Just 80 days after first issuing an emergency use authorization (EUA) for oral formulations of chloroquine phosphate (CQ) and hydroxychloroquine sulfate (HCQ) in treating COVID-19, the FDA is revoking that authorization in light of clinical data and scientific literature that raised questions about whether benefits of the treatment outweigh the risks.

Following the review, the agency has determined that the suggested dosing regimens for CQ and HCQ detailed in earlier health provider fact sheets are unlikely to produce and antiviral effect. Furthermore, the agency said, earlier reports of decreased viral shedding following treatment with the drugs have not been consistently replicated, and recent data from a randomized controlled trial (RCT) found no difference between HCQ and standard of care alone.

In particular, the agency cited results of the Recovery trial, sponsored by Oxford University in collaboration with several foundations and British government agencies. That study, the FDA noted, "showed no evidence of benefit for mortality or other outcomes such as hospital length of stay or need for mechanical ventilation of HCQ treatment in hospitalized patients with COVID-19."

In conclusion, the agency said in a letter to a U.S. Biomedical Advanced Research and Development official that, "based on the totality of scientific evidence available, it is no longer reasonable to believe that CQ and HCQ may be effective in treating COVID-19 for the authorized uses detailed."