Gilead Sciences Inc said on Monday its antiviral drug remdesivir had mixed results in a late stage study of people with moderate COVID-19, as patients given a five-day course of the treatment showed statistically significant improvement, while those given it for 10-days did not.
Gilead shares fell about 2.7 percent in early trading.
Remdesivir is being closely watched after the U.S. Food and Drug Administration granted emergency use authorization last month, citing results from another study run by the National Institutes of Health that showed the drug reduced hospitalization stays by 31%, or about four days, compared to a placebo.
The promising Coronavirus drug
Remdesivir, which previously failed as a treatment for Ebola, is designed to disable the mechanism by which certain viruses, including the new coronavirus, make copies of themselves and potentially overwhelm their host's immune system.
The results announced by Gilead on Monday are from a study designed to evaluate the safety and efficacy of 5- and 10-day treatment with remdesivir in addition to standard of care for patients with moderate COVID-19, compared with standard care alone.
At Day 11, more patients in the 5-day treatment group showed improvement in clinical status versus the standard of care group, Gilead said.
The drugmaker said the odds of improvement with the 10-day treatment course of remdesivir versus standard of care were also favorable, trending toward but not reaching statistical significance.
Jefferies analyst Michael Yee said the improvements seen in the trial patients were only modest.
"COVID-19 patients entering the hospital are likely to get the drug given there are no other major alternatives, but it is understood the drug is meant to be more helpful (and not a cure) in a moderate population, where patients are generally healthier and the mortality rate is expected to be very low," Yee wrote in a research note.