CIDRAP People who started taking the antiviral drug ensitrelvir within 72 hours after a household member tested positive for COVID-19 were significantly less likely to be infected, according to results from an international phase 3 clinical trial presented last week at the Conference on Retroviruses and Opportunistic Infections in San Francisco.
Made by Japanese pharmaceutical firm Shionogi, ensitrelvir is approved in Japan for the treatment of mild to moderate COVID-19.
Researchers conducted the double-blind Stopping COVID-19 pRogression with early Protease InhibitOr treatment—Post-Exposure Prophylaxis (SCORPIO-PEP) trial evaluating a 5-day course of oral ensitrelvir for post-exposure infection prevention from June 2023 to September 2024. Among all participants, 37% had at least one risk factor for serious COVID-19 complications.
67% risk reduction
Of the 2,387 trial participants aged 12 years and older in countries that included the United States, 9.0% of placebo recipients contracted COVID-19 from a household member, compared with 2.9% of ensitrelvir recipients, for a 67% reduction in the risk of symptomatic infection, and the two groups had a similar risk of adverse events.