Diana Brainard is nowhere near close to celebrating.

Dr. Brainard is the head of antiviral clinical research at Gilead Sciences, the Bay Area biotech giant whose drug portfolio includes the antiviral medicine remdesivir. On Thursday, Stat, the superb medical-news website, reported some of the leaked results of a pair of Phase 3 clinical trials of the drug at the University of Chicago. Of 113 patients with severe cases of Covid-19 who were treated with daily infusions of remdesivir, most were discharged from the hospital in under a week, and only two died.

That sounds like fantastically good news, but Dr. Brainard has caveats and cautions. The Chicago story, she told me in a phone interview this week, is still anecdotal. The trial did not include a control group. Hard data, once it comes, can be hard to interpret. “We have to assess whether the drug is working without having a clear picture of what is typical with this disease,” she says.

But whether remdesivir turns out to be effective or not — and it’s always wise to curb one’s enthusiasm about supposed miracle cures — the remarkable thing is that it’s available at all. It began life in 2009 as a potential treatment for hepatitis C, but didn’t work as hoped. It got a second chance during an Ebola outbreak in Congo. It showed limited effects but proved safe to use on people.

Lab tests, however, suggested it might have potent effects against coronaviruses such as those that cause SARS and MERS. As it became clear that Covid-19 was also caused by a coronavirus, remdesivir was one of the few potentially helpful drugs ready to be in clinical trials. Gilead began distributing it on a compassionate-use basis on Jan. 25.