Gilead Sciences Inc.’s drug remdesivir showed only a limited benefit in a large trial of more moderate patients with Covid-19, a result that may shift perceptions of the therapy already cleared for use in severe cases of the disease.

In the phase 3 trial, a group of moderately ill, hospitalized patients getting the drug for five days showed a modest improvement compared to those getting the standard of care, the company said in a statement. But another group getting the drug for 10 days didn’t show a statistically significant improvement, which is likely to raise questions about why a longer course doesn’t help more. Severely ill patients weren’t included in the trial.

Gilead’s drug has become a symbol of efforts to reopen the economy and effectively treat patients stricken with the coronavirus. A working therapy would help reduce the risk for people who become sick, providing greater certainty to efforts to reopen economies around the globe.