dministered prior to SARS-CoV-2 infection of VeroE6 cells, EC50 values for CQ were >100 μM and 18.01 μM, and the EC50 values for HCQ were 6.14 μM and 0.72 μM, at 24 and 48 h, respectively [18]. These results showed that the anti-SARS-CoV-2 activity of CQ was worse than HCQ in vitro. The conflicting results of these two studies may be related to different cell culture methods and experimental conditions. In short, these in vitro studies show that CQ/HCQ have strong anti-SARS-CoV-2 activity.

4.  Mechanisms of CQ/HCQ in treating COVID-19

4.1.  Antiviral activity

4.1.1.  Hindrance of receptor recognition process
The S protei