Transmembrane protease serine 2 (TMPRSS2) inhibitors may be used to block SARS-CoV-2 infection and then used to treat COVID-19.31 ACE2 is a metal peptidase, expressed on major viral target cells such as lung cells and intestinal epithelial cells, and its catalytic domain binds to the S protein of SARS-CoV with high affinity.32 For viral infectivity, host cell proteases affect the S protein cleavage is crucial. The gene discussed is PROS1; the disease is COVID-19.