Gilead Sciences Inc. shares climbed in early trading Friday after a report that a group of patients being treated in Chicago were “seeing rapid recoveries in fever and respiratory symptoms.”

The report, from the medical news publication Stat, cited a video made by a researcher at the University of Chicago who is helping conduct a trial of Gilead’s drug remdesivir. The researcher, infectious disease professor Kathleen Mullane, said that most patients had been discharged from the hospital and only two had died, according to Stat.

Gilead’s drug is one of the most-watched therapies being studied for treatment of Covid-19 patients. It’s conducting two trials of the drug in moderate and severe patients, with the goal of enrolling 4,000 people in the trials. The University of Chicago enrolled 125 patients, most of whom had severe disease, according to Stat.

Shares of the company surged 11% in trading before the market opened Friday. The stock has been one few to buck the global market rout as the outbreak spread, with shares adding 18% this year through Thursday on optimism for its Covid-19 treatment, while the S&P 500 fell 13%.

The Chicago results are a tiny but promising sliver of the overall trial. Almost all patients recover from the disease, which has made it important to conduct tests which compare treatments against a placebo. While the trial in moderate patients contains a placebo group, Gilead’s trial of severe patients does not.

The University of Chicago warned against forming conclusions from the limited data and said the information had been released without authorization.

“Partial data from an ongoing clinical trial is by definition incomplete and should never be used to draw conclusions about the safety or efficacy of a potential treatment that is under investigation,” spokeswoman Lorna Wong said in a statement to Bloomberg. “Drawing any conclusions at this point is premature and scientifically unsound.”

Analysts say the report shows encouraging evidence on the drug’s efficacy, but it’s too early to judge its true potential.

“We are cautiously optimistic about whether these anecdotes will play out in a clinical trial setting with a placebo control conducted at multiple sites,” Cantor Fitzgerald analyst Alethia Young wrote in a note. “Promising activity was seen in a NEJM publication also in severe patients. For example, we have no idea if these patients were in one or both studies or even in the portion of the expanded study (not part of this analysis).

Research on remdesivir’s potential to treat Covid-19 first began in February, at the peak of China’s virus outbreak. Chinese researchers had initially planned to enroll more than 700 patients in Wuhan with mild to severe symptoms to evaluate the drug’s safety and efficacy and said it would announce the trial results on April 27.

But with China’s epidemic ebbing, researchers have not been able to find enough qualifying patients to reach the trial’s original enrollment target, according to a clinical trial registry. The challenge of adequate patient enrollment has been compounded by a surge of trials studying everything from flu therapies and malaria drugs to recovered patient’s plasma and traditional Chinese medicine, which are all competing for patients.

Researchers have collected information from the first 400 patients enrolled in the trial and Gilead plans to “lock” the data on Thursday, meaning the results could come soon, Stat said.

--With assistance from Jeremy R. Cooke, Michelle Fay Cortez and Dong Lyu.