
Early research suggested that CRISPR-Cas9 effectors can inhibit the replication of ssRNA viruses with DNA intermediates in mammalian cells. While several studies have estimated that only 2.5% of those viruses have DNA intermediates that could be targeted using Cas9, RNA-targeting CRISPR effectors could offer a promising therapeutic alternative to ssRNA viruses. However, stealth startup Carver Bioscience has turned a different CRISPR RNA-cutting nuclease enzyme—Cas13—into an antiviral that can be programmed to detect and destroy RNA-based viruses in human cells . . .