Background
Cystic fibrosis (CF) is a chronic, life-limiting disease caused by mutations in the CF transmembrane conductance regulator (
CFTR
) gene leading to abnormal airway surface ion transport, ...chronic lung infections, inflammation and eventual respiratory failure. With the exception of the small-molecule potentiator, ivacaftor (Kalydeco
®
, Vertex Pharmaceuticals, Boston, MA, USA), which is suitable for a small proportion of patients, there are no licensed therapies targeting the basic defect. The UK Cystic Fibrosis Gene Therapy Consortium has taken a cationic lipid-mediated
CFTR
gene therapy formulation through preclinical and clinical development.
Objective
To determine clinical efficacy of the formulation delivered to the airways over a period of 1 year in patients with CF.
Design
This was a randomised, double-blind, placebo-controlled Phase IIb trial of the
CFTR
gene–liposome complex pGM169/GL67A. Randomisation was performed via InForm™ version 4.6 (Phase Forward Incorporated, Oracle, CA, USA) and was 1 : 1, except for patients in the mechanistic subgroups (2 : 1). Allocation was blinded by masking nebuliser chambers.
Settings
Data were collected in the clinical and scientific sites and entered onto a trial-specific InForm, version 4.6 database.
Participants
Patients with CF aged ≥ 12 years with forced expiratory volume in the first second (FEV
1
) between 50% and 90% predicted and any combination of
CFTR
mutations. The per-protocol group (≥ 9 doses) consisted of 54 patients receiving placebo (62 randomised) and 62 patients receiving gene therapy (78 randomised).
Interventions
Subjects received 5 ml of nebulised pGM169/G67A (active) or 0.9% saline (placebo) at 28 (±5)-day intervals over 1 year.
Main outcome measures
The primary end point was the relative change in percentage predicted FEV
1
over the 12-month period. A number of secondary clinical outcomes were assessed alongside safety measures: other spirometric values; lung clearance index (LCI) assessed by multibreath washout; structural disease on computed tomography (CT) scan; the Cystic Fibrosis Questionnaire – Revised (CFQ-R), a validated quality-of-life questionnaire; exercise capacity and monitoring; systemic and sputum inflammatory markers; and adverse events (AEs). A mechanistic study was performed in a subgroup in whom transgene deoxyribonucleic acid (DNA) and messenger ribonucleic acid (mRNA) was measured alongside nasal and lower airway potential difference.
Results
There was a significant (
p
= 0.046) treatment effect (TE) of 3.7% 95% confidence interval (CI) 0.1% to 7.3% in the primary end point at 12 months and in secondary end points, including forced vital capacity (FVC) (
p
= 0.031) and CT gas trapping (
p
= 0.048). Other outcomes, although not reaching statistical significance, favoured active treatment. Effects were noted by 1 month and were irrespective of sex, age or
CFTR
mutation class. Subjects with a more severe baseline FEV
1
had a FEV
1
TE of 6.4% (95% CI 0.8% to 12.1%) and greater changes in many other secondary outcomes. However, the more mildly affected group also demonstrated benefits, particularly in small airway disease markers such as LCI. The active group showed a significantly (
p
= 0.032) greater bronchial chloride secretory response. No difference in treatment-attributable AEs was seen between the placebo and active groups.
Conclusions
Monthly application of the pGM169/GL67A gene therapy formulation was associated with an improvement in lung function, other clinically relevant parameters and bronchial CFTR function, compared with placebo.
Limitations
Although encouraging, the improvement in FEV
1
was modest and was not accompanied by detectable improvement in patients’ quality of life.
Future work
Future work will focus on attempts to increase efficacy by increasing dose or frequency, the coadministration of a CFTR potentiator, or the use of modified viral vectors capable of repeated administration.
Trial registration
ClinicalTrials.gov NCT01621867.
Funding
This project was funded by the Efficacy and Mechanism Evaluation (EME) programme, a Medical Research Council and National Institute for Health Research partnership.
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