OSAKA, Japan - Shionogi & Co., Ltd. (Head Office: Osaka, Japan; Chief Executive Officer: Isao Teshirogi, Ph.D.; hereafter 'Shionogi') 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 publication reports 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.1 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.1

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.

'We're pleased to present the data from our Phase 3 study conducted in Asia in this peer-reviewed article. These results demonstrate accelerated resolution in a range of symptoms, reinforcing the potential of ensitrelvir across multiple patient profiles. Additionally, ensitrelvir reduced viral RNA levels and time to first negative viral titer, suggesting it could help reduce transmission of SARS-CoV-2,' said Takeki Uehara, Ph.D., Senior Vice President, Drug Development and Regulatory Science at Shionogi. 'This study was conducted in a largely vaccinated population that included patients infected with Omicron. The patients also had varying risk factors for severe disease. This is relevant as there is a lack of data and a need for additional treatment options for this population.'

Key Secondary Endpoints

The study also met its two key secondary endpoints (primary analysis population), as previously presented at the Conference on Retroviruses and Opportunistic Infections 2023. The amount of viral RNA was significantly lower on Day 4 in the 125 mg ensitrelvir group compared with placebo (least squares mean change from baseline -2.48 log10 copies/mL versus -1.01 log10 copies/mL, p

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