Cystic fibrosis (CF) is a hereditary, progressive and lethal multi-organ disorder affecting 85,000 people worldwide. CF is caused by mutations in CFTR, which codes for a chloride/bicarbonate channel in the apical membrane of (airway) epithelial cells. Over 2000 CFTR mutations have been described of which 432 disease-causing. Potentiators and correctors have been market approved to functionally correct about 40 different mutations, accounting for 90% of patients. However, 92% of CFTR mutations cannot be corrected by any available small-molecules . With the advent of CRISPR-Cas gene editing, a new era of precision medicine has evolved, with the potential to cure diseases at the genetic level. In this project, I will develop a base or prime editing strategy to functionally rescue drug- refractory mutations G85E, L227R, L927P and N1303K in cell lines, patient-derived intestinal organoids and airway cultures. As prolonged CRISPR-Cas exposure in target tissue compromises gene editing safety, I will develop airway-tropic virus like particles (VLPs) to transiently deliver CRISPR-Cas to human airway cells for CFTR correction. I will profile on-target editing efficiency and map potential off-targets. Finally, I will evaluate if the developed systems are fit for future ex vivo/in vivo gene therapy by delivery of the gene editors to human CF airway epithelial cells with the goal of correcting these missense mutations to WT-CFTR at single cell level.