Lessons learnt from the preclinical discovery and development of ensitrelvir as a COVID-19 therapeutic option.

Ensitrelvir was developed in a late phase of the pandemic when the availability of patients that can be candidate to enter the clinical trial was limited with consequences for the possibility of assessing certain outcomes and for the robustness of results. Although the evidence about the benefits of ensitrelvir in COVID-19 is not questionable, the problems of interactions with other drugs, emerging resistant variants, the availability of alternative therapeutic options, costs, and accessibility will concur to its probable limited clinical use in the future.