oxadiazoles and Cystic-Fibrosis

The treatment of cystic fibrosis (CF) with CF transmembrane conductance regulator (CFTR) modulators continues to develop at a fast pace. These compounds are potentially disease modifying but are only available to certain patient subsets based on genotype. This review discusses the role of theratyping in CF and the potential to assess all patients' response to current and emerging therapies.. There are limitations to treatment determined by mutation, as variable clinical response to CFTR modulators has been observed within the same genotype. Patients with rare mutations not currently licensed for CFTR modulator therapy have demonstrated response to these medications. Patient-specific cellular models called organoids can be used to demonstrate response to different CFTR modulators in vitro prior to their clinical application and represent a method of theratyping.. Theratyping charts patients' clinical response to different treatments on an individual basis. This overcomes the limitations of genotype being used to predict response to individual therapies and includes all patients regardless of mutation. The use of organoids in high throughput screening allows numerous compounds to be tested on patient-specific tissue preclinically. This could lead to the extension of theratyping beyond CFTR modulators.

Topics: Aminophenols; Aminopyridines; Benzodioxoles; Chloride Channel Agonists; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Drug Combinations; Gene Editing; Genetic Therapy; Genotype; Humans; Indoles; Mutation; Organoids; Oxadiazoles; Precision Medicine; Quinolones

Topics: Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Humans; Mutation; Oxadiazoles; Randomized Controlled Trials as Topic; Risk Assessment; Treatment Outcome

Cystic fibrosis (CF) is one of the most common genetically-acquired life-limiting conditions worldwide. The underlying defect is dysfunction of the cystic fibrosis transmembrane-conductance regulator (CFTR) which leads to progressive lung disease and other multi-system effects. Around 10% of people with CF have a class I nonsense mutation that leads to production of shortened CFTR due to a premature termination codon (PTC). Areas covered: We discuss the discovery of the small-molecule drug ataluren, which in vitro has been shown to allow read-through of PTCs and facilitate synthesis of full-length protein. We review clinical studies that have been performed involving ataluren in CF. Early-phase short-term cross-over studies showed improvement in nasal potential difference. A follow-up phase III randomised controlled trial did not show a significant difference for the primary outcome of lung function, however a post-hoc analysis suggested possible benefit in patients not receiving tobramycin. A further randomised controlled trial in patients not receiving tobramycin has been reported as showing no benefit but has not yet been published in full peer-reviewed form. Expert opinion: A small-molecule approach to facilitate read-through of PTCs in nonsense mutations makes intuitive sense. However, at present there is no high-quality evidence of clinical efficacy for ataluren in people with CF.

Topics: Codon, Nonsense; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Drug Discovery; Humans; Oxadiazoles; Randomized Controlled Trials as Topic; Treatment Outcome

Cystic fibrosis is a common life-shortening genetic disorder in the Caucasian population (less common in other ethnic groups) caused by the mutation of a single gene that codes for the production of the cystic fibrosis transmembrane conductance regulator protein. This protein coordinates the transport of salt (and bicarbonate) across cell surfaces and the mutation most notably affects the airways. In the lungs of people with cystic fibrosis, defective protein results in a dehydrated surface liquid and compromised mucociliary clearance. The resulting thick mucus makes the airway prone to chronic infection and inflammation, which consequently damages the structure of the airways, eventually leading to respiratory failure. Additionally, abnormalities in the cystic fibrosis transmembrane conductance regulator protein lead to other systemic complications including malnutrition, diabetes and subfertility.Five classes of mutation have been described, depending on the impact of the mutation on the processing of the cystic fibrosis transmembrane conductance regulator protein in the cell. In class I mutations, the presence of premature termination codons prevents the production of any functional protein resulting in a severe cystic fibrosis phenotype. Advances in the understanding of the molecular genetics of cystic fibrosis has led to the development of novel mutation-specific therapies. Therapies targeting class I mutations (premature termination codons) aim to mask the abnormal gene sequence and enable the normal cellular mechanism to read through the mutation, potentially restoring the production of the cystic fibrosis transmembrane conductance regulator protein. This could in turn make salt transport in the cells function more normally and may decrease the chronic infection and inflammation that characterises lung disease in people with cystic fibrosis.. To evaluate the benefits and harms of ataluren and similar compounds on clinically important outcomes in people with cystic fibrosis with class I mutations (premature termination codons).. We searched the Cochrane Cystic Fibrosis Trials Register which is compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched the reference lists of relevant articles. Last search of Group's register: 24 October 2016.We searched clinical trial registries maintained by the European Medicines Agency, the US National Institutes of Health and the WHO. Last search of clinical trials registries: 28 November 2016.. Randomised controlled trials of parallel design comparing ataluren and similar compounds (specific therapies for class I mutations) with placebo in people with cystic fibrosis who have at least one class I mutation. Cross-over trials were reviewed individually to evaluate whether data from the first treatment arm could be included. We excluded trials that combined therapies for premature termination codon class I mutations with other mutation-specific therapies.. The authors independently assessed the risk of bias and extracted data from the included trial; they contacted trial authors for additional data.. Our searches identified 28 references to eight trials; five trials were excluded (three were cross-over and one was not randomised and one did not have relevant outcomes), one cross-over trial is awaiting classification pending provision of data and one trial is ongoing. The included parallel randomised controlled trial compared ataluren to placebo for a duration of 48 weeks in 238 participants (age range 6 to 53 years) with cystic fibrosis who had at least one nonsense mutation (a type of class I mutation).The quality of evidence and risk of bias assessments for the trial were moderate overall. Random sequence generation, allocation concealment and blinding of trial personnel were well-documented; participant blinding was less clear. Some participant data were excluded from the analysis. The trial was assessed as high risk of bias for selective outcome reporting, especially when reporting on the trial's post hoc subgroup of participants by chronic inhaled antibiotic use.The trial was sponsored by PTC Therapeutics Incorporated with grant support by the Cystic Fibrosis Foundation, the Food and Drug Administration's Office of Orphan Products Development and the National Institutes of Health (NIH).The trial reported no significant difference between treatment groups in quality of life, assessed by the Cystic Fibrosis Questionnaire-Revised respiratory domain score and no improvement in respiratory function measures (mean difference of relative change in forced expiratory volume at one second 2.97% (95% confidence interval -0.58 to 6.52)). Ataluren was associated with a significantly higher rate of episodes of renal impairment, risk ratio 17.70 (99% confidence interval 1.28 to 244.40). The trial reported no significant treatment effect for ataluren for the review's secondary outcomes: pulmonary exacerbation; computerised tomography score; weight; body mass index; and sweat chloride. No deaths were reported in the trial.A post hoc subgroup analysis of participants not receiving chronic inhaled tobramycin (n = 146) demonstrated favourable results for ataluren (n = 72) for relative change in % predicted forced expiratory volume at one second and pulmonary exacerbation rate. Participants receiving chronic inhaled tobramycin appeared to have a reduced rate of pulmonary exacerbation compared to those not receiving chronic inhaled tobramycin. This drug interaction was not anticipated and may affect the interpretation of the trial results.. There is currently insufficient evidence to determine the effect of ataluren as a therapy for people with cystic fibrosis with class I mutations. Future trials should carefully assess for adverse events, notably renal impairment and consider the possibility of drug interactions. Cross-over trials should be avoided given the potential for the treatment to change the natural history of cystic fibrosis.

