Outcome measures for development of new therapies in cystic fibrosis: are we making progress and what are the next steps?

Assessment of repeatability of hyperpolarized gas MR ventilation functional imaging in cystic fibrosis

RATIONALE AND OBJECTIVES

Hyperpolarized (HP) gas magnetic resonance imaging (MRI) is an advanced imaging technique that provides high-resolution regional information on lung function without using ionizing radiation. Before this modality can be considered for assessing clinical or investigational interventions, baseline repeatability needs to be established. We assessed repeatability of lung function measurement using HP helium-3 MRI (HP (3)He MRI) in a small cohort of patients with cystic fibrosis (CF).

MATERIALS AND METHODS

We examined repeatability of HP (3)He MR images of five patients with CF in four scanning sessions over a 4-week period. We acquired images on a Philips 3.0 Tesla Achieva MRI scanner using a quadrature, flexible, wrap-around, (3)He radiofrequency coil with a fast gradient-echo pulse sequence. We determined ventilation volume and ventilation defect volume using an advanced semiautomatic segmentation algorithm and also quantified ventilation heterogeneity.

RESULTS

There were no significant differences in total ventilation volume, ventilation defect volume, ventilation defect percentage, or mean ventilation heterogeneity (repeated-measures analysis of variance, P = .2116, P = .2825, P = .2871, and P = .7265, respectively) in the patients across the four scanning sessions.

CONCLUSIONS

Our results indicate that total ventilation volume, ventilation defect volume, ventilation defect percentage, and mean ventilation heterogeneity as assessed by HP gas MRI in CF patients with stable health are reproducible over time. This repeatability and the technique's capability to provide noninvasive high-resolution data on regional lung function without ionizing radiation make (3)He MRI a potentially useful outcome measure for CF-related clinical trials.

In vivo readout of CFTR function: ratiometric measurement of CFTR-dependent secretion by individual, identifiable human sweat glands

To assess CFTR function in vivo, we developed a bioassay that monitors and compares CFTR-dependent and CFTR-independent sweat secretion in parallel for multiple (~50) individual, identified glands in each subject. Sweating was stimulated by intradermally injected agonists and quantified by optically measuring spherical sweat bubbles in an oil-layer that contained dispersed, water soluble dye particles that partitioned into the sweat bubbles, making them highly visible. CFTR-independent secretion (M-sweat) was stimulated with methacholine, which binds to muscarinic receptors and elevates cytosolic calcium. CFTR-dependent secretion (C-sweat) was stimulated with a β-adrenergic cocktail that elevates cytosolic cAMP while blocking muscarinic receptors. A C-sweat/M-sweat ratio was determined on a gland-by-gland basis to compensate for differences unrelated to CFTR function, such as gland size. The average ratio provides an approximately linear readout of CFTR function: the heterozygote ratio is ~0.5 the control ratio and for CF subjects the ratio is zero. During assay development, we measured C/M ratios in 6 healthy controls, 4 CF heterozygotes, 18 CF subjects and 4 subjects with 'CFTR-related' conditions. The assay discriminated all groups clearly. It also revealed consistent differences in the C/M ratio among subjects within groups. We hypothesize that these differences reflect, at least in part, levels of CFTR expression, which are known to vary widely. When C-sweat rates become very low the C/M ratio also tended to decrease; we hypothesize that this nonlinearity reflects ductal fluid absorption. We also discovered that M-sweating potentiates the subsequent C-sweat response. We then used potentiation as a surrogate for drugs that can increase CFTR-dependent secretion. This bioassay provides an additional method for assessing CFTR function in vivo, and is well suited for within-subject tests of systemic, CFTR-directed therapeutics.

Managing treatment complexity in cystic fibrosis: challenges and opportunities

Cystic fibrosis (CF) is a complex, chronic, multisystem disease for which there is currently no cure. Nonetheless, advances in management have led to dramatic improvements in patient survival. With this development, new issues have arisen for CF patients and their care providers, including an increased symptom burden and increased frequency of co-morbidities as patients reach older ages, leading to the need for a highly complicated and time-consuming regimen of treatments. Such high symptom and treatment burden often leads to non-adherence and low levels of competence with administration of therapy, both of which may have detrimental impacts on CF outcomes. Optimal management is also hindered by other patient-related factors, including inadequacies in disease education which may lead to issues with self-management. This is particularly important during the transition from parent-directed therapy to independent self-management that occurs during adolescence and early adulthood. Clinicians are also faced with a considerable challenge when selecting interventions for individual patients; although the paradigm of aggressive care necessitates a wide range of therapies, there is a limited evidence base with which to compare available therapeutic regimens. Novel pharmacological agents are being developed to target the underlying cause of CF, while non-pharmacological interventions aim to improve competence and maximize adherence and health outcomes. Comparative effectiveness research is needed to simplify management and facilitate the implementation of appropriate treatment strategies.

