Alnylam v. Moderna and the judicious use of definitions: The European perspective

The recent decision of the US Court of Appeal of the Federal Circuit in Alnylam v Moderna relates to the ongoing complex and high-stakes dispute over mRNA vaccine delivery technology. In a blow for Alnylam, the Federal Circuit found that Moderna did not infringe Alnylam's LNP platform patents in view of a definition of a technical term included in the description that narrowed the claims. The Federal Circuit concluded that, by including this definition in the description, Alnylam had acted as its own lexicographer and deliberately narrowed the meaning of the term. The decision in Alnylam v Moderna thus confirms the established US case law whereby the description of a patent may serve as a dictionary for the claims. The clear US case law in this area contrasts with the current uncertainty in Europe over how and if the description should be used to interpret the claims of European patent (G 1/24). As with the EBA referral in G 1/24, Alnylam v Moderna is further confirmation of the perils inherent in the overuse of boilerplate in patent specifications (IPKat).

Checking the dictionary definition

Legal background: Lexicography in US patent law

Under established US patent law doctrine, claim terms are generally given their plain and ordinary meaning as understood by a person of ordinary skill in the art. However, this presumption can be rebutted in two specific circumstances. First, where a patentee acts as their own lexicographer and clearly sets forth a definition of a claim term other than its plain and ordinary meaning. Second, where the patentee disavows the full scope of a claim term either in the specification or during prosecution (file wrapper estoppel) (IPKat). The threshold for establishing either exception is deliberately demanding. In particular, for the lexicography exclusion to apply, the evidence must clearly set forth or clearly redefine a claim term so as to put one reasonably skilled in the art on notice that the patentee intended to redefine the claim term (MPEP 2111.01, MPEP 2173.01, CCS Fitness, Inc. v. Brunswick Corp., CAFC 2022). 

Case Background: LNP vaccine dispute

The decision in this case relates to the ongoing patent dispute over delivery technology for mRNA-based vaccines, including the COVID vaccine. In this particular case, Alnylam brought two patent infringement suits against Moderna. Alnylam argued that Moderna's mRNA-based COVID-19 vaccine SPIKEVAX infringed Alnylam's patents US 11246933 and US 11382979, relating to lipid nanoparticles (LNPs) used for delivery of nucleic acids to the body. The broader LNP/COVID-19 vaccine dispute is hugely complex and a classic example of the important intersection between freedom to operate and patentability for technologies with both product and platform IP (IPKat). 

The central issue in this case related to the definition of a technical term in the claims: "branched alkyl". The claims of the patents specified "a branched alkyl, where the branching occurs at the α-position relative to the biodegradable group". In chemistry, the term "branched alkyl" is normally understood to mean a non-straight hydrocarbon chain, which could include secondary carbons (bonded to 2 other carbons) at branch points. However, contrasting with the normal definition, Alnylam's patent specification provided its own, more restrictive, definition of the term. The specification stated that "Unless otherwise specified, the term 'branched alkyl' refer[s] to an alkyl group in which one carbon atom in the group (1) is bound to at least three other carbon atoms and (2) is not a ring atom of a cyclic group."

The District Court found that it was clear from this definition that Alnylam was acting as its own lexicographer for the term and had narrowed the meaning of "branched alkyl" as used in the claims to mean an alkyl group in which one carbon atom in the group is bound to at least three other carbon atoms. Under this narrower definition, Moderna was found not to infringe the patents. 

On appeal, the Federal Circuit confirmed the District Court finding. The Federal Circuit particularly noted a number of facts that supported the narrowing effect of the description definition. First, the relevant sentence appeared under the title "Definitions." Second, the term to be defined, "branched alkyl," was set off in quotation marks. Third, the sentence used the term "refer to," which generally conveys an intent for the sentence to be definitional. Fourth, elsewhere in the Definitions section, Alnylam had used non-limiting terms that contrasted with the "refer to" language at issue. Finally, the inclusion of the phrase "[u]nless otherwise specified" suggested that the rest of the sentence laid out a generally applicable rule or definition.

