Researchers from Rutgers, the University of South Florida and Catholic University of America, whose work has yet to undergo peer review, identified 66 prevalent Mpro mutations located at the nirmatrelvir binding site, where Paxlovid attaches itself to the virus. Many of the mutations hindered the Mpro’s ability to cleave the substrate, a hint that the mutant virus will be less fit than the wild-type (WT) virus in replication and transmission. However, what is worrisome is that the researchers found 11 Mpro mutants that resisted Paxlovid but maintained a similar level of enzymatic activity as the WT, suggesting that they should be monitored closely for possible clinical evidence of Paxlovid resistance. To read the full story.