Fibrosis Transmembrane Conductance Regulator Modulators Research Articles

Update in Cystic Fibrosis 2014.

The clinical face of cystic fibrosis (CF) has significantly changed over the 25 years since its basic genetic defect was discovered (1). Increasing numbers of patients are diagnosed at newborn screening, and soon the majority of the CF population will be adult patients (2). With the 2012 approval of the first cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapy, ivacaftor, the CF community has been able to experience the clinical and biological impact of this therapeutic approach in a small subset of patients with the G551D mutation (3). The findings are very encouraging and push investigators and clinicians to move forward with the development of additional modulators to improve the health of the majority of patients in the future. As a result, worldwide scientific collaborations have contributed to advances in therapeutics with the eventual goal of early intervention before the onset of symptoms. At the same time, the research community continues to elucidate the fundamental mechanisms of disease. In this article, we highlight some of the important scientific developments of 2014 with a focus on CFTR function and its complex role in mucociliary clearance (MCC), microbiology, and inflammation of the airway. In addition, advances in novel therapeutics and clinical outcomes are reviewed, with discussion of how those advances are impacting the field. CFTR Function and Its Role in MCC

Cystic fibrosis transmembrane conductance regulator modulators: the end of the beginning.

Cystic fibrosis (CF) represents one of the success stories of modern medicine with sustained incremental increases in the survival from one of childhood death to one of adult survival into the middle decades over the past 30 years. Improving survival has focused on multidisciplinary management centered on treating the consequences of this genetic disease. It has been firmly established for more than 20 years that mutations in the CF transmembrane conductance regulator (CFTR) gene result in a defective protein that normally functions as a chloride channel on epithelial cell surfaces. Until recently, modulating CFTR dysfunction was only a research aspiration, however, greater focus placed upon addressing the primary defect of CF has developed several clinical therapeutic strategies in this area. This review highlights the evidence to date on efforts to modulate CFTR and restore robust functional protein to the cell surface. This approach has now led to the licensing of one CFTR potentiator, which has been shown to have significant clinical improvements in a subset of CF patients. This success represents the beginning for CFTR modulation and further research is ongoing which aims to broaden the applicability of these techniques.

Targeting a genetic defect: cystic fibrosis transmembrane conductance regulator modulators in cystic fibrosis

Cystic fibrosis (CF) is caused by genetic mutations that affect the cystic fibrosis transmembrane conductance regulator (CFTR) protein. These mutations can impact the synthesis and transfer of the CFTR protein to the apical membrane of epithelial cells, as well as influencing the gating or conductance of chloride and bicarbonate ions through the channel. CFTR dysfunction results in ionic imbalance of epithelial secretions in several organ systems, such as the pancreas, gastrointestinal tract, liver and the respiratory system. Since discovery of the CFTR gene in 1989, research has focussed on targeting the underlying genetic defect to identify a disease-modifying treatment for CF. Investigated management strategies have included gene therapy and the development of small molecules that target CFTR mutations, known as CFTR modulators. CFTR modulators are typically identified by high-throughput screening assays, followed by preclinical validation using cell culture systems. Recently, one such modulator, the CFTR potentiator ivacaftor, was approved as an oral therapy for CF patients with the G551D-CFTR mutation. The clinical development of ivacaftor not only represents a breakthrough in CF care but also serves as a noteworthy example of personalised medicine.

Cystic Fibrosis Transmembrane Conductance Regulator–Modifying Medications: The Future of Cystic Fibrosis Treatment