The Federal Circuit concluded by explaining the common policy rationale behind its strict approach: "There are familiar reasons that definitions in the patent context deserve at least as much force: Public notice is a central policy, public reliance is a known reality, precision is at a premium, and the applicant has ample control over provision of definitions, so when a definition is expressly stated, the public is generally entitled to expect clear notice of exceptions" (page 12).

The Federal Circuit thus affirmed the District Court's claim construction and judgment of noninfringement. 

The European perspective

The US Federal Circuit's clear decision and reasoning in Alnylam v Moderna contrasts with the current uncertainty in Europe surrounding claim interpretation and the importance, or otherwise, of description definitions. It is hoped that the pending referral to the Enlarged Board of Appeal (EBA) in G 1/24 will resolve some of the uncertainty in Europe. 

G1/24 arose from a Philip Morris patent for heat-not-burn e-cigarettes requiring "a gathered sheet of aerosol-forming material," where the key novelty question was whether prior art disclosing tobacco that "may be spirally wound" anticipated a "gathered" sheet of tobacco. The definition of the term "gathered" tobacco as understood in the art would not normally be understood to include spirally wound tobacco. However, for reasons lost to the mists of time, the description of the patent defined "gathered" more broadly as "convoluted, folded, or otherwise compressed or constricted" tobacco. Under this broader definition, the term was broad enough to encompass the prior art's spirally wound tobacco. In view of a cited conflict on the case law on how the description should be used to interpret the claims, the EBA has been asked to clarify whether the description should be referred to when interpreting the claims and whether the specification can be a dictionary of definitions for the patent, i.e. as the US would put it, whether a patentee may be their own lexicographer. 

In this Kat's view, the question of whether a patentee can be their own lexicographer is different to the questions of whether the claims should be read in the context of the description as a whole and/or whether the description should be used to resolve a lack of clarity in the claims (IPKat). However, we await the EBA's interpretation and decision on the case. 

Final thoughts

Whatever the outcome of the case in G1/24, the take-home message is nonetheless the same as that for Alnylam v Moderna. Patentees in both the US and Europe should be exceedingly wary of using boilerplate definitions in their specifications. As shown in Alnylam v Moderna, an overly narrow definition may lead to problems of enforcement. Equally, as highlighted in G 1/24, an overly broad definition may lead to unforeseen validity issues. In Europe, amendment of description definitions, e.g. to bring the description in line with the claims, or to describe background prior art, also presents the additional risk of contravening the EPO's strict approach to added matter (IPKat). 

In this Kat's view, the use of boilerplate definitions of commonly understood terms in a patent specification is in most circumstances unnecessary. If a patentee wishes to narrow or broaden the scope of their invention to something different, the best and safest place to do this is the claims, and not via the back-door of description definitions (IPKat). 

However, there are cases where definitional language is required, for example in Europe unusual parameters must be defined. Interestingly, the decision of the Federal Circuit in Alnylam v Moderna case contrasts with that in Baxalta Inc. v. Genentech (CAFC, 2022), in which a narrowing definition of "antibody" was found not to limit the claims, in view of the more general tone of the definitional statements. What Alnylam v Moderna really teaches us therefore is, not that all definitions should be avoided at all cost, but instead that we should be cautious in how definitions are presented and to provide definitions in a manner as non-limiting as possible.

Further reading

• IPWatchdog: CAFC Affirms Moderna’s Win, Holding Alnylam Narrowly Defined ‘Branched Alkyl’
• Beware of boilerplate: Practical lessons for patent drafting from G1/24 (Claim interpretation) (April 2025)
• The description of a patent should "always" be used to interpret the claims (DexCom vs. Abbott, UPC_CFI_230/2023) (Feb 2025)
• US Supreme Court decision in Amgen v Sanofi: The European Perspective
• Can amending the description to summarize the prior art add matter to the patent application as filed? (T 0471/20) (Jan 2022)