Gilead Sciences' (NASDAQ:GILD) remdesivir cut the risk of death by 62% in severe COVID-19 patients. After 14 days, 7.6% of severe COVID-19 patients treated with remdisivir had died compared to 12.5% of patient who didn't receive the drug.

While the results, which were presented at the Virtual COVID-19 Conference as part of the 23rd International AIDS Conference, sound great, they come from a retrospective analysis comparing results from two different data sources. The remdesivir mortality rate comes from results of patients in Gilead's phase 3 SIMPLE-Severe clinical trial. But that study didn't have a placebo control, so Gilead compared the remdesivir results with a real-world retrospective cohort of severe COVID-19 patients who were treated with standard of care.

The results are likely to be in the ballpark of being accurate, but without prospectively enrolling patients and randomizing them to remdesivir or placebo, there's no way to know for sure whether remdesivir was the only factor that contributed to the difference.

Gilead admits as much in the press release announcing the result, calling it "an important finding that requires confirmation in prospective clinical trials."

Doctor in protective equipment talking to face-masked patient seated on bed.

Image source: Getty Images.

The biotech also released data from its compassionate-use program for remdesivir in children as well as pregnant and postpartum women. Like the SIMPLE-Severe study, the compassionate-use program doesn't have a placebo-treated population to be compared to, and given the small numbers, Gilead didn't even bother trying.

Among 77 pediatric patients treated with remdesivir in the program, 73% were discharged by day 28, while 12% remained hospitalized, and 4% had died. An analysis of 86 pregnant and postpartum women treated with remdesivir in the program showed 96% of pregnant and 89% of postpartum women achieved improvement in oxygen support levels.