Effect of elexacaftor/tezacaftor/ivacaftor on airway and systemic inflammation in cystic fibrosis

Cystic fibrosis year in review 2023

This past year, there were many important advances for patients with cystic fibrosis (CF). Of the many publications related to CF in 2023, there was further evaluation of highly effective modulator therapy, new assessments and guidelines for clinical manifestations and therapies for CF, advances in newborn screening and diagnosis, and evaluation of outcomes for people with CF transmembrane conductance regulator-related metabolic syndrome/CF screen positive, inconclusive diagnosis. The aim of this review article is not to provide a full assessment of the wide range of articles published in 2023, but to provide a brief review of publication that may lead to changes in clinical care.

Cystic Fibrosis: Understanding Cystic Fibrosis Transmembrane Regulator Mutation Classification and Modulator Therapies

A common life-threatening hereditary disease, Cystic Fibrosis (CF), affects primarily Caucasian infants. High sweat-salt levels are observed as a result of a single autosomal mutation in chromosome 7 that affects the critical function of the cystic fibrosis transmembrane regulator (CFTR). For establishing tailored treatment strategies, it is important to understand the broad range of CFTR mutations and their impacts on disease pathophysiology. This study thoroughly investigates the six main classes of classification of CFTR mutations based on their functional effects. Each class is distinguished by distinct molecular flaws, such as poor protein synthesis, misfolding, gating defects, conduction defects, and decreased CFTR expression at the apical membrane. Furthermore, this paper focuses on the emerging field of CFTR modulators, which intend to restore CFTR function or mitigate its consequences. These modulators, which are characterized by the mode of action and targeted mutation class, have the potential to provide personalized therapy regimens in CF patients. This review provides valuable insights into the genetic basis of CF pathology, and highlights the potential for precision medicine methods in CF therapy by thoroughly investigating CFTR mutation classification and related modulators.

Akt-driven TGF-β and DKK1 Secretion Impairs F508del Cystic Fibrosis Airway Epithelium Polarity

Epithelial polarity is fundamental in maintaining barrier integrity and tissue protection. In cystic fibrosis (CF), apicobasal polarity of the airway epithelium is altered, resulting in increased apical fibronectin deposition and enhanced susceptibility to bacterial infections. Here, we evaluated the effect of highly effective modulator treatment (HEMT) on fibronectin apical deposition and investigated the intracellular mechanisms triggering the defect in polarity of the CF airway epithelium. To this end, primary cultures of CF (F508del variant) human airway epithelial cells (HAECs) and a HAEC line, Calu-3, knocked down for CFTR (CF transmembrane conductance regulator) were compared with control counterparts. We show that CFTR mutation in primary HAECs and CFTR knockdown cells promote the overexpression and oversecretion of TGF-β1 and DKK1 when cultured at an air-liquid interface. These dynamic changes result in hyperactivation of the TGF-β pathway and inhibition of the Wnt pathway through degradation of β-catenin leading to imbalanced proliferation and polarization. The abnormal interplay between TGF-β and Wnt signaling pathways is reinforced by aberrant Akt signaling. Pharmacological manipulation of TGF-β, Wnt, and Akt pathways restored polarization of the F508del CF epithelium, a correction that was not achieved by HEMT. Our data shed new insights into the signaling pathways that fine-tune apicobasal polarization in primary airway epithelial cells and may provide an explanation to the mitigated efficacy of HEMT on lung infection in people with CF.

Pharmacological Improvement of Cystic Fibrosis Transmembrane Conductance Regulator Function Rescues Airway Epithelial Homeostasis and Host Defense in Children with Cystic Fibrosis

