Limitations of the murine nose in the development of nonviral airway gene transfer.

A clinical program to assess whether lipid GL67A-mediated gene transfer can ameliorate cystic fibrosis (CF) lung disease is currently being undertaken by the UK CF Gene Therapy Consortium. We have evaluated GL67A gene transfer to the murine nasal epithelium of wild-type and CF knockout mice to assess this tissue as a test site for gene transfer agents. The plasmids used were regulated by either (1) the commonly used short-acting cytomegalovirus promoter/enhancer or (2) the ubiquitin C promoter. In a study of approximately 400 mice with CF, vector-specific CF transmembrane conductance regulator (CFTR) mRNA was detected in nasal epithelial cells of 82% of mice treated with a cytomegalovirus-plasmid (pCF1-CFTR), and 62% of mice treated with an ubiquitin C-plasmid. We then assessed whether CFTR gene transfer corrected a panel of CFTR-specific endpoint assays in the murine nose, including ion transport, periciliary liquid height, and ex vivo bacterial adherence. Importantly, even with the comparatively large number of animals assessed, the CFTR function studies were only powered to detect changes of more than 50% toward wild-type values. Within this limitation, no significant correction of the CF phenotype was detected. At the current levels of gene transfer efficiency achievable with nonviral vectors, the murine nose is of limited value as a stepping stone to human trials.

An immunocytochemical assay to detect human CFTR expression following gene transfer.

BACKGROUND: To assess gene therapy treatment for cystic fibrosis (CF) in clinical trials it is essential to develop robust assays that can accurately detect transgene expression in human airway epithelial cells. Our aim was to develop a reproducible immunocytochemical assay for human CFTR protein which can measure both endogenous CFTR levels and augmented CFTR expression after gene delivery. METHODS: We characterised an antibody (G449) which satisfied the criteria for use in clinical trials. We optimised our immunocytochemistry method and identified G449 dilutions at which endogenous CFTR levels were negligible in CF samples, thus enhancing detection of transgenic CFTR protein. After developing a transfection technique for brushed human nasal epithelial cells, we transfected non-CF and CF cells with a clinically relevant CpG-free plasmid encoding human CFTR. RESULTS: The optimised immunocytochemistry method gave improved discrimination between CF and non-CF samples. Transfection of a CFTR expression vector into primary nasal epithelial cells resulted in detectable RNA and protein expression. CFTR protein was present in 0.05-10% of non-CF cells and 0.02-0.8% of CF cells. CONCLUSION: We have developed a sensitive, clinically relevant immunocytochemical assay for CFTR protein and have used it to detect transgene-expressed CFTR in transfected human primary airway epithelial cells.

Repeated nebulisation of non-viral CFTR gene therapy in patients with cystic fibrosis: a randomised, double-blind, placebo-controlled, phase 2b trial.

BACKGROUND: Lung 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. METHODS: We 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. FINDINGS: Between 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. INTERPRETATION: Monthly 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. FUNDING: Medical Research Council/National Institute for Health Research Efficacy and Mechanism Evaluation Programme.