(Reuters) – The U.S. Food and Drug Administration on Monday revoked its emergency use authorization for hydroxychloroquine to treat COVID-19, the drug championed by U.S. President Donald Trump to stave off the coronavirus, and for an older related medicine.

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

The request to revoke the authorization came from Gary Disbrow, deputy assistant secretary at the Biomedical Advanced Research and Development Authority (BARDA).

The move comes after several studies of the decades-old malaria pills suggested they were not effective, including a widely anticipated trial earlier this month that showed hydroxychloroquine failed to prevent infection in people who had been exposed to the virus.

The drug’s anti-inflammatory and antiviral properties suggested it might help treat COVID-19, and the FDA authorized its emergency use in March at the height of a pandemic for which there were no approved treatments.

While it did appear to neutralize the virus in laboratory experiments, hydroxychloroquine, which is also used to treat lupus and rheumatoid arthritis, has failed to prove its worth in human COVID-19 trials, thus far. Chloroquine, which is not approved for any use in the United States, has also demonstrated mixed results in coronavirus studies.

In March, Trump said hydroxychloroquine 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, and he urged others to try it.

Doctors in recent weeks had already pulled back on the use of hydroxychloroquine for COVID-19, after several studies suggested it is not effective and may pose heart risks for certain patients.

Half of hospitals responding to a mid-May survey conducted by the American Society of Health-System Pharmacists (ASHP) reported excess supplies of hydroxychloroquine that they expected to return to wholesalers.

“Hospitals who have received supply through the Strategic National Stockpile now have inventory on hand,” said Michael Ganio, ASHP’s senior director of pharmacy practice and quality.

Today’s FDA action “seems to imply that drug can now be sold or dispensed for FDA-approved indications, or a hospital can contact BARDA to work on returning the product,” he said.

Current U.S. government treatment guidelines do not recommend use of the malaria drugs for COVID-19 patients outside of a clinical trial.

France, Italy and Belgium late last month moved to halt the use of hydroxychloroquine to treat COVID-19 patients. But the United States last month supplied Brazil with 2 million doses for use against the coronavirus, as the South American country has emerged as the pandemic’s latest epicenter.

Meanwhile, some 400 trials are listed as using hydroxychloroquine or chloroquine as interventions for COVID-19, more than half of them still ongoing, according to a recent analysis from research firm GlobalData.

In the United States, the National Institute of Allergy and Infectious Diseases last month launched a trial designed to show whether hydroxychloroquine in combination with azithromycin can prevent hospitalization and death from COVID-19.