New Therapeutic Approaches to Modulate and Correct Cystic Fibrosis Transmembrane Conductance Regulator

Cystic fibrosis transmembrane conductance regulator (CFTR) modulators are clinically available personalized medicines approved for some individuals with cystic fibrosis (CF) to target the underlying defect of disease. This review summarizes strategies used to develop CFTR modulators as therapies that improve function and availability of CFTR protein. Lessons learned from dissemination of ivacaftor across the CF population responsive to this therapy and future approaches to predict and monitor treatment response of CFTR modulators are discussed. The goal remains to expand patient-centered and personalized therapy to all patients with CF, ultimately improving life expectancy and quality of life for this disease.

Highlights from the 2015 North American Cystic Fibrosis Conference

The 29th Annual North American Cystic Fibrosis Conference was held in Phoenix, Arizona on October 8-10, 2015. Abstracts were published in a supplement to Pediatric Pulmonology.(1) In this review, we summarize presentations in several of the topic areas addressed at the conference. Our goal is to provide an overview of presentations with relevance to emerging or changing concepts in several areas rather than a comprehensive review. Citations from the conference are by first author and abstract number or symposium number, as designated in the supplement. Pediatr Pulmonol. 2016;51:650-657. © 2016 Wiley Periodicals, Inc.

The effect of oxygen content during an initial sustained inflation on heart rate in asphyxiated near-term lambs

OBJECTIVE

At birth, an initial sustained inflation (SI) uniformly aerates the lungs, increases arterial oxygenation and rapidly improves circulatory recovery in asphyxiated newborns. We hypothesised that lung aeration, in the absence of an increase in arterial oxygenation, can increase heart rate (HR) in asphyxiated near-term lambs.

INTERVENTIONS

Lambs were delivered and instrumented at 139±2 days of gestation. Asphyxia was induced by umbilical cord clamping and then delaying the onset of ventilation until mean carotid arterial pressures (CAPs) had decreased <20 mm Hg. Lambs then received a single 30-s SI using nitrogen (N2; n=6), 5% oxygen (O2; n=6), 21% O2 (n=6) or 100% O2 (n=6) followed by ventilation in air for 30 min.

MAIN OUTCOME MEASURES

HR, CAP and pulmonary blood flow (PBF) were continuously recorded.

RESULTS

HR and PBF increased more quickly in lambs resuscitated with 100% and 21% O2 than with 5% O2 or N2. HR and PBF recovery in the 5% O2 group was delayed relative to all other oxygen SI groups. HR in 5%, 21% and 100% O2 groups reached 100 bpm before the SI was complete. HR and PBF in the N2 group did not increase until 10 s after the SI was completed and ventilation was initiated with air. CAP tended to increase quicker in all O2 groups than in N2 group.

CONCLUSIONS

Oxygen content during an SI is important for circulatory recovery in asphyxiated lambs. This increase in HR is likely driven by the increase in PBF and venous return to the heart.

The precision and accuracy of Nellcor and Masimo oximeters at low oxygen saturations (70%) in newborn lambs

BACKGROUND

Administration of oxygen in the delivery room is informed by oxygen saturation (SpO₂). An oxygen saturation range of 60%-70% is the threshold for administering oxygen in the first minutes after birth. The accuracy of newer generation oximeters to measure SpO₂ has not been compared against the 'gold standard', direct arterial blood oxygen saturation (SaO₂) when SaO₂ is low. The aim of this study was to determine the accuracy and precision of Nellcor and Masimo oximeters to measure SpO₂ when SaO₂ <70%.

METHOD

Prospective observational study in ventilated anaesthetised newborn lambs with an indwelling carotid artery catheter. Ventilation was adjusted to achieve hypoxaemia. Nellcor (Oxi-Max 600 with Max-N sensor) and Masimo (Rad 4 with low noise optical probe (LNOP) sensor) sensors were applied to the right forelimb (preductal). An arterial blood sample was collected at 1-5 min intervals when the animal was hypoxic. The displayed SpO₂ was recorded. We used Bland-Altman analysis to determine precision and accuracy of each oximeter when SaO₂ <70%.

RESULTS

17 lambs were studied, 165 measurements were obtained, 123 were SaO₂ <70%. The mean difference (±1.96 SD) Nellcor SpO₂-SaO₂ when SaO₂ <70% was 17% (-12% to 46%). The mean difference (±1.96 SD) Masimo SpO₂-SaO₂ when SaO2 <70% was 13% (-19% to 45%).

CONCLUSIONS

At SaO₂<70%, both monitors overestimated oxygen saturation (SpO₂) compared with the gold standard. Both oximeters were equally inaccurate when SaO₂ was low.

