The Food and Drug Administration has granted emergency use authorization for Gilead Sciences' remdesivir drug to treat Covid-19, the disease caused by the coronavirus, President Donald Trump announced Friday.

Trump made the announcement in the Oval Office alongside Gilead CEO Daniel O’Day.

“We want to thank the collaborators that brought remdesivir to this point and many of our people that have been part of this, in fact, the caregivers,” O’Day told reporters. Gilead is donating 1.5 million vials of remdesivir.

Gilead shares pared losses on the news, and closed Friday down 4.8% at $79.95. However, the stock was up nearly 2% in extended trading. It has a market value of about $101 billion and has gained 21% since the start of the year.

The EUA means that remdesivir has not undergone the same level of review as an FDA-approved treatment, according to a fact sheet from the agency on the drug. However, doctors will be allowed to use the drug on patients hospitalized with the disease even though the drug has not been formally approved by the agency.

The intravenous drug has helped shorten the recovery time of some hospitalized Covid-19 patients, new clinical trial data suggests. Without other proven treatments, health-care workers will likely be considering its use.

The FDA previously authorized the emergency use of malaria drugs chloroquine and hydroxychloroquine to treat Covid-19. However, it later issued a warning against taking the drugs outside a hospital or formal clinical trial setting after it became aware of reports of “serious heart rhythm problems” in patients.

Earlier in the week, White House health advisor Dr. Anthony Fauci said data from a coronavirus drug trial testing Gilead’s drug showed “quite good news” and sets a new standard of care for Covid-19 patients. The National Institute of Allergy and Infectious Diseases released results from its study showing Covid-19 patients who took remdesivir usually recovered after 11 days, four days faster than those who didn’t take the drug.

Gilead also released preliminary results from its own study, showing at least 50% of the patients treated with a five-day dosage of remdesivir improved. The clinical trial involved 397 patients with severe cases of Covid-19. The severe study is “single-arm,” meaning it did not evaluate the drug against a control group of patients who didn’t receive the drug.

″[The National Institutes of Health], FDA, and scientists across America and around the world have worked tirelessly with patients to get us this new potential treatment for COVID-19,” Health and Human Services Secretary Alex Azar said in a statement Friday.

Trump has touted remdesivir as a potential treatment for the virus, which has infected more than 3.3 million people worldwide and killed at least 237,000 people, according to data compiled by Johns Hopkins University. Earlier this week, he said he wanted the FDA to move “as quickly as they can” to approve the drug. 

“We would like to see very quick approvals, especially with things that work,” he said at a roundtable at the White House with business executives Wednesday evening.

The drug has not been formally approved to treat the virus, and U.S. health officials caution new data on the drug has yet to be peer-reviewed. Even though the drug was granted for emergency use, there are still several ongoing clinical trials testing the drug to see if it’s effective in stopping the coronavirus from replicating.

Remdesivir has shown some promise in treating SARS and MERS, which are also caused by coronaviruses. Some health authorities in the U.S., China and other parts of the world have been using remdesivir, which was tested as a possible treatment for the Ebola outbreak, in hopes that the drug can improve the outcomes for Covid-19 patients.

Side effects of the drug can include nausea and vomiting as well as possible damage to the liver, researchers have noted.

On Thursday, the company said it expects to produce more than 140,000 rounds of its 10-day treatment regimen by the end of May and anticipates it can make 1 million rounds by the end of this year. Gilead said it will be able to produce “several million” rounds of its antiviral drug next year.

Under the EUA, the FDA will allow the drug to be administered for either a five-day or a 10-day dose. A 10-day treatment regimen is preferred for intubated patients.

“That’s going to allow Gilead to effectively double the supply,” former FDA Commissioner Scott Gottlieb said during an interview on CNBC’s “Closing Bell.” 

The company said it will continue to support clinical trials and expand so-called compassionate use programs for remdesivir.