by Dennis Crouch
In an important opinion exploring the relationship between patent validity and after-arising technology, the Federal Circuit has reversed a district court’s invalidation of a pharmaceutical patent covering Novartis’s blockbuster heart failure drug Entresto. Novartis Pharmaceuticals Corp. v. Torrent Pharma Inc., Nos. 2023-2218, 2023-2220, 2023-2221 (Fed. Cir. Jan. 10, 2025).
The case centers on U.S. Patent 8,101,659, which claims a pharmaceutical composition combining valsartan (an angiotensin receptor blocker) and sacubitril (a neutral endopeptidase inhibitor) “in combination.” When Novartis originally filed the patent application in 2002, it disclosed administering these active ingredients together, such as in a physical mixture. Several years later, Novartis scientists discovered that the two compounds could be combined into a “complex” that ties the molecules together using non-covalent bonds. Generic drug makers filed abbreviated new drug applications (ANDAs) seeking to market generic versions of Entresto which uses the complex combination; Novartis sued for patent infringement.
The patent claims (as construed) are broad enough to cover both the physical mixture and the later-discovered complex, but the complex was not discussed within the patent document. This sets up a battle over the scope of enablement and written description required when the accused product involves after-invented technology. Following a bench trial, the district court split the decision – finding that the patent satisfied the enablement requirement but that the claims lacked adequate written description. On appeal, the Federal Circuit has sided with the patentee, affirming that the claims were enabled and reversing the written description invalidation.
In reversing the district court’s written description determination, the Federal Circuit emphasized a key point: the written description requirement only demands that a patent describe what is actually claimed. As Circuit Judge Lourie explained, “[t]he invention is, for purposes of the ‘written description’ inquiry, whatever is now claimed.” Vas-Cath Inc. v. Mahurkar, 935 F.2d 1555 (Fed. Cir. 1991). The ‘659 patent claims a pharmaceutical composition comprising valsartan and sacubitril administered “in combination” – it does not specifically claim the complex form.
The fact that the ’659 patent does not describe a complexed form of valsartan and sacubitril does not affect the validity of the patent.
Although not cited, this outcome aligns with the Federal Circuit’s 2017 statement that “evidence illuminating the state of the art subsequent to the priority date is not relevant to written description.” Amgen Inc. v. Sanofi, 872 F.3d 1367 (Fed. Cir. 2017).
In reading the written description portion of the opinion, it is fairly disappointing because it fails to deal with a number of written description nuances. The biggest of these though is that the opinion does not directly face the key precedent relied upon by the district court: Chiron Corp. v. Genentech, Inc., 363 F.3d 1247 (Fed. Cir. 2004). The patent at issue claimed “monoclonal antibodies” that were construed to encompass both mouse-based and chimeric antibodies. The problem though was that the 1984 priority application failed to provide written description support for claims encompassing chimeric antibodies because that technology did not even exist at the time of filing. The court held that it would be axiomatically impossible for Chiron’s scientists to have possessed and disclosed chimeric antibody technology in February 1984 when that technology wasn’t successfully created until several months later. This seems to be directly in opposition to the holding here in Novartis. But, the two are distinguishable once you dig into the facts. The difference is that Chiron had filed a continuation-in-part that particularly defined the claim term “monoclonal antibodies” to include chimeric antibodies. That definition transformed the picture so that now chimeric antibodies were expressly claimed and thus fair game for challenging in particular.
On enablement, the Federal Circuit affirmed the district court’s finding of validity, emphasizing that like written description, enablement only requires enabling what is actually claimed. The court relied on longstanding precedent establishing that “later-existing state of the art may not be properly considered in the enablement analysis.” In re Hogan, 559 F.2d 595 (CCPA 1977).
The Federal Circuit emphasized the policy rationale behind this rule, quoting Hogan‘s explanation that “[t]he 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 therein.” This would undermine a core function of the patent system – encouraging incremental improvements on prior inventions.
In Hogan, the inventors developed a solid polymer and described its creation in crystalline form using a chromium oxide catalyst. Years later, others discovered how to make amorphous forms of the same polymer using different catalysts and techniques that weren’t known in 1953. The Patent Office rejected Hogan’s claims as not enabled, arguing that the broad claims to a “solid polymer” weren’t supported because the specification only taught how to make the crystalline form, not the later-discovered amorphous form that would fall within the claim scope. The Court of Customs and Patent Appeals (The Federal Circuit’s predecessor) reversed, explaining that it would be “an impossible burden on inventors” to require them to enable technologies that didn’t exist when they filed their applications.
I’ll note that the the accused infringer here also suggested that the court revisit Hogan based upon the full scope enablement statement in the Supreme Court’s 2023 Amgen v Sanofi decision.
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The Federal Circuit also affirmed the district court’s rejection of obviousness challenges, finding no clear error in determining that skilled artisans in 2002 would not have been motivated to select and combine valsartan and sacubitril specifically.