Topics: Adolescent; Adult; Anti-Bacterial Agents; Child; Codon, Nonsense; Cystic Fibrosis; Disease Progression; Female; Humans; Male; Middle Aged; Oxadiazoles; Quality of Life; Randomized Controlled Trials as Topic; Tobramycin

Cystic fibrosis (CF) is a monogenic autosomal recessive disorder that affects about 70,000 people worldwide. The clinical manifestations of the disease are caused by defects in the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The discovery of the CFTR gene in 1989 has led to a sophisticated understanding of how thousands of mutations in the CFTR gene affect the structure and function of the CFTR protein. Much progress has been made over the past decade with the development of orally bioavailable small molecule drugs that target defective CFTR proteins caused by specific mutations. Furthermore, there is considerable optimism about the prospect of gene replacement or editing therapies to correct all mutations in cystic fibrosis. The recent approvals of ivacaftor and lumacaftor represent the genesis of a new era of precision medicine in the treatment of this condition. These drugs are having a positive impact on the lives of people with cystic fibrosis and are potentially disease modifying. This review provides an update on advances in our understanding of the structure and function of the CFTR, with a focus on state of the art targeted drugs that are in development.

Topics: Aminophenols; Aminopyridines; Benzodioxoles; Clinical Trials as Topic; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Drug Discovery; Drug Therapy, Combination; Forced Expiratory Volume; Forecasting; Genetic Therapy; Homozygote; Humans; Molecular Targeted Therapy; Mutation; Oxadiazoles; Phosphodiesterase 5 Inhibitors; Practice Guidelines as Topic; Precision Medicine; Quinolones

According to previous reports, nearly one in 10 genetic diseases are caused by nonsense mutations around the world. Nonsense mutations lead to premature transcription terminations in cells, which in turn generate non-functional, truncated proteins. In recent years, read-through drugs are playing increasing prominent roles in the researches related to genetic diseases caused by nonsense mutations. However, due to the fact that the mechanisms lying behind translation termination still remain to be elucidated, the mechanistic research and clinical application of read-through drugs are facing new challenges. This review mainly discusses about the pathogenesis of genetic diseases caused by nonsense mutations, and then introduces the current clinical application of read-through drugs. Finally, we display some problems that remain to be solved and propose some possible coping strategies.

Topics: Aminoglycosides; Codon, Nonsense; Cystic Fibrosis; Genetic Diseases, Inborn; Humans; Muscular Dystrophy, Duchenne; Oxadiazoles

Cystic fibrosis (CF) is the most common genetic life-shortening condition in Caucasians. Despite being a multi-organ disease, CF is classically diagnosed by symptoms of acute/chronic respiratory disease, with persistent pulmonary infections and mucus plugging of the airways and failure to thrive. These multiple symptoms originate from dysfunction of the CF transmembrane conductance regulator (CFTR) protein, a channel that mediates anion transport across epithelia. Indeed, establishment of a definite CF diagnosis requires proof of CFTR dysfunction, commonly through the so-called sweat Cl(-) test. Many drug therapies, including mucolytics and antibiotics, aim to alleviate the symptoms of CF lung disease. However, new therapies to modulate defective CFTR, the basic defect underlying CF, have started to reach the clinic, and several others are in development or in clinical trials. The novelty of these therapies is that, besides targeting the basic defect underlying CF, they are mutation specific. Indeed, even this monogenic disease is influenced by a large number of different genes and biological pathways as well as by environmental factors that are difficult to assess. Accordingly, every person with CF is unique and so functional assessment of patients' tissues ex vivo is key for diagnosing and predicting the severity of this disease. Of note, such assessment will also be crucial to assess drug responses, in order to effectively treat all CF patients. It is not because it is a monogenic disorder that personalized treatment for CF is much easier than for complex disorders.

Topics: Aminoglycosides; Aminophenols; Anti-Bacterial Agents; Anti-Inflammatory Agents; Biomarkers; Codon, Nonsense; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Evidence-Based Medicine; Frameshift Mutation; Genistein; Humans; Oxadiazoles; Phenotype; Precision Medicine; Purinergic Antagonists; Quinolones; Rare Diseases; Severity of Illness Index; Sweat Glands

Therapy for cystic fibrosis (CF) has progressed during the past several decades. Much of this progress is because of advances in genetic testing to precisely identify the underlying cause of CF transmembrane regulator (CFTR) dysfunction. However, with more than 1900 mutations that can produce a faulty CFTR, the management of CF can remain a challenge. Several innovative drugs recently approved by the Food and Drug Administration, termed genetic modulators, target the underlying disease by modulating the CFTR defect. This review provides physicians with an established simple classification scheme to guide their use of these drugs. The treatment challenge of 1900 CFTR mutations has been simplified into 6 physiologic classes, each paired with an available therapy to offer patients the most functional improvement. Drug therapy monitoring, adverse effects, and indications for discontinuation must also be considered.

