Abstract: The instant specification provides for evolved base editors which overcome deficiencies of those in art (including increased efficiency and/or decreased requirement for specific sequence-context at an editing site) and which are obtained a result of a phage-assisted continuous evolution (PACE) system. In particular, the instant specification provides for evolved cytidine base editors (e.g., based on APOBEC1, CDA, or AID cytidine deaminase domains) which overcome deficiencies of those in art (including increased efficiency and/or decreased requirement for specific sequence-context at an editing site) and which are obtained a result of a phage-assisted continuous evolution (PACE) system.

Abstract: The present disclosure provides adenine base editors (ABEs) that are variants of known adenine base editors. The adenosine deaminase domain of a known ABE was modified to produce adenosine deaminase variants. The deaminase variants provided herein have broader compatibility with diverse napDNAbp domains, such as Cas homologs, for base editing applications. The ABEs provided herein comprise a deaminase variant and a napDNAbp domain. The ABEs provided herein exhibit reduced off-target editing effects while retaining high on-target editing efficiencies. These ABEs exhibit reduced off-target DNA editing effects and reduced off-target editing effects in cellular mRNA. In addition, methods for targeted nucleic acid editing are provided. Further provided are pharmaceutical compositions comprising the ABEs. Also provided are vectors and kits useful for the generation and delivery of the ABEs, including vector systems for engineering the ABEs through directed evolution.