All it takes is some digging to find facts. Highlighting mine.

CHLOROQUINE EFFECTIVENESS VS. CORONAVIRUSES WAS DOCUMENTED IN 2005

".....In 2005, an article was published in Virology Journal titled “Chloroquine is a potent inhibitor of SARS coronavirus infection and spread. The eight authors were associated with the Centers for Disease Control and Montreal’s Clinical Research Institute. The study described in the article was conducted in the wake of the SARS epidemic: ....."

".....Note that this study found chloroquine to be effective prophylactically, as well as as a treatment. The drug should have been on CDC’s radar from the beginning......"

https://www.powerlineblog.com/archives/2020/04/chloroquine-effectiveness-vs-coronaviruses-was-documented-in-2005.php