A ketone-based peptide, named decanoyl-RVKR-chloromethylketone (CMK), has been previously demonstrated as a potent inhibitor of furin belonging to SARS-CoV-1 [12] and Middle East respiratory syndrome (MERS) [13], and it exhibited a marked activity in the inhibition of syncytia formation and virus infection. The gene discussed is FURIN; the disease is Middle East respiratory syndrome.