The biotech company that makes mRNA-delivery technology for Pfizer’s PFE.N Covid-19 vaccine sued Arbutus Biopharma Corp ABUS.O in Manhattan federal court on Friday, seeking to head off claims that the vaccine infringes Arbutus’ patents.

Canada-based Acuitas Therapeutics Inc said Arbutus and partner Genevant Sciences have threatened to sue for potentially billions of dollars in “unjustified royalties” over the vaccine Pfizer developed with Germany’s BioNTech SE BNTX.O.

Acuitas asked the court to find that the Pfizer/BioNTech vaccine does not infringe Arbutus patents and that several Arbutus patents are invalid. A representative for Arbutus did not immediately respond to a request for comment on Acuitas’ claims.

Acuitas Chief Executive Thomas Madden said in a statement that the company remains confident in its technology but otherwise declined to comment on the lawsuit.

The lawsuit is part of a growing web of patent disputes over Covid-19 vaccine technology. Arbutus sued Moderna MRNA.O over its mRNA technology last month, but has not yet sued Pfizer or Acuitas.

Pfizer and Moderna were hit with patent lawsuits on Thursday by Alnylam Pharmaceuticals Inc ALNY.O, which argued its own lipid nanoparticle mRNA-delivery technology was “essential” to both of the widely used Covid-19 vaccines.

Pfizer said last month that it expected $32 billion in revenue from its vaccine this year. Moderna has said its vaccine earned the company $17.7 billion in revenue in 2021.