Cystic Fibrosis Transmembrane Regulator Protein Research Articles

Virtual Drug Repositioning as a Tool to Identify Natural Small Molecules That Synergize with Lumacaftor in F508del-CFTR Binding and Rescuing

Cystic fibrosis is a hereditary disease mainly caused by the deletion of the Phe 508 (F508del) of the cystic fibrosis transmembrane conductance regulator (CFTR) protein that is thus withheld in the endoplasmic reticulum and rapidly degraded by the ubiquitin/proteasome system. Cystic fibrosis remains a potentially fatal disease, but it has become treatable as a chronic condition due to some CFTR-rescuing drugs that, when used in combination, increase in their therapeutic effect due to a synergic action. Also, dietary supplementation of natural compounds in combination with approved drugs could represent a promising strategy to further alleviate cystic fibrosis symptoms. On these bases, we screened by in silico drug repositioning 846 small synthetic or natural compounds from the AIFA database to evaluate their capacity to interact with the highly druggable lumacaftor binding site of F508del-CFTR. Among the identified hits, nicotinamide (NAM) was predicted to accommodate into the lumacaftor binding region of F508del-CFTR without competing against the drug but rather stabilizing its binding. The effective capacity of NAM to bind F508del-CFTR in a lumacaftor-uncompetitive manner was then validated experimentally by surface plasmon resonance analysis. Finally, the capacity of NAM to synergize with lumacaftor increasing its CFTR-rescuing activity was demonstrated in cell-based assays. This study suggests the possible identification of natural small molecules devoid of side effects and endowed with the capacity to synergize with drugs currently employed for the treatment of cystic fibrosis, which hopefully will increase the therapeutic efficacy with lower doses.

Drug treatment of cystic fibrosis.

Cystic fibrosis is the most common life-limiting autosomal recessive condition in Australia. A defect in the cystic fibrosis transmembrane conductance regulator protein affects chloride transport across epithelial cells. Patients with cystic fibrosis produce thick sticky mucus. This causes problems in multiple organs, particularly the lungs. Cystic fibrosis modulator therapies can partially correct the underlying pathophysiology and improve chloride transport, thereby improving morbidity. Life expectancy is improving, so many patients are now developing chronic diseases associated with ageing. All health professionals should be aware that the cystic fibrosis modulator therapies are metabolised via cytochrome P450 pathways in the liver. There are therefore significant drug-drug interactions with medicines metabolised by the same pathways.

678 Role of adenylate cyclase 6 autophagy complex in the rescue and function of F508del cystic fibrosis transmembrane conductance regulator protein

678 Role of adenylate cyclase 6 autophagy complex in the rescue and function of F508del cystic fibrosis transmembrane conductance regulator protein

Modulator Combination Improves In Vitro the Microrheological Properties of the Airway Surface Liquid of Cystic Fibrosis Airway Epithelia.

Cystic fibrosis (CF) is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) protein, a plasma membrane protein expressed on the apical surface of secretory epithelia of the airways. In the airways, defective or absent function of the CFTR protein determines abnormalities of chloride and bicarbonate secretion and, in general, of the transepithelial homeostasis that lead to alterations of airway surface liquid (ASL) composition and properties. The reduction of ASL volume impairs ciliary beating with the consequent accumulation of a sticky mucus. This situation prevents normal mucociliary clearance, favoring the survival and proliferation of bacteria and contributing to the genesis of the CF pulmonary disease. We explored the potential of some CFTR modulators, namely ivacaftor, tezacaftor, elexacaftor and their combination KaftrioTM, capable of partially recovering the basic defects of the CFTR protein, to ameliorate the transepithelial fluid transport and the viscoelastic properties of the mucus when used singly or in combination. Primary human bronchial epithelial cells obtained from CF and non-CF patients were differentiated into a mucociliated epithelia in order to assess the effects of correctors tezacaftor, elexacaftor and their combination with potentiator ivacaftor on the key properties of ASL, such as fluid reabsorption, viscosity, protein content and pH. The treatment of airway epithelia bearing the deletion of a phenylalanine at position 508 (F508del) in the CFTR gene with tezacaftor and elexacaftor significantly improved the pericilial fluid composition, reducing the fluid reabsorption, correcting the ASL pH and reducing the viscosity of the mucus. KaftrioTM was more effective than single modulators in improving all the evaluated parameters, demonstrating once more that this combination recently approved for patients 6 years and older with cystic fibrosis who have at least one F508del mutation in the CFTR gene represents a valuable tool to defeat CF.

