We used an adenine base editor (ABE8e Cas9) and guide RNA (sgRNA)/enhanced green fluorescent protein (EGFP) plasmids encapsulated in receptor targeted nanoparticles (RTN), delivered to Bmi-1 transduced basal human CF airway epithelial cells harbouring the homozygous CFTR G542X variant, to convert the stop codon to G542R, a variant which is amenable to modulator therapy. This evidence concerns the gene CFTR and cystic fibrosis.