When drafting patent applications, inventors must carefully choose between using claim language that is broad as compared to claim language that is sufficiently definite so that it complies with 35 USC 112(b), which requires that "[t]he specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention."
In addition, when working with cutting edge technology, such as technology that is evolving rapidly, inventors sometimes find it useful to be innovative with the terminology in the specification. It is well understood that a patentee "may choose to be his own lexicographer and use terms in a manner other than their ordinary meaning, as long as the special definition of the term is clearly stated in the patent specification or file history." Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed. Cir. 1996) (citing Hoechst Celanese Corp. v. BP Chemicals Ltd., 78 F.3d 1575, 1578 (Fed. Cir. 1996)). In fact, many patent specifications include a section that is typically labelled "Definitions" and which include specific definitions of terms used throughout the specification and claims.
Another well known axiom in U.S. patent practice is that it is generally improper to "read" limitations from the specification into the claims. In other words, one typically cannot add limitations to a claim that are not explicitly stated in the claim language. The specification's role is to provide context and support for the claims, but it should not be used to narrow the claim scope beyond what the claim language itself conveys.
However, these two principles may, on occasion, create a difficulty in interpreting the meaning of a claim term. Such was the issue confronting the parties in Alnylam Pharmaceuticals, Inc. V. Moderna, Inc., decided by the Court of Appeals for the Federal Circuit on June 4, 2025.
U.S. Patent No. 11,246,933 relates to a cationic lipid having one or more biodegradable groups located in a lipidic moiety (e.g., a hydrophobic chain) of the cationic lipid. In a section identified as "Definitions", the specification states:
Unless otherwise specified, the terms "branched alkyl", "branched alkenyl", and "branched alkynyl" refer to an alkyl, alkenyl, or alkynyl 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. For example, a spirocyclic group in an alkyl, alkenyl, or alkynyl group is not considered a point of branching.
Claim 18 defines a cationic lipid comprising a primary group and two biodegradable hydrophobic tails, wherein...for at least one biodegradable hydrophobic tail, the terminal hydrophobic chain in the biodegradable hydrophobic tail is a branched alkyl, where the branching occurs at the α-position relative to the biodegradable group and the biodegradable hydro-phobic tail has the formula —R12-M1-R13, where R12 is a C4-C14 alkylene or C4-C14 alkenylene, M1 is the biodegradable group, R13 is a branched C10-C20 alkyl, and the total carbon atom content of the tail —R12-M1-R13 is 21 to 26..."
The parties stipulated that the defendant Moderna would not infringe the asserted patent if the claims were limited to the above-mentioned definition, because Moderna's product does not meet the "branched alkyl" requirement of a carbon atom bound to at least three other carbons. The district court concluded that the claims were so limited to the definition in the specification, and entered final judgment finding no infringement by Moderna.
On appeal, the Court of Appeals for the Federal Circuit reviewed the district court's claim construction without deference determining the proper claim construction based on the intrinsic evidence alone, and affirmed the decision, i.e., claim construction, of the district court.
The decision is instructive in its analysis of numerous factors that a court should consider in determining whether to limit a claim term to a definition set forth in the specification.
Initially, the decision states that "the intrinsic 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 so redefine the claim term," citing Bell Atlantic Network Services, Inc. v. Covad Communications Group, Inc., 262 F.3d 1258, 1268 (Fed. Cir. 2001). By "intrinsic evidence", the court appears to be referring to the language in the specification. The court then discussed several factors:
First: The court was influenced by the fact that the definition was included under a heading titled "Definitions", noting that the court has previously found binding lexicography where the specification used the phrase "defined below".
Second: The term to be defined, "branched alkyl," is set off in quotation marks, indicating that this is often a strong indication that what follows is a definition.
Third: The sentence uses the term "refer to", which generally "conveys an intent for [that sentence] to be definitional.
Fourth: Elsewhere in the Definitions section, Alnylam used non-limiting terms that contrast with the "refer to" language at issue here. The court referred to other examples that were preceded by terms such as "for example", "non-limiting examples", "include", and "include, but are not limited to".
Fifth: The inclusion of the phrase "[u]nless otherwise specified" within the potentially lexicographic sentence suggests that the rest of the sentence lays out a generally applicable rule or definition.
The court concluded that the foregoing characteristics, at least taken together, confirm that the language at issue is definitional, and should therefore limit the term in the claims. The court further added that, as a general matter, "once the high threshold for lexicography is met in a patent, it makes sense that a high threshold would have to be met before finding a departure from that controlling definition." The court concluded that it did not find such a reason to depart from the stated definition.
The decision then provided a very technical analysis of the specific chemistry, concluding that the technical descriptions throughout the specification were consistent with the conclusion that the term should be limited as set forth in the specification's definition. The specific nature of that analysis is not instructive for providing general guidance, and is thus not discussed herein.
Thus, definitions embedded in the specification may be helpful, and perhaps in some cases even necessary, to avoid indefiniteness. However, inventors should be aware of the potentially limiting impact on the scope of the claim terms, and pay careful attention to the factors set forth above.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
