CureVac said that it claimed intellectual property rights based on more than two decades of work on mRNA technology that was used by BioNTech and Pfizer for the development and sale of their Comirnaty coronavirus vaccine.
"CureVac's intellectual property portfolio protects several inventions relevant to the design and the development of BioNTech's SARS CoV-2 mRNA vaccines, among others, that are considered essential," the company said.
German-listed CureVac shares extended gains after the news, rising 4.4% to 14.16 euros at 1135 GMT.
BioNTech shares was trading 0.8% higher at 151.95 euros.
BioNTech declined to comment when contacted by Reuters.
The court in Duesseldorf, where CureVac submitted its lawsuit, did not want to give an official comment.
CureVac added that it was not seeking an injunction, nor does it intend to take legal action that would impede the production, sale or distribution of the vaccine.
"At the height of the pandemic, it would not have occurred to any of us to point out patent infringement. Now that there is better control over the pandemic, we believe it is the right time to do so," said a spokesperson for CureVac.
After failed efforts to bring a COVID-19 vaccine to market last year, CureVac intensified its work with partner GlaxoSmithKline on improved versions of vaccine.
CureVac and GSK said in April that their second-generation vaccine candidate targeting two recent COVID-19 variants had been shown to be highly effective in preclinical studies on mice.
(Reporting by Patricia Weiss; writing by Miranda Murray; editing by Paul Carrel and Jason Neely)