Chloroquine and hydroxychloroquine for COVID-19: Perspectives on their failure in repurposing.

The strategy to repurpose CQ/HCQ to combat COVID-19 infection is overshadowed by concerns about their QT liability, resulting in choice of potentially subtherapeutic doses. Although the risk of QT-related proarrhythmia is real, it is low and manageable by careful monitoring. Recent discontinuation of HCQ from at least four large studies effectively marks the end of efforts at repurposing of CQ or HCQ for COVID-19 infection. This episode leaves behind important questions on dose selection and risk/benefit balance in repurposing drugs generally.