Improving transition from paediatric to adult cystic fibrosis care: programme implementation and evaluation

BACKGROUND

The paradigm of cystic fibrosis (CF) care has changed as effective therapies extend the lives of patients well into adulthood. Preparing for and maintaining high quality CF care into the adult healthcare setting is critical for prolonged survival. Unfortunately, this transfer process from the paediatric to the adult CF centre is met with a variety of challenges.

OBJECTIVE AND METHODS

The objective of this quality improvement (QI) project was to develop, implement and evaluate a theory-based programme for transition from paediatric to adult CF care. In a multi-phase process, the paediatric and adult programmes developed a transition curriculum, addressed care standards and standardised patient transfer protocols. We evaluated the impact of this process through staff surveys, review of field notes from QI meetings, tracking transfers and responses of patients to the Transition Readiness Assessment Questionnaire (TRAQ) at the start of the programme and 18 months after initiation.

RESULTS

The collaboration between the paediatric and adult teams continued through quarterly meetings over the past 4 years. This has provided a forum that sustained our transition programme, harmonised care across CF centres and addressed other needs of our CF centre. Discussion of transition with families in the paediatric centre increased twofold (35% to 73% p<0.001), and resulted in a trend towards improved patient TRAQ self-advocacy scores and decreased in-hospital transfer.

CONCLUSIONS

We successfully created a curriculum and process for transition from paediatric to adult CF care at our centres. This collaboration shapes the communication between our paediatric and adult CF care teams and enables ongoing feedback among patients, families and providers. The impact of our transition programme on long-term patient morbidity will require future evaluation.

Ratio of angiopoietin-2 to angiopoietin-1 as a predictor of mortality in acute lung injury patients

OBJECTIVE

To test the hypothesis that the concentration of angiopoietin-2 relative to angiopoietin-1 may be a useful biological marker of mortality in acute lung injury patients. We also tested the association of concentration of angiopoietin-2 relative to angiopoietin-1 with physiologic and biological markers of activated endothelium.

DESIGN

Prospective, observational cohort study.

SETTING

Intensive care units in a tertiary care university hospital and a university-affiliated city hospital.

PATIENTS

Fifty-six mechanically ventilated patients with acute lung injury.

INTERVENTIONS

Baseline plasma samples and pulmonary dead-space fraction measurements were collected within 48 hrs of acute lung injury diagnosis.

MEASUREMENTS AND MAIN RESULTS

Plasma levels of angiopoietin-1 and angiopoietin-2 and of biomarkers of endothelial activation were measured by enzyme-linked immunosorbent assay. Baseline concentration of angiopoietin-2 relative to angiopoietin-1 was significantly higher in patients who died (median, 58 [interquartile range, 17-117] vs. 14 [interquartile range, 6-35]; p = .01). In a multivariable analysis stratified by dead-space fraction, concentration of angiopoietin-2 relative to angiopoietin-1 was an independent predictor of death, with an adjusted odds ratio of 4.3 (95% confidence interval, 1.3-13.5; p = .01) in those with an elevated pulmonary dead-space fraction (p = .03 for interaction between pulmonary dead-space fraction and concentration of angiopoietin-2 relative to angiopoietin-1). Moderate to weak correlation was found with biological markers of endothelial activation.

CONCLUSIONS

The ratio of concentration of angiopoietin-2 relative to angiopoietin-1 may be a prognostic biomarker of endothelial activation in acute lung injury patients and, along with pulmonary dead-space fraction, may be useful for risk stratification of acute lung injury patients, particularly in identifying subgroups for future research and therapeutic trials.

Alveolar fluid clearance is faster in women with acute lung injury compared to men

PURPOSE

Studies suggest that there is a sex difference in the development and outcomes of acute lung injury (ALI). Few studies have directly addressed the association of sex and alveolar fluid clearance (AFC), a process that is critical to ALI resolution.

MATERIALS AND METHODS

To test the hypothesis that female sex is associated with an increased AFC rate, we measured AFC rates in 150 mechanically ventilated patients with acute pulmonary edema and a pulmonary edema fluid-to-plasma protein ratio (EF/PL) diagnostic of low permeability (EF/PL <0.65, n = 69) or high permeability (EF/PL ≥0.65, n = 81) edema. We measured protein concentration in serial samples of undiluted EF collected within 6 hours of intubation and calculated net rate of AFC. In addition, plasma levels of receptor for advanced glycation end products were measured as a surrogate marker for alveolar epithelial injury.

RESULTS

In patients with ALI, women had higher rates of net AFC at 4 hours compared to men (11.9% per hour vs 4.3% per hour, P = .017) and more women had maximal rates of AFC. There were no differences in circulating levels of receptor for advanced glycation end products between men and women.

CONCLUSIONS

These findings may have significant implications for future ALI studies and potential therapies.