rAAV-CFTRΔR Rescues the Cystic Fibrosis Phenotype in Human Intestinal Organoids and Cystic Fibrosis Mice

RATIONALE

Gene therapy holds promise for a curative mutation-independent treatment applicable to all patients with cystic fibrosis (CF). The various viral vector-based clinical trials conducted in the past have demonstrated safety and tolerance of different vectors, but none have led to a clear and persistent clinical benefit. Recent clinical breakthroughs in recombinant adeno-associated viral vector (rAAV)-based gene therapy encouraged us to reexplore an rAAV approach for CF.

OBJECTIVES

We evaluated the preclinical potential of rAAV gene therapy for CF to restore chloride and fluid secretion in two complementary models: intestinal organoids derived from subjects with CF and a CF mouse model, an important milestone toward the development of a clinical rAAV candidate for CF gene therapy.

METHODS

We engineered an rAAV vector containing a truncated CF transmembrane conductance regulator (CFTRΔR) combined with a short promoter (CMV173) to ensure optimal gene expression. A rescue in chloride and fluid secretion after rAAV-CFTRΔR treatment was assessed by forskolin-induced swelling in CF transmembrane conductance regulator (CFTR)-deficient organoids and by nasal potential differences in ΔF508 mice.

MEASUREMENTS AND MAIN RESULTS

rAAV-CFTRΔR transduction of human CFTR-deficient organoids resulted in forskolin-induced swelling, indicating a restoration of CFTR function. Nasal potential differences demonstrated a clear response to low chloride and forskolin perfusion in most rAAV-CFTRΔR-treated CF mice.

CONCLUSIONS

Our study provides robust evidence that rAAV-mediated gene transfer of a truncated CFTR functionally rescues the CF phenotype across the nasal mucosa of CF mice and in patient-derived organoids. These results underscore the clinical potential of rAAV-CFTRΔR in offering a cure for all patients with CF in the future.

Rattlesnake Phospholipase A2 Increases CFTR-Chloride Channel Current and Corrects ∆F508CFTR Dysfunction: Impact in Cystic Fibrosis

Deletion of Phe508 in the nucleotide binding domain (∆F508-NBD1) of the cystic fibrosis transmembrane regulator (CFTR; a cyclic AMP-regulated chloride channel) is the most frequent mutation associated with cystic fibrosis. This mutation affects the maturation and gating of CFTR protein. The search for new high-affinity ligands of CFTR acting as dual modulators (correctors/activators) presents a major challenge in the pharmacology of cystic fibrosis. Snake venoms are a rich source of natural multifunctional proteins, potential binders of ion channels. In this study, we identified the CB subunit of crotoxin from Crotalus durissus terrificus as a new ligand and allosteric modulator of CFTR. We showed that CB interacts with NBD1 of both wild type and ∆F508CFTR and increases their chloride channel currents. The potentiating effect of CB on CFTR activity was demonstrated using electrophysiological techniques in Xenopus laevis oocytes, in CFTR-HeLa cells, and ex vivo in mouse colon tissue. The correcting effect of CB was shown by functional rescue of CFTR activity after 24-h ΔF508CFTR treatments with CB. Moreover, the presence of fully glycosylated CFTR was observed. Molecular docking allowed us to propose a model of the complex involving of the ABCβ and F1-like ATP-binding subdomains of ΔF508-NBD1. Hydrogen-deuterium exchange analysis confirmed stabilization in these regions, also showing allosteric stabilization in two other distal regions. Surface plasmon resonance competition studies showed that CB disrupts the ∆F508CFTR-cytokeratin 8 complex, allowing for the escape of ∆F508CFTR from degradation. Therefore CB, as a dual modulator of ΔF508CFTR, constitutes a template for the development of new anti-CF agents.

