By Blake Brittain

June 4 (Reuters) - Moderna MRNA.O convinced a U.S. appeals court on Wednesday to uphold a ruling that undercut patent infringement claims by biotech company Alnylam Pharmaceuticals ALNY.O over Moderna's blockbuster COVID-19 vaccine Spikevax.

The U.S. Court of Appeals for the Federal Circuit upheld a Delaware federal court's decision to interpret Alnylam's two patents in a manner that foreclosed its infringement arguments.

Alnylam lost a similar dispute in a related Moderna case last year. It has filed separate, ongoing patent lawsuits over Pfizer's COVID shots.

An Alnylam spokesperson said the company is reviewing the Wednesday ruling and considering its options. A Moderna spokesperson said it was pleased with the decision and that its vaccine was "a product of many years of pioneering mRNA platform research and development."

Cambridge, Massachusetts-based Alnylam first sued Moderna and Pfizer for patent infringement in 2022 for allegedly using its lipid nanoparticle (LNP) technology in their vaccines to deliver genetic material into the body. The lawsuits are part of a web of patent disputes between biotech companies over COVID shots, which includes a lawsuit filed by Moderna against Pfizer later that year.

Moderna and Alnylam jointly agreed to dismiss Alnylam's patent claims in the first case in 2023 after U.S. District Judge Colm Connolly interpreted the patents to cover a type of lipid that Spikevax did not have. A three-judge Federal Circuit panel upheld Connolly's interpretation on Wednesday.

The case is Alnylam Pharmaceuticals Inc v. Moderna Inc, U.S. Court of Appeals for the Federal Circuit, No. 23-2357.

For Alnylam: Paul Hughes of McDermott Will & Emery

For Moderna: Jeffrey Lamken of MoloLamken

Read more:

Alnylam files patent infringement lawsuits against Pfizer, Moderna

Alnylam to appeal ruling on patents related to Moderna's COVID vaccines

Moderna fends off Alnylam US patent lawsuit over COVID shots, for now

(Reporting by Blake Brittain in Washington)