Experience of using lumacaftor/ivacaftor in children with cystic fibrosis in the Astrakhan region

Background. Targeted therapy in patients with cystic fibrosis, which aims to restore the function of the cystic fibrosis transmembrane conductance regulator protein, is currently revolutionary in the treatment of the disease. The first drug available in Russia for the treatment of patients with this genetic disease is lumacaftor/ivacaftor (Orkambi®), which was registered on December 2, 2020.The aim. To study the efficacy of lumacaftor/ivacaftor during 12 weeks of administration in children in Astrakhan region.Materials and methods. This article presents the clinical experience of Orkambi medicine use in 3 children with F508del/F508del genotype and a severe course of cystic fibrosis for 12 weeks. According to the study design, such indices as body mass index, indexes of external respiratory function, character of respiratory tract microbiota, level of chloride in sweat fluid and pancreatic elastase in feces, dynamics of biochemical blood indexes were evaluated. The study was performed within the time periods specified in the study protocol, namely, before the start of therapy, 2, 4, and 12 weeks of treatment.Results. Two patients had a decrease in sweat test values by 11 and 19 mmol/l from the baseline, a significant increase in forced vital capacity of lungs. One patient had an adverse event in the form of hepatobiliary disorders manifested by increased liver transaminase activity, which was the reason for discontinuing the drug.Conclusions. The short-term experience of using pathogenetic therapy with lumacaftor/ ivacaftor in children in the Astrakhan region demonstrated both the expected effect on chlorine channel function and the possibility of side effects, including severe ones, that can lead to withdrawal of the drug.

Cystic Fibrosis Modulator Therapies.

Cystic fibrosis (CF) is an inherited multisystemic disease that can cause progressive bronchiectasis, pancreatic endocrine and exocrine insufficiency, distal intestinal obstruction syndrome, liver dysfunction, and other disorders. Traditional therapies focused on the treatment or prevention of damage to each organ system with incremental modalities such as nebulized medications for the lungs, insulin for diabetes, and supplementation with pancreatic enzymes. However, the advent of highly effective modulator therapies that target specific cystic fibrosis transmembrane conductance regulator protein malformations resulting from individual genetic mutations has transformed the lives and prognosis for persons with CF.

Problems and achievements in the study of clinical and genetic aspects of cystic fibrosis

Cystic fibrosis is a common hereditary autosomal recessive disease characterized by pronounced genetic heterogeneity, associated clinical polymorphism, severe course and prognosis. The disease occurs worldwide in representatives of various populations and ethnic groups, with equal frequency among the male and female population. The molecular pathogenesis of the disease is based on disturbances in the synthesis, structure and function of the cystic fibrosis transmembrane conductance regulator protein (CFTR), which leads to various functional disorders in the work of chloride channels. As a result, the viscosity of secretions increases and exocrinopathy develops, which leads to disruption in the functioning of all organs and systems. The main cause of cystic fibrosis is a mutation in the CFTR gene. There are seven genetic classes of mutations in the CFTR gene, they mainly determine the severity of the disease. The main criterion in the diagnosis of cystic fibrosis is an increase in the concentration of chlorine ions in the secretion of sweat glandsof more than 60mmol/l when performing a sweat test using the classical GibsonCook method. An exception is a mutation in the CFTR 3849+10kbCT gene, which is associated with anormal or borderline sweat test result. For a long time, the treatment of patients suffering from cystic fibrosis was symptomatic, while the course of the disease remained severe and led to early mortality of patients. However, in recent decades, modern achievements in the field of studying the molecular genetic aspects of cystic fibrosis have made it possible to make a scientific breakthrough in the creation of pathogenetic therapy for this disease. New effective drugs that improve the health of patients and their quality of life have appeared. The relevance of studying the molecular mechanism of the disease for the development of a personalized approach in the treatment of cystic fibrosis is increasing, which is a promising direction on the way to gaining health for this category of patients.

Therapeutic Drug Monitoring of Ivacaftor, Lumacaftor, Tezacaftor, and Elexacaftor in Cystic Fibrosis: Where Are We Now?

