TMPRSS2 and COVID-19: First, SARS-CoV2 binds to a serine protease, which acts as a receptor for the ectoenzyme angiotensin-converting enzyme 2 (ACE2), whereas another transmembrane serine protease 2 (TMPRSS2) is necessary for priming the viral spike protein required to enter the cell, leading to COVID-19 [3,4].