A Randomized Trial of Nafamostat for Covid-19Nafamostat mesylate is a potent in vitro antiviral that inhibits the host transmembrane protease serine 2 enzyme used by SARS-CoV-2 for cell entry. Morpeth et al report the results of an open-label randomized clinical trial of nafamostat for noncritically ill patients with Covid-19.