A breakthrough medication may help stop COVID-19 before it starts for people exposed at home, offering hope for families with high-risk loved ones.
The SCORPIO-PEP trial found the drug ensitrelvir, already approved in Japan to treat people with mild to moderate COVID-19, may protect against the illness. In the study, uninfected people who began taking the antiviral within 72 hours of a household member developing symptoms were significantly less likely to contract COVID-19 than people who were given a placebo.
Among the more than 2,000 trial participants in the United States and abroad, 9% of those taking the placebo developed confirmed COVID-19, compared to 2.9% of those taking ensitrelvir – a 67% reduction in risk.
“In addition to vaccination, post-exposure prophylaxis with timely use of an oral antiviral would be a valuable way to help prevent COVID-19 illness in people who have been exposed, especially people at high risk for severe disease,” said University of Virginia School of Medicine emeritus professor Dr. Frederick G. Hayden, who helped design the trial and presented the results Wednesday at the Conference on Retroviruses and Opportunistic Infections in San Francisco.
University of Virginia School of Medicine emeritus professor Dr. Frederick G. Hayden says the oral antiviral “would be a valuable way to help prevent COVID-19 illness in people who have been exposed, especially people at high risk for severe disease.” (University Communications photo)
Preventing COVID-19
The SCORPIO-PEP trial, conducted between June 2023 and September 2024, was double-blinded, meaning neither researchers nor participants knew if they received ensitrelvir or the placebo. Those who took a five-day course of ensitrelvir after exposure to COVID-19 were less likely to get sick, with no increase in adverse effects compared to the placebo group.
Among the trial participants, 37% had at least one risk factor for developing serious and potentially life-threatening complications. Their risk of developing COVID-19 was significantly reduced by 76%. There were no hospitalizations or deaths in either group.
Researchers describe ensitrelvir as effective and generally well tolerated for COVID-19 prevention. Before the drug could become available in the United States, the Food and Drug Administration would have to approve it for that purpose. Hayden and his collaborators say these results are a key step in that process.
“This is the first clinical trial of an oral antiviral drug to show significant protection against COVID-19,” said Hayden, part of the Division of Infectious Diseases and International Health at the School of Medicine. “If approved by the Food and Drug Administration for this purpose, it would be an important addition to current preventive strategies.”
