Background: Recent studies demonstrated that the triple combination cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapy elexacaftor/tezacaftor/ivacaftor (ETI) improves lung function and reduces pulmonary exacerbations in cystic fibrosis (CF) patients with at least oneF508delallele. However, effects of ETI on downstream consequences of CFTR dysfunction,i.e.abnormal viscoelastic properties of airway mucus, chronic airway infection and inflammation have not been studied. The aim of this study was to determine the longitudinal effects of ETI on airway mucus rheology, microbiome and inflammation in CF patients with one or twoF508delalleles aged ≥12 years throughout the first 12 months of therapy.Methods: In this prospective observational study, we assessed sputum rheology, the microbiome, inflammation markers and proteome before and 1, 3 and 12 months after initiation of ETI.Results: In total, 79 patients with CF and at least oneF508delallele and 10 healthy controls were enrolled in this study. ETI improved the elastic modulus and viscous modulus of CF sputum at 3 and 12 months after initiation (all p<0.01). Furthermore, ETI decreased the relative abundance ofPseudomonas aeruginosain CF sputum at 3 months and increased the microbiome α-diversity at all time points.In addition, ETI reduced interleukin-8 at 3 months (p<0.05) and free neutrophil elastase activity at all time points (all p<0.001), and shifted the CF sputum proteome towards healthy.Conclusions: Our data demonstrate that restoration of CFTR function by ETI improves sputum viscoelastic properties, chronic airway infection and inflammation in CF patients with at least oneF508delallele over the first 12 months of therapy; however, levels close to healthy were not reached.

Rationale: Early onset and progression of lung disease in children with cystic fibrosis (CF) indicates that sensitive noninvasive outcome measures are needed for diagnostic monitoring and early intervention clinical trials. The lung clearance index (LCI) and chest magnetic resonance imaging (MRI) were shown to detect early lung disease in CF; however, the relationship between the two measures remains unknown. Objectives: To correlate the LCI with abnormalities detected by MRI and compare the sensitivity of the two techniques to detect responses to therapy for pulmonary exacerbations in children with CF. Methods: LCI determined by age-adapted multiple breath washout techniques and MRI studies were performed in 97 clinically stable children with CF across the pediatric age range (0.2–21.1 yr). Furthermore, LCI (n = 26) or MRI (n = 10) were performed at the time of pulmonary exacerbation and after antibiotic therapy. MRI was evaluated using a dedicated morphofunctional score. Measurements and Main Results: The LCI correlated with the global MRI score as well as MRI-defined airway wall abnormalities, mucus plugging, and abnormal lung perfusion in infants and toddlers (P < 0.05 to P < 0.001) and in older children (P < 0.001) with CF. LCI and MRI were sensitive to detect response to antibiotic therapy for pulmonary exacerbations. Conclusions: Our results indicate that LCI and MRI may be useful complementary tools for noninvasive monitoring and as quantitative endpoints in early intervention trials in children with CF. In this context, MRI enables detection of disease heterogeneity, including regional mucus plugging associated with abnormal lung perfusion in early CF lung disease. Clinical trial registered with www.clinicaltrials.gov (NCT 02270476).

Rationale: The CFTR (cystic fibrosis transmembrane conductance regulator) modulator combination elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) was shown to improve clinical outcomes and sweat chloride concentration in patients with cystic fibrosis (CF) and one or two F508del alleles. However, the effect of ELX/TEZ/IVA on CFTR function in the airways and intestine has not been studied. Objectives: To assess the effect of ELX/TEZ/IVA on CFTR function in airway and intestinal epithelia in patients with CF and one or two F508del alleles aged 12 years and older. Methods: This prospective, observational, multicenter study assessed clinical outcomes including FEV₁% predicted and body mass index and the CFTR biomarkers sweat chloride concentration, nasal potential difference, and intestinal current measurement before and 8–16 weeks after initiation of ELX/TEZ/IVA. Measurements and Main Results: A total of 107 patients with CF including 55 patients with one F508del and a minimal function mutation and 52 F508del homozygous patients were enrolled in this study. In patients with one F508del allele, nasal potential difference and intestinal current measurement showed that ELX/TEZ/IVA improved CFTR function in nasal epithelia to a level of 46.5% (interquartile range [IQR], 27.5–72.4; P < 0.001) and in intestinal epithelia to 41.8% of normal (IQR, 25.1–57.6; P < 0.001). In F508del homozygous patients, ELX/TEZ/IVA exceeded improvement of CFTR function observed with TEZ/IVA and increased CFTR-mediated Cl⁻ secretion to a level of 47.4% of normal (IQR, 19.3–69.2; P < 0.001) in nasal and 45.9% (IQR, 19.7–66.6; P < 0.001) in intestinal epithelia. Conclusions: Treatment with ELX/TEZ/IVA results in effective improvement of CFTR function in airway and intestinal epithelia in patients with CF and one or two F508del alleles. Clinical trial registered with www.clinicaltrials.gov (NCT04732910).

