White House health advisor Dr. Anthony Fauci said Wednesday that data from a coronavirus drug trial testing Gilead Sciences' antiviral drug remdesivir showed "quite good news" and sets a new standard of care for Covid-19 patients.

Speaking to reporters from the White House, Fauci said he was told data from the trial showed a "clear-cut positive effect in diminishing time to recover."

Fauci said the median time of recovery for patients taking the drug was 11 days, compared with 15 days in the placebo group. He said the mortality benefit of remdesivir "has not yet reached statistical significance."

The results suggested a survival benefit, with a mortality rate of 8% for the group receiving remdesivir versus 11.6% for the placebo group, according to a statement from the National Institutes of Health released later Wednesday.

"This will be the standard of care," Fauci, director of the National Institute of Allergy and Infectious Diseases, added. "When you know a drug works, you have to let people in the placebo group know so they can take it."

"What it has proven is a drug can block this virus," he said.

U.S. health officials are expected to release the full results of a drug trial conducted by the National Institute of Allergy and Infectious Diseases later Wednesday. Gilead Sciences announced earlier in the day that the study had met its primary endpoint but did not provide further details.

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 Food and Drug Administration, in the meantime, has been in "sustained and ongoing" discussions with Gilead to make remdesivir available to Covid-19 patients "as quickly as possible, as appropriate," said FDA senior advisor Michael Felberbaum.

Shares of Gilead were up by more than 5% at close and by more than 2% in extended hours trading.

There are no proven treatments for Covid-19, which has infected more than 3.1 million people worldwide and killed at least 217,569 as of Wednesday, according to data compiled by Johns Hopkins University. U.S. health officials say producing a vaccine to prevent the disease will take at least 12 to 18 months, making finding an effective drug treatment soon even more crucial.