Gilead Sciences said additional data from a late-stage study showed its antiviral remdesivir reduced the risk of death and significantly improved the conditions of severely ill Covid-19 patients.

The company, which had initially released the data from the trial in April, said the finding requires confirmation in clinical trials.

Remdesivir has been at the forefront of the battle against Covid-19 after the intravenously administered medicine helped shorten hospital recovery times in a clinical trial.

Several countries have approved the use of the treatment in severe patients but there are concerns over supply of the drug, which is also being tested as an inhaled version.

Gilead said it analyzed data from 312 patients treated in a late-stage study and a separate real-world retrospective cohort of 818 patients with similar characteristics and disease severity as in the study.

Gilead’s late-stage study evaluated the safety and efficacy of five-day and 10-day dosing durations of remdesivir administered intravenously in hospitalized patients with severe manifestations of Covid-19, caused by the new coronavirus.

Dr. Susan Olender from Columbia University Irving Medical Center said in the Gilead statement that the analysis draws from a real-world setting and serves as an important adjunct to clinical trial data even as it is not as vigorous as a randomized controlled trial.

Findings from the analysis of its late-stage study showed that 74.4% of remdesivir-treated patients recovered by Day 14 versus 59.0% of patients receiving standard of care, the company said.

The mortality rate for patients treated with remdesivir in the analysis was 7.6% at Day 14, compared with 12.5% among patients not on remdesivir.

Gilead also said the rates and likelihood of recovery were lower in patients who received hydroxychloroquine as well as remdesivir compared with patients treated with remdesivir who did not receive hydroxychloroquine.