Frank J. Accurso

Guidelines for Diagnosis of Cystic Fibrosis in Newborns through Older Adults: Cystic Fibrosis Foundation Consensus Report

Newborn screening (NBS) for cystic fibrosis (CF) is increasingly being implemented and is soon likely to be in use throughout the United States, because early detection permits access to specialized medical care and improves outcomes. The diagnosis of CF is not always straightforward, however. The sweat chloride test remains the gold standard for CF diagnosis but does not always give a clear answer. Genotype analysis also does not always provide clarity; more than 1500 mutations have been identified in the CF transmembrane conductance regulator (CFTR) gene, not all of which result in CF. Harmful mutations in the gene can present as a spectrum of pathology ranging from sinusitis in adulthood to severe lung, pancreatic, or liver disease in infancy. Thus, CF identified postnatally must remain a clinical diagnosis. To provide guidance for the diagnosis of both infants with positive NBS results and older patients presenting with an indistinct clinical picture, the Cystic Fibrosis Foundation convened a meeting of experts in the field of CF diagnosis. Their recommendations, presented herein, involve a combination of clinical presentation, laboratory testing, and genetics to confirm a diagnosis of CF.

Effect of VX-770 in persons with cystic fibrosis and the G551D-CFTR mutation

BACKGROUND A new approach in the treatment of cystic fibrosis involves improving the function of mutant cystic fibrosis transmembrane conductance regulator (CFTR). VX-770, a CFTR potentiator, has been shown to increase the activity of wild-type and defective cell-surface CFTR in vitro. METHODS We randomly assigned 39 adults with cystic fibrosis and at least one G551D-CFTR allele to receive oral VX-770 every 12 hours at a dose of 25, 75, or 150 mg or placebo for 14 days (in part 1 of the study) or VX-770 every 12 hours at a dose of 150 or 250 mg or placebo for 28 days (in part 2 of the study). RESULTS At day 28, in the group of subjects who received 150 mg of VX-770, the median change in the nasal potential difference (in response to the administration of a chloride-free isoproterenol solution) from baseline was -3.5 mV (range, -8.3 to 0.5; P=0.02 for the within-subject comparison, P=0.13 vs. placebo), and the median change in the level of sweat chloride was -59.5 mmol per liter (range, -66.0 to -19.0; P=0.008 within-subject, P=0.02 vs. placebo). The median change from baseline in the percent of predicted forced expiratory volume in 1 second was 8.7% (range, 2.3 to 31.3; P=0.008 for the within-subject comparison, P=0.56 vs. placebo). None of the subjects withdrew from the study. Six severe adverse events occurred in two subjects (diffuse macular rash in one subject and five incidents of elevated blood and urine glucose levels in one subject with diabetes). All severe adverse events resolved without the discontinuation of VX-770. CONCLUSIONS This study to evaluate the safety and adverse-event profile of VX-770 showed that VX-770 was associated with within-subject improvements in CFTR and lung function. These findings provide support for further studies of pharmacologic potentiation of CFTR as a means to treat cystic fibrosis. (Funded by Vertex Pharmaceuticals and others; ClinicalTrials.gov number, NCT00457821.).