Topics: Aminophenols; Aminopyridines; Benzodioxoles; Chloride Channel Agonists; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; DNA; DNA Mutational Analysis; Humans; Mutation; Oxadiazoles; Quinolones

We present the recent therapeutic advances in the cystic fibrosis care. It concerns improvements in symptomatic treatment with the development of dry powder inhaled antibiotics that improved quality of life, and innovative treatments namely the modulators of the cystic fibrosis transmembrane protein conductance regulator (CFTR), molecules which act specifically at the level of the defective mechanisms implied in the disease. The life expectancy of cystic fibrosis patients born after 2000, is estimated now to be about 50 years. This improvement of survival was obtained with the organization of the care within the specialized centers for cystic fibrosis (Centre de ressource et de compétences de la mucoviscidose) and remains still based on heavy symptomatic treatments. Dry powder inhaled antibiotics constitute a significant time saving for patients to whom all the care can achieve two hours daily. Since 2012, the modulators of CFTR, molecules allowing a pharmacological approach targeted according to the type of the mutations, allows a more specific approach of the disease. Ivacaftor (Kalydeco(®)) which potentialises the function of the CFTR protein expressed on the cellular surface is now available for patients with the G551D mutation. Lumacaftor is going to be tested in association with ivacaftor in patients with the F508del mutation, that is present in at least 75% of the patients. The ataluren which allows the production of a functional protein CFTR in patients with a no sense mutation is the third representing of this new therapeutic class. We presently have numerous symptomatic treatments for the cystic fibrosis care. The development of CFTR modulators, today available to a restricted number of patients treated with ivacaftor represents a very promising therapeutic avenue. It will represent probably the first step to a personalized treatment according to CFTR genotype.

Topics: Aminophenols; Aminopyridines; Benzodioxoles; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Humans; Mutation; Oxadiazoles; Quinolones

Cystic fibrosis (CF) is a genetic disease due to a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel in epithelial cells. There are about 1900 mutations, divided in several groups, for example, stop mutations, mutations affecting the permeability of the channel, and mutations in which the mutated CFTR is recognized as abnormal and destroyed. Pharmacological treatment has become possible for stop mutations (about 10% of the patients), and for a rare mutation affecting channel permeability. For the majority of patients, however, that have a mutation in which the mutated CFTR is destroyed on its way to the cell membrane, research is still in progress, although a number of compounds have been identified that (at least partly) corrects the error in chloride transport.

Topics: Chlorides; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Humans; Mutation; Nitric Oxide; Oxadiazoles; S-Nitrosoglutathione

Cystic fibrosis is caused by dysfunction or deficiency of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, an epithelial chloride channel that has a key role in maintaining homoeostasis of the airway surface liquid layer in the lungs. More than 1900 CFTR mutations that might result in a disease phenotype have been identified; these can be grouped into classes on the basis of their effect on CFTR protein production, trafficking, function, and stability. In the past 2 years, landmark clinical trials have shown that correction of CFTR function leads to substantial clinical benefit for individuals with cystic fibrosis. These findings are ushering in a new era of cystic fibrosis treatments designed to correct the underlying CFTR defect caused by different mutation classes. With analysis of continuing trials and available patient registries, here we assess mutation types and the number and geographical distribution of patients who are likely to benefit from CFTR-correcting treatment.

Topics: Aminophenols; Biological Transport; Clinical Trials as Topic; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Forecasting; Humans; Mutation; Oxadiazoles; Precision Medicine; Protein Biosynthesis; Quinolones; Respiratory System Agents; Treatment Outcome

Premature termination codons (PTCs) are a cause of numerous genetic disorders spanning diseases that affect children and adults, and are produced by base pair substitutions that create abnormal stop codons within the open reading frame. Several ribosome-binding drugs, including select aminoglycosides and synthetic novel small molecules, induce 'translational readthrough' of PTCs, restoring full-length functional protein in a number of preclinical and clinical settings. In this review, we examine the mechanistic underpinnings of PTC suppression, including the nature of the interactions between agents that suppress PTCs and the eukaryotic ribosome regulation of transcript levels in eukaryotic cells, and the importance of the mRNA context in suppression of PTCs. We also examine results from proof-of-concept studies in preclinical model systems and clinical trials (with a focus on PTC124). Several of the published studies in cystic fibrosis have reported improvements in cystic fibrosis transmembrane conductance regulator (CFTR) biomarkers during short-term evaluation, including topical and systemic aminoglycoside treatment, and oral dosing with PTC124. These results, coupled with our improved understanding of how translation termination is regulated at PTCs, will help guide future directions of research involving this innovative treatment strategy for genetic diseases.

Topics: Aminoglycosides; Animals; Clinical Trials as Topic; Codon, Nonsense; Cystic Fibrosis; Genetic Diseases, Inborn; Humans; Muscular Dystrophies; Oxadiazoles; Protein Biosynthesis

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.

Topics: Aminophenols; Aminopyridines; Anti-Infective Agents; Anti-Inflammatory Agents; Benzodioxoles; Biomarkers; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Genetic Markers; Genetic Therapy; Humans; Mutation; Oxadiazoles; Quinolones; Respiratory System Agents; Saline Solution, Hypertonic

Approximately one-third of alleles causing genetic diseases carry premature termination codons (PTCs), which lead to the production of truncated proteins. The past decade has seen considerable interest in therapeutic approaches aimed at readthrough of in-frame PTCs to enable synthesis of full-length proteins. However, attempts to readthrough PTCs in many diseases resulted in variable effects. Here, we focus on the efforts of such therapeutic approaches in cystic fibrosis and Duchenne muscular dystrophy and discuss the factors contributing to successful readthrough and how the nonsense-mediated mRNA decay (NMD) pathway regulates this response. A deeper understanding of the molecular basis for variable response to readthrough of PTCs is necessary so that appropriate therapies can be developed to treat many human genetic diseases caused by PTCs.

Topics: Alleles; Codon, Nonsense; Cystic Fibrosis; Genetic Diseases, Inborn; Humans; Models, Biological; Muscular Dystrophy, Duchenne; Oxadiazoles; RNA Stability; RNA, Messenger

Although the gene for cystic fibrosis was discovered in 1989, a definitive cure remains elusive for this deadly orphan disease. Advances in nutritional rehabilitation, antibiotics, mucolytics and delivery of care have improved survival to a median age of 37.5 years; however, the psychosocial, personal and financial burdens of this lifelong chronic illness remain considerable. The current portfolio of investigational therapeutics is explored here and placed in a context of therapeutic target and predicted clinical benefit. Partnership between large and small pharma, the Cystic Fibrosis Foundation and academia should be fostered to accelerate therapeutic development.