Drugs modulating the cystic fibrosis transmembrane conductance regulator (CFTR) protein, namely ivacaftor, lumacaftor, tezacaftor, and elexacaftor, are currently revolutionizing the management of patients with cystic fibrosis (CF), particularly those with at least one F508del variant (up to 85% of patients). These “caftor” drugs are mainly metabolized by cytochromes P450 3A, whose enzymatic activity is influenced by environmental factors, and are sensitive to inhibition and induction. Hence, CFTR modulators are characterized by an important interindividual pharmacokinetic variability and are also prone to drug–drug interactions. However, these CFTR modulators are given at standardized dosages, while they meet all criteria for a formal therapeutic drug monitoring (TDM) program that should be considered in cases of clinical toxicity, less-than-expected clinical response, drug or food interactions, distinct patient subgroups (i.e., pediatrics), and for monitoring short-term adherence. While the information on CFTR drug exposure–clinical response relationships is still limited, we review the current evidence of the potential interest in the TDM of caftor drugs in real-life settings.

ACEing premature codon termination using anticodon-engineered sup-tRNA-based therapy

ACEing premature codon termination using anticodon-engineered sup-tRNA-based therapy

Cystic fibrosis: a comprehensive review

With almost 100 000 people affected worldwide, cystic fibrosis (CF) represents one of the most fatal inherited conditions found in Caucasian individuals, being clinically characterized by a progressive pulmonary dysfunction, pancreatic insufficiency, and male infertility. Alterations in the gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR) protein has been found to be the sole responsible for the disease, with over 2000 defects being identified since 1989. Here we present, at a basic descriptive level, the current understanding of the clinical and genetic traits of CF gene modifications, the challenges associated with the early diagnosis and management strategies but also new emerging therapies that can improve the individual’s life expectancy by enabling patient-specific treatment.

Effectiveness and Safety of Cystic Fibrosis Transmembrane Conductance Regulator Modulators in Children With Cystic Fibrosis: A Meta-Analysis.

Background and AimCystic fibrosis (CF) is a genetic disease that is difficult to treat and caused by dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Small molecules have been used to treat the symptom caused by CFTR mutations by restoring CFTR protein function. However, the data on children with CF are scarce. This meta-analysis aimed to evaluate the effectiveness and safety of this therapy in children diagnosed with CF.Materials and MethodsRelevant studies were identified through searching medical databases before April 1, 2022. The primary outcomes of ppFEV1, lung clearance index2.5 (LCI2.5), sweat chloride concentration (SwCI), and Cystic Fibrosis Questionnaire-Revised (CFQ-R) score were pooled and analyzed. The secondary outcomes were nutritional status (weight, BMI, stature, and their z-score) and adverse events under therapy.ResultsA total of twelve studies were included. Compared with the placebo group, the pooled outcome of the ppFEV1, LCI2.5, SwCI, and CFQ-R score were improved by 7.91 {[95% confidence interval (CI), 3.71–12.12], –1.00 (95% CI, –1.38 to –0.63), –35.22 (95% CI, –55.51 to –14.92), and 4.45 (95% CI, 2.31–6.59), respectively}. Compared with the placebo group, the pooled result of the change in weight was improved by 1.53 (95% CI, 0.42–2.63). All the aforementioned results were also improved in single-arm studies. No clear differences in adverse events were found between CFTR modulator therapy and the placebo group.ConclusionCFTR modulators could improve multiaspect function in children with CF and result in comparable adverse events.

Cirrhosis and Portal Hypertension in Compound Heterozygous People With Cystic Fibrosis Harboring One F508del CFTR Gene Mutation

Cirrhosis and Portal Hypertension in Compound Heterozygous People With Cystic Fibrosis Harboring One F508del CFTR Gene Mutation

Targeted quantitation of CFTR protein expression in vivo using immunoprecipitation & parallel reaction monitoring tandem mass spectrometry

Abstract Background The cystic fibrosis transmembrane conductance regulator (CFTR) protein is a low-abundance membrane protein. The dysfunction of CFTR protein is the fundamental cause of cystic fibrosis (CF), a fatal genetic disease. In recent years, the novel messenger RNA (mRNA)-based therapy shows high potential to treat CF disease, by delivering CFTR mRNA into lung epithelial cells to generate fully functional CFTR replacement protein. To evaluate mRNA drug efficacy, a targeted quantitative proteomics method is needed to estimate the expression level of mRNA encoded CFTR protein. Methods In this paper, a method combining membrane protein extraction, immunoprecipitation (IP), and nanoLC-MS/MS for quantifying CFTR in lung tissue samples was reported for the first time. Absolute quantification was performed by constructing a standard curve by spiking recombinant human CFTR protein in mouse lung tissue matrix. Results This method was qualified, with good linearity of standard curve and lower limit of quantification of human CFTR at 1.4 pg per mg tissue. The coefficient of variation of back calculated concentration of all standards and their back-calculation errors were < 20%. The CFTR expression level in mouse lungs dosed with mRNA encapsulated lipid nanoparticle (LNP), and the endogenous level in wild type human lungs were measured successfully. Conclusions The result demonstrated high sensitivity, precision and accuracy of this proteomics method for quantifying low-abundance CFTR protein in lung tissue sample.

