5 minOn June 1, Shionogi & Co., Ltd. announced that the U.S. Food and Drug Administration (FDA) has approved its oral antiviral, XOCOVA® (ensitrelvir), for the post-exposure prophylaxis (PEP) of COVID-19 in adults and adolescents aged 12 and older.
The approval was granted more than two weeks ahead of the Prescription Drug User Fee Act (PDUFA) target date of June 16. This milestone marks the arrival of the first and only oral antiviral drug approved in the United States for post-exposure prophylaxis, filling a critical gap in the clinical prevention landscape.
Clinical Core Data: A 67% Reduction in Infection Risk
The approval of XOCOVA is based on the positive results from the pivotal Phase 3 SCORPIO-PEP study—the only Phase 3 trial for an oral antiviral to successfully meet the primary endpoint of preventing symptomatic COVID-19 following exposure.
Key Efficacy Metrics:
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Reduced Risk of Illness: Among uninfected individuals exposed to a confirmed COVID-19 case, those treated with XOCOVA saw a 67% reduction in the risk of symptomatic COVID-19 compared to the placebo group through Day 10 (XOCOVA n=1,030; placebo n=1,011).
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Dosing Regimen: The treatment is a five-day oral regimen: three tablets on the first day, followed by one tablet daily from days two through five.
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Safety Profile: XOCOVA demonstrated a favorable tolerability profile in clinical trials. Adverse event rates were comparable between groups (15.1% for the XOCOVA group vs. 15.5% for the placebo group). Common adverse events occurring at a frequency of ≥1% were headache, diarrhea, and cough. Notably, there were no reports of drug-attributed dysgeusia (altered taste).
Filling the Prevention Gap: From Exposure to Onset
While vaccines (e.g., Pfizer-BioNTech, Moderna, Novavax) and post-symptomatic treatments (e.g., Paxlovid, Veklury, Lagevrio) are currently available, there has been a significant void in effective oral interventions for the critical window between viral exposure and the onset of symptoms.
Dr. Frederick Hayden, Richardson Professor Emeritus of Clinical Virology at the University of Virginia School of Medicine, stated: “The FDA approval of XOCOVA provides an important new approach to preventing COVID-19. Beyond household settings, this strategy has significant potential for use in outbreaks within nursing homes, acute care facilities, and following travel-related exposures.”
Why Post-Exposure Prophylaxis Matters
Despite the evolution of Omicron and its subvariants, SARS-CoV-2 remains highly transmissible. Data shows that up to 47% of household contacts living with an infected individual are at risk of contracting the virus.
CDC monitoring data highlights the ongoing public health burden:
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High Case Volume: Between October 2025 and May 2026, there were an estimated 3.8 to 12.4 million new COVID-19 cases in the U.S.
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Healthcare Impact: These cases resulted in 800,000–2.3 million outpatient visits, 120,000–240,000 hospitalizations, and 13,000–42,000 deaths.
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Long-term Effects: Evidence shows that COVID-19 infection correlates with an increased risk of neurological, cardiovascular, respiratory, and renal conditions during the year following recovery.
Innovative Mechanism: Precision Inhibition
XOCOVA is a SARS-CoV-2 main protease inhibitor. This enzyme is essential for viral replication; XOCOVA selectively inhibits this protease, effectively blocking the virus from replicating within the host.
“XOCOVA is the first and only oral option clinically proven to help prevent symptomatic COVID-19 after exposure, regardless of vaccination status or baseline immunity,” said Nathan McCutcheon, President and CEO of Shionogi Inc. “It provides a new way for exposed individuals to act early to protect themselves.”
XOCOVA previously received emergency regulatory approval in Japan in November 2022 and full approval for the treatment of COVID-19 in March 2024. This FDA approval marks a significant step forward in Shionogi’s global strategy to combat infectious diseases.
