This Federal Circuit opinion analyzes lexicography in the context of claim construction.

Background

Alnylam Pharmaceuticals owns U.S. Patent Nos. 11,246,933 (parent) and 11,382,979 (child). These patents relate to biodegradable lipids and their use for the delivery of active agents such as nucleic acids.

Alnylam accused Moderna, Inc., ModernaTX, Inc., and Moderna US, Inc. (collectively, “Moderna”) of patent infringement in the District Court of Delaware. Specifically, Alnylam alleged that Moderna’s activities involving its mRNA-based COVID-19 vaccine SPIKEVAX® infringed the ’933 and ’979 patents.

The “branched alkyl” claim term was at issue with respect to claim construction. Generally, a cationic lipid includes three distinct domains: a head group, a linker, and hydrophobic tails. In one example of a cationic lipid from the specification, each of two hydrophobic tails is made up of an alkyl group R¹², a biodegradable group M¹, and an alkenyl group R¹³. Carbon atoms immediately next to a M¹ biodegradable group are located at the “alpha position” relative to that biodegradable group. The claim construction dispute concerned the degree of “branching” at that position that is required by the claims: whether the alpha-position carbon must be bound to at least three other carbon atoms (in which case it must be a “tertiary” or “quaternary” carbon) or whether it need only be bound to at least two other carbon atoms (in which case it can also be a “secondary” carbon).

The District Court of Delaware agreed with Moderna that there was clear and unequivocal lexicography of the “branched alkyl” claim term as defined in the patents’ specification. The specification states: “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.” (emphasis added). Accordingly, the district court construed “branched alkyl” as follows: A saturated hydrocarbon moiety 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 further concluded that Alnylam had not pointed to any part of the claims or written description that showed a “clear and unmistakable” departure from this definition.

Based on the above claim construction, the district court entered a final judgment of noninfringement. Alnylam appealed to the Federal Circuit on the issue of lexicography: Alnylam argued the district court erred in holding that Alnylam acted as a lexicographer, and in the alternative that, even if the relevant disclosure was definitional, the definition still covered a secondary carbon at the alpha position under the “[u]nless otherwise specified” portion of the definition.

Issues

1. Whether Alnylam acted as a lexicographer based on the patents’ specification?
2. Even if the relevant disclosure in the patents’ specification was definitional, does the definition cover a secondary carbon at the alpha position in the asserted claims under the “[u]nless otherwise specified” portion of the definition?

Holdings

1. Yes. Alnylam acted as a lexicographer because the relevant disclosure in the patents’ specification was definitional.
2. No. The “otherwise specified” clause did not support Alnylam’s bottom-line position that the claims at issue cover a secondary carbon at the alpha position.

Reasoning

1. Definitional disclosure. The Federal Circuit reasoned the relevant disclosure in the patents’ specification was definitional because (i) the sentence in question appeared under the title “Definitions”, (ii) the term to be defined, “branched alkyl”, was set off in quotation marks, (iii) the sentence used the term “refer to”, (iv) elsewhere in the “Definitions” section, Alnylam used non-limiting terms that contrast with the “refer to” language at issue here, and (v) the inclusion of the phrase “[u]nless otherwise specified” within the potentially lexicographic sentence suggested that the rest of the sentence laid out a generally applicable rule or definition. The foregoing characteristics, at least taken together, confirmed that the relevant language at issue was definitional.
2. The “otherwise specified” clause. The Federal Circuit reasoned that nothing in the (i) claims, (ii) specification, or (iii) prosecution history specified a different definition of a “branched alkyl” for purposes of the asserted claims. The language itself, “[u]nless otherwise specified”, connotes notions of specificity and definiteness, and strongly suggests that any such exception must be explicitly stated. Generally, once the high threshold for lexicography is met in a patent, a high threshold would similarly have to be met before finding a departure from that controlling definition. Under (i) the claims, the Federal Circuit noted it did not find a clear reason to conclude that “branched alkyl” as it is used in the asserted claims encompassed a secondary carbon at the alpha position. The Federal Circuit reasoned it would be odd to conclude that “otherwise specified” is a loose or lenient standard if the effect is to nullify the very purpose of the first part of the definition. Nor did unasserted dependent claim 14[1] help support Alnylam’s argument that the corresponding independent claim has to be construed broadly compared to said limiting dependent claim. Even though independent claims are generally construed to have a broader scope than their dependent claims, dependent claim 14 still narrows the scope of the independent claim on which it depends in a way that does not require allowance of a secondary carbon. Under (ii) the specification, the Federal Circuit noted the specification also failed to specify that the asserted claims cover a branched alkyl with a secondary carbon at the alpha position where the claimed branching occurs. The Federal Circuit’s reasoning included that nearly all of the embodiments fall outside the scope of the asserted claims and there are missing links between the embodiments and the asserted claims. Under (iii) the prosecution history, although this came closest to suggesting that Alnylam understood a branched alkyl to include a secondary carbon, the Federal Circuit still concluded that it was not sufficiently decisive to override the relevant disclosed definitional language. Though there was some support for Alnylam’s assertion of what it understood, the Federal Circuit found this might rather be read as merely stating an example of what branching at an alpha position could look like, and that this was not sufficient to counter the express definition in the specification and the need for specificity to establish an exception.

Conclusion

The Federal Circuit affirmed. The Federal Circuit concluded that Alnylam acted as a lexicographer in its requirement of a carbon bound to at least three other carbons “[u]nless otherwise specified”, and that Alnylam did not otherwise specify for purposes of the asserted claims. This opinion highlights the significance that a clear and unequivocal lexicography can have during claim construction and the high threshold required to find a departure from a controlling definition.

FOOTNOTES

[1] This claim further requires that “the branched alkyl group has only one carbon atom which is bound to three other carbon atoms”.