OSAKA, Japan, October 29, 2024 – Shionogi & Co., Ltd. (Head Office: Osaka, Japan; Chief Executive Officer: Isao Teshirogi, Ph.D.; hereafter “Shionogi”) today announced that its double-blind, randomized, placebo-controlled global Phase 3 study, Stopping COVID-19 pRogression with early Protease InhibitOr treatment – Post Exposure Prophylaxis (SCORPIO-PEP), met its primary endpoint. Once-daily ensitrelvir (Generic name: ensitrelvir fumaric acid, Code No.: S-217622, hereafter “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. 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.