Rationale: We recently demonstrated that triple-combination CFTR (cystic fibrosis transmembrane conductance regulator) modulator therapy with elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) improves CFTR function in airway and intestinal epithelia to 40–50% of normal in patients with cystic fibrosis (CF) with one or two F508del alleles. In previous studies, this improvement of CFTR function was shown to improve clinical outcomes; however, effects on the lung clearance index (LCI) determined by multiple-breath washout and abnormalities in lung morphology and perfusion detected by magnetic resonance imaging (MRI) have not been studied. Objectives: To examine the effect of ELX/TEZ/IVA on LCI and lung MRI scores in patients with CF and one or two F508del alleles aged ⩾12 years. Methods: This prospective, observational, multicenter, postapproval study assessed LCI and lung MRI scores before and 8–16 weeks after initiation of ELX/TEZ/IVA. Measurements and Main Results: A total of 91 patients with CF, including 45 heterozygous for F508del and a minimal function mutation (MF) and 46 homozygous for F508del, were enrolled in this study. Treatment with ELX/TEZ/IVA improved LCI in F508del/MF (−2.4; interquartile range [IQR], −3.7 to −1.1; P < 0.001) and F508del homozygous (−1.4; IQR, −2.4 to −0.4; P < 0.001) patients. Furthermore, ELX/TEZ/IVA improved the MRI global score in F508del/MF (−6.0; IQR, −11.0 to −1.3; P < 0.001) and F508del homozygous (−6.5; IQR, −11.0 to −1.3; P < 0.001) patients. Conclusions: Our data demonstrate that improvement of CFTR function by ELX/TEZ/IVA improves lung ventilation and abnormalities in lung morphology, including airway mucus plugging and wall thickening, in adolescent and adult patients with CF and one or two F508del alleles in a real-world, postapproval setting. Clinical trial registered with www.clinicaltrials.gov (NCT04732910).

Rationale: Cystic fibrosis (CF) lung disease starts in early infancy, suggesting that preventive treatment may be most beneficial. Lung clearance index (LCI) and chest magnetic resonance imaging (MRI) have emerged as promising endpoints of early CF lung disease; however, randomized controlled trials testing the safety and efficacy of preventive therapies in infants with CF are lacking. Objectives: To determine the feasibility, safety, and efficacy of preventive inhalation with hypertonic saline (HS) compared with isotonic saline (IS) in infants with CF, including LCI and MRI as outcome measures. Methods: In this randomized, double-blind, controlled trial, 42 infants with CF less than 4 months of age were randomized across five sites to twice-daily inhalation of 6% HS (n = 21) or 0.9% IS (n = 21) for 52 weeks. Measurements and Main Results: Inhalation of HS and IS was generally well tolerated by infants with CF, and the number of adverse events did not differ between groups (P = 0.49). The change in LCI from baseline to Week 52 was larger in infants with CF treated with HS (−0.6) than in those treated with IS (−0.1; P < 0.05). In addition, weight gain was improved in infants with CF treated with HS (P < 0.05), whereas pulmonary exacerbations and chest MRI scores did not differ in the HS group versus the IS group. Conclusions: Preventive inhalation with HS initiated in the first months of life was safe and well tolerated and resulted in improvements in LCI and weight gain in infants with CF. Our results support the feasibility of LCI as an endpoint in randomized controlled trials in infants with CF. Clinical trial registered with www.clinicaltrials.gov (NCT01619657).

Background: The multiple breath nitrogen washout (N₂MBW) technique is increasingly used to assess the degree of ventilation inhomogeneity in school-aged children with lung disease. However, reference values for healthy children are currently not available. The aim of this study was to generate reference values for N₂MBW outcomes in a cohort of healthy Caucasian school-aged children.Methods: N₂MBW data from healthy Caucasian school-age children between 6 and 18 years old were collected from four experienced centres. Measurements were performed using an ultrasonic flowmeter (Exhalyzer D, Eco Medics AG, Duernten, Switzerland) and were analysed with commercial software (Spiroware version 3.2.1, Eco Medics AG). Normative values and upper limits of normal (ULN) were generated for lung clearance index (LCI) at 2.5% (LCI_2.5%) and at 5% (LCI_5%) of the initial nitrogen concentration and for moment ratios (M₁/M₀and M₂/M₀). A prediction equation was generated for functional residual capacity (FRC).Results: Analysis used 485 trials from 180 healthy Caucasian children aged from 6 to 18 years old. While LCI increased with age, this increase was negligible (0.04 units·year^–1for LCI_2.5%) and therefore fixed ULN were defined for this age group. These limits were 7.91 for LCI_2.5%, 5.73 for LCI_5%, 1.75 for M₁/M₀and 6.15 for M₂/M₀, respectively. Height and weight were found to be independent predictors of FRC.Conclusion: We report reference values for N₂MBW outcomes measured on a commercially available ultrasonic flowmeter device (Exhalyzer D, Eco Medics AG) in healthy school-aged children to allow accurate interpretation of ventilation distribution outcomes and FRC in children with lung disease.