Mutations in GAS8, a Gene Encoding a Nexin-Dynein Regulatory Complex Subunit, Cause Primary Ciliary Dyskinesia with Axonemal Disorganization

Primary ciliary dyskinesia (PCD) is an autosomal recessive disease characterized by chronic respiratory infections of the upper and lower airways, hypofertility, and, in approximately half of the cases, situs inversus. This complex phenotype results from defects in motile cilia and sperm flagella. Among the numerous genes involved in PCD, very few-including CCDC39 and CCDC40-carry mutations that lead to a disorganization of ciliary axonemes with microtubule misalignment. Focusing on this particular phenotype, we identified bi-allelic loss-of-function mutations in GAS8, a gene that encodes a subunit of the nexin-dynein regulatory complex (N-DRC) orthologous to DRC4 of the flagellated alga Chlamydomonas reinhardtii. Unlike the majority of PCD patients, individuals with GAS8 mutations have motile cilia, which, as documented by high-speed videomicroscopy, display a subtle beating pattern defect characterized by slightly reduced bending amplitude. Immunofluorescence studies performed on patients' respiratory cilia revealed that GAS8 is not required for the proper expression of CCDC39 and CCDC40. Rather, mutations in GAS8 affect the subcellular localization of another N-DRC subunit called DRC3. Overall, this study, which identifies GAS8 as a PCD gene, unveils the key importance of the corresponding protein in N-DRC integrity and in the proper alignment of axonemal microtubules in humans.

US Cystic Fibrosis Foundation and European Cystic Fibrosis Society consensus recommendations for the management of non-tuberculous mycobacteria in individuals with cystic fibrosis: executive summary

Non-tuberculous mycobacteria (NTM) are ubiquitous environmental organisms that can cause chronic pulmonary infection, particularly in individuals with pre-existing inflammatory lung disease, such as cystic fibrosis (CF). Pulmonary disease (PD) caused by NTM has emerged as a major threat to the health of individuals with CF, but remains difficult to diagnose and problematic to treat. In response to this challenge, the US Cystic Fibrosis Foundation (CFF) and the European Cystic Fibrosis Society (ECFS) convened a panel of 19 experts to develop consensus recommendations for the screening, investigation, diagnosis and management of NTM-PD in individuals with CF. PICO (population, intervention, comparison, outcome) methodology and systematic literature reviews were employed to inform draft recommendations, which were then modified to achieve consensus and subsequently circulated for public consultation within the USA and European CF communities. We have thus generated a series of pragmatic, evidence-based recommendations as an initial step in optimising management for this challenging condition.

US Cystic Fibrosis Foundation and European Cystic Fibrosis Society consensus recommendations for the management of non-tuberculous mycobacteria in individuals with cystic fibrosis

Non-tuberculous mycobacteria (NTM) are ubiquitous environmental organisms that can cause chronic pulmonary infection, particularly in individuals with pre-existing inflammatory lung disease such as cystic fibrosis (CF). Pulmonary disease caused by NTM has emerged as a major threat to the health of individuals with CF but remains difficult to diagnose and problematic to treat. In response to this challenge, the US Cystic Fibrosis Foundation (CFF) and the European Cystic Fibrosis Society (ECFS) convened an expert panel of specialists to develop consensus recommendations for the screening, investigation, diagnosis and management of NTM pulmonary disease in individuals with CF. Nineteen experts were invited to participate in the recommendation development process. Population, Intervention, Comparison, Outcome (PICO) methodology and systematic literature reviews were employed to inform draft recommendations. An anonymous voting process was used by the committee to reach consensus. All committee members were asked to rate each statement on a scale of: 0, completely disagree, to 9, completely agree; with 80% or more of scores between 7 and 9 being considered ‘good’ agreement. Additionally, the committee solicited feedback from the CF communities in the USA and Europe and considered the feedback in the development of the final recommendation statements. Three rounds of voting were conducted to achieve 80% consensus for each recommendation statement. Through this process, we have generated a series of pragmatic, evidence-based recommendations for the screening, investigation, diagnosis and treatment of NTM infection in individuals with CF as an initial step in optimising management for this challenging condition.