Downregulation of epithelial sodium channel (ENaC) activity in cystic fibrosis cells by epigenetic targeting

The pathogenic mechanism of cystic fibrosis (CF) includes the functional interaction of the cystic fibrosis transmembrane conductance regulator (CFTR) protein with the epithelial sodium channel (ENaC). The reduction of ENaC activity may constitute a therapeutic option for CF. This hypothesis was evaluated using drugs that target the protease-dependent activation of the ENaC channel and the transcriptional activity of its coding genes. To this aim we used: camostat, a protease inhibitor; S-adenosyl methionine (SAM), showed to induce DNA hypermethylation; curcumin, known to produce chromatin condensation. SAM and camostat are drugs already clinically used in other pathologies, while curcumin is a common dietary compound. The experimental systems used were CF and non-CF immortalized human bronchial epithelial cell lines as well as human bronchial primary epithelial cells. ENaC activity and SCNN1A, SCNN1B and SCNN1G gene expression were analyzed, in addition to SCNN1B promoter methylation. In both immortalized and primary cells, the inhibition of extracellular peptidases and the epigenetic manipulations reduced ENaC activity. Notably, the reduction in primary cells was much more effective. The SCNN1B appeared to be the best target to reduce ENaC activity, in respect to SCNN1A and SCNN1G. Indeed, SAM treatment resulted to be effective in inducing hypermethylation of SCNN1B gene promoter and in lowering its expression. Importantly, CFTR expression was unaffected, or even upregulated, after treatments. These results open the possibility of CF patients’ treatment by epigenetic targeting.

Distinct proteostasis states drive pharmacologic chaperone susceptibility for cystic fibrosis transmembrane conductance regulator misfolding mutants.

Pharmacological chaperones represent a class of therapeutic compounds for treating protein misfolding diseases. One of the most prominent examples is the FDA-approved pharmacological chaperone lumacaftor (VX-809), which has transformed cystic fibrosis (CF) therapy. CF is a fatal disease caused by mutations in the CF transmembrane conductance regulator (CFTR). VX-809 corrects folding of F508del CFTR, the most common patient mutation, yet F508del exhibits only mild VX-809 response. In contrast, rarer mutations P67L and L206W are hyperresponsive to VX-809, while G85E is nonresponsive. Despite the clinical success of VX-809, the mechanistic origin for the distinct susceptibility of mutants remains unclear. Here we use interactomics to characterize the impact of VX-809 on proteostasis interactions of P67L and L206W and compare these with F508del and G85E. We determine that hyperresponsive mutations P67L and L206W exhibit decreased interactions with proteasomal and autophagy degradation machinery compared with F508del and G85E. We then show inhibiting the proteasome attenuates P67L and L206W VX-809 response. Our data suggest a previously unidentified but required role for protein degradation in VX-809 correction. Furthermore, we present an approach for identifying proteostasis characteristics of mutant-specific therapeutic response to pharmacological chaperones.

The use of targeted therapy lumacaftor/ivacaftor in patients with cystic fibrosis

