The US Food and Drug Administration on Thursday approved Gilead Sciences Inc's antiviral drug remdesivir for treating patients hospitalized with COVID-19, making it the first and only drug approved for the disease in the United States.

Remdesivir, given intravenously, was one of the drugs used to treat US President Donald Trump during his bout with COVID-19.

It has been available under an FDA emergency use authorization since May, after a study led by the National Institutes of Health showed it reduced hospital stays by five days. But the World Health Organization (WHO) last week said its global trial of COVID-19 therapies found that remdesivir did not have a substantial effect on patients’ length of hospital stay or chances of survival. That study has not been reviewed by outside experts.

Gilead has questioned the potential for bias in the WHO study, which was not "blinded," meaning that participants and their doctors were aware of which treatments were being used.

Remdesivir, which will be sold under the brand name Veklury, costs $3,120 for a five-day treatment course, or $2,340 for government purchasers such as the Department of Veterans Affairs. Shares of Gilead rose 4.3 percent in after hours trading to $63.30.

Gilead said it is currently meeting real-time demand for the drug in the United States and anticipates meeting global demand by the end of October.

The company said its drug has regulatory approvals or temporary authorizations in about 50 additional countries.

Also on Thursday, the FDA issued a new emergency use authorization for remdesivir to treat hospitalized pediatric patients under age 12 who weigh enough to receive an intravenous drug.

Gilead said it is still working to understand the full potential of Veklury, in different settings and as part of combination therapy approaches.

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