Ensitrelvir for the treatment of COVID-19: Final analysis of a post-marketing surveillance from Japan

Background: Ensitrelvir received approval in Japan for emergency use in the management of patients with coronavirus disease (COVID-19) in November 2022. A post-marketing surveillance (PMS) was conducted to evaluate the safety and effectiveness of ensitrelvir in Japanese real-world clinical practice, and the interim analysis results (data cutoff: July 20, 2023) have been published. This report describes the final analysis of the PMS for ensitrelvir in a Japanese clinical setting. Methods: A continuous survey method was used for this PMS (November 2022 to December 2023), and the observation period was 28 days from the start date of ensitrelvir administration. Patients with COVID-19 who received ensitrelvir for the first time and provided written informed consent to collect and use their data were included in this survey. The outcomes included patient characteristics, adverse drug reactions (ADRs), and time to resolution of COVID-19 symptoms. Results: A total of 3760 and 3638 patients were included in the safety and effectiveness analysis sets, respectively. In the safety analysis set, the mean +/- standard deviation age was 43.6 +/- 17.7 years, 48.5 % were male, 97.5 % had mild COVID-19, and 73.4 % had a vaccination history. Of the 379 ADRs reported, 374 were not serious and 5 were serious. None of the ADRs resulted in sequelae or death. The median time to resolution of fever and all symptoms was 36.0 and 156.0 h, respectively. Conclusion: This PMS including >3000 patients suggested the safety of ensitrelvir for the treatment of patients with COVID-19 in Japan, with no new safety concern.