Although it has been postulated that enzymatically active ACE2 might treat or prevent acute respiratory distress syndrome (ARDS) in patients with COVID-19, largely based on the preclinical finding that soluble ACE2 protects against ARDS in a murine acid aspiration model (50), results from two phase 2 clinical trials have failed to demonstrate a clinical benefit in patients. Here, ACE2 is linked to COVID-19.