Nafamostat mesylate, another serine protease inhibitor that has been used in Japan for more than 30 years for pancreatitis and as an anticoagulant of perfused blood known to inhibit TMPRSS2-mediated host-cell entry of MERS-CoV (Figure 3) and presumptively of SARS-CoV-2 (Iwata-Yoshikawa et al., 2019), has been recently employed alone, to block activation of SARS-CoV-2 (Hoffmann et al., 2020b), or in combination with heparin as an anti-enhanced fibrinolysis therapy for the coagulopathies observed in severe cases of COVID-19 (Asakura and Ogawa, 2020). Here, TMPRSS2 is linked to blood coagulation disease.