ArticlesCationic lipid-mediated CFTR gene transfer to the lungs and nose of patients with cystic fibrosis: a double-blind placebo-controlled trial
Introduction
The cystic fibrosis transmembrane conductance regulator (CFTR) gene encodes a protein, one function of which is to act as a cyclic-AMP-dependent chloride channel in the epithelia of affected organs such as the lungs and intestinal tract.1 Mutations in this gene result in impaired chloride movement. This, combined with increased sodium absorption also present in the airway epithelial cells of patients with cystic fibrosis,2 is associated with susceptibility to colonisation by several organisms (in particular Pseudomonas aeruginosa).3 Repeated respiratory infections and inflammation result in a current mean life expectancy of about 30 years.4 These abnormalities provide several endpoints that can be used to assess whether administration of a normal copy of the CFTR gene can correct the basic biochemical defect. Gene therapy for cystic fibrosis has reached the stage of clinical studies. These studies have focused on administration of the CFTR gene with adenoviruses,5, 6, 7, 8, 9, 10 cationic liposomes,11, 12, 13, 14 or, most recently, adeno-associated virus.15
Given the easy access to the nasal mucosa, which demonstrates the characteristic electrophysiological defects, all published studies to date have included this organ in the assessment of gene transfer.5, 6, 7, 8, 9, 10, 11, 12, 13, 14 Some degree of correction of the chloride, but not of the sodium, abnormality has been reported with both viral and cationic-lipid-mediated gene transfer. However, this has not been a consistent finding, with some studies unable to detect these changes.6 One interpretation of these data is that the degree of gene transfer and subsequent correction is small when measured against a background of fairly difficult and hence variable in-vivo and ex-vivo assays. Few, if any, safety problems have been encountered with the nasal epithelium as a model system. Clearly, one goal of such gene-therapy studies is to correct the abnormality within the lungs of people with cystic fibrosis as a precursor to demonstrating clinical benefit. To date, there have been two uncontrolled trials of adenovirus-mediated gene transfer to the lungs. Crystal and colleagues.7, 8 demonstrated CFTR protein in one of four patients, whilst Bellon and colleagues10 detected CFTR mRNA in two of six patients and CFTR protein in two of six patients following aerosolisation. Neither study included measurements of functional changes in the lower airways. No studies of cationic-lipid-mediated gene transfer have been undertaken for cystic fibrosis or any other disease within the lungs.
Several groups have reported significant advances in gene-transfer efficiency using cationic lipids, and a series of studies have suggested that the second-generation cationic lipid GL-67 may provide better transfection efficiency in vivo within the pulmonary epithelium.16 We therefore assessed the safety of administration of this lipid by nebulisation to the lungs of 15 normal volunteers in a dose escalation study,17 finding no toxic effects. In addition, we developed several assays to measure the chloride and sodium abnormalities in vivo within the lungs18 and in ex-vivo samples.19 We also developed an assay to measure the characteristically increased adherence of P aeruginosa to epithelial cells in cystic fibrosis.20
We have now extended our studies of liposome-mediated gene transfer in cystic fibrosis in a double-blind placebo-controlled study to assess both the safety and efficacy of a GL67-CFTR complementary DNA (cDNA) complex administered by nebulisation to the lungs of patients with cystic fibrosis. 1 week later, complex was administered to the nasal epithelium; this provided an intra-patient comparison of whether changes in the nasal epithelium predicted those within the lung, and a comparison between trials of the data we and others have obtained using first-generation cationic lipids.
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Patients
We enrolled 16 male patients with cystic fibrosis who had been proven infertile by semen analysis. The genotypes of these patients were: 12 ΔDRF508/ΔDRF508, one ΔF508/W1282X, and three ΔF508/other (ie, no mutation detected after screening for mutations present in 92–94% of UK patients with cystic fibrosis).21 All patients met accepted diagnostic criteria for cystic fibrosis, including an abnormal sweat test, and all patients had a forced expiratory volume in 1 s of at least 70% predicted. Eight
Safety
Seven patients in the active group developed influenza-like symptoms—myalgia, headache, and a high temperature (38·3°C [SE 0·3]) with an onset of roughly 6 h after nebulisation, and which returned to normal within 30 h. This reaction was treated symptomatically with paracetamol, resolved spontaneously, and did not recur on nasal administration. Blood cultures, a viral screen, and a chest radiograph were done on the first two patients who developed fevers, and showed no abnormalities. Three
Discussion
We have shown a significant correction of the basic electrophysiological defect in cystic fibrosis using the cationic lipid GL-67/DOPE/DMPE-PEG5000 as the gene transfer agent. Administration was associated with two groups of mild symptoms, which resolved spontaneously. Subsequent nasal administration also resulted in a significant change in chloride transport in the active-treatment group but not in the placebo group.
The principal priority of this study was to assess the safety of administering
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