Rationale: Pharmacological improvement of cystic fibrosis transmembrane conductance regulator (CFTR) function with elexacaftor/tezacaftor/ivacaftor (ETI) provides unprecedented improvements in lung function and other clinical outcomes in patients with cystic fibrosis (CF). However, ETI effects on impaired mucosal homeostasis and host defense at the molecular and cellular levels in the airways of patients with CF remain unknown. Objectives: To investigate effects of ETI on the transcriptome of nasal epithelial and immune cells from children with CF at the single-cell level. Methods: Nasal swabs from 13 children with CF and at least one F508del allele aged 6 to 11 years were collected at baseline and 3 months after initiation of ETI, subjected to single-cell RNA sequencing, and compared with swabs from 12 age-matched healthy children. Measurements and Main Results: Proportions of CFTR-positive cells were decreased in epithelial basal, club, and goblet cells, but not in ionocytes, from children with CF at baseline and were restored by ETI therapy to nearly healthy levels. Single-cell transcriptomics revealed an impaired IFN signaling and reduced expression of major histocompatibility complex classes I and II encoding genes in epithelial cells of children with CF at baseline, which was partially restored by ETI. In addition, ETI therapy markedly reduced the inflammatory phenotype of immune cells, particularly of neutrophils and macrophages. Conclusions: Pharmacological improvement of CFTR function improves innate mucosal immunity and reduces immune cell inflammatory responses in the upper airways of children with CF at the single-cell level, highlighting the potential to restore epithelial homeostasis and host defense in CF airways by early initiation of ETI therapy.

Anti-inflammatory effects of elexacaftor/tezacaftor/ivacaftor in adults with cystic fibrosis heterozygous for F508del

Inflammation is a key driver in the pathogenesis of cystic fibrosis (CF). We assessed the effectiveness of elexacaftor/tezacaftor/ivacaftor (ETI) therapy on downregulating systemic and immune cell-derived inflammatory cytokines. We also monitored the impact of ETI therapy on clinical outcome. Adults with CF, heterozygous for F508del (n = 19), were assessed at baseline, one month and three months following ETI therapy, and clinical outcomes were measured, including sweat chloride, lung function, weight, neutrophil count and C-reactive protein (CRP). Cytokine quantifications were measured in serum and following stimulation of peripheral blood mononuclear cells (PBMCs) with lipopolysaccharide (LPS) and adenosine triphosphate and analysed using LEGEND plex™ Human Inflammation Panel 1 by flow cytometry (n = 19). ASC specks were measured in serum and caspase-1 activity and mRNA levels determined from stimulated PBMCs were determined. Patients remained stable over the study period. ETI therapy resulted in decreased sweat chloride concentrations (p < 0.0001), CRP (p = 0.0112) and neutrophil count (p = 0.0216) and increased percent predicted forced expiratory volume (ppFEV1) (p = 0.0399) from baseline to three months, alongside a trend increase in weight. Three months of ETI significantly decreased IL-18 (p< 0.0011, p < 0.0001), IL-1β (p<0.0013, p = 0.0476), IL-6 (p = 0.0109, p = 0.0216) and TNF (p = 0.0028, p = 0.0033) levels in CF serum and following PBMCs stimulation respectively. The corresponding mRNA levels were also found to be reduced in stimulated PBMCs, as well as reduced ASC specks and caspase-1 levels, indicative of NLRP3-mediated production of pro-inflammatory cytokines, IL-1β and IL-18. While ETI therapy is highly effective at reducing sweat chloride and improving lung function, it also displays potent anti-inflammatory properties, which are likely to contribute to improved long-term clinical outcomes.

The long-term effect of elexacaftor/tezacaftor/ivacaftor on cardiorespiratory fitness in adolescent patients with cystic fibrosis: a pilot observational study

BACKGROUND

Physical activity is a crucial demand on cystic fibrosis treatment management. The highest value of oxygen uptake (VO2peak) is an appropriate tool to evaluate the physical activity in these patients. However, there are several other valuable CPET parameters describing exercise tolerance (Wpeak, VO2VT1, VO2VT2, VO2/HRpeak, etc.), and helping to better understand the effect of specific treatment (VE, VT, VD/VT etc.). Limited data showed ambiguous results of this improvement after CFTR modulator treatment. Elexacaftor/tezacaftor/ivacaftor medication improves pulmonary function and quality of life, whereas its effect on CPET has yet to be sufficiently demonstrated.

METHODS

We performed a single group prospective observational study of 10 adolescent patients with cystic fibrosis who completed two CPET measurements between January 2019 and February 2023. During this period, elexacaftor/tezacaftor/ivacaftor treatment was initiated in all of them. The first CPET at the baseline was followed by controlled CPET at least one year after medication commencement. We focused on interpreting the data on their influence by the novel therapy. We hypothesized improvements in cardiorespiratory fitness following treatment. We applied the Wilcoxon signed-rank test. The data were adjusted for age at the time of CPET to eliminate bias of aging in adolescent patients.

