The study involved 125 patients, of whom 113 had severe cases, STAT reported. Only two of the patients died, while most of the others were discharged within a week, according to the report, which cited a recording of a video discussion among researchers at the University of Chicago.
Similar trials are being run in many other locations.
The report quoted a 57-year-old factory worker who was admitted to the hospital on April 3 with shortness of breath and a fever of 104 degrees who agreed to participate in the study. He said his fever dropped almost immediately after the first treatment with remdesivir and that he recovered enough to leave the hospital by April 7.
Remdesivir is one of several treatments in various stages of development being tested for use against COVID-19. Researchers around the world are also pursuing a vaccine for the illness as well as improved and faster diagnostic testing.
The coronavirus pandemic has infected more than 2 million people around the world since emerging in China at the end of 2019. More than 145,000 people have died of COVID-19 including more than 34,000 in the United States.
Shares of Gilead jumped $10.87, or 14%, to $87.41 in after-hours trading.
In regular action Thursday, gainers lead losers among coronavirus stocks.
Dynavax (DVAX) - Get Report shares rose 28 cents, or 9.09%, to $3.36. Dynavax is working with the Coalition for Epidemic Preparedness Innovations to give companies access to its adjuvant technology which can boost vaccine effectiveness.
Among coronavirus stocks lagging Thursday, Vaxart (VXRT) - Get Report shares fell 9 cents, or 4.41%, to $1.95. Vaxart is in preclinical stages of development of an oral vaccine. It is planning Phase 1 clinical trials sometime in the second half of the year.
CytoDyn CYDY shares fell 9 cents, or 3.75%, to $2.31 in over-the-counter action Thursday. CytoDyn is moving into Phase 2 trials of an experimental drug called leronlimab to treat respiratory complications in patients with COVID-19.