Shionogi enrols first participant in SARS-CoV-2 therapy trial in Japan

By Isabel Cameron

- Last updated on GMT

© Getty Images
© Getty Images

Related tags SARS-COV-2 COVID-19 Clinical trials

Shionogi has enrolled the first participant in Japan in its phase 3 clinical trial of oral antiviral ensitrelvir to stop the post-infection progression of Covid-19.

The global study will evaluate the safety and efficacy of the novel Covid-19 oral antiviral ensitrelvir for the prevention of symptomatic SARS-CoV-2 infection in study participants exposed to household contacts who are symptomatic and tested positive for SARS-CoV-2, when compared to placebo.


Ensitrelvir is an investigational oral antiviral that suppresses the replication of SARS-CoV-2 by selectively inhibiting the viral 3CL protease.

Known as Xocova in Japan, ensitrelvir received emergency regulatory approval from the Ministry of Health, Labour and Welfare (MHLW) for the treatment of SARS-CoV-2 infection in November 2022, but remains an investigational drug outside Japan.

In April 2023, ensitrelvir was granted Fast Track designation by the U.S. Food and Drug Administration.

The study

The randomized, double-blind, placebo-controlled global study will recruit approximately 2,200 participants across North America, South America, Europe, Africa and Asia.

Study participants who have a negative screening test for SARS-CoV-2 infection and have had exposure to a household person with symptomatic COVID-19 will be randomly assigned in a 1:1 ratio to receive ensitrelvir or placebo.

The primary endpoint for the study is the proportion of participants who are infected with SARS-CoV-2 and have COVID-19 symptoms onset through Day 10.

In addition, the first participant is expected to be enrolled in the US in July, with Shionogi also revealing that it has filed for full approval of ensitrelvir in Japan.

“There remains a need to develop therapeutics that can prevent infection after exposure. Part of managing COVID-19 in the longer term is identifying strategies to minimize the spread of the virus,” said Isao Teshirogi, president of Shionogi.

“This study will add further data to that obtained in the Phase 3 part of the pivotal SCORPIO-SR trial (Phase 2/3 study), conducted in Asia, which demonstrated that ensitrelvir can effectively treat patients with mild-to-moderate COVID-19, leading to a statistically significant reduction in the time it takes to resolve the typical COVID-19-related symptoms.”

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