More: Read the full statement from Gilead Sciences

Gilead’s drug, remdesivir, is one of the most closely-watched therapies of the dozens being developed and tested as a potential treatment for Covid-19 patients. The World Health Organization, which has been helping coordinate the global response to the virus, said it accidentally posted the results on a website that helps track therapies for the disease.

The summary was quickly removed, but details of the post were reported by the Financial Times and posted by the publication Stat. They showed that the drug wasn’t associated with patients getting better more quickly; and 13.9% of patients getting the drug died, versus 12.8% getting standard care.

Gilead’s stock has been sent swinging by incremental reports on the drug, as investors grasp for any sign of data that the company’s compound could be an effective therapy for Covid-19 patients. The shares surged 9.7% on April 17 after a report that the drug appeared to have helped a group of Chicago patients who were part of a separate trial.

Gilead Response

The drug company and a scientist involved in the trial disputed the characterizations of the result as an outright failure, however.

“That is not correct,” said Frederick Hayden, an infectious disease expert at the University of Virginia School of Medicine, when asked whether the results showed remdesivir had flopped. Hayden helped the Chinese doctors conduct the study. “My interpretation of them is not consistent with that headline.”

Gilead, in a statement, said that the summary mischaracterizes the results of the study, which was stopped early after not enough patients could be found. A study with low enrollment can lead to results that are less conclusive. Hayden said there was a mistake in the original manuscript and that it had since been revised.

He said that the study was under review at a journal, which he would not identify. He declined further comment until the study was published.

Gilead, in its statement, said that “trends in the data suggest a potential benefit for remdesivir, particularly among patients treated early.” The company said that the full data are being submitted for review and publication.

Severe Patients

The study in question was one of two main trials in China of remdesivir, and looked at patients with severe cases of Covid-19. This group was considered one of the hardest to treat with antiviral drugs, since by the time the disease becomes advanced there may already be significant lung damage. In addition, the immune system may spin out of control in some patients with advanced disease, a process that antivirals like the Gilead drug won’t help with.

“This is disappointing to not show at least positive trends on efficacy or safety, so expectations will come down now for the Gilead-sponsored studies coming up,” said Michal Yee, an analyst at Jefferies Financial Group Inc. in New York. “However, this may not be shocking in severe patients who are too far gone.”

Results from the company’s study in severe patients are expected next week, Yee said. The trial’s lack of a comparison group may make it difficult to evaluate. Another study in moderate patients, which does include a control group, is due by the end of May.

Gilead has previously said that healthier patients and those who were treated early, before they were completely overwhelmed by the infection, may fare best, Yee said.

“The moderate study in May against a placebo may show some modest benefit but it’s not a magic cure pill,” he said.

Not Enough Patients

The China-led study was headed by Bin Cao, a pulmonologist from Beijing who went to Wuhan when the pandemic began taking hold, and who started the trial on Feb. 6. At the time, the number of cases in the city were increasing rapidly and doctors were looking for any potential therapies to help their patients survive.

But with aggressive lockdowns in place across the region, the study — originally designed to sign up 450 patients — was unable to find enough patients. It was halted on March 30 after signing up a little more than half its target.

Insufficient enrollment in a trial can make it more likely to show an inconclusive result, unless the drug was massively beneficial or massively harmful.

Remdesivir, an infused anti-viral medication, was developed in part to fight Ebola and showed promise in laboratory tests against SARS and MERS, two earlier coronaviruses that sparked outbreaks.

Tarik Jasarevic, a WHO spokesman, said the study is undergoing peer review and the health agency is awaiting a final version before making any comments.