A majority of a small group of patients showed improvements after being treated with an experimental coronavirus drug made by Gilead Sciences, bolstering hopes for finding a treatment for the disease, according to a study published in the New England Journal of Medicine on Friday.

The group of patients received the antiviral drug remdesivir as part of a “compassionate use'' trial, not a double-blind, placebo-controlled trial that would offer more definitive evidence. Also, the cohort of patients was small, only 53 patients in the United States and around the world. Those limiting factors prevent scientists from declaring that the drug works.

Still, the improvements offered positive news about a drug seen by global health authorities as offering the best shot at becoming a treatment for the disease.

Thirty-six patients out of 53 — or about two-thirds — showed improvement in oxygen support, trial authors said. Seventeen of 30 patients who were on ventilators were able to be taken off the life-support machines.

“We cannot draw definitive conclusions from these data, but the observations from this group of hospitalized patients who received remdesivir are hopeful,” said Jonathan D. Grein, Hospital Epidemiology director at Cedars-Sinai Medical Center in Los Angeles, and lead author of the journal article. “We look forward to the results of controlled clinical trials to potentially validate these findings.”

While 68 percent of the patients showed improvement in the level of oxygen support they needed, 13 percent died, the NEJM study said. That 13 percent compares favorably to mortality rates of 17 to 78 percent in China among severely ill patients, the authors wrote.

Gilead’s stock has been bolstered for weeks by expectations over remdesivir.

“It’s still a promising drug, but it doesn’t definitively prove anything,” said Paul Goepfert, an infectious disease specialist at the University of Alabama at Birmingham who was not involved in the study but is enrolling patients locally in a 600-patient placebo-controlled clinical trial of remdesivir sponsored by the National Institutes of Health. “The main thing you can gather from this study is it doesn’t cause any untoward harm.”

The 13 percent mortality rate for hospitalized patients is difficult to interpret, he said, because the death rate among hospitalized coronavirus patients is not yet known. Overall, the death rate of patients in the global pandemic is about 2 percent, he said.

A senior scholar at the Center for Health Security at Johns Hopkins University’s Bloomberg School of Public Health, Amesh Adalja, called the results “encouraging,” while cautioning that they needed to be kept in perspective.

“It’s unclear because it was not a controlled study whether they would have gotten better with or without it. That’s the problem that you have,” he said.

Remdesivir was discovered by Gilead in the hunt for antiviral drugs about a decade ago, and the National Institutes of Health has partnered with the company to explore its benefits. It was shown to work against an array of viruses in laboratory tests.

It showed effectiveness in primates infected with Ebola but failed in a trial with humans who had the deadly disease in the Congo. It has shown effectiveness as a preventive therapy in primates for MERS, which is a coronavirus cousin of covid-19.

There are no treatments approved by the Food and Drug Administration to treat the coronavirus, but the FDA has granted an emergency use authorization for the use of hydroxychloroquine and chloroquine, two decades-old anti-malarial drugs. There is scant evidence that the therapy works, but President Trump has repeatedly boosted the promise of the drugs.

Even while multiple full clinical trials of remdesivir continue, Gilead has been swamped with requests for “compassionate use” of the drug. Under compassionate-use rules, physicians can obtain experimental drugs for their seriously ill patients when there is nothing else to try.

Gilead said last week that it had enough of the experimental drug on hand to treat up to 140,000 people under compassionate-use programs.