The United States recently secured 1.7 million doses of a compound that could help to treat Covid-19 patients. In preliminary studies, Molnupiravir reduced the transmission of the Sars-CoV-2 coronavirus. Researchers at the Max Planck Institute for Biophysical Chemistry in Göttingen and the Julius Maximilians University Würzburg have now elucidated the underlying molecular mechanism. The antiviral agent incorporates RNA-like building blocks into the RNA genome of the virus.