Accepted, basic therapy of cystic fibrosis (CF), until recently, was symptomatic and aimed at slowing down pathological processes, mainly from the respiratory system and gastrointestinal tract, caused by a defect in the CFTR gene. New strategic opportunities have emerged since 2012 and are aimed at correcting a defect in a gene or its product. A mutation in the cystic fibrosis gene disrupts the function of the cystic fibrosis transmembrane conductance regulator protein (CFTR or CFTR in English transcription), which is located on the surface of the apical membrane of epithelial cells and functions as a chloride channel. The basic achievement for the new CF therapy was the discovery of small molecules that restore the processes of synthesis, transport to the membrane, or the functioning of the defective CFTR protein. The effectiveness of drugs that restore CFTR function is related to the ability of the molecules to deliver an adequate amount of the CFTR protein to the surface of the epithelial cell and/or improve its functional activity. Among them, correctors and potentiators for pharmacological modulation of ion transport are distinguished in clinical practice. Correctors are medicinal substances that allow the mutant CFTR protein to pass through the system of intracellular quality control and take the correct location on the apical membrane (with class II mutations). The action of potentiators is aimed at restoring (activating) the function of the ion channel formed by the mutant CFTR protein (class III–IV mutations). The purpose of this article is to analyze the literature sources, the results of clinical trials on the use of CFTR modulators, including combinations of a potentiator and a corrector. Their effectiveness and safety were evaluated. Literature sources (20) are used and own clinical observation is given. A positive assessment of the action of the modulator, the combination of a potentiator and a corrector, its safety and good tolerability is given. In conclusion, the place and indications for prescribing drugs of this class, the number of patients in the Russian Federation in need of such treatment are determined.

CFTR Modulator Therapy in an Individual With Cystic Fibrosis Caused by a N1303K CFTR Variant and Infected With Mycobacterium abscessus.

This report describes a case of a 15-year-old male with cystic fibrosis caused by N1303K and Q493X cystic fibrosis transmembrane conductance regulator (CFTR) protein variants. In this case, CFTR modulators including tezacaftor-ivacaftor and subsequently elexacaftor-tezacaftor-ivacaftor were used and resulted in clinical stability and improvement.

Pharmacogenomics: Relevance and opportunities for clinical pharmacology

Pharmacogenomics: Relevance and opportunities for clinical pharmacology

Efficacy and Safety of Triple Combination Cystic Fibrosis Transmembrane Conductance Regulator Modulators in Patients With Cystic Fibrosis: A Meta-Analysis of Randomized Controlled Trials

Background: Cystic fibrosis is a rare, recessive, progressive genetic disease caused by dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Small molecules have recently been developed to treat the molecular consequences of CFTR mutations and restore CFTR protein function. However, the data on triple combination therapy (mainly from Vertex Pharmaceuticals, which is most tested in clinical trials) are limited. This meta-analysis was aimed to assess the efficacy and safety of this therapy according to different mutation genotypes and comparators. Methods: Relevant publications were identified through searching several medical databases before 31 December 2021. The primary outcomes of ppFEV1, sweat chloride concentration and Cystic Fibrosis Questionnaire-Revised (CFQ-R) score were pooled and analyzed. The secondary outcomes were adverse events in triple combination therapy. Results: Six randomized controlled trials were eligible for analysis. The total outcome of the ppFEV1 change was higher with triple combination therapy than triple placebo or active control (mean difference, MD, 13.6% and 8.74%, respectively). The pooled result of sweat chloride concentrations with triple combination therapy was lower than that of triple placebo or active control (MD, −44.13 and −39.26, respectively). The pooled estimate of the CFQ-R score was higher with triple combination therapy than triple placebo or active control (MD, 19.8% and 14.63%, respectively). No clear differences in adverse events were found between triple combination therapy and the control (placebo or active control). Conclusion: CFTR modulators in triple combination achieve better clinical results than placebo and active control, and result in comparable adverse events. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021293402, identifier PROSPERO 2021 CRD42021293402.

Assays of CFTR Function In Vitro, Ex Vivo and In Vivo.

Cystic fibrosis, a multi-organ genetic disease, is characterized by abnormal function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, a chloride channel at the apical membrane of several epithelia. In recent years, therapeutic strategies have been developed to correct the CFTR defect. To evaluate CFTR function at baseline for diagnosis, or the efficacy of CFTR-restoring therapy, reliable tests are needed to measure CFTR function, in vitro, ex vivo and in vivo. In vitro techniques either directly or indirectly measure ion fluxes; direct measurement of ion fluxes and quenching of fluorescence in cell-based assays, change in transmembrane voltage or current in patch clamp or Ussing chamber, swelling of CFTR-containing organoids by secondary water influx upon CFTR activation. Several cell or tissue types can be used. Ex vivo and in vivo assays similarly evaluate current (intestinal current measurement) and membrane potential differences (nasal potential difference), on tissues from individual patients. In the sweat test, the most frequently used in vivo evaluation of CFTR function, chloride concentration or stimulated sweat rate can be directly measured. Here, we will describe the currently available bio-assays for quantitative evaluation of CFTR function, their indications, advantages and disadvantages, and correlation with clinical outcome measures.