An antiviral drug called remdesivir is
the first treatment to show efficacy against the coronavirus.

Preliminary results from a clinical trial
comparing the drug with a placebo suggest that remdesivir
speeds recovery from COVID-19 by 31 percent
, the U.S. National Institute of
Allergy and Infectious Diseases said April 29 in a news release.

The international trial randomly assigned
1,063 people hospitalized with COVID-19 to get intravenous infusions of either
remdesivir or a placebo. In the remdesivir group, the median time to recovery
was 11 days, compared with 15 days for those on the placebo. Recovery was
defined as being discharged from the hospital or being well enough to resume
normal activity. Eight percent of people in the remdesivir group died, compared
with 11 percent in the placebo group.

“Although a 31 percent improvement
doesn’t seem like a knockout 100 percent, it is a very important proof of
concept,” Anthony Fauci, director of the NIAID, said April 29 during a news
briefing at the White House. “It has proven that a drug can block
this virus
.”

Normally, researchers would have waited
to make the announcement until the results had been reviewed by other
scientists, but the team chose to make the announcement early, Fauci said.
“Whenever you have clear-cut evidence that a drug works, you have an ethical
obligation to immediately let the people who are in the placebo group know so
that they can have access.”

Remdesivir will now be the standard of
care by which other drugs are judged, Fauci said. The trial will be adapted to add
to the remdesivir treatment an antibody that may protect against inflammation,
he said.

Remdesivir, developed by biopharmaceutical
company Gilead Sciences, headquartered in Foster City, Calif., mimics a
building block of RNA, the coronavirus’s genetic material. When the virus
copies its RNA, remdesivir is incorporated instead of the usual RNA components,
stopping the virus’s replication.

In studies in lab dishes and animals,
remdesivir has been effective against a wide variety of RNA-containing viruses,
including those that cause MERS and SARS. “It’s passed every single milestone.
It works against every coronavirus we’ve tested,” says Mark Denison, a
virologist at Vanderbilt University Medical Center in Nashville, who was not
involved in the study.

Remdesivir has been most effective in
animal studies when given early in infections, Denison says. The drug can stop
or slow viral replication but doesn’t block the body’s overzealous immune
system responses that cause additional damage for many severely ill COVID-19
patients. He likens remdesivir to a fire extinguisher. “If there’s a fire, and
you put it out with the fire extinguisher, you’re not going to get burned. But
if you fall in [the fire] and burn your arm, you can apply the fire
extinguisher and maybe you’ll limit the burn, but you can’t heal it.”

If the drug can be given early in the infection — difficult to do with a drug like remdesivir that is given intravenously and must be administered by trained medical professionals — then people might never become ill enough to need to go to the hospital. “You [could] convert this from being a lethal disease, to being a manageable, survivable disease,” Denison says.  

A similar compound given as an oral drug
might even be used to prevent infections, Denison says. 

Gilead also announced results of another
remdesivir trial on April 29. That study compared a five-day course of
remedisivir with 10 days of treatment. There was no control group that didn’t
get the drug. It took 10 days for half of people on the shorter course of
remdesivir to have clinical improvement compared with 11 days for those in the
longer-treatment group.

“The study demonstrates the potential
for some patients to be treated with a 5-day regimen, which could
significantly expand the number of patients who could be treated
with our
current supply of remdesivir. This is particularly important in the setting of
a pandemic, to help hospitals and health care workers treat more patients in
urgent need of care,” the company said in a news release.

Of the 200 people in the five-day
treatment group, 129 went home from the hospital by day 14, while 106 of the
197 people who got the longer treatment were discharged by day 14.

Treating earlier was also beneficial. Sixty-two
percent of patients who got treatment within 10 days of their symptoms starting
were able to go home after two weeks in the hospital, but only 49 percent of
those who got treatment later in the infection were discharged after two weeks
in the hospital.

A smaller, incomplete study published
April 29 in the Lancet appears to
counter the results of the NIAID study. The Lancet
study, conducted in 10 hospitals in Wuhan, China, where the pandemic first
started, found no
statistically significant improvement in recovery time
in severely ill
COVID-19 patients given remdesivir, compared with those who got a placebo.

In that study, the median time to
recovery for patients taking remdesivir was 21 days, compared with 23 days for
those getting a placebo. There was a trend that remdesivir sped recovery for
people who had symptoms for less than 10 days, but that result didn’t meet
statistical thresholds. That trial stopped early because Wuhan’s lockdown
effectively stopped transmission so that researchers weren’t able to recruit
enough patients to fill the trial’s slots. As a result, the trial lacked the
statistical power to detect differences between the groups, Denison says. 

Previous results from a study of patients given remdesivir for “compassionate use” when no clinical trial was available showed that 36 of 53 people given the drug needed less supplemental oxygen afterward, researchers reported April 10 in the New England Journal of Medicine.