FURIN and obesity due to melanocortin 4 receptor deficiency: Unbalancedactivity of furin and other PCs is connected to severalpathologies such as rheumatoid arthritis, obesity, and cancer as wellas infections by bacteria and viruses.1,2 Many viralglycoproteins require cleavage by furin, including the S protein ofsevere acute respiratory syndrome virus 2 (SARS-CoV-2).6−8 Several studies have shown that furin inhibitors are efficient suppressorsof viral replication.9 Acquisition of afurin cleavage site is regarded as a major pathogenicity factor ofviruses.