Shionogi’s ensitrelvir demonstrated reduction of symptoms in phase 3 trial.
Japan-based Shionogi announced today that its antiviral, ensitrelvir, demonstrated a statistically significant reduction in the proportion of participants with symptomatic SARS-CoV-2 infection after exposure to household contacts with COVID-19 when compared to placebo. SCORPIO-PEP is the first phase 3 trial with Post-Exposure Prophylactic Use (PEP) of an oral antiviral to meet the primary endpoint of preventing symptomatic COVID-19 infection.
Specifically, the primary endpoint assessed COVID-19 symptoms onset through Day 10. Ensitrelvir was well tolerated by study participants and no new safety concerns were identified. “COVID-19 remains an important public health priority, yet there are currently no oral antiviral medications approved for post-exposure prophylactic use. There is a need for convenient, preventive approaches to protect ourselves and those close to us from contracting SARS-CoV-2,” Simon Portsmouth, MD, FRCP, senior vice president, head of Clinical Development, said in a statement.
SCORPIO-PEP is a global study that included approximately 2,400 participants aged 12 years and older across the US and several countries in South America, Africa and Asia. Study participants with a negative screening test for SARS-CoV-2 infection and no symptoms, who were exposed to a person living in their household with symptomatic COVID-19, were randomly assigned in a 1:1 ratio to receive ensitrelvir (125 mg) or placebo once daily. Study participants began treatment within three days of when the household member with COVID-19 began showing symptoms. Participants then continued ensitrelvir or placebo for 5 days.
The phase 3 trial demonstrated that ensitrelvir significantly reduced the risk of symptomatic COVID-19 infection among household contacts exposed to the virus, compared to a placebo.
Ensitrelvir was well tolerated by participants, with no new safety concerns identified, highlighting its potential as a safe preventive option for COVID-19 exposure.
This study included around 2,400 participants across multiple continents, supporting the broader applicability of ensitrelvir.
“These data demonstrate a new potential for post exposure prophylactic use of ensitrelvir, expanding on the breadth of clinical and real-world evidence that establish its activity in those infected with SARS-CoV-2,” Portsmouth said.
Detailed results from SCORPIO-PEP will be submitted for a presentation at a future scientific conference, according to the company.
Ensitrelvir is an investigational antiviral that suppresses the replication of SARS-CoV-2 by selectively inhibiting the viral 3CL protease. Ensitrelvir was granted Fast Track designation by the FDA last year for COVID-19 treatment. In Japan, ensitrelvir, known as Xocova, received emergency regulatory approval in 2022 and full approval in March 2024 for the treatment of COVID-19. Ensitrelvir was also made available in Singapore based on the Special Access Route application in 2023. It remains an investigational drug outside of Japan and Singapore.
