When a cell is infected, SARS-CoV-2 not only causes the host cell to produce new virus particles. The virus also suppresses host cell defence mechanisms. The virus protein nsP3 plays a central role in this. Using structural analyses, researchers at Goethe University in cooperation with the Swiss Paul Scherrer Institute have now discovered that a decomposition product of the virostatic agent remdesivir binds to nsP3. This points to a further, previously unknown effective mechanism of remdesivir which may be important for the development of new drugs to combat SRS-CoV-2 and other RNA viruses.