In this study, to demonstrate seamless gene correction in human iPSCs derived from a CF patient homozygous for the W1282X Class I CFTR mutation, we performed a two-step approach: first by using CRISPR/Cas9 nickases (CRISPR/Cas9n) to generate DSBs and catalyze gene correction of the W1282X mutation by HDR with a wild type CFTR exon 23 targeting vector that contained a puromycin resistance-Herpes virus thymidine kinase (PuroΔTK) expression cassette. This evidence concerns the gene CFTR and cystic fibrosis.