To review and evaluate cystic fibrosis transmembrane conductance regulator (CFTR) modulators for the treatment of cystic fibrosis (CF). Literature was accessed through MEDLINE (1977-January 2012), the Cochrane Library, and International Pharmaceutical Abstracts (1977-March 2012). Search terms included ivacaftor, VX-770, VX-809, ataluren, PTC 124, CFTR modulator, and cystic fibrosis. All English-language articles identified from the data sources were evaluated for inclusion. Clinical trials and relevant review articles were evaluated for each CFTR modulator. CF is caused by a mutation in the gene that encodes for the CFTR protein; mutations can be separated into 5 different classes. Ivacaftor is a new CFTR potentiator that helps the CFTR channel open properly in patients with the CFTR mutation, G551D. Patients in one study had significant decreases in sweat chloride values and increases in pulmonary function tests. Ivacaftor was approved by the Food and Drug Administration (FDA) to be taken orally at a dose of 150 mg twice a day in G551D CF patients older than 6 years. Additional studies are investigating the use of ivacaftor in other gating mutations and in younger patients. VX-809 is a CFTR corrector that modulates the folding and trafficking of CFTR. VX-809 was originally studied alone in patients with F508del mutation but is now being used in combination with ivacaftor in Phase 2 studies. Ataluren allows the read through of premature stop codons, and studies in patients with CF with nonsense mutations show an increase in chloride transportation. Ataluren requires 3 times a day dosing and is currently in a Phase 3 placebo-controlled study. Three new agents, ivacaftor, VX-809, and ataluren, target the basic defects in CFTR production. Ivacaftor was recently FDA approved, while the other 2 agents are still in clinical trials. Patients with CF will benefit from personalized medicine based on their specific genotype.

Results of a phase IIa study of VX-809, an investigational CFTR corrector compound, in subjects with cystic fibrosis homozygous for the F508del-CFTR mutation

BackgroundVX-809, a cystic fibrosis transmembrane conductance regulator (CFTR) modulator, has been shown to increase the cell surface density of functional F508del-CFTR in vitro.MethodsA randomised, double-blind, placebo-controlled study evaluated the safety,...

Identification of Synergistic Combinations of F508del Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Modulators

Cystic fibrosis (CF) is an inherited, life-threatening disease caused by mutations in the gene encoding cystic fibrosis transmembrane conductance regulator (CFTR), an ABC transporter-class protein and ion channel that transports ions across epithelial cell membranes. The most common mutation leads to the deletion of a single phenylalanine, and the resulting protein, F508del-CFTR, shows reduced trafficking to the membrane and defective channel gating. The ideal therapeutic approach would address both of these defects and restore channel function at the same time. We describe here the application of a combination high-throughput screening to search for synergistic modulators of F508del-CFTR. With the adapted Fischer rat thyroid-yellow fluorescent protein halide flux assay to the combination high-throughput screening platform, we identified many interesting single agents as CFTR modulators from a library of approved drugs and mechanistic probe compounds, and combinations that synergistically modulate F508del-CFTR channel function in Fischer rat thyroid cells, demonstrating the potential for combination therapeutics to address the defects that cause CF.

1025 Liprotamase, a Microbial Enzyme Therapy, Reveresed Impaired Growth in a Model of Cystic Fibrosis: Pigs With Total Exocrine Pancreatic Insufficiency (EPI Pigs)

Cystic fibrosis transmembrane conductance regulator (CFTR) modulators improve pulmonary outcomes in subjects with cystic fibrosis (CF); however, the effects on pancreatic manifestations are not well characterized. We hypothesized that CFTR modulators would improve measures of exocrine pancreatic function and outcomes.We performed a systematic search to identify studies reporting measures of the exocrine pancreas in humans treated with CFTR modulators. Only studies reporting baseline and on-treatment assessments were included.Of 630 identified studies, 41 met inclusion criteria. CFTR modulators reduced acute pancreatitis events by 85% overall (rate ratio 0.15, 95% confidence interval (CI) 0.04, 0.52), with a greater effect seen in the subgroup with pancreas sufficient CF (PS-CF) (rate ratio 0.13 (95% CI 0.03, 0.53). Among 293 subjects with baseline and on-treatment evaluation of pancreas sufficiency, 253 were pancreas insufficient at baseline and 54 (21.3%) converted to pancreas sufficiency. Of 32 subjects with baseline FE-1 values <200 mcg/g, 16 (50%) increased to ≥200 mcg/g. Serum trypsin decreased by a mean of 565.9 ng/mL (standard deviation (SD) 311.8), amylase decreased by 38.2 U/L (SD 57.6), and lipase decreased by 232.3 U/L (SD 247.7).CFTR modulator use reduces acute pancreatitis frequency and improves indirect measures of exocrine pancreas function. Future interventional studies that evaluate the mechanism and impact of CFTR modulators on acute pancreatitis and pancreas sufficiency in patients with CFTR dysfunction are warranted.

