On Jun. 20, 2020, the National Institutes of Health (NIH) announced that a clinical trial to evaluate the safety and effectiveness of hydroxychloroquine for the treatment of adults hospitalized with coronavirus disease 2019 (COVID-19) had been stopped.

A data and safety monitoring board (DSMB) determined that while there was no harm, the study drug was very unlikely to be beneficial to hospitalized patients with COVID-19. After its fourth interim analysis the DSMB, which regularly monitors the trial, recommended to the NIH, to stop the study.