Ensitrelvir Meets Primary and Key Secondary Endpoints in Pivotal Phase 3 Study
In the Study, ensitrelvir met the primary endpoint, demonstrating a statistically significant reduction compared to placebo in the time to resolution of five typical COVID-19-related symptoms in the current Omicron-dominant phase of the pandemic – runny/stuffy nose, sore throat, cough, feeling hot or feverish, and low energy/tiredness. The Study was also the first to show a statistically significant reduction (p<0.0001) in the time to negative infectious viral titer versus placebo, a key secondary endpoint. Regarding safety, ensitrelvir was well tolerated, and there were no serious treatment-related adverse events or deaths in the Study. Among the most common treatment-related adverse events were temporary decreases in high-density lipoprotein and increased blood triglycerides, as observed in previous studies.
- Primary endpoint: the time to resolution of five symptoms of COVID-19 was 167.9 hours in patients treated with 125 mg ensitrelvir, compared to 192.2 hours in the placebo group, a difference of a median time of 24.3 hours (p=0.0407).
- Secondary endpoint: the time to achieve a negative infectious viral titer was significantly shorter in the ensitrelvir 125 mg group compared with placebo (a median time of 36.2 hours versus 65.3 hours, p<0.0001).
- Safety: ensitrelvir was well-tolerated, with no serious adverse drug reactions, and no deaths.
Exploratory Data Shows Relative Risk Reduction of Long COVID Symptoms
At CROI, Shionogi also presented exploratory data (not included as primary or secondary endpoints) from the Phase 3 part of the Study evaluating the potential of ensitrelvir to have an effect on the symptoms of long COVID. Symptoms of long COVID were examined at three and/or six months (Day 85 and/or Day 169) after initiating treatment within five days of symptom onset.
About ensitrelvir
Ensitrelvir (known in Japan as Xocova®), an oral antiviral drug for COVID-19 currently approved under the emergency regulatory approval system in Japan, is a 3CL protease inhibitor created through joint research between Hokkaido University and Shionogi. SARS-CoV-2 has an enzyme called 3CL protease, which is essential for the replication of the virus. Ensitrelvir suppresses the replication of SARS-CoV-2 by selectively inhibiting 3CL protease. Ensitrelvir is the first antiviral agent to show both clinical symptomatic efficacy for five typical Omicron-related symptoms (primary endpoint) and antiviral efficacy (key secondary endpoint) in a predominantly vaccinated population of patients with mild to moderate SARS-CoV-2 infection, regardless of risk factors in the Phase 3 part of the Phase 2/3 study conducted during the Omicron-dominant phase of the epidemic. With regard to safety, ensitrelvir was well tolerated, and there were no serious treatment-related adverse events or deaths in the study. Among the most common treatment-related adverse events were temporary decreases in high-density lipoprotein and increased blood triglycerides, as observed in previous studies. Currently, the Phase 2b/3 part of the Phase 2/3 study targeting SARS-CoV-2 infected persons who were asymptomatic or only had mild symptoms is being conducted in Asia, mainly in Japan.
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