Cystic Fibrosis Transmembrane Conductance Regulator Modulators for Personalized Drug Treatment of Cystic Fibrosis

This article considers the issue of personalized drug discovery for the orphan disease cystic fibrosis (CF) to deliver a candidate for therapeutic development. CF is a very complicated disease due to numerous anomalies of the gene leading to progressive severity and morbidity. Despite extensive research efforts, 20 years after the cloning of the CF gene, CF patients are still waiting for a curative treatment as prescribed medications still target the secondary manifestations of the disease rather than the gene or the CF transmembrane conductance regulator (CFTR) protein. New therapeutics aimed at improving mutant CFTR functions, also known as 'protein repair therapy' are nevertheless hoped and predicted to replace some of the currently used therapy, while improving the quality of life as well as life expectancy of CF patients. Although there is substantial variability in the cost of treating CF between countries, a protein repair therapy should also alleviate the financial burden of medical costs for CF patients and their families. Finding new drugs or rediscovering old ones for CF is critically dependent on the delivery of molecular and structural information on the CFTR protein, on its mutated version and on the network of CFTR-interacting proteins. The expertise needed to turn compounds into marketable drugs for CF will depend on our ability to provide biological information obtained from pertinent models of the disease and on our success in transferring safe molecules to clinical trials. Predicting a drug-induced response is also an attractive challenge that could be rapidly applied to patients.

Update on new pulmonary therapies

Understanding the molecular and cellular processes responsible for the development of lung disease in cystic fibrosis (CF) has led to evaluation of a broad range of new therapies within multiple therapeutic classes. For these reasons, clinical research in CF is accelerating, as new agents progress through the early stages of drug development, move into clinical trials and are offered to study patients. This review focuses on the most notable clinical trials of pulmonary therapies reported in the last year. Progress in gene therapy remains slow, but is offset by significant gains in development of cystic fibrosis transmembrane conductance regulator modulators and drugs that restore airway surface liquid. Although addressing downstream consequences of CF lung pathophysiology, the substantial burden of chronic infection makes both antibiotic and anti-inflammatory therapies a critical component of treatment, such that additional agents to manage sustained inflammation and resistant microorganisms along with improved delivery systems are needed. The pace of drug development in CF will require an expanding pool of patients willing to participate in clinical research to test new agents. Although these potential therapies will likely improve quality of life for people with CF and contribute to improved survival, it will be important to avoid adding excessively to the already high burden of treatment. If the demands on patients' time continue to grow, a decrease in adherence to effective therapies may paradoxically lead to worse outcomes and negate the benefits new treatments bring.

A CFTR chloride channel activator prevents HrpN ea-induced cell death in Arabidopsis thaliana suspension cells

Erwinia amylovora is a necrogenic bacterium that causes fire blight of the Maloideae subfamily of Roseacae, such as apple and pear. It provokes necrosis in aerial parts of susceptible host plants and the typical hypersensitive reaction in non-host plants. The secreted harpin, HrpN ea, is able by itself to induce an active cell death in non-host plants. Ion flux modulations were shown to be involved early in such processes but very few data are available on the plasma membrane ion channel activities responsible for the pathogen-induced ion fluxes. We show here that HrpN ea induces cell death in non-host Arabidopsis thaliana suspension cells. We further show that two cystic fibrosis transmembrane conductance regulator modulators, glibenclamide and bromotetramisole, can regulate anion channel activities and HrpN ea-induced cell death.