ACE2 and COVID-19: Serpin E2 inhibits the activity of furin protein and plasmin, and in drug treatment for COVID-19, serpin E2 expression is increased using a mineralocorticosteroid receptor antagonist, which reduces plasmin and furin protein activity, thereby inhibiting proteolysis, binding of COVID-19 to ACE2, and reducing viral infectivity (Wilcox and Pitt, 2020).