(Reuters) – The U.S. Food and Drug Administration on Monday revoked the emergency use authorization for malaria drug hydroxychloroquine as a treatment for COVID-19, the use of which has been championed by U.S. President Donald Trump.

The FDA said based on new evidence, it was no longer reasonable to believe that oral formulations of hydroxychloroquine and the related drug chloroquine may be effective in treating the respiratory illness caused by the novel coronavirus.

The move comes after several studies of the drug suggested it was not effective, including a widely anticipated trial earlier this month showed it failed to prevent infection in people who have been exposed to the virus.

In March, Trump said hydroxychloroquine used in combination with the antibiotic azithromycin had “a real chance to be one of the biggest game changers in the history of medicine”, with little evidence to back up that claim.

He later said he took the drugs preventively after two people who worked at the White House were diagnosed with COVID-19.