FDA Approves Xocova as First Oral COVID-19 Post-Exposure Prevention Drug, Based on Phase 3 Trial Showing 67% Risk Reduction
The FDA has approved Shionogi's ensitrelvir (Xocova) for post-exposure prophylaxis of COVID-19, the first oral antiviral cleared for that indication in the US.
Overview
The US Food and Drug Administration approved ensitrelvir — sold under the brand name Xocova — on June 1, 2026, making it the first and only oral antiviral cleared in the United States for post-exposure prophylaxis of COVID-19. The approval, granted two weeks ahead of its scheduled deadline, covers adults and adolescents aged 12 and older who have been exposed to a person infected with SARS-CoV-2, according to Shionogi, the Japanese pharmaceutical company that developed the drug.
The decision follows positive results from SCORPIO-PEP, a global Phase 3 randomized trial published on May 13, 2026, in the New England Journal of Medicine, which showed the drug reduced the risk of symptomatic COVID-19 by 67% compared with placebo.
What the Trial Found
SCORPIO-PEP was a double-blind, placebo-controlled, global Phase 3 study conducted between June 2023 and September 2024. The trial enrolled 2,387 participants aged 12 and older who were household contacts of a symptomatic, PCR-confirmed COVID-19 case. The primary analysis focused on 2,041 participants who tested negative for SARS-CoV-2 at baseline. Participants were randomized 1:1 to ensitrelvir or placebo, with treatment initiated within 72 hours of the index case’s symptom onset.
The primary endpoint — symptomatic, PCR-confirmed COVID-19 by day 10 — was met with a 67% relative risk reduction, according to Shionogi’s NEJM publication announcement. Among participants who received ensitrelvir, 2.9% developed symptomatic COVID-19, compared with 9.0% in the placebo group (risk ratio 0.33; 95% CI 0.22–0.49; p<0.0001).
A prespecified high-risk subgroup of 756 participants — those with at least one risk factor for severe disease — showed an even larger effect: 2.4% of the ensitrelvir arm developed COVID-19, compared with 9.9% of those on placebo, corresponding to a 76% relative risk reduction (risk ratio 0.24; 95% CI 0.12–0.49). No COVID-related hospitalizations or deaths were observed in the treatment arm during the trial period. Benefits were consistent across age groups and vaccination status.
Dosing and Mechanism
Xocova is an inhibitor of the SARS-CoV-2 main protease, also known as the 3CL protease or Mpro — a conserved viral enzyme required for replication. The drug is administered as a five-day oral regimen: three tablets on day one (375 mg) followed by one tablet daily on days two through five (125 mg each), as noted by Pharmaceutical Executive.
Unlike Paxlovid (nirmatrelvir/ritonavir), which requires the inclusion of ritonavir as a pharmacokinetic booster — creating significant drug interaction concerns for older or immunocompromised patients — ensitrelvir does not require ritonavir, according to OneDayMD. Because the drug targets a conserved viral protein rather than the spike protein, it is also expected to retain activity against emerging SARS-CoV-2 variants.
Safety Profile
The safety data from SCORPIO-PEP showed adverse event rates that were closely matched between the two groups: 15.1% in the ensitrelvir arm (n=1,190) and 15.5% in the placebo arm (n=1,187). The most common adverse events in the treatment group were headache, diarrhea, and cough, according to Shionogi. Notably, no dysgeusia — the altered taste that has been reported with some antiviral treatments — was observed among ensitrelvir recipients.
Regulatory Context
Xocova’s US approval covers only post-exposure prophylaxis; it is not approved in the United States for the treatment of active COVID-19 infections, noted Pharmaceutical Executive. In Japan, where the drug was first authorized, it received emergency approval for treatment in November 2022, followed by full approval in March 2024, and supplemental approval for post-exposure prophylaxis on March 23, 2026, with approval extending to children aged six and older. The drug is also approved for treatment in Singapore.
“XOCOVA is the first and only oral option clinically proven to help prevent symptomatic COVID-19 after exposure,” said Nathan McCutcheon in Shionogi’s announcement.
What We Don’t Know
Several questions about Xocova’s practical impact remain open. The trial was conducted between 2023 and 2024, and it is unclear how well the 67% efficacy figure will translate to currently circulating SARS-CoV-2 variants. Pricing and insurance coverage have not yet been announced, which will shape access for high-risk populations such as the elderly and immunocompromised. Additionally, the trial’s 72-hour treatment window assumes rapid diagnosis of the index case and prompt prescription access — conditions that may be difficult to meet in non-clinical settings. It is also not yet known whether Xocova will be recommended for use alongside existing post-exposure vaccination strategies or as an alternative for those with contraindications to available vaccines.