Topics: Animals; Chloride Channel Agonists; Chloride Channels; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Drugs, Investigational; Humans; Oxadiazoles

Ataluren was developed for potential treatment of nonsense-mutation cystic fibrosis (CF). A previous phase 3 ataluren study failed to meet its primary efficacy endpoint, but post-hoc analyses suggested that aminoglycosides may have interfered with ataluren's action. Thus, this subsequent trial (NCT02139306) was designed to assess the efficacy and safety of ataluren in patients with nonsense-mutation CF not receiving aminoglycosides.. Eligible subjects with nonsense-mutation CF (aged ≥6 years; percent predicted (pp) FEV. 279 subjects were enrolled; 138 subjects in the ataluren arm and 136 in the placebo arm were evaluable for efficacy. Absolute ppFEV. Neither ppFEV

Topics: Administration, Oral; Codon, Nonsense; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Double-Blind Method; Drug Monitoring; Female; Forced Expiratory Volume; Humans; Male; Oxadiazoles; Respiratory Function Tests; Symptom Flare Up; Treatment Outcome

A phase 3 randomized double blind controlled, trial in 238 people with cystic fibrosis (CF) and at least one nonsense mutation (nmCF) investigated the effect of ataluren on FEV1. The study was of 48 weeks duration and failed to meet its primary endpoint. Unexpectedly, while FEV1 declined, chest computed tomography (CT) scores using the Brody-II score as secondary outcome measures did not show progression in the placebo group. Based on this observation it was concluded that the role of CT scans in CF randomized clinical trials was limited. However, more sensitive scoring systems were developed over the last decade warranting a reanalysis of this unique dataset. The aim of our study was to reanalyse all chest CT scans, obtained in the ataluren phase 3 study, using 2 independent scoring systems to characterize structural lung disease in this cohort and to compare progression of structural lung disease over the 48 weeks between treatment arms. 391 study CT scans from 210 patients were reanalysed in random order by 2 independent observers using the CF-CT and Perth-Rotterdam Annotated Grid Morphometric Analysis for CF (PRAGMA-CF) scoring systems. CF-CT and PRAGMA-CF subscores were expressed as %maximal score and %total lung volume, respectively. PRAGMA-CF subscores %Disease (p = 0.008) and %Mucus Plugging (p = 0.029) progressed over 48 weeks. CF-CT subscores did not show progression. There was no difference in progression of structural lung disease between treatment arm and placebo independent of tobramycin use. PRAGMA-CF Chest CT scores can be used as an outcome measure to study the effect of potential disease modifying drugs in CF on lung structure.

Topics: Adolescent; Adult; Child; Cystic Fibrosis; Disease Progression; Double-Blind Method; Female; Forced Expiratory Volume; Humans; Linear Models; Male; Outcome Assessment, Health Care; Oxadiazoles; Thorax; Tomography, X-Ray Computed; Young Adult

Ataluren was developed to restore functional protein production in genetic disorders caused by nonsense mutations, which are the cause of cystic fibrosis in 10% of patients. This trial was designed to assess the efficacy and safety of ataluren in patients with nonsense-mutation cystic fibrosis.. This randomised, double-blind, placebo-controlled, phase 3 study enrolled patients from 36 sites in 11 countries in North America and Europe. Eligible patients with nonsense-mutation cystic fibrosis (aged ≥ 6 years; abnormal nasal potential difference; sweat chloride >40 mmol/L; forced expiratory volume in 1 s [FEV1] ≥ 40% and ≤ 90%) were randomly assigned by interactive response technology to receive oral ataluren (10 mg/kg in morning, 10 mg/kg midday, and 20 mg/kg in evening) or matching placebo for 48 weeks. Randomisation used a block size of four, stratified by age, chronic inhaled antibiotic use, and percent-predicted FEV1. The primary endpoint was relative change in percent-predicted FEV1 from baseline to week 48, analysed in all patients with a post-baseline spirometry measurement. This study is registered with ClinicalTrials.gov, number NCT00803205.. Between Sept 8, 2009, and Nov 30, 2010, 238 patients were randomly assigned, of whom 116 in each treatment group had a valid post-baseline spirometry measurement. Relative change from baseline in percent-predicted FEV1 did not differ significantly between ataluren and placebo at week 48 (-2.5% vs -5.5%; difference 3.0% [95% CI -0.8 to 6.3]; p=0.12). The number of pulmonary exacerbations did not differ significantly between treatment groups (rate ratio 0.77 [95% CI 0.57-1.05]; p=0.0992). However, post-hoc analysis of the subgroup of patients not using chronic inhaled tobramycin showed a 5.7% difference (95% CI 1.5-10.1) in relative change from baseline in percent-predicted FEV1 between the ataluren and placebo groups at week 48 (-0.7% [-4.0 to 2.1] vs -6.4% [-9.8 to -3.7]; nominal p=0.0082), and fewer pulmonary exacerbations in the ataluern group (1.42 events [0.9-1.9] vs 2.18 events [1.6-2.7]; rate ratio 0.60 [0.42-0.86]; nominal p=0.0061). Safety profiles were generally similar for ataluren and placebo, except for the occurrence of increased creatinine concentrations (ie, acute kidney injury), which occurred in 18 (15%) of 118 patients in the ataluren group compared with one (<1%) of 120 patients in the placebo group. No life-threatening adverse events or deaths were reported in either group.. Although ataluren did not improve lung function in the overall population of nonsense-mutation cystic fibrosis patients who received this treatment, it might be beneficial for patients not taking chronic inhaled tobramycin.. PTC Therapeutics, Cystic Fibrosis Foundation, US Food and Drug Administration's Office of Orphan Products Development, and the National Institutes of Health.