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

Background VX-809, a cystic fibrosis transmembrane conductance regulator (CFTR) modulator, has been shown to increase the cell surface density of functional F508del-CFTR in vitro. Methods A randomised, double-blind, placebo-controlled study evaluated the safety, tolerability and pharmacodynamics of VX-809 in adult patients with cystic fibrosis (n=89) who were homozygous for the F508del-CFTR mutation. Subjects were randomised to one of four VX-809 28 day dose groups (25, 50, 100 and 200 mg) or matching placebo. Results The type and incidence of adverse events were similar among VX-809- and placebo-treated subjects. Respiratory events were the most commonly reported and led to discontinuation by one subject in each active treatment arm. Pharmacokinetic data supported a once-daily oral dosing regimen. Pharmacodynamic data suggested that VX-809 improved CFTR function in at least one organ (sweat gland). VX-809 reduced elevated sweat chloride values in a dose-dependent manner (p=0.0013) that was statistically significant in the 100 and 200 mg dose groups. There was no statistically significant improvement in CFTR function in the nasal epithelium as measured by nasal potential difference, nor were there statistically significant changes in lung function or patient-reported outcomes. No maturation of immature F508del-CFTR was detected in the subgroup that provided rectal biopsy specimens. Conclusions In this study, VX-809 had a similar adverse event profile to placebo for 28 days in F508del-CFTR homozygous patients, and demonstrated biological activity with positive impact on CFTR function in the sweat gland. Additional data are needed to determine how improvements detected in CFTR function secondary to VX-809 in the sweat gland relate to those measurable in the respiratory tract and to long-term measures of clinical benefit. Clinical trial number NCT00865904

Elastase-mediated phosphatidylserine receptor cleavage impairs apoptotic cell clearance in cystic fibrosis and bronchiectasis

Cystic fibrosis is characterized by an early and sustained influx of inflammatory cells into the airways and by release of proteases. Resolution of inflammation is normally associated with the orderly removal of dying apoptotic inflammatory cells through cell recognition receptors, such as the phosphatidylserine receptor, CD36, and alpha v integrins. Accordingly, removal of apoptotic inflammatory cells may be impaired in persistent inflammatory responses such as that seen in cystic fibrosis airways. Examination of sputa from cystic fibrosis and non-cystic fibrosis bronchiectasis patients demonstrated an abundance of apoptotic cells, in excess of that seen in patients with chronic bronchitis. In vitro, cystic fibrosis and bronchiectasis airway fluid directly inhibited apoptotic cell removal by alveolar macrophages in a neutrophil elastase-dependent manner, suggesting that elastase may impair apoptotic cell clearance in vivo. Flow cytometry demonstrated that neutrophil elastase cleaved the phosphatidylserine receptor, but not CD36 or CD32 (Fc gamma RII). Cleavage of the phosphatidylserine receptor by neutrophil elastase specifically disrupted phagocytosis of apoptotic cells, implying a potential mechanism for delayed apoptotic cell clearance in vivo. Therefore, defective airway clearance of apoptotic cells in cystic fibrosis and bronchiectasis may be due to elastase-mediated cleavage of phosphatidylserine receptor on phagocytes and may contribute to ongoing airway inflammation.

Molecular identification of bacteria in bronchoalveolar lavage fluid from children with cystic fibrosis.

Culture of bronchoalveolar lavage fluid (BALF) is the gold standard for detection of pathogens in the lower airways in cystic fibrosis (CF). However, current culture results do not explain all clinical observations in CF, including negative culture results during pulmonary exacerbation and inflammation in the absence of pathogens. We hypothesize that organisms not routinely identified by culture occur in the CF airway and may contribute to disease. To test this hypothesis we used a culture-independent molecular approach, based on use of rRNA sequence analysis, to assess the bacterial composition of BALF from children with CF and disease controls (DC). Specimens from 42 subjects (28 CF) were examined, and ≈6,600 total clones were screened to identify 121 species of bacteria. In general, a single rRNA type dominated clone libraries from CF specimens, but not DC. Thirteen CF subjects contained bacteria that are not routinely assessed by culture. In four CF subjects, candidate pathogens were identified and include the anaerobe Prevotella denticola, a Lysobacter sp., and members of the Rickettsiales. The presumptive pathogens Tropheryma whipplei and Granulicatella elegans were identified in cases from the DC group. The presence of unexpected bacteria in CF may explain inflammation without documented pathogens and consequent failure to respond to standard treatment. These results show that molecular techniques provide a broader perspective on airway bacteria than do routine clinical cultures and thus can identify targets for further clinical evaluation.

Defective lipoxin-mediated anti-inflammatory activity in the cystic fibrosis airway.

