Positive results in COVID-19 therapy phase 3 trials show effectiveness against five symptoms

Shionogi has announced that ensitrelvir – a protease inhibitor being evaluated as an antiviral treatment for COVID-19 – has achieved its primary endpoint in the phase 3 element of its study in Asia.

The research was conducted among patients with mild to moderate symptoms of COVID-19 and assessed clinical symptom resolution with ensitrelvir for five days compared to placebo. A total of 1,821 patients were enrolled, across 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 involved the time it took to resolve 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 Omicron variant.

The 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 US Food and Drug Administration (FDA), based on their scientific and medical validity.

In this population, the median time to first resolution of the five COVID-19 symptoms was significantly reduced in those treated with the low dose of ensitrelvir compared to placebo. Following a higher dose, ensitrelvir showed an even greater significant difference versus placebo.

In terms of 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.

The emergency approval of ensitrelvir was deliberated in the Pharmaceutical Affairs and Food Sanitation Council meeting held in July and the review will continue based on the results of the phase 3 part of the study. The topline results of the phase 3 part have been reported to MHLW and PMDA.