A part of the immune system that appears to be suppressed in severe COVID-19 cases is now being used in a clinical trial against the infectious disease at the University of Minnesota.

A female COVID-19 patient in her 50s received an infusion on Wednesday with an experimental therapy containing natural killer (NK) cells, innate components of the immune system that can wipe out tumors or infected cells.

"They attack sick cells, and when we say sick that typically means malignant or virally infected cells," said Dr. Joshua Rhein, the U physician leading the trial.

The U's work with NK cells until now has primarily been in the development of therapies for leukemia and other cancers. The COVID-19 trial is using an experimental therapy called FT516, which is manufactured by Fate Therapeutics and was developed through U research.

U researchers have spent months planning the COVID-19 clinical trial and gaining the signoff of the U.S. Food and Drug Administration, said Dr. Jeffrey Miller, deputy director of the U's Masonic Cancer Center and a national leader in NK cell research.

Given that many cases of severe COVID-19 involve inflammation and an overreaction by the immune system, there is concern about using a therapy that boosts the immune system, Rhein said. On the other hand, NK cells have antiviral properties. And research in China showed a suppression of NK cells in severe COVID-19 patients, suggesting they are not part of the immune system overreaction and could instead be a solution.

"We think that the cells are going to help as an antiviral," Rhein said, "but there's that possibility that somebody who is headed toward that inflammation type of picture — the worry was that we could push them over the edge."

Researchers are seeking patients who have been hospitalized with COVID-19 and have biomarkers that suggest they are at risk for such an immune system overreaction — but haven't suffered it yet. Infusions are happening one patient at a time to monitor the outcomes, with doses increasing in subsequent patients.

The NK study is the latest in an aggressive response by the U to the COVID-19 pandemic. U researchers launched the first double-blind, placebo-controlled trials of hydroxychloroquine, ultimately determining that it did not prevent the onset of COVID-19 or the development of symptoms in people exposed to the virus. The U also was part of the national study of remdesivir, an antiviral that has been federally approved for treatment of hospitalized COVID-19 patients.

Jeremy Olson • 612-673-7744