Lessons from a French collaborative case-control study in cystic fibrosis patients during the 2009 A/H1N1 influenza pandemy

Background

Viral infections such as influenza are thought to impact respiratory parameters and to promote infection with Pseudomonas aeruginosa in patients with cystic fibrosis (CF). However, the real morbidity of the influenza virus in CF needs to be further investigated because previous studies were only observational.

Methods

CF patients were included in a case–control study (n = 44 cases and n = 371 controls) during the 2009 pandemic A/H1N1 influenza. Cases were patients with polymerase reaction chain-confirmed influenza A/H1N1 infection. Controls did not report any influenza symptoms during the same period. Sputum colonization and lung function were monitored during 1 year after inclusion.

Results

Cases were significantly younger than controls (mean(SD) 14.9 years(11) versus 20.1 years (13.2) and significantly less frequently colonized with P. aeruginosa (34 % versus 53 %). During influenza infection, 74 % of cases had pulmonary exacerbation, 92 % had antibiotics adapted to their usual sputum colonization and 82 % were treated with oseltamivir. Two cases required lung transplantation after A/H1N1 infection (one had not received oseltamivir and the other one had been treated late). The cases received a mean number of antibiotic treatments significantly higher during the year after the influenza infection (mean(SD) 2.8 (2.4) for cases versus 1.8(2.1) for controls; p = 0.002). An age-matched comparison did not demonstrate any significant modification of bronchopulmonary bacterial colonization during the year after influenza infection nor any significant change in FEV1 at months 1, 3 and 12 after A/H1N1 infection.

Conclusions

Our results do not demonstrate any change in sputum colonization nor significant lung disease progression after pandemic A/H1N1 influenza.

Trial registration

Clinical Trials.gov registration number: NCT01499914

Genetic deletion of keratin 8 corrects the altered bone formation and osteopenia in a mouse model of cystic fibrosis

Patients with cystic fibrosis (CF) display low bone mass and alterations in bone formation. Mice carrying the F508del genetic mutation in the cystic fibrosis conductance regulator (Cftr) gene display reduced bone formation and decreased bone mass. However, the underlying molecular mechanisms leading to these skeletal defects are unknown, which precludes the development of an efficient anti-osteoporotic therapeutic strategy. Here we report a key role for the intermediate filament protein keratin 8 (Krt8), in the osteoblast dysfunctions in F508del-Cftr mice. We found that murine and human osteoblasts express Cftr and Krt8 at low levels. Genetic studies showed that Krt8 deletion (Krt8(-/-)) in F508del-Cftr mice increased the levels of circulating markers of bone formation, corrected the expression of osteoblast phenotypic genes, promoted trabecular bone formation and improved bone mass and microarchitecture. Mechanistically, Krt8 deletion in F508del-Cftr mice corrected overactive NF-κB signaling and decreased Wnt-β-catenin signaling induced by the F508del-Cftr mutation in osteoblasts. In vitro, treatment with compound 407, which specifically disrupts the Krt8-F508del-Cftr interaction in epithelial cells, corrected the abnormal NF-κB and Wnt-β-catenin signaling and the altered phenotypic gene expression in F508del-Cftr osteoblasts. In vivo, short-term treatment with 407 corrected the altered Wnt-β-catenin signaling and bone formation in F508del-Cftr mice. Collectively, the results show that genetic or pharmacologic targeting of Krt8 leads to correction of osteoblast dysfunctions, altered bone formation and osteopenia in F508del-Cftr mice, providing a therapeutic strategy targeting the Krt8-F508del-CFTR interaction to correct the abnormal bone formation and bone loss in cystic fibrosis.

