Alnylam Pharms., Inc. v. Moderna, Inc

Authored by: Jeremy J. Gustrowsky

In a recent decision, the Federal Circuit affirmed a district court’s ruling in the high-profile patent dispute between Alnylam Pharmaceuticals, Inc. and Moderna, Inc. over Moderna’s COVID-19 vaccine, SPIKEVAX®. The case centered on the meaning of the term “branched alkyl” in Alnylam’s U.S. Patent Nos. 11,246,933 and 11,382,979, which relate to lipid nanoparticles used for delivering nucleic acids, such as mRNA, into cells. Alnylam claimed that Moderna’s use of a specific lipid, SM-102, infringed its patents, but the outcome hinged on how narrowly or broadly “branched alkyl” should be interpreted.

The heart of the dispute was whether “branched alkyl” should be limited to a carbon atom bound to at least three other carbon atoms (a tertiary or quaternary carbon), as defined in the patent’s specification, or if it could also include a secondary carbon (bound to only two other carbons). The district court found that Alnylam had acted as its own lexicographer—meaning it had clearly defined “branched alkyl” in the patent’s “Definitions” section. Because Moderna’s lipid did not meet this stricter definition, the parties agreed there was no infringement.

On appeal, Alnylam argued that the definition should be broader or that the claims otherwise specified a different meaning. However, the Federal Circuit held firm, emphasizing that when a patent provides a clear definition for a term, that definition controls unless the patent “otherwise specifies” with equal clarity. The court found no such exception in the claims, specification, or prosecution history, and stressed the importance of public notice and clarity in patent documents.

This case is a reminder to patent drafters and litigators alike: when a patent applicant defines a term in the specification, that definition will govern—potentially narrowing the scope of protection. Precision in drafting and awareness of the implications of in-specification definitions are crucial.