Arbutus and Genevant said in their lawsuit that Moderna infringed on their patent for what is called lipid nanoparticle technology, which they say was key in the development of Moderna's mRNA vaccine and took scientists from Arbutus and Genevant "years of painstaking work to develop and refine." The suit had been expected after Moderna lost a U.S. Court of Appeals ruling last year in the protracted patent battle.

Moderna, a 10-year-old Cambridge, Mass.-based biotechnology firm that had not marketed any product before the pandemic, has said it expects coronavirus vaccine sales to top $19 billion in 2022. Arbutus and Genevant — a company spearheaded by former Arbutus scientists — could demand some of that as royalties if their challenge succeeds.

The suit is one of two high-profile legal fights Moderna faces over its blockbuster vaccine, which was developed in less than a year and has been key to fighting the pandemic.