[NUTRITIONAL STATUS ASSESSMENT IN PATIENTS WITH CYSTIC FIBROSIS]

Prognosis of cystic fibrosis has been largely modified over the past 30 years. Optimization of nutrition is one of the most important contributing factors of this improvement. Nutritional defect result from the conjunction of loss of calories, maldigestion, hypercatabolism and insufficient intake. Pancreatic opotherapy and ADEK vitamin administration is mandatory in pancreatic insufficient patients. Nutritional status must be evaluated at each clinics to detect nutritional defect as early as possible. Nutritional intake must be hypercaloric, normalipidic and adapted to the tastes of the patient. The clinician must be aware of at risk nutritional period: first year of life, puberty, infectious exacerbation, respiratory worsening and diabetes, In neonatal screened babies, recovery of birth weight percentile must be targeted at 6 months, and for the height must be in accordance to genetic height at 2 years. In all cases it is mandatory to treat denutrition by oral supplementation and if necessay enteral nutrition.

An unexpected effect of TNF-α on F508del-CFTR maturation and function

Cystic fibrosis (CF) is a multifactorial disease caused by mutations in the cystic fibrosis transmembrane conductance regulator gene ( CFTR), which encodes a cAMP-dependent Cl (-) channel. The most frequent mutation, F508del, leads to the synthesis of a prematurely degraded, otherwise partially functional protein. CFTR is expressed in many epithelia, with major consequences in the airways of patients with CF, characterized by both fluid transport abnormalities and persistent inflammatory responses. The relationship between the acute phase of inflammation and the expression of wild type (WT) CFTR or F508del-CFTR is poorly understood. The aim of the present study was to investigate this effect. The results show that 10 min exposure to TNF-alpha (0.5-50ng/ml) of F508del-CFTR-transfected HeLa cells and human bronchial cells expressing F508del-CFTR in primary culture (HBE) leads to the maturation of F508del-CFTR and induces CFTR chloride currents. The enhanced CFTR expression and function upon TNFα is sustained, in HBE cells, for at least 24 h. The underlying mechanism of action involves a protein kinase C (PKC) signaling pathway, and occurs through insertion of vesicles containing F508del-CFTR to the plasma membrane, with TNFα behaving as a corrector molecule. In conclusion, a novel and unexpected action of TNFα has been discovered and points to the importance of systematic studies on the roles of inflammatory mediators in the maturation of abnormally folded proteins in general and in the context of CF in particular.

Effect of ivacaftor treatment in patients with cystic fibrosis and the G551D-CFTR mutation: patient-reported outcomes in the STRIVE randomized, controlled trial

BACKGROUND

Cystic fibrosis (CF) is an inherited, rare autosomal recessive disease that results in chronically debilitating morbidities and high premature mortality. We evaluated how ivacaftor treatment affected CF symptoms, functioning, and well-being, as measured by the Cystic Fibrosis Questionnaire-Revised (CFQ-R), a widely-used patient-reported outcome (PRO) measure.

METHODS

STRIVE, a double-blind, placebo-controlled randomized trial, evaluated ivacaftor (150 mg) in CF patients aged 12+ with the G551D-CFTR mutation for 48 weeks. Treatment effect analysis used a mixed-effects repeated measures model. Treatment benefit analyses applied the cumulative distribution function and a categorical analysis of change scores ("improvement," "no change," or "decline"). Content-based interpretation examined treatment effect on specific item responses.

RESULTS

Data from 152 patients with a baseline CFQ-R assessment were analyzed. The treatment effect analysis favored treatment with ivacaftor over placebo on the Body Image, Eating, Health Perceptions, Physical Functioning, Respiratory, Social Functioning, Treatment Burden, and Vitality scales. Findings were supported by the analysis of categorical change. On all CFQ-R scales, the percentage of patients who improved was greater for ivacaftor. In the content-based analysis, the treatment benefit was characterized by better scores across a broad range of domains.

CONCLUSIONS

Results illustrate broad benefits of ivacaftor treatment across many domains: respiratory symptoms, physical and social functioning, health perceptions, and vitality, as measured by the CFQ-R. The breadth of improvements reflects the systemic mechanism of action of ivacaftor compared to other therapies. Findings support the patient-reported value of ivacaftor treatment in this patient population.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00909532.

