Chloroquine and Hydroxychloroquine: Old Drugs in a New COVID-19 World

The COVID-19 pandemic is challenging the slow and highly regulated drug-approval process in the United States. On March 28, 2020, the U.S. FDA authorized use of the antimalarial drugs chloroquine (CQ) and hydroxychloroquine (HCQ) to treat COVID-19 patients for whom a clinical trial is not available, despite inconclusive clinical evidence of effectiveness.

What sparked interest in these drugs? Most COVID-19 patients probably are in an antiviral-susceptible stage before clinical presentation. Following a primary phase marked by the usual respiratory symptoms, fevers, and malaise, patients most affected by COVID-19 develop a severe inflammatory respiratory illness, driven largely by the host immune response. Laboratory data show evidence of mas…