Topics: Acute Kidney Injury; Adolescent; Adult; Anti-Bacterial Agents; Child; Chlorides; Codon, Nonsense; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Disease Progression; Double-Blind Method; Female; Forced Expiratory Volume; Humans; Male; Middle Aged; Oxadiazoles; Sweat; Tobramycin; Young Adult

In a subset of patients with cystic fibrosis (CF), nonsense mutations (premature stop codons) disrupt production of full-length, functional CF transmembrane conductance regulator (CFTR). Ataluren (PTC124) allows ribosomal readthrough of premature stop codons in mRNA. We evaluated drug activity and safety in patients with nonsense mutation CF who took ataluren three times daily (morning, midday and evening) for 12 weeks at either a lower dose (4, 4 and 8 mg·kg(-1)) or higher dose (10, 10 and 20 mg·kg(-1)). The study enrolled 19 patients (10 males and nine females aged 19-57 yrs; dose: lower 12, higher seven) with a classic CF phenotype, at least one CFTR nonsense mutation allele, and an abnormal nasal total chloride transport. Both ataluren doses were similarly active, improving total chloride transport with a combined mean change of -5.4 mV (p<0.001), and on-treatment responses (at least -5 mV improvement) and hyperpolarisations (values more electrically negative than -5 mV) in 61% (p<0.001) and 56% (p = 0.002) of patients. CFTR function was greater with time and was accompanied by trends toward improvements in pulmonary function and CF-related coughing. Adverse clinical and laboratory findings were uncommon and usually mild. Chronic ataluren administration produced time-dependent improvements in CFTR activity and clinical parameters with generally good tolerability.

Topics: Adult; Codon, Nonsense; Codon, Terminator; Cough; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Female; Humans; Male; Middle Aged; Oxadiazoles; Prognosis; Ribosomes; Treatment Outcome

Nonsense (premature stop codon) mutations in mRNA for the cystic fibrosis transmembrane conductance regulator (CFTR) cause cystic fibrosis (CF) in approximately 10% of patients. Ataluren (PTC124) is an oral drug that permits ribosomes to readthrough premature stop codons in mRNA to produce functional protein.. To evaluate ataluren activity, safety, and pharmacokinetics in children with nonsense mutation CF.. Patients were assessed in two 28-day cycles, comprising 14 days on and 14 days off ataluren. Patients took ataluren three times per day (morning, midday, and evening) with randomization to the order of receiving a lower dose (4, 4, and 8 mg/kg) and a higher dose (10, 10, and 20 mg/kg) in the two cycles.. The study enrolled 30 patients (16 male and 14 female, ages 6 through 18 yr) with a nonsense mutation in at least one allele of the CFTR gene, a classical CF phenotype, and abnormal baseline nasal epithelial chloride transport. Ataluren induced a nasal chloride transport response (at least a -5-mV improvement) or hyperpolarization (value more electrically negative than -5 mV) in 50% and 47% of patients, respectively, with more hyperpolarizations at the higher dose. Improvements were seen in seven of nine nonsense mutation genotypes represented. Ataluren significantly increased the proportion of nasal epithelial cells expressing apical full-length CFTR protein. Adverse events and laboratory abnormalities were infrequent and usually mild. Ataluren pharmacokinetics were similar to those in adults.. In children with nonsense mutation CF, ataluren can induce functional CFTR production and is well tolerated.

Topics: Adolescent; Child; Codon, Nonsense; Cross-Over Studies; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Dose-Response Relationship, Drug; Female; Gene Expression Regulation; Humans; Male; Nasal Mucosa; Oxadiazoles

In about 10% of patients worldwide and more than 50% of patients in Israel, cystic fibrosis results from nonsense mutations (premature stop codons) in the messenger RNA (mRNA) for the cystic fibrosis transmembrane conductance regulator (CFTR). PTC124 is an orally bioavailable small molecule that is designed to induce ribosomes to selectively read through premature stop codons during mRNA translation, to produce functional CFTR.. This phase II prospective trial recruited adults with cystic fibrosis who had at least one nonsense mutation in the CFTR gene. Patients were assessed in two 28-day cycles. During the first cycle, patients received PTC124 at 16 mg/kg per day in three doses every day for 14 days, followed by 14 days without treatment; in the second cycle, patients received 40 mg/kg of PTC124 in three doses every day for 14 days, followed by 14 days without treatment. The primary outcome had three components: change in CFTR-mediated total chloride transport; proportion of patients who responded to treatment; and normalisation of chloride transport, as assessed by transepithelial nasal potential difference (PD) at baseline, at the end of each 14-day treatment course, and after 14 days without treatment. The trial was registered with who.int/ictrp, and with clinicaltrials.gov, number NCT00237380.. Transepithelial nasal PD was evaluated in 23 patients in the first cycle and in 21 patients in the second cycle. Mean total chloride transport increased in the first treatment phase, with a change of -7.1 (SD 7.0) mV (p<0.0001), and in the second, with a change of -3.7 (SD 7.3) mV (p=0.032). We recorded a response in total chloride transport (defined as a change in nasal PD of -5 mV or more) in 16 of the 23 patients in the first cycle's treatment phase (p<0.0001) and in eight of the 21 patients in the second cycle (p<0.0001). Total chloride transport entered the normal range for 13 of 23 patients in the first cycle's treatment phase (p=0.0003) and for nine of 21 in the second cycle (p=0.02). Two patients given PTC124 had constipation without intestinal obstruction, and four had mild dysuria. No drug-related serious adverse events were recorded.. In patients with cystic fibrosis who have a premature stop codon in the CFTR gene, oral administration of PTC124 to suppress nonsense mutations reduces the epithelial electrophysiological abnormalities caused by CFTR dysfunction.

Topics: Adolescent; Adult; Chlorides; Codon, Nonsense; Codon, Terminator; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Female; Humans; Male; Middle Aged; Oxadiazoles; Treatment Outcome

During protein synthesis, nonsense mutations, resulting in premature stop codons (PSCs), produce truncated, inactive protein products. Such defective gene products give rise to many diseases, including cystic fibrosis, Duchenne muscular dystrophy (DMD), and some cancers. Small molecule nonsense suppressors, known as TRIDs (translational read-through-inducing drugs), stimulate stop codon read-through. The best characterized TRIDs are ataluren, which has been approved by the European Medicines Agency for the treatment of DMD, and G418, a structurally dissimilar aminoglycoside. Previously [1], we applied a highly purified in vitro eukaryotic translation system to demonstrate that both aminoglycosides like G418 and more hydrophobic molecules like ataluren stimulate read-through by direct interaction with the cell's protein synthesis machinery. Our results suggested that they might do so by different mechanisms. Here, we pursue this suggestion through a more-detailed investigation of ataluren and G418 effects on read-through. We find that ataluren stimulation of read-through derives exclusively from its ability to inhibit release factor activity. In contrast, G418 increases functional near-cognate tRNA mispairing with a PSC, resulting from binding to its tight site on the ribosome, with little if any effect on release factor activity. The low toxicity of ataluren suggests that development of new TRIDs exclusively directed toward inhibiting termination should be a priority in combatting PSC diseases. Our results also provide rate measurements of some of the elementary steps during the eukaryotic translation elongation cycle, allowing us to determine how these rates are modified when cognate tRNA is replaced by near-cognate tRNA ± TRIDs.

