Ensitrelvir, sold under the brand name Xocova is an antiviral medication used as a treatment for COVID-19. It was developed by Shionogi in partnership with Hokkaido University and acts as an orally active 3C-like protease inhibitor. It is taken by mouth.

The most common adverse events include transient decreases in high-density lipoprotein and increased blood triglycerides.

Ensitrelvir is indicated for the treatment of COVID-19.

As of 2022^[update], ensitrelvir had reached Phase III clinical trials. The Japanese government is reportedly considering allowing Shionogi permission to apply for approval for medical use before the final steps of trials are completed, potentially speeding up the release for sale. This conditional early approval system has previously been used in Japan to accelerate the progression to market of other antiviral drugs targeting COVID-19, including remdesivir and molnupiravir. In a study of 428 patients, viral load was reduced, but symptoms were not significantly reduced.

In February 2022, the company sought emergency approval from regulators in Japan.

Shionogi announced they had reached a preliminary agreement to supply 1 million doses to the Japanese government once the drug is approved. The CEO said they could have capacity to make 10 million doses a year.

Ensitrelvir may be effective in treating smell and taste loss from COVID-19 infection. In a 2023 study, the drug was associated with a 39% reduction in these symptoms.

Ensitrelvir was approved for emergency use in Japan in November 2022, before gaining full approval in March 2024. It was approved in Singapore in November 2023.