The Trump administration announced Friday that it has authorized physicians to use remdesivir, an experimental drug to combat COVID-19, before it has won Food and Drug Administration approval.

The FDA issued an emergency use authorization to drugmaker Gilead Sciences in a letter Friday. The drug has been authorized to be administered intravenously for patients with severe COVID-19 who require help to breathe.

The FDA has not approved remdesivir for any use, the agency said.

“We need final data from clinical trials included in an FDA application to determine whether remdesivir is safe and effective,” FDA Center for Drug Evaluation and Research Director Janet Woodcock said in a tweet.

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The agency said it was reasonable to believe that remdesivir may be effective in treating COVID-19, and that, given there are no approved alternative treatments, the benefits currently outweigh the risks of the drug’s use.

Preliminary results from a randomized, double-blinded, placebo-controlled National Institutes of Health clinical trial released by the agency Wednesday that showed the recovery time for patients who received remdesivir was four days shorter than for patients who received a placebo. Those results have not yet undergone the peer review process by other experts.

Anthony Fauci, director of the NIH’s National Institute of Allergy and Infectious Diseases, said Wednesday in an announcement from the White House the early data showed an important “proof of concept.” Remdesivir is thought to inhibit viral RNA synthesis, slowing down replication of the virus.

Fauci said that remdesivir showed promise as an early treatment that could be built upon for more effective courses of treatment.

The emergency use authorization applies under the COVID-19 public health emergency, which Health and Human Services Secretary Alex Azar declared on Feb. 4.