New data from Japan shows early resolution of common Covid-19 symptoms

The trial met its primary and key secondary endpoints, making ensitrelvir the first antiviral agent to show both clinical symptom improvement and antiviral effect in a predominantly vaccinated population with Omicron infection.

The study found that once-daily administration of ensitrelvir led to a statistically significant reduction in the time to resolution of five typical COVID-19 symptoms characteristic of Omicron, runny nose, sore throat, cough, fever and tiredness, versus placebo.

More than 90% of patients in the trial had received two or more doses of the SARS-CoV-2 vaccine and patients were included regardless of risk factors for severe disease.

“We’re pleased to present the data from our Phase 3 study conducted in Asia in this peer-reviewed article. These results demonstrate accelerated resolution in a range of symptoms, reinforcing the potential of ensitrelvir across multiple patient profiles,” said Takeki Uehara, senior vice president, drug development and regulatory science at Shionogi.

“Additionally, ensitrelvir reduced viral RNA levels and time to first negative viral titer, suggesting it could help reduce transmission of SARS-CoV-2. This study was conducted in a largely vaccinated population that included patients infected with Omicron. The patients also had varying risk factors for severe disease. This is relevant as there is a lack of data and a need for additional treatment options for this population.”

Known as Xocova in Japan, ensitrelvir received emergency regulatory approval from the Ministry of Health, Labour and Welfare in Japan for the treatment of SARS-CoV-2 infection back in 2022.

In addition, the therapy was approved in Singapore in November 2023, based on the Special Access Route application, but remains an investigational drug outside of Japan and Singapore. Ensitrelvir was also granted Fast Track designation by the U.S. Food and Drug Administration. 

Despite vaccines and some therapeutics available to treat COVID-19, the World Health Organization has emphasized that more treatment options are still needed for the disease.

“We continue to see COVID-19 surges and we need additional treatment options for more patients, irrespective of risk factors for severe disease, as the virus continues to evolve, adapt, infect and re-infect people across the world,” said Yohei Doi, professor of Medicine, Fujita Health University, Japan, and one of the study authors.

“Seeing the comprehensive data from the study in Asia signals that ensitrelvir has promising potential to treat patients with many common COVID-19 symptoms.”