Decanoyl-Arg-Val-Lys-Arg-chlororomethylketone, also called Subtilisin/Kex2p-like proprotein convertase inhibitor, is a small, synthetic, irreversible and cell-permeable modified RVKR peptide that inhibits the seven pro-protein convertases: furin and PC1, PC2, PC4, PACE4, PC5, PC7. Proprotein convertases cleave proproteins to generate bioactive peptides or to activate enzymes and growth factors, thus regulating critical biological processes and playing a role in pathologies such as cancer or viral infection. Therefore, they represent potential therapeutic targets in a number of diseases. As an inhibitor of furin, Decanoyl-RVKR-CMK blocks the fusion of flavaviruses and coronaviruses, including SARS-CoV-2, with the membrane of human host cells. It also inhibits the processing of