The SARS-CoV-2 S protein interaction process is mediated by proteases such as transmembrane protease serine 2 (TMPRSS2), cellular protease furin and cathepsin L. Interestingly, we measured PAPP-A expression in the nasopharyngeal samples of 90 COVID-19 patients but did not observe any change between the control group and patients (data not shown), so this does not seem to be the case. This evidence concerns the gene CTSL and COVID-19.