Shortly after the first COVID-19 outbreak, it was already known that binding of the Spike (S) coronavirus protein to host angiotensin-converting enzyme 2 (ACE2) allows the virus to enter infected cells, but this requires previous proteolytic processing of viral S protein by the TMPRSS2 and/or endosomal papain-like cathepsins L/B [62,63]. This evidence concerns the gene TMPRSS2 and COVID-19.