SARS-CoV-2, the virus responsible for COVID-19, enters human cells by attaching to ACE2 and utilizing TMPRSS2. Drugs that block ACE2 or inhibit the enzyme could help treat the coronavirus, but only during early infection. As the infection progresses, SARS-CoV-2 becomes engulfed in human cells, reducing the number of ACE2 receptors on a cell and leading to an increase of angiotensin II in the blood. Angiotensin II triggers an inflammatory pathway, providing a positive feedback cycle, named IL-6 amplifier, resulting in excessive immune activation and the cytokine storm associated with severe COVID-19.
