1. Introduction
SARS-CoV-2 infection, illness, infectious respiratory illness
CORONAVIRUS, CORONAVIRUS DISEASE 2019, SEVERE ACUTE RESPIRATORY SYNDROME, SARS-COV-2 INFECTION
Coronavirus disease 2019 (COVID-19) is an infectious respiratory illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)The SARS-CoV-2 Omicron is a variant of concern designated by WHO.As of April 2022, several therapeutic antiviral drugs against SARS-CoV-2 infection are available worldwide.Ensitrelvir fumaric acid (S-217622, hereafter ensitrelvir) is a novel oral SARS-CoV-2 3CL protease inhibitor that originated through collaborative research efforts between Shionogi & Co., Ltd., and Hokkaido University.In this manuscript, we describe the protocol for a phase 3 study, with emphasis on the study rationale and key endpoints designed to assess the efficacy and safety of ensitrelvir in patients with mild-to-moderate COVID-19, irrespective of their risk status of developing severe illness and vaccination history.