We found 2 wild-type cells (2/28, 7.1%) with the genotype of A−28G−25/A−28G−25, proving precise repair of both mutant alleles (Fig. 2D and 2E). Additionally, only one mutant allele (A−28G−25/G−28G−25) was repaired in 3/28 (10.7%) cells, resulting in heterozygosity (Fig. 2E). Consistent with our previous data using human cell lines (Fig. 1D), we also found G>A conversion at G−25 of the target site in 3/28 (10.7%) cells, highlighting the need for developing base editor variants with a narrower deamination window to improve the precision of base editing (Figs. 1D and 2E). Here, these data showed that 5/28 (17.8%) cells was repaired precisely, demonstrating the feasibility of repairing HBB −28 (A>G) mutation in situ.