XNAzymes, artificial enzymes that can precisely cut long RNA molecules, could be harnessed to quickly develop antiviral therapies, a new study appearing in Nature Communications says. A University of Cambridge team designed site-specific RNA endonuclease XNAzymes that target different parts of the SARS-CoV-2 RNA genome. The team reports that they were able to design, synthesis, and screen a number of RNA endonuclease XNAzymes targeting five SARS-CoV-2 sites in about a week. Three of these XNAzymes were further active under physiological conditions and could knockdown the SARS-CoV-2 RNA genome both in vitro and in vivo, showing a proof-of-concept of their approach. "It's really encouraging that for the first time – and this has been a big goal of the field – we actually have them working as enzymes inside cells, and inhibiting replication of live virus," first author Pehuén Pereyra Gerber from Cambridge says in a statement. The researchers add that the next step is to optimize the intracellular activity and pharmacokinetic activity of the XNAzymes.