Shionogi & Co., Ltd. announced the first peer-reviewed publication of the Phase 3 portion of its pivotal, double-blind, randomized, placebo-controlled Phase 2/3 study (SCORPIO-SR) in patients with mild to moderate COVID-19 in Japan, South Korea and Vietnam in JAMA Network Open. The trial met its primary and key secondary endpoints, making ensitrelvir (Generic name: ensitrelvir fumaric acid, Code No.: S-217622, hereafter ?ensitrelvir?) the first antiviral agent to show both clinical symptom improvement and antiviral effect in a predominantly vaccinated population with Omicron infection regardless of risk factors. The publicationreports that treatment with once-daily ensitrelvir in the primary analysis population led to a statistically significant reduction in the time to resolution of five typical COVID-19 symptoms characteristic of Omicron (runny/stuffy nose, sore throat, cough, feeling hot or feverish, and low energy/tiredness1) versus placebo (p=0.04).

The median time to symptom resolution was approximately one day shorter in the 125 mg ensitrelvir group versus placebo (approximately 7 days versus 8 days, respectively).1 Patients included in the primary analysis population were randomized less than 72 hours from symptom onset. More than 90% of patients had received two or more doses of the SARS-CoV-2 vaccine and patients were included regardless of risk factors for severe disease. Known as Xocova® in Japan, ensitrelvir received emergency regulatory approval from the Ministry of Health, Labour and Welfare in Japan for the treatment of SARS-CoV-2 infection in 2022.

Ensitrelvir was approved in Singapore in November 2023 based on the Special Access Route application. It remains an investigational drug outside of Japan and Singapore. Ensitrelvir was granted Fast Track designation by the U.S. Food and Drug Administration.