Abstract

Although gene editing offers durable therapeutic potential for genetic disorders such as hypercholesterolemia, widely used adenine base editors (ABEs) face translational obstacles due to potential off-target effects inherent in gene-editing systems. ABE8e has strong clinical potential owing to its high efficiency and rapid editing kinetics, but its genome-wide off-target effects remain poorly characterized. Here, we uncovered substantial genome-wide off-target edits of ABE8e using the GOTI (Genome-wide Off-target analysis by Two-cell embryo Injection) assay, including in oncogenes and tumor suppressors, highlighting significant risks for clinical translation. We therefore engineered a next-generation precision base editor, erABE, through electrostatic remodeling of the TadA8e deaminase. erABE reduces ABE8e’s genome-wide off-target activity by ~36.5-fold to background levels while retaining an efficiency indistinguishable from ABE8e. In mice, a single low-dose delivery of erABE packaged in lipid nanoparticles achieved robust Pcsk9 knockdown, resulting in a sustained, ~90% reduction in plasma PCSK9 protein and ~60% reduction in low-density lipoprotein cholesterol for at least 6 months. erABE also potently suppresses PCSK9 expression in human liver organoids. These results highlight the safety and durable therapeutic effects of erABE, supporting its translation as a clinical genome-editing platform.