IDWeek 2026: New Exploratory Analyses Evaluate XOCOVA® (ensitrelvir) Following COVID-19 Exposure, Including Breakthrough Infections and Infection Present at Baseline
A pooled analysis from the global SCORPIO clinical program showed potent antiviral activity with ensitrelvir across age, vaccination status and risk for severe disease
New data underscores that even mild-to-moderate COVID-19 may worsen and exacerbate underlying chronic conditions, supporting the importance of prevention
OSAKA, Japan, October 21, 2026--Shionogi & Co., Ltd. (Head Office: Osaka, Japan; Chief Executive Officer: Isao Teshirogi, Ph.D.; hereafter "Shionogi") will present new exploratory analyses from the global Phase 3 SCORPIO-PEP study, virology data from across the ensitrelvir phase 3 program, and new insights on the continued burden of COVID-19 at IDWeek 2026.
XOCOVA® (ensitrelvir) was approved in May 2026 by the U.S. Food and Drug Administration (FDA) for post-exposure prophylaxis (PEP) of COVID‑19 in adults and adolescents 12 years of age and older following contact with an individual who has COVID-19.1 The approval was based on positive results from SCORPIO-PEP, a global, double-blind, randomized, placebo-controlled Phase 3 study.
In the primary analysis population, XOCOVA significantly reduced the risk of developing symptomatic COVID-19 by 67% in individuals following exposure to an infected individual through Day 10 compared with placebo (ensitrelvir n=1,030; placebo n=1,011).1,2
In SCORPIO-PEP, XOCOVA was generally well tolerated, with similar rates of adverse events across groups (15.1% in the ensitrelvir group (n=1,190) and 15.5% in the placebo group (n=1,187)).2 The most common adverse events (regardless of causality) occurring in greater than or equal to 1% of the XOCOVA group and at a greater frequency compared to placebo were headache, diarrhea, and cough.1,2 There were no reports of altered taste (dysgeusia) attributed to XOCOVA in the trial.2,3
Exploratory SCORPIO-PEP Analyses Describe Symptom Severity and Viral Outcomes Among Participants with Breakthrough Infection or Infection Present at Baseline
In an oral presentation at IDWeek 2026, Shionogi will report new exploratory analyses from the SCORPIO-PEP study evaluating participants who had breakthrough infections or were already infected at baseline.4
Among breakthrough infection cases (based on RT-PCR positivity regardless of symptoms) in the primary analysis population, the mean maximum viral RNA levels were lower in participants receiving ensitrelvir compared to those receiving placebo (3.1 vs 4.3 mean log10 copies/mL, respectively, seen in 144 and 217 breakthrough infection cases, respectively).4 In household contacts who were infected with SARS-CoV-2 at the time of enrollment (confirmed positive by baseline central RT-PCR despite testing negative on a local screening test and being asymptomatic; n=237), numerically lower mean viral RNA levels were also observed with ensitrelvir in comparison to placebo on Days 3 and 6.4