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Dr. Jordan Feld at UHN’s Francis Family Liver Clinic in Toronto.Courtesy of UHN

Canadian scientists have shown that the drug interferon lambda can shorten the duration of a COVID-19 infection, potentially heading off a hospital stay and reducing the likelihood that the disease will spread to others over the course of an illness.

In a relatively small clinical trial involving 60 participants, researchers found that 80 per cent of those who had high viral loads and were given the drug in a one-shot dose were clear of the virus after seven days. In comparison, only 38 per cent of those with the same level of infection who received a placebo were virus free in the same time period.

“We believe that with a single dose, that within a few days, we are making almost everybody if not everybody non-infectious,” said Jordan Feld, a physician and senior scientist with Toronto’s University Health Network, who led the study. The results were published Friday in the journal Lancet Respiratory Medicine.

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Dr. Feld and his colleagues say their results are significant enough to launch a large-scale clinical trial to see if interferon lambda can provide a more effective and convenient option for preventing serious COVID-19 than monoclonal antibodies – the only authorized treatment currently available for outpatients who are infected.

Monoclonal antibodies are administered intravenously, which makes treatment cumbersome. And unlike antibodies, interferon lambda has the advantage that its effectiveness does not depend on its ability to interact directly with the coronavirus. Therefore, its power is undiminished when an infection is caused by a new variant of COVID-19.

Interferons, a class of molecules that are naturally occurring, are the immune system’s early responders. They are typically released at the onset of an infection before the body knows precisely what kind of infectious agent it is dealing with. Their roles are to trigger a series of responses in cells that can make it harder for viruses and other pathogens to do their work.

Previous research has shown that the ability to disable interferon is one of the ways that the virus that causes COVID-19 gains a foothold at the beginning on an infection. Since the pandemic began, several research groups have been investigating various types of interferons to help treat the disease. The worry associated with the approach is that interferons may overstimulate the immune system, which can make the illness worse and potentially more dangerous.

Dr. Feld, who specializes in liver disease, said the advantage of interferon lambda is that it mostly provokes a response in tissues that are likely to be affected by a coronavirus infection, such as in the lining of airways, rather than throughout the body. Its effect is to raise the body’s defences where they are needed most.

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Patients who enrolled in the study were randomly given interferon lambda or a placebo within seven days of the first onset of symptoms or of a positive COVID-19 test if they were asymptomatic. The results suggest that the biggest effect was to bring down the virus count more rapidly than would typically occur without the drug.

“The patients who are likely to benefit from this treatment are those with relatively high viral load at the beginning,” said Ludmila Prokunina-Olsson, a senior investigator at the National Institutes of Health in Bethesda, Md., who was not involved in the study.

Dr. Prokunina-Olsson added that the single dose therapy did not appear to cause any of the side effects that are associated with interferons when they are used over a longer period of time to treat chronic disease.

Srinivas Murthy, a pediatric infectious diseases physician at BC Children’s Hospital, called the study by Dr. Feld’s team “very well done.”

Dr. Murthy, who is leading Canada’s portion of an international effort to investigate antivirals for effectiveness against COVID-19, said some other studies have not shown benefits from interferon. This could be, he said, because the drug was given too late during the course of illness. He said that a larger Canadian study should focus on administering the drug early on to those who are at higher risk of serious disease.

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