Although clinical trials of the drug for treatment of the novel coronavirus, SARS-CoV-2, have produced mixed results, the largest study to date suggested that up to 50 percent of those given the drug for a five-day period showed improvement in symptoms.
Roughly the same percentage were well enough to be discharged from the hospital within two weeks of receiving their first dose of the drug, which is delivered intravenously.
The agency said the drug has not been approved as a general treatment for COVID-19. Rather, it is only intended for emergency use on severely ill patients who have been hospitalized.
"Today's action is an important step in our efforts to collaborate with innovators and researchers to provide sick patients timely access to new therapies where appropriate, while at the same time supporting research to further evaluate whether they are safe and effective," FDA Director Stephen Hahn said in a statement.
The larger study, conducted by the drug's manufacturer Gilead Sciences, found participants who received the drug within 10 days of symptom onset had improved outcomes compared to those treated after more than 10 days.
The time to clinical improvement for 50 percent of patients was 10days on a five-day regimen of the drug and 11 days for patients on a 10-day regimen.
By day 14 of treatment, 65 percent of the participants in the five-day treatment group and 54 percent in the 10-day treatment group achieved clinical recovery.
By day 14, 62 percent of patients treated early were also able to be discharged from the hospital, compared with 49 percent of patients who were treated late, Gilead said.
Another study published earlier this week by The Lancet found that COVID-19 patients treated with remdesivir were twice as likely to develop severe breathing problems, including acute respiratory distress syndrome, than those treated with placebo.
However, the study also said that those given the drug recovered up to five days faster than those who received standard care without it.