Carmofur is a derivative of fluorouracil an is an antineoplastic agent showing antitumor activity against several cells including L1210 leukemia and L5178Y lymphoma cells. Carmofur interferes with nucleotide metabolism and consequently with synthesis of RNA and DNA, leading to cytotoxic and antineoplastic effects. Carmofur inhibits also other enzymes such as lysosomal acid ceramidase and the main protease from coronaviruses. For the SARS-CoV-2 main protease Mpro, carmofur was characterised as a covalent inhibitor with IC50 of 1.82uM and EC50 of 24.30uM.