Here's Why Hydroxychloroquine Doesn't Block The Coronavirus in Human Lung Cells - ScienceAlert

A paper came out in Nature on July 22 that further underscores earlier studies that show that neither the malaria drug hydroxychloroquine nor chloroquine prevents SARS-CoV-2 – the virus that causes COVID-19 – from replicating in lung cells.

But it does not inhibit the virus in human lung cells – the primary site of infection for the SARS-CoV-2 virus.

Depending on the cell type, some, like kidney cells, need an enzyme called cathepsin L for the virus to successfully infect them.

In the green monkey kidney cells, both hydroxychloroquine and chloroquine decrease the acidity, which then disables the cathepsin L enzyme, blocking the virus from infecting the monkey cells.

In human lung cells, which have very low levels of cathepsin L enzyme, the virus uses the enzyme TMPRSS2 to enter the cell.