Ensitrelvir shows promise preventing COVID-19 after household exposure

A recent clinical trial shows the oral antiviral Ensitrelvir can prevent COVID-19 after exposure, a milestone in a drug effort that traces back to a key genomic insight from the start of the pandemic.

In January 2020, the full-length genome sequence of a strain of the SARS-CoV-2 virus was posted on an online discussion forum for virologists. The sequence revealed that SARS-CoV-2, like its relative SARS-CoV-1, keeps most of its proteins as one long chain. The individual proteins are then cut from this chain and released by enzymes called proteases.

That protease mechanism became a drug target. The recent phase III trial, published in NEJM in 2024, tested Ensitrelvir as post-exposure prophylaxis.