Pediatric hospital medicine and children with medical complexity: past, present, and future

Children with medical complexity, regardless of underlying diagnoses, share similar functional and resource use consequences, including: intensive service needs, reliance on technology, polypharmacy, and/or home care or congregate care to maintain a basic quality of life, high health resource utilization, and, an elevated need for care coordination. The emerging field of complex care is focused on the holistic medical care of these children, which requires both broad general pediatrics skills and specific expertise in care coordination and communication with patients, families, and other medical and non-medical care providers. Many pediatric hospitalists have developed an interest in care coordination for CMC, and pediatric hospitalists are in an ideal location to embrace complex care. As a result of these factors, complex care has emerged as a field with many pediatric hospitalists at the helm, in arenas ranging from clinical care of these patients, research into their care, and education of future providers. The objective of this section of the review article is to outline the past, present, and possible future of children with medical complexity within several arenas in the field of pediatric hospital medicine, including practice management, clinical care, research, education, and quality improvement.

A novel respiratory symptom scoring system for CF pulmonary exacerbations

BACKGROUND

There is currently no simple scoring system to evaluate change in symptoms during a pulmonary exacerbation (PEx) in adult cystic fibrosis (CF) patients.

PATIENTS AND METHODS

We evaluated 265 episodes in 58 adult CF patients. A simple symptom score was administered at the start and the end of each PEx. The score evaluated four symptoms: cough, sputum, breathlessness and fatigue. Each symptom was scored from one (mild symptoms) to four (severe symptoms). The total symptom score was the summation of all the four symptoms. The total symptom score was compared with CF Respiratory Questionnaire (CFRQ) and with spirometry.

RESULTS

There was significant internal correlation between scores for each pair of symptoms. The total symptom score correlated with the functional activity score and the respiratory score domains and with the summary score for CFRQ. The total symptom score correlated with spirometry values. Symptom score improved after 2-week treatment with intravenous (IV) antibiotics in 88.3%, remained unchanged in 7.3% and worsened in 4.4% of all episodes. Changes in symptom score after IV treatment correlated with changes of all main spirometry measurements.

CONCLUSION

This new symptom score is simple and sensitive to change over a short period. It correlates with established quality-of-life questionnaires and with spirometry. The changes of symptom score over a short period correlate with changes in spirometry. This score can be used as an added tool to assess the outcome of CF PExs.

Protein biomarkers in cystic fibrosis research: where next?

Cystic fibrosis is one of the most common life-limiting inherited disorders. Its clinical impact manifests chiefly in the lung, pancreas, gastrointestinal tract and sweat glands, with lung disease typically being most detrimental to health. The median age for survival has increased dramatically over the past decades, largely thanks to advances in understanding of the mechanisms and consequences of disease, leading to the development of better therapies and treatment regimes. The discovery of dysregulated protein biomarkers linked to cystic fibrosis has contributed considerably to this end. This article outlines clinical trials targeting known protein biomarkers, and the current and future contributions of proteomic techniques to cystic fibrosis research. The treatments described range from those designed to provide functional copies of the mutant protein responsible for cystic fibrosis, to others addressing the associated symptoms of chronic inflammation. Preclinical research has employed proteomics to help elucidate pathways and processes implicated in disease that might present opportunities for therapy or prognosis. Global analyses of cystic fibrosis have detected the differential expression of proteins involved in inflammation, proteolytic activity and oxidative stress, which are recognized symptoms of the cystic fibrosis phenotype. The dysregulation of other processes, such as the complement and mitochondrial systems, has also been implicated. A number of studies have focused specifically on proteins that interact with the cystic fibrosis protein, with the goal of restoring its normal proteostasis. Consequently, proteins involved in synthesis, folding, degradation, translocation and localization of the protein have been identified as potential therapeutic targets. Cystic fibrosis patients are prone to lung infections that are thought to contribute to chronic inflammation, and thus proteomic studies have also searched for microbiological biomarkers to use in early infection diagnosis or as indicators of virulence. The review concludes by proposing a future role for proteomics in the high-throughput validation of protein biomarkers under consideration as outcome measures for use in clinical trials and routine disease monitoring.