Topics: Aminoglycosides; Animals; Artemia; Codon, Nonsense; Codon, Terminator; Cystic Fibrosis; Muscular Dystrophy, Duchenne; Oxadiazoles; Peptide Chain Elongation, Translational; Protein Biosynthesis; Protein Synthesis Inhibitors; Ribosomes; RNA, Transfer; Saccharomyces

Topics: Adult; Aminophenols; Codon, Nonsense; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Drug Combinations; Female; Humans; Oxadiazoles; Quinolones; Treatment Outcome

Cystic fibrosis (CF) patients develop a severe form of the disease when the cystic fibrosis transmembrane conductance regulator (CFTR) gene is affected by nonsense mutations. Nonsense mutations are responsible for the presence of a premature termination codon (PTC) in the mRNA, creating a lack of functional protein. In this context, translational readthrough-inducing drugs (TRIDs) represent a promising approach to correct the basic defect caused by PTCs. By using computational optimization and biological screening, we identified three new small molecules showing high readthrough activity. The activity of these compounds has been verified by evaluating CFTR expression and functionality after treatment with the selected molecules in cells expressing nonsense-CFTR-mRNA. Additionally, the channel functionality was measured by the halide sensitive yellow fluorescent protein (YFP) quenching assay. All three of the new TRIDs displayed high readthrough activity and low toxicity and can be considered for further evaluation as a therapeutic approach toward the second major cause of CF.

Topics: Cells, Cultured; Codon, Nonsense; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Gene Expression Regulation; Humans; Mutation; Oxadiazoles; Protein Biosynthesis; RNA, Messenger

Rapid in situ detection of pathogens coupled with high resolution imaging in the distal human lung has the potential to provide new insights and diagnostic utility in patients in whom pneumonia is suspected. We have previously described an antimicrobial peptide (AMP) Ubiquicidin (fragment UBI

Topics: Animals; Antimicrobial Cationic Peptides; Bacteria; Cells, Cultured; Cystic Fibrosis; Disease Models, Animal; Fluorescent Dyes; Fungi; Humans; Hydrophobic and Hydrophilic Interactions; Inflammation; Lung; Models, Biological; Oxadiazoles; Pneumonia; Sheep; Signal-To-Noise Ratio

Premature termination codon read-through drugs offer opportunities for treatment of multiple rare genetic diseases including cystic fibrosis. We here analyzed the read-through efficacy of PTC124 and G418 using human cystic fibrosis intestinal organoids (E60X/4015delATTT, E60X/F508del, G542X/F508del, R1162X/F508del, W1282X/F508del and F508del/F508del). G418-mediated read-through induced only limited CFTR function, but functional restoration of CFTR by PTC124 could not be confirmed. These studies suggest that better read-through agents are needed for robust treatment of nonsense mutations in cystic fibrosis.

Topics: Cells, Cultured; Coccidiostats; Codon, Nonsense; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Gentamicins; Humans; Organoids; Oxadiazoles; RNA

Premature stop codons are the result of nonsense mutations occurring within the coding sequence of a gene. These mutations lead to the synthesis of a truncated protein and are responsible for several genetic diseases. A potential pharmacological approach to treat these diseases is to promote the translational readthrough of premature stop codons by small molecules aiming to restore the full-length protein. The compound PTC124 (Ataluren) was reported to promote the readthrough of the premature UGA stop codon, although its activity was questioned. The potential interaction of PTC124 with mutated mRNA was recently suggested by molecular dynamics (MD) studies highlighting the importance of H-bonding and stacking π-π interactions. To improve the readthrough activity we changed the fluorine number and position in the PTC124 fluoroaryl moiety. The readthrough ability of these PTC124 derivatives was tested in human cells harboring reporter plasmids with premature stop codons in H2BGFP and FLuc genes as well as in cystic fibrosis (CF) IB3.1 cells with a nonsense mutation. Maintaining low toxicity, three of these molecules showed higher efficacy than PTC124 in the readthrough of the UGA premature stop codon and in recovering the expression of the CFTR protein in IB3.1 cells from cystic fibrosis patient. Molecular dynamics simulations performed with mutated CFTR mRNA fragments and active or inactive derivatives are in agreement with the suggested interaction of PTC124 with mRNA.

Topics: Codon, Nonsense; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Dose-Response Relationship, Drug; HeLa Cells; Humans; Molecular Dynamics Simulation; Molecular Structure; Mutation; Oxadiazoles; Peptide Chain Elongation, Translational; Structure-Activity Relationship; Tumor Cells, Cultured

Topics: Aminophenols; Aminopyridines; Benzodioxoles; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Genetic Therapy; Humans; Molecular Targeted Therapy; Mutation; Oxadiazoles; Quinolones

Leukocytes have previously been shown to express detectable levels of the protein cystic fibrosis transmembrane conductance regulator (CFTR). This study aims to evaluate the application of flow cytometric (FC) analysis to detect CFTR expression, and changes thereof, in these cells. Aliquots (200 μL) of peripheral whole blood from 12 healthy control volunteers (CTRLs), 12 carriers of a CFTR mutation (CFC), and 40 patients with cystic fibrosis (CF) carrying various combinations of CFTR mutations were incubated with specific fluorescent probes recognizing CFTR protein expressed on the plasma membrane of leukocytes. FC was applied to analyze CFTR expression in monocytes, lymphocytes, and polymorphonuclear (PMN) cells. CFTR protein was detected in monocytes and lymphocytes, whereas inconclusive results were obtained from the analysis of PMN cells. Mean fluorescence intensity (MFI) ratio value and %CFTR-positive cells above a selected threshold were the two parameters selected to quantify CFTR expression in cells. Lowest variability and the highest reproducibility were obtained when analyzing monocytes. ANOVA results indicated that both parameters were able to discriminate monocytes of healthy controls and CF individuals according to CFTR mutation classes with high accuracy. Significantly increased MFI ratio values were recorded in CFTR-defective cells that were also able to improve CFTR function after ex vivo treatment with PTC124 (Ataluren), an investigative drug designed to permit the ribosome to read through nonsense CFTR mutations. The method described is minimally invasive and may be used in the monitoring of responses to drugs whose efficacy can depend on increased CFTR protein expression levels. © 2014 International Society for Advancement of Cytometry.

