Moderna Inc said on Friday, July 25 its formula used in developing a Covid-19 vaccine was not covered under patents owned by Arbutus Biopharma, Reuters reports.

Moderna Therapeutics is a Cambridge, Mass.-based biotech company co-founded by Armenian entrepreneur Noubar Afeyan.

An administrative court run by the U.S. Patent and Trademark Office on Thursday rejected Moderna’s arguments to invalidate a U.S. patent owned by Arbutus, sparking worries over its efforts to develop next-generation vaccines, including a coronavirus vaccine.

Moderna said the court’s ruling relates to actions it took in response to “longstanding aggressive posture” taken by Arbutus against developers of nucleic acid-based therapeutics and began well before the development of mRNA-1273, its Covid-19 vaccine candidate.

Moderna shares were up slightly in extended trading, while Arbutus shares closed down 20% on Friday.