Lung clearance index at 4 years predicts subsequent lung function in children with cystic fibrosis

RATIONALE

The markedly improved life expectancy of children with cystic fibrosis (CF) has created a new challenge, as traditional markers of lung disease are frequently normal in young children. This prevents identification of individuals who may benefit from more aggressive therapy and also obliges large study numbers and prolonged duration for intervention studies. There is an urgent need for alternative surrogates that detect early lung disease and track through early childhood.

OBJECTIVES

This study aimed to determine whether multiple-breath washout (MBW) results at preschool age can predict subsequent abnormal lung function.

METHODS

Preschool children (3-5 yr) with CF and healthy control subjects underwent spirometry and MBW with testing repeated during early school age (6-10 yr). Primary outcomes were FEV1 from spirometry and lung clearance index (LCI) from MBW.

MEASUREMENTS AND MAIN RESULTS

Forty-eight children with CF and 45 healthy children completed testing. Thirty-five (73%) children with CF had abnormal LCI at preschool age, whereas only five had abnormal FEV1. The positive predictive value of preschool LCI for predicting any abnormal school-age result was 94%, with a negative predictive value of 62%. Only one child with abnormal FEV1 at school age had had a normal preschool LCI. In contrast, for preschool FEV1 the positive predictive value was 100%, but negative predictive value was only 25%.

CONCLUSIONS

This study demonstrates that an abnormal preschool LCI predicts subsequent lung function abnormalities, whereas a normal preschool LCI usually remains normal. MBW has potential as a clinical and research outcome in young children with CF.

Measuring and improving respiratory outcomes in cystic fibrosis lung disease: opportunities and challenges to therapy

Cystic fibrosis (CF) is a life-shortening disease with significant morbidity. Despite overall improvements in survival, patients with CF experience frequent pulmonary exacerbations and declining lung function, which often accelerates during adolescence. New treatments target steps in the pathogenesis of lung disease, such as the basic defect in CF (CF Transmembrane Conductance Regulator [CFTR]), pulmonary infections, inflammation, and mucociliary clearance. These treatments offer hope but also present challenges to patients, clinicians, and researchers. Comprehensive assessment of efficacy is critical to identify potentially beneficial treatments. Lung function and pulmonary exacerbation are the most commonly used outcome measures in CF clinical research. Other outcome measures under investigation include measures of CFTR function; biomarkers of infection, inflammation, lung injury and repair; and patient-reported outcomes. Molecular diagnostics may help elucidate the complex CF airway microbiome. As new treatments are developed for patients with CF, efforts should be made to balance treatment burden with quality of life. This review highlights emerging treatments, obstacles to optimizing outcomes, and key future directions for research.

Potential role of high-mobility group box 1 in cystic fibrosis airway disease

RATIONALE

High-mobility group box 1 (HMGB1) is a potent inflammatory mediator elevated in sepsis and rheumatoid arthritis, although its role in cystic fibrosis (CF) lung disease is unknown.

OBJECTIVES

To determine whether HMGB1 contributes to CF lung inflammation, including neutrophil chemotaxis and lung matrix degradation.

METHODS

We used sputum and serum from subjects with CF and a Scnn1b-transgenic (Scnn1b-Tg) mouse model that overexpresses beta-epithelial Na(+) channel in airways and mimics the CF phenotype, including lung inflammation. Human secretions and murine bronchoalveolar lavage fluid (BALF) was assayed for HMGB1 by Western blot and ELISA. Neutrophil chemotaxis was measured in vitro after incubation with human neutrophils. The collagen fragment proline-glycine-proline (PGP) was measured by tandem mass spectroscopy.

MEASUREMENTS AND MAIN RESULTS

HMGB1 was detected in CF sputum at higher levels than secretions from normal individuals. Scnn1b-Tg mice had elevated levels of HMGB1 by Western blot and ELISA. We demonstrated that dose-dependent chemotaxis of human neutrophils stimulated by purified HMGB1 was partially dependent on CXC chemokine receptors and that this could be duplicated in CF sputum and BALF from Scnn1b-Tg mice. Neutralization by anti-HMGB1 antibody, in both the sputum and BALF-reduced chemotaxis, which suggested that HMGB1 contributed to the chemotactic properties of these samples. Intratracheal administration of purified HMGB1 induced neutrophil influx into the airways of mice and promoted the release of PGP. PGP was also elevated in Scnn1b-Tg mice and CF serum.

CONCLUSIONS

HMGB1 expression contributes to pulmonary inflammation and lung matrix degradation in CF airway disease and deserves further investigation as a biomarker and potential therapeutic target.