Fauci has known since 2005 that chloroquine is an effective inhibitor of coronaviruses. The Virology Journal, the official publication of Fauci’s National Institutes of Health published an article about this in 2005. According to this article:
HCQ functions as both a cure and a VACCINE

We report that chloroquine has strong antiviral effects on SARS-CoV infection of primate cells. These inhibitory effects are observed when the cells are treated with the drug either before or after exposure to the virus, suggesting both prophylactic and therapeutic advantage

Chloroquine is effective in preventing the spread of SARS CoV in cell culture. Favorable inhibition of virus spread was observed when the cells were either treated with chloroquine prior to or after SARS CoV infection. In addition, the indirect immunofluorescence assay described herein represents a simple and rapid method for screening SARS-CoV antiviral compounds

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1232869/