Reporter-based screening identifies small-molecule CBL0137 as an enhancer of CRISPR cytosine base editor and prime...

Recently developed CRISPR base editors (BEs) and prime editors (PEs) enable precise genome editing without inducing double-strand breaks, making them highly promising tools for therapeutic applications. However, their efficiency remains a major barrier to clinical translation, particularly at difficult-to-target sites. To address this limitation, we used a high-throughput GFP reporter system responsive to cytosine base editor (CBE) activity to screen small molecules involved in DNA damage response, cell cycle, and apoptosis pathways. This screen identified CBL0137 as a candidate that significantly enhanced editing efficiency at both the reporter and endogenous target sites, with up to an 80 % improvement. Mechanistic studies revealed that CBL0137 acts through activation of the p53 pathway and inhibition of NF-κB. Interestingly, the enhancement was largely specific to CBEs, while in PEs, CBL0137 selectively improved multi-site mutations and fragment insertions without affecting single-point edits or deletions. Collectively, these results identify CBL0137 as a selective enhancer of specific genome editing activities, providing a strategy to increase editing efficiency and advancing the translational potential of next-generation genome editing tools for therapeutic applications.