- Ensitrelvir achieved the primary endpoint in the Phase 3 part of the Asian Phase 2/3 clinical trial, demonstrating a significant reduction vs placebo in the time to resolution of five typical Omicron-related symptoms. This study was conducted in a predominantly vaccinated patient population with mild/moderate COVID-19, irrespective of risk factors for severe complications.
- Ensitrelvir also showed a significant reduction in viral RNA on day 4 (following the third dose) relative to placebo (a greater than 1.4 log10 copies/mL vs. placebo for change from baseline on day 4).
- With the results of this study, conducted during the Omicron phase of the pandemic, ensitrelvir has become the first investigational oral antiviral to demonstrate a statistically significant effect compared to placebo in the time to resolution of symptoms.
This study was conducted in patients with mild/moderate symptoms of COVID-19 and assessed clinical symptom resolution with ensitrelvir (2 dose groups; high dose and low dose), orally administered once daily for five days, compared to placebo. A total of 1,821 patients were enrolled, in Japan, South Korea, and Vietnam, irrespective of risk factors for COVID-19 progression. The majority of patients were previously vaccinated. The primary endpoint in the study was the time to resolution of five key COVID-19 symptoms (stuffy or runny nose, sore throat, cough, feeling hot or feverish, and low energy or tiredness) which are characteristic of infection with the SARS-CoV-2 Omicron variant, in patients randomized within 72 hours from the onset of symptoms. The five assessed symptoms were selected in consultation with medical experts and regulatory authorities including the Ministry of Health, Labor and Welfare (MHLW), the Pharmaceuticals and Medical Devices Agency (PMDA) in Japan and the U.S. Food and Drug Administration (FDA), based on their scientific and medical validity.
In this population, the median time to resolution of the five COVID-19 symptoms was significantly reduced in those treated with the low dose of ensitrelvir (the dose level submitted for approval in Japan) compared to placebo: 167.9 hours versus 192.2 hours, a statistically significant difference of 24 hours (p=0.04). In addition, with respect to the key secondary endpoint of reduction in viral RNA on day 4 (following the third dose), ensitrelvir showed a significant difference versus placebo (p<0.0001) in the Least Squares mean change from baseline in viral RNA; a reduction of more than 1.4 log10 copies/mL versus placebo, similar to the results observed in previous studies1-3. With regard to safety, both doses of ensitrelvir were well tolerated, and there were no serious adverse events or deaths in this study. In the low-dose group, the most common treatment-related adverse events were decreased high-density lipoprotein and increased blood triglycerides, as observed in previous studies.
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About ensitrelvir fumaric acid (S-217622)
- 1Press release on February 7, 2022. Shionogi Presents Phase 2/3 Clinical Trial Results (Phase 2a Part) for the COVID-19 Therapeutic Drug S-217622
- 2Press release on February 25, 2022. Notice Regarding the Signing of a Basic Agreement with the Ministry of Health, Labor and Welfare for Domestic Supply of S-217622, a Therapeutic Drug for COVID-19
- 3Press release on April 24, 2022. New Data for Shionogi’s COVID-19 Once-Daily Oral Antiviral S-217622 Show Rapid Virus Clearance