To be noted, we confirmed that all drugs lack potent inhibitory activity on the viral PLpro and 3CLpro (Supplementary Fig. S14), and also on human furin and TMPRSS2 (Supplementary Fig. S15) under the highest tested concentrations used in this infection study, indicating that the antiviral activities of these compounds are most likely due to the CTSL-specific inhibition. Here, TMPRSS2 is linked to infection.