Development of CpG‐Depleted CFTR Plasmid‐Based Nanoparticles for Nonviral Gene Therapy in Lung Cystic Fibrosis Disease

Nonviral gene therapy holds promise as a potential treatment for lung cystic fibrosis (CF). However, the transient expression of the CF transmembrane conductance regulator (CFTR) protein has limited its clinical application. To circumvent this challenge, a CpG-depleted CFTR plasmid was developed. The CpG-depleted CFTR plasmid could be compacted into DNA nanoparticles and modified with the addition of highly branched poly(β-amino ester)s (HPAEs), leading to an improved and sustained CFTR protein expression. Using a CpG-depleted and codon-optimized CFTR sequence, around 20-fold increase in CFTR protein production was achieved 48 h after treatment, compared with healthy human bronchial epithelial cells (16HBE14o-). To evaluate the duration of CFTR protein expression induced by the plasmid based on human elongation factor 1α (hEFIα) and cytomegalovirus (CMV) promoters, a time course study was conducted in human CF bronchial epithelial (CFBE14o-) cells. hEFIα promoter revealed a remarkable 2.26-fold increase in CFTR protein expression at 7 days after transfection compared with 16HBE14o- cells. This level of CFTR protein expression outperformed the commonly used CMV promoter. The in vitro results demonstrated that CpG-depleted CFTR plasmid could be used to achieve high efficacy in subsequent in vivo evaluations, which, if validated, may provide promising prospects for the development of a novel and effective treatment for lung cystic fibrosis.