The experimental drug remdesivir has been approved to treat hospitalized patients with severe Covid-19, the US Food and Drug Administration said in a letter on Friday.

Remdesivir is the first authorized therapy drug for Covid-19 in the United States, FDA Commissioner Stephen Hahn said on Friday.

This is an important clinical advance that showed a statistically significant reduction in time to recovery for patients with Covid-19 and is the first authorized therapy for Covid-19.” Hahn said.

The FDA issued an emergency-use authorization on Friday, saying the benefits of the drug outweigh its risks in patients. An emergency-use authorization is a lower regulatory bar than full FDA approval.

Denise Hinton, the FDA’s chief scientist, said in the authorization letter that there is “no adequate, approved, and available alternative to the emergency use of remdesivir for the treatment of COVID-19.”

The FDA limited its authorization of the drug to people with suspected or laboratory-confirmed Covid-19 and severe disease, which includes low blood oxygen levels, the need for oxygen therapy or the need for a ventilator or other intensive breathing support.��

Possible side-effects of remdesivir include increased levels of liver enzymes — which may be a sign of inflammation or damage to cells in the liver — and infusion-related reactions like low blood pressure, nausea, vomiting, sweating and shivering, the FDA said.