After failures in demonstrating the potential of the protease inhibitor ensitrevir as a treatment for COVID-19 in U.S. patients, Shionogi & Co. has received FDA approval for the drug in the preventive category.
Shionogi’s oral drug, sold under the name Xocova and available in Japan starting in 2022, is approved for post-exposure prophylaxis (PEP) against COVID-19 in adults and adolescents 12 years and older in the United States who have been in contact with someone infected with COVID-19.
Shionogi & Co. said in a June 1 press release that the FDA’s approval earns Xocova the distinction of being the first oral drug approved for post-exposure prophylaxis against COVID-19 in the United States. The drug is taken over 5 days, starting with 3 tablets on the first day and only 1 tablet on the next 4th day.
The FDA gave the go-ahead more than two weeks early, with the agency originally scheduled to consider Shionogi’s Xocova application by June 16.
In addition to the currently approved COVID-19 vaccines from Pfizer-BioNTech, Moderna, and Novavax, the U.S. has also approved antiviral drugs such as Pfizer’s Paxlobid, Gilead’s Vekluri, and Merck & Co.’s Radebrio, all of which are intended for treatment after symptoms develop.
Meanwhile, Shionogi’s drug “could potentially benefit anyone who wants to avoid contracting COVID-19,” Frederick Hayden, M.D., professor emeritus of clinical virology at the University of Virginia School of Medicine, said in a company release.
Beyond home use, Zokova could also be an attractive preventive measure in other exposure events, such as outbreaks in nursing homes and long-term care facilities, and infections following travel-related contact, Hayden added.
FDA approval hinges on Shionogi’s SCORPIO-PEP study. In this trial, Zokova reduced the risk of symptomatic COVID-19 infection by 67% over 10 days in uninfected people after contact with an infected person compared to a placebo.
Shionogi’s trial enrolled 2,387 participants who had a negative local screening test for the SARS-CoV-2 virus and were asymptomatic at enrollment after exposure to an infected family member. The company’s primary analysis was based on 2,041 household contacts who tested negative at baseline.
The Osaka-based company noted that its antiviral drugs are generally well-tolerated, with the most common side effects seen in Xocova patients being headache, diarrhea, and cough.
“Zoxova is the first and only oral option clinically proven to help prevent symptomatic COVID-19 infection following exposure in study participants, regardless of vaccination status or baseline immunity from previous infection,” Nathan McCutcheon, president and CEO of Shionogi’s U.S. division, said in a statement. The drug “allows people who have been exposed to COVID-19 to act early to protect themselves,” he added.
Although the heyday of COVID-19 vaccine and drug sales has long waned, as evidenced by continued earnings pressures at Pfizer and Moderna, Shionogi feels there is still an important niche for Zokova to fill, as the disease remains highly contagious.
Shionogi & Co. estimates that up to 47% of people who live with someone infected with the coronavirus are at risk of developing the disease themselves, and points out that the CDC estimates that between early October last year and May 23, 2026, there were approximately 3.8 million to 12.4 million new coronavirus infections in the United States. These infections caused hundreds of thousands of outpatient visits, approximately 240,000 hospitalizations, and between 13,000 and 42,000 deaths. to the data.
In Japan, Shionogi & Co.’s home country, Zocova is also approved as a post-exposure prophylactic drug. The antiviral drug was initially granted emergency approval for the treatment of COVID-19 in November 2022, and received full approval in early 2024.
This drug is also available in Singapore.
Shionogi found a new niche in the U.S. market for Xocova, praising its protective effects, but the late-stage SCORPIO-HR trial in May 2024 disappointed. In this study, the antiviral drug failed to show a statistically significant reduction in time to sustained resolution of 15 common coronavirus symptoms. This performance prevented the study from meeting its primary endpoint.
Shionogi’s management acknowledged at the time that the data was mixed, but supported the potential of the asset and pledged to continue working with regulators to make ensitrelvir more widely available.
Shionogi & Co., Ltd. said in an approval announcement Monday that Zocova is approved as a prophylactic drug and is not available in the U.S. as a treatment for the coronavirus.