Persistent Bordetella bronchiseptica infection in a child with cystic fibrosis: Relationship to bacterial phenotype

Bordetella bronchiseptica is an opportunistic bacteria infecting the respiratory tract of patients with cystic fibrosis. We present a case of B. bronchiseptica chronic pulmonary infection and documentation of some phenotypic attributes of the clinical isolates allowing the microorganism to induce progressive respiratory degradation and chronic sputum colonization. We recommend implementing adequate treatment aiming eradication from the first isolation of this bacterium. We advise for practices that minimize opportunities for zoonotic transmission of B. bronchiseptica from family pets.

European Cystic Fibrosis Society Standards of Care: Best Practice guidelines

Specialised CF care has led to a dramatic improvement in survival in CF: in the last four decades, well above what was seen in the general population over the same period. With the implementation of newborn screening in many European countries, centres are increasingly caring for a cohort of patients who have minimal lung disease at diagnosis and therefore have the potential to enjoy an excellent quality of life and an even greater life expectancy than was seen previously. To allow high quality care to be delivered throughout Europe, a landmark document was published in 2005 that sets standards of care. Our current document builds on this work, setting standards for best practice in key aspects of CF care. The objective of our document is to give a broad overview of the standards expected for screening, diagnosis, pre-emptive treatment of lung disease, nutrition, complications, transplant/end of life care and psychological support. For comprehensive details of clinical care of CF, references to the most up to date European Consensus Statements, Guidelines or Position Papers are provided in Table 1. We hope that this best practice document will be useful to clinical teams both in countries where CF care is developing and those with established CF centres.

Long-term safety and efficacy of ivacaftor in patients with cystic fibrosis who have the Gly551Asp-CFTR mutation: a phase 3, open-label extension study (PERSIST)

BACKGROUND

Ivacaftor, a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator, is approved for the treatment of patients with cystic fibrosis aged 6 years or older with Gly551Asp-CFTR. We assessed the safety and efficacy of ivacaftor during 96 weeks of PERSIST in patients with cystic fibrosis who completed a previous 48-week, placebo-controlled trial of the drug (STRIVE or ENVISION).

METHODS

In this phase 3, open-label extension study, patients received ivacaftor 150 mg every 12 h in addition to their prescribed cystic fibrosis therapies. Patients who received placebo in their previous study initiated ivacaftor in this extension study. Patients were eligible if they had a Gly551Asp-CFTR mutation on at least one allele. The primary objective was to assess the long-term safety profile of ivacaftor as assessed by adverse events, clinical laboratory assessments, electrocardiograms, vital signs, and physical examination; secondary measures included change in forced expiratory volume in one second (FEV1), weight, and pulmonary exacerbations. This study is registered with ClinicalTrials.gov, number NCT01117012 and EudraCT, number 2009-012997-11.

FINDINGS

Between July 8, 2010, and April 8, 2013, 144 adolescents/adults (≥12 years) from STRIVE and 48 children (6-11 years) from ENVISION were enrolled. Across both trials, 38 (20%) patients had a serious adverse event during the first 48 weeks and 44 (23%) during the subsequent 48 weeks. Two adults (1%) and one child (<1%) discontinued because of adverse events. The most common adverse events were pulmonary exacerbation, cough, and upper respiratory tract infection. Patients previously treated with ivacaftor had sustained improvements in FEV1, weight, and rate of pulmonary exacerbations for up to 144 weeks of treatment. Among adolescents/adults and children who previously received ivacaftor, absolute change in FEV1 at week 96 (144 weeks ivacaftor) was 9·4 and 10·3 % points and absolute increase in weight was 4·1 kg and 14·8 kg, respectively. For adolescents/adults only, the pulmonary exacerbation rate remained suppressed compared with that of patients who received placebo in the placebo-controlled study.

INTERPRETATION

At 144 weeks of treatment, ivacaftor was well tolerated, with no new safety concerns. Ivacaftor also provided durable effects for 144 weeks in patients who had received active treatment in the placebo-controlled study. Those patients who previously received placebo had improvements comparable to those of patients treated with ivacaftor in the placebo-controlled study.

FUNDING

Vertex Pharmaceuticals Inc.