Topics: Adolescent; Adult; Aged; Cell Membrane; Child; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Female; Flow Cytometry; Fluorescent Dyes; Humans; Leukocytes; Lymphocytes; Male; Middle Aged; Monocytes; Mutation; Neutrophils; Oxadiazoles; Young Adult

Topics: Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Female; Humans; Male; Oxadiazoles

The most common mutation causing cystic fibrosis (CF) is deletion of phenylalanine residue 508 in the cystic fibrosis transmembrane regulator conductance (CFTR) protein. Small molecules that are able to correct the misfolding of defective ΔF508-CFTR have considerable promise for therapy. Reported here are the design, preparation, and evaluation of five more hydrophilic bisazole analogs of previously identified bithiazole CF corrector 1. Interestingly, bisazole ΔF508-CFTR corrector activity was not increased by incorporation of more H-bond acceptors (O or N), but correlated best with the overall bisazole molecular geometry. The structure activity data, together with molecular modeling, suggested that active bisazole correctors adopt a U-shaped conformation, and that corrector activity depends on the molecule's ability to access this molecular geometry.

Topics: Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Humans; Imidazoles; Kinetics; Molecular Conformation; Oxadiazoles; Oxazoles; Protein Binding; Structure-Activity Relationship; Thermodynamics; Thiadiazoles; Thiazoles; Water

Topics: Aminophenols; Aminopyridines; Benzodioxoles; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Humans; Lung; Mutation; Oxadiazoles; Quinolones

Topics: Aminophenols; Clinical Trials, Phase III as Topic; Cystic Fibrosis; Humans; Molecular Targeted Therapy; Mutation; Oxadiazoles; Precision Medicine; Quinolones

Topics: Adolescent; Adult; Aminophenols; Animals; Anti-Bacterial Agents; Child; Child, Preschool; Congresses as Topic; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Disease Models, Animal; Drugs, Investigational; Female; Genetic Therapy; Humans; Infant; Infant, Newborn; Male; Mice; Mice, Transgenic; Molecular Targeted Therapy; Mutation; Neonatal Screening; Oxadiazoles; Practice Guidelines as Topic; Prognosis; Quinolones; Respiratory Function Tests; Treatment Outcome; Young Adult

The airways of patients with cystic fibrosis (CF) exhibit decreased nitric oxide (NO) concentrations, which might affect airway function. The aim of this study was to determine the effects of NO on ion transport in human airway epithelia. Primary cultures of non-CF and CF bronchial and bronchiolar epithelial cells were exposed to the NO donor sodium nitroprusside (SNP), and bioelectric variables were measured in Ussing chambers. Amiloride was added to inhibit the Na(+) channel ENaC, and forskolin and ATP were added successively to stimulate cAMP- and Ca(2+)-dependent Cl(-) secretions, respectively. The involvement of cGMP was assessed by measuring the intracellular cGMP concentration in bronchial cells exposed to SNP and the ion transports in cultures exposed to 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one, an inhibitor of the soluble guanylate cyclase (ODQ), or to 8Z, a cocktail of 8-bromo-cGMP and zaprinast (phosphodiesterase 5 inhibitor). SNP decreased the baseline short-circuit current (I(sc)) and the changes in I(sc) induced by amiloride, forskolin, and ATP in non-CF bronchial and bronchiolar cultures. The mechanism of this inhibition was studied in bronchial cells. SNP increased the intracellular cGMP concentration ([cGMP](i)). The inhibitory effect of SNP was abolished by 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, an NO scavenger (PTIO) and ODQ and was partly mimicked by increasing [cGMP](i). In CF cultures, SNP did not significantly modify ion transport; in CF bronchial cells, 8Z had no effect; however, SNP increased the [cGMP](i). In conclusion, exogenous NO may reduce transepithelial Na(+) absorption and Cl(-) secretion in human non-CF airway epithelia through a cGMP-dependent pathway. In CF airways, the NO/cGMP pathway appears to exert no effect on transepithelial ion transport.

Topics: Adenosine Triphosphate; Adult; Aged; Amiloride; Bronchi; Chloride Channels; Colforsin; Cyclic GMP; Cyclic N-Oxides; Cystic Fibrosis; Epithelial Sodium Channel Blockers; Epithelial Sodium Channels; Free Radical Scavengers; Guanylate Cyclase; Humans; Imidazoles; Middle Aged; Nitric Oxide; Nitric Oxide Donors; Nitroprusside; Oxadiazoles; Purinones; Quinoxalines; Young Adult

Approximately one-third of the alleles causing genetic diseases carry premature termination codons (PTCs). Therapeutic approaches for mutations generating in-frame PTCs are aimed at promoting translational readthrough of the PTC, to enable the synthesis and expression of full-length functional proteins. Interestingly, readthrough studies in tissue culture cells, mouse models, and clinical trials revealed a wide variability in the response to the readthrough treatments. The molecular basis for this variability includes the identity of the PTC and its sequence context, the chemical composition of the readthrough drug, and, as we showed recently, the level of PTC-bearing transcripts. One post-transcriptional mechanism that specifically regulates the level of PTC-bearing transcripts is nonsense-mediated mRNA decay (NMD). We have previously shown a role for NMD in regulating the response of CF patients carrying CFTR PTCs to readthrough treatment. Here we describe all the protocols for analyzing CFTR nonsense transcript levels and for investigating the role of NMD in the response to readthrough treatment. This includes inhibition of the NMD mechanism, quantification of CFTR nonsense transcripts and physiologic NMD substrates, and analysis of the CFTR function.

