix Pharms. LLC v. Gilead Scis. Inc., 941 F.3d 1149 (Fed. Cir. 2019).
The Hogan-Entresto Line: Holdings that after-arising technology is irrelevant to validity and that ensnaring after-arising technology for infringement does not risk invalidity.
The Schering Line: Decisions narrowly construing claims to exclude after-arising technology and finding no infringement. Schering Corp. v. Amgen Inc., 222 F.3d 1347 (Fed. Cir. 2000).
The SuperGuide Line: Decisions broadly construing claims to cover after-arising technology and finding infringement. SuperGuide Corp., v. DirecTV Enters., Inc., 358 F.3d 870 (Fed. Cir. 2004).
MSN argues this creates a "double standard" where patentees can claim broadly for infringement purposes while avoiding the disclosure obligations that broad claims should entail. The petition argues that this violates the fundamental principle of patent law, which is that the scope of a claim must be consistent for both infringement and validity analyses.
Historical Precedent
MSN invokes Incandescent Lamp, where the Supreme Court invalidated Sawyer and Man's patent for claiming Edison's after-arising bamboo filament technology without adequately describing it. In that case, the patentees had claimed "carbonized fibrous or textile material" broadly enough to capture Edison's later-invented bamboo filament. Still, the Court held the patent invalid because the inventors had not actually invented or described the bamboo technology.
Policy Arguments
The petition argues the Hogan-Entresto approach undermines the constitutional patent bargain by allowing inventors to "reap the benefits of broad claims that cover after-arising technologies while avoiding the disclosure obligations that those claims entail". This allegedly stifles innovation and enables gamesmanship, particularly allowing pharmaceutical companies to "deploy aging patents to delay the entry of generic medications".
Key Takeaways
This case illuminates several critical issues in modern patent law:
The After-Arising Technology Doctrine
The Federal Circuit's decision crystallizes a fundamental split in how courts treat after-arising technology. The majority approach now clearly permits patents to capture later-developed improvements without describing them, provided the later technology falls within the properly construed claim scope as understood at the time of filing. This represents a significant advantage for patentees and a departure from the strict symmetry between infringement and validity analyses.
Policy Tensions
The case highlights competing policy considerations: encouraging pioneering inventions through broad patent protection versus ensuring adequate disclosure to enable follow-on innovation. The Federal Circuit's approach prioritizes the former, while critics argue it undermines the constitutional quid pro quo of the patent system.
Pharmaceutical Patent Strategy
For pharmaceutical companies, this decision provides a roadmap for leveraging early filed patents to capture later-developed drug formulations and delivery mechanisms. However, it also demonstrates the importance of careful claim drafting and prosecution strategy, as the scope of protection depends heavily on the specific claim language and its construction.
What to Watch at the Supreme Court
Several factors suggest the Supreme Court may grant certiorari in this case:
Doctrinal Confusion
The petition effectively demonstrates the Federal Circuit's inconsistent treatment of after-arising technology across decades of conflicting precedent. The Supreme Court has historically intervened when circuit courts create confusion in critical areas of federal law.
Recent Amgen Decision
The Court's decision in Amgen v. Sanofi, 598 U.S. 594 (2023), addressed the enablement requirements but did not resolve the question of after-arising technology. Granting certiorari in this case would enable the Court to provide comprehensive guidance on patent disclosure obligations in the modern technological landscape.
Constitutional Implications
The case presents fundamental questions about the constitutional limits of patent protection and whether the Patent Act permits inventors to claim more than they actually invented. These constitutional dimensions increase the likelihood of Supreme Court review.
Economic Impact
With billions of dollars in pharmaceutical sales at stake and implications across all technology sectors, the economic significance of this doctrine strongly favors Supreme Court intervention.
Timing Considerations
The petition's timing, which follows closely after Amgen, presents an ideal opportunity for the Court to comprehensively address patent disclosure doctrine while lower courts are still implementing the teachings of Amgen.
If the Supreme Court grants certiorari, practitioners should expect a decision that either endorses the Federal Circuit's approach (allowing the capture of after-arising technology without description) or reverses it (requiring full disclosure of claimed subject matter, regardless of when it was invented). Either outcome will have profound implications for patent prosecution strategies, licensing negotiations, and litigation tactics across all industries where technological advancements outpace the timelines for patent filing.
The case ultimately presents the Court with a choice between two competing visions of the patent system: one that prioritizes rewarding early pioneers with broad protection, and another that demands complete disclosure as the price of that protection. The resolution of this tension will shape patent law for generations to come.
This post was written by Lisa Mueller.