There are early signs that an experimental treatment for people who become very sick from the coronavirus may start working within 24 hours of the first dose.
The treatment, an antiviral therapy called remdesivir, is thought to work by blocking the virus from reproducing itself in the body.
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"It basically stops the production of the virus," Dr. Gregory Poland, an infectious diseases expert and director of the Mayo Clinic's Vaccine Research Group in Rochester, Minnesota, told NBC News.
Preliminarily, it seems at least two hospitalized patients who got the drug started to feel better the next day.
Chris Kane, 55, was diagnosed with the coronavirus and hospitalized at Providence Regional Medical Center in Everett, Washington, this month.
"He was really sick," his wife, Susan Kane, told NBC News. "They put him on oxygen right away."
His doctors decided to try remdesivir after it had shown promise in at least one earlier patient.
Research in animals had shown the drug, developed by Gilead Sciences, might treat MERS, another type of coronavirus.
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It was also widely promoted as a potential treatment for Ebola, but failed to show any significant benefit.
Then came COVID-19, which has now sickened well over 200,000 people worldwide, including nearly 10,000 in the United States. Pressure to develop and study effective treatments has mounted over the past few months.
About two weeks before Chris Kane arrived at the hospital, his doctors had treated a 35-year-old man who'd recently returned to his Washington home after traveling in Wuhan, China.
The unidentified man became the first person in the U.S. to be diagnosed with the coronavirus.
Within a week of being admitted to the hospital, the man's condition deteriorated. His physicians, including the doctor who would later treat Chris Kane, worked with the federal health authorities to try remdesivir through what's called compassionate use, reserved for unapproved drugs in specific, potentially life-saving situations.
The doctors published details about that first case in the New England Journal of Medicine.
"Treatment with intravenous remdesivir was initiated on the evening of day seven," they wrote.
On day eight, the man's condition started to improve. He was able to be taken off the ventilator and got his appetite back. His fever resolved and his cough slowly dissipated.
But questions remain about the quick recovery. Was it the drug that lead to the improvement? Or would the man have gotten better the next day anyway?
Susan Kane said remdesivir appeared to work quickly for her husband, too.
"On the very next day, he said: 'You know, I think it's lifting. I think I'm starting to feel better,'" she recalled.
Chris Kane is now home and, although he still gets winded easily, he is improving, according to his wife.
"We are 100,000 percent convinced that the remdesivir turned things around for him," Susan Kane said.
Because remdesivir is now officially in clinical trials at Providence Regional Medical Center, Kane's doctors declined an interview with NBC News, as they are unable to comment on the efficacy of the drug before results are made public. First results are expected in late April.
"We can't discuss any particular patient's care aside from the first one (published in the New England Journal of Medicine case report)," a spokesman for the hospital system wrote in an email.
In partnership with Gilead, the spokesman said, up to 1,000 patients will be enrolled in the clinical trial. Patients are slowly being recruited into the trials, not only in Washington, but also at the University of Nebraska Medical Center, and Emory Vaccine Center in Atlanta.
Other potential treatments for the coronavirus are under investigation, including a drug used to treat malaria, called chloroquine, and a combination of HIV drugs, lopinavir and ritonavir, sold under the brand name Kaletra.
However, on Wednesday, the first major study to look at the HIV drug combination found it has no benefits on treating the virus.
Poland said there are valid reasons to assume remdesivir would work, at least in theory, but cautioned that early anecdotal success of a drug doesn't always pan out in the long run.
"The medical literature is littered with literally thousands upon thousands of studies starting out this same way," Poland said.
"Will it work in terms of actual human infection? It's going to require careful study, clinical trials and different phases of clinical trials," he added.
"It's only at that point that we'd know if there's any real benefit."