In cystic fibrosis, dysregulated neutrophilic inflammation and chronic infection lead to progressive destruction of the airways. The underlying mechanisms have remained unclear. Lipoxins are anti-inflammatory lipid mediators that modulate neutrophilic inflammation. We report here that lipoxin concentrations in airway fluid were significantly suppressed in patients with cystic fibrosis compared to patients with other inflammatory lung conditions. We also show that administration of a metabolically stable lipoxin analog in a mouse model of the chronic airway inflammation and infection associated with cystic fibrosis suppressed neutrophilic inflammation, decreased pulmonary bacterial burden and attenuated disease severity. These findings suggest that there is a pathophysiologically important defect in lipoxin-mediated anti-inflammatory activity in the cystic fibrosis lung and that lipoxins have therapeutic potential in this lethal autosomal disease.

Diagnostic accuracy of oropharyngeal cultures in infants and young children with cystic fibrosis

The objective of this study was to assess the diagnostic accuracy of oropharyngeal (OP) cultures relative to simultaneous bronchoalveolar lavage (BAL) cultures in very young children with CF, and to examine the effects of bacterial density, age, and study cohort on diagnostic accuracy. Respiratory culture data were analyzed from three independent, prospective studies involving simultaneous collection of 286 OP and BAL cultures from 141 children with CF <5 years of age.

Cystic Fibrosis Foundation Evidence-Based Guidelines for Management of Infants with Cystic Fibrosis

Newborn screening for cystic fibrosis (CF) offers the opportunity for early medical and nutritional intervention that can lead to improved outcomes. Management of the asymptomatic infant diagnosed with CF through newborn screening, prenatal diagnosis, or sibling screening is different from treatment of the symptomatically diagnosed individual. The focus of management is on maintaining health by preventing nutritional and respiratory complications. The CF Foundation convened a committee to develop recommendations based on a systematic review of the evidence and expert opinion. These guidelines encompass monitoring and treatment recommendations for infants diagnosed with CF and are intended to help guide families, primary care providers, and specialty care centers in the care of infants with CF.

Role of respiratory syncytial virus in early hospitalizations for respiratory distress of young infants with cystic fibrosis

To determine the frequency of respiratory syncytial virus (RSV) as the cause of hospitalization for acute pulmonary exacerbations in young infants with cystic fibrosis (CF), and to assess the clinical effects of RSV infections, we prospectively followed 48 children with a diagnosis of CF after identification by newborn screening. At a mean follow-up age of 28.8 months (range 5 to 59), 18 infants (38%) had been hospitalized a total of 30 times for acute respiratory distress. At the time of admission, 18 infants (60%) were less than 12 months, 8 (27%) between 12 and 24 months, and 4 more than 2 years of age. The RSV was identified in seven hospitalized infants, as determined by fluorescent antibody, immunoassay, or culture. Before admission with RSV infection, one of the seven infants had chronic respiratory signs, none had Brasfield chest x-ray scores below 20, and a previous throat culture was positive for Staphylococcus aureus in one infant. Hospitalizations were prolonged (mean duration 22 days), and were characterized by significant morbidity, with three infants (43%) requiring mechanical ventilation and five infants (71%) requiring home oxygen therapy for persistent hypoxemia at discharge. At a mean follow-up age of 26 months, these infants more frequently have chronic respiratory signs (p less than 0.01) and lower chest radiograph scores (p less than 0.05) than other CF infants. These findings demonstrate that RSV is an important cause of early acute respiratory tract morbidity in young infants with CF, and suggest the need for studying new strategies to implement early and aggressive antiviral therapy in young infants with CF.

Ataluren for the treatment of nonsense-mutation cystic fibrosis: a randomised, double-blind, placebo-controlled phase 3 trial

BACKGROUND 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. METHODS 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. FINDINGS 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. INTERPRETATION 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. FUNDING PTC Therapeutics, Cystic Fibrosis Foundation, US Food and Drug Administrations Office of Orphan Products Development, and the National Institutes of Health.