fauci already knows. the NIH, while fauci was director, determined in 2005 that HCQ would treat, and stop the spread of Sars-Cov 1. which was the SARS virus. it does so by inhibiting the virus' interaction with the ACE-2 receptors mostly found in the lungs. the exact same way Sars-Cov-2 (COVID) infects the body.
https://pubmed.ncbi.nlm.nih.gov/16115318/