Topics: Alleles; Animals; Blotting, Western; Cell Line, Tumor; Chlorides; Codon, Nonsense; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Genetic Techniques; Gentamicins; Humans; Nasal Mucosa; Oxadiazoles; Plasmids; RNA Helicases; RNA-Binding Proteins; RNA, Messenger; Trans-Activators; Transcription Factors; Transfection

Topics: Clinical Trials as Topic; Cystic Fibrosis; Humans; Muscular Dystrophy, Duchenne; Oxadiazoles; RNA Processing, Post-Transcriptional

Topics: Amiloride; Animals; Bacterial Infections; Biomarkers; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Deoxycytosine Nucleotides; Disease Progression; Humans; Inflammation; Lung; Oxadiazoles; Respiratory Function Tests; Sodium Channel Blockers; Uridine

Topics: Codon, Nonsense; Codon, Terminator; Cystic Fibrosis; Genetic Therapy; Humans; Oxadiazoles; Retroelements

Topics: Clinical Trials, Phase II as Topic; Codon, Nonsense; Codon, Terminator; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Humans; Oxadiazoles; Radiography

Topics: Administration, Inhalation; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Deoxycytosine Nucleotides; Genetic Therapy; Humans; Mutation; Oxadiazoles; Purinergic P2 Receptor Agonists; Receptors, Purinergic P2Y2; Uridine

Topics: Clinical Trials as Topic; Codon, Nonsense; Cystic Fibrosis; Drug Design; Drug Industry; Humans; Muscular Dystrophy, Duchenne; Oxadiazoles; Therapies, Investigational

Nonsense mutations inactivate gene function and are the underlying cause of a large percentage of the individual cases of many genetic disorders. PTC124 is an orally bioavailable compound that promotes readthrough of premature translation termination codons, suggesting that it may have the potential to treat genetic diseases caused by nonsense mutations. Using a mouse model for cystic fibrosis (CF), we show that s.c. injection or oral administration of PTC124 to Cftr-/- mice expressing a human CFTR-G542X transgene suppressed the G542X nonsense mutation and restored a significant amount of human (h)CFTR protein and function. Translational readthrough of the premature stop codon was demonstrated in this mouse model in two ways. First, immunofluorescence staining showed that PTC124 treatment resulted in the appearance of hCFTR protein at the apical surface of intestinal glands in Cftr-/- hCFTR-G542X mice. In addition, functional assays demonstrated that PTC124 treatment restored 24-29% of the average cAMP-stimulated transepithelial chloride currents observed in wild-type mice. These results indicate that PTC124 can effectively suppress the hCFTR-G542X nonsense mutation in vivo. In light of its oral bioavailability, safety toxicology profile in animal studies, and efficacy with other nonsense alleles, PTC124 has the potential to be an important therapeutic agent for the treatment of inherited diseases caused by nonsense mutations.

Topics: Administration, Oral; Alleles; Animals; Base Sequence; Biological Availability; Chloride Channels; Codon, Nonsense; Cyclic AMP; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Disease Models, Animal; DNA Primers; Fluorescent Antibody Technique; Gene Expression; Humans; Injections, Subcutaneous; Mice; Mice, Transgenic; Oxadiazoles; Reverse Transcriptase Polymerase Chain Reaction

PTC-124, a 1,2,4-oxadiazole compound, is in development by PTC Therapeutics Inc as an orally active small molecule that can override nonsense stop translation signals to produce full-length proteins. PTC-124 is currently being evaluated in phase II clinical trials against cystic fibrosis (CF) and Duchenne muscular dystrophy (DMD). The functional properties of PTC-124 are similar to the aminoglycoside antibiotic gentamicin, but the two compounds are chemically distinct and PTC-124 does not exhibit any antibiotic characteristics. In vitro experiments showed PTC-124 to be superior to gentamicin at ribosomal read-through of nonsense mutations. In vivo investigations revealed that PTC-124 was effective in restoring the production of full-length protein in animal models of CF and DMD. Phase I clinical trials reported that PTC-124 was well tolerated in healthy patients. The author concludes that the encouraging results observed to date make PTC-124 an attractive option for further well-designed, long-term human studies on larger sample populations. The author also predicts that if results continue to be positive, PTC-124 could also be trialed in other single gene disorders with nonsense mutations such as hemophilia, neurofibromatosis, retinitis pigmentosa, bullous skin diseases and lysosomal storage disorders.

Topics: Animals; Clinical Trials as Topic; Cystic Fibrosis; Humans; Muscular Dystrophy, Duchenne; Oxadiazoles; Protein Synthesis Inhibitors

We characterized the effects of nitric oxide (NO) on whole-cell current in pancreatic epithelial cell lines from control (PANC-1) and cystic fibrosis patients (CFPAC-1). The nitric oxide donor S-nitrosoglutathione (GSNO) significantly reduced whole-cell current in CFPAC-1 cells but had no effect in PANC-1 cells. This inhibitory effect of NO could be eliminated by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) or charybdotoxin, suggesting the involvement of DIDS-sensitive Cl- channels and charybdotoxin-sensitive K+ channels. Pretreatment of cells with a selective inhibitor of soluble guanylate cyclase (sGC), 1H-[1,2,4]oxadiazolo[4,3,1]quinoxalin-1-one (ODQ, 10 microM), eliminated the inhibitory effect of NO, but not 8-bromo-cyclic guanosine monophosphate (8-Br-cGMP; 1 mM), indicating that NO acts via a cGMP-dependent pathway. There was a striking difference in cGMP production in response to GSNO in CFPAC-1 cells as compared with PANC-1 cells. GSNO induced a 90-fold increase in cGMP level in CFPAC-1 cells, compared with a threefold increase in PANC-1. Similarly, CFPAC-1 cells showed elevated levels of sGC and constitutive nitric oxide synthase activity as compared with PANC-1 cells. Therefore excessive production of NO, as is seen in inflammatory states, may contribute to the CF phenotype by inhibiting transepithelial ion movement and preventing secretion of digestive enzymes produced by the pancreas.

Topics: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Amiloride; Calcium Channel Blockers; Cell Line; Charybdotoxin; Cyclic AMP; Cyclic GMP; Cystic Fibrosis; Diltiazem; Enzyme Inhibitors; Epithelial Cells; Glutathione; Humans; Membrane Potentials; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitroso Compounds; Oxadiazoles; Pancreas; Patch-Clamp Techniques; Penicillamine; Quinoxalines; S-Nitroso-N-Acetylpenicillamine; S-Nitrosoglutathione