SummaryBackgroundLung delivery of plasmid DNA encoding the CFTR gene complexed with a cationic liposome is a potential treatment option for patients with cystic fibrosis. We aimed to assess the efficacy of non-viral CFTR gene therapy in patients with cystic fibrosis.MethodsWe did this randomised, double-blind, placebo-controlled, phase 2b trial in two cystic fibrosis centres with patients recruited from 18 sites in the UK. Patients (aged ≥12 years) with a forced expiratory volume in 1 s (FEV1) of 50–90% predicted and any combination of CFTR mutations, were randomly assigned, via a computer-based randomisation system, to receive 5 mL of either nebulised pGM169/GL67A gene–liposome complex or 0·9% saline (placebo) every 28 days (plus or minus 5 days) for 1 year. Randomisation was stratified by % predicted FEV1 (<70 vs ≥70%), age (<18 vs ≥18 years), inclusion in the mechanistic substudy, and dosing site (London or Edinburgh). Participants and investigators were masked to treatment allocation. The primary endpoint was the relative change in % predicted FEV1. The primary analysis was per protocol. This trial is registered with ClinicalTrials.gov, number NCT01621867.FindingsBetween June 12, 2012, and June 24, 2013, we randomly assigned 140 patients to receive placebo (n=62) or pGM169/GL67A (n=78), of whom 116 (83%) patients comprised the per-protocol population. We noted a significant, albeit modest, treatment effect in the pGM169/GL67A group versus placebo at 12 months' follow-up (3·7%, 95% CI 0·1–7·3; p=0·046). This outcome was associated with a stabilisation of lung function in the pGM169/GL67A group compared with a decline in the placebo group. We recorded no significant difference in treatment-attributable adverse events between groups.InterpretationMonthly application of the pGM169/GL67A gene therapy formulation was associated with a significant, albeit modest, benefit in FEV1 compared with placebo at 1 year, indicating a stabilisation of lung function in the treatment group. Further improvements in efficacy and consistency of response to the current formulation are needed before gene therapy is suitable for clinical care; however, our findings should also encourage the rapid introduction of more potent gene transfer vectors into early phase trials.FundingMedical Research Council/National Institute for Health Research Efficacy and Mechanism Evaluation Programme.

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Cystic fibrosis is a fatal genetic disorder which afflicts 50,000 people worldwide. A viable animal model would be invaluable for investigating and combating this disease. The mouse cystic fibrosis transmembrane conductance regulator gene was disrupted in embryonal stem cells using an insertional gene targeting vector. Germ-line chimaeras were derived and the offspring of heterozygous crosses studied. These homozygous mutant mice survive beyond weaning. In vivo electrophysiology demonstrates the predicted defect in chloride ion transport in these mice and can distinguish between each genotype. Histological analysis detects important hallmarks of human disease pathology, including abnormalities of the colon, lung and vas deferens. This insertional mouse mutation provides a valid model system for the development and testing of therapies for cystic fibrosis patients.

We report gene transfer to the Edinburgh insertional mutant mouse (cf/cf), delivering CFTR cDNA-liposome complexes into the airways by nebulization. We show full restoration of cAMP related chloride responses in some animals and demonstrate, in the same tissues, human CFTR cDNA expression. Overall, a range of correction was seen with restoration of about 50% of the deficit between wild type mice and untreated cf/cf controls. We report modest correction in the intestinal tract following direct instillation and provide initial encouraging safety data for both the respiratory and intestinal tract following the liposome mediated gene delivery. The non-viral nature and potentially lower immunogenicity of DNA-liposomes suggest that this may offer a therapeutic alternative to adenoviral therapies.

We have generated a mouse carrying the human G551D mutation in the cystic fibrosis transmembrane conductance regulator gene (CFTR) by a one‐step gene targeting procedure. These mutant mice show cystic fibrosis pathology but have a reduced risk of fatal intestinal blockage compared with ‘null’ mutants, in keeping with the reduced incidence of meconium ileus in G551D patients. The G551D mutant mice show greatly reduced CFTR‐related chloride transport, displaying activity intermediate between that of cftr(mlUNC) replacement (‘null’) and cftr(mlHGU) insertional (residual activity) mutants and equivalent to approximately 4% of wild‐type CFTR activity. The long‐term survival of these animals should provide an excellent model with which to study cystic fibrosis, and they illustrate the value of mouse models carrying relevant mutations for examining genotype‐phenotype correlations.