A base editing strategy to efficiently correct the IVS1-110 (G>A) mutation. (A) gRNAs 1 to 6 were manually designed to place the IVS1-110 (G>A) mutation in positions 3 to 8 of the protospacer. The mutation is highlighted with a grey box. (B) Overview of the cell collection for testing the ability of gRNA/BE combinations to correct the IVS1-110 (G>A) mutation. (C) Frequency of corrected alleles (normalized to the frequency of GFP⁺ cells) and indels as assessed by Sanger sequencing in T cells electroporated with different combinations of synthetic gRNAs and ABE mRNAs. Data are expressed as mean ± standard error of the mean (SEM) (n = 3, 2 donors). (D) Representative percent composition of Sanger sequencing traces measured to be significantly different from noise (in red), as assessed by EditR following Sanger sequencing in T cells electroporated with gRNA1/SpRY-ABE8e (cor) or with TE buffer (TE). The target base position is outlined with a red box and the observed bystander edits with black boxes. Single nucleotide polymorphisms rs777028217 (G>A) and rs1480884739 (T>C) mapped to positions 6 and 8 are not associated with a clinical phenotype. PBMC, peripheral blood mononuclear cells; cor, corrected.