RESULTS

We observed significant improvement in peak workload, VO2 peak, VO2VT1, VO2VT2, VE/VCO2 slope, VE, VT, RQ, VO2/HR peak and RR peak. The mean change in VO2 peak was 5.7 mL/kg/min, or 15.9% of the reference value (SD ± 16.6; p= 0.014). VO2VT1 improved by 15% of the reference value (SD ± 0.1; p= 0.014), VO2VT2 improved by 0.5 (SD ± 0.4; p= 0.01). There were no differences in other parameters.

CONCLUSION

Exercise tolerance improved after elexacaftor/tezacaftor/ivacaftor treatment initiation. We suggest that the CFTR modulator alone is not enough for recovering physical decondition, but should be supplemented with physical activity and respiratory physiotherapy. Further studies are needed to examine the effect of CFTR modulators and physical therapy on cardiopulmonary exercise tolerance.

Adjunctive Systemic Corticosteroids for Pulmonary Exacerbations of Cystic Fibrosis

Rationale: Pulmonary exacerbations (PEx) remain the most common cause of morbidity, recurrent hospitalization, and diminished survival in people with cystic fibrosis (PWCF) and are characterized by excess inflammation. Corticosteroids are potent, widely available antiinflammatory drugs. However, corticosteroid efficacy data from randomized controlled trials in PWCF are limited. Objectives: To determine whether adjunctive systemic corticosteroid therapy is associated with improved outcomes in acute CF PEx. Methods: We performed a secondary analysis of Standardized Treatment of Pulmonary Exacerbations 2 (STOP2), a large multicenter randomized controlled trial of antimicrobial treatment durations for adult PWCF presenting with PEx, that included the use of corticosteroids as a stratification criterion in its randomization protocol. Corticosteroid treatment effects were determined after propensity score matching for covariates including age, sex, baseline forced expiratory volume in 1 second (FEV1), genotype, and randomization arm. The primary outcome measure was the change in percentage predicted FEV1 (ppFEV1). Symptoms, time to next PEx, and the incidence of adverse events (AEs) and serious adverse events (SAEs) were assessed as secondary endpoints. Phenotypic factors associated with the clinical decision to prescribe steroids were also investigated. Results: Corticosteroids were prescribed for 168 of 982 PEx events in STOP2 (17%). Steroid prescription was associated with decreased baseline ppFEV1, increased age, and female sex. Cotreatment with corticosteroids was independent of treatment arm allocation and did not result in greater mean ppFEV1 response, longer median time to next PEx, or more substantial symptomatic improvement compared with propensity-matched PWCF receiving antibiotics alone. AEs were not increased in corticosteroid-treated PWCF. The total number of SAEs-but not the number of corticosteroid-related or PEx-related SAEs-was higher among patients receiving corticosteroids. Conclusions: Empiric, physician-directed treatment with systemic corticosteroids, although common, is not associated with improved clinical outcomes in PWCF receiving antibiotics for PEx. Clinical trial registered with www.clinicaltrials.gov (NCT02781610).

Key inflammatory markers in bronchoalveolar lavage predict bronchiectasis progression in young children with CF

INTRODUCTION

Inflammation appears early in cystic fibrosis (CF) pathogenesis, with specific elevated inflammatory markers in bronchoalveolar lavage fluid (BALF) correlating with structural lung disease. Our aim was to identify markers of airway inflammation able to predict bronchiectasis progression over two years with high sensitivity and specificity.

METHODS

Children with CF with two chest computed tomography (CT) scans and bronchoscopies at a two-year interval were included (n= 10 at 1 and 3 years and n= 27 at 3 and 5 years). Chest CTs were scored for increase in bronchiectasis (Δ%Bx), using the PRAGMA-CF score. BALF collected with the first CT scan were analyzed for neutrophil% (n= 36), myeloperoxidase (MPO) (n= 25), neutrophil elastase (NE) (n= 26), and with a protein array for inflammatory and fibrotic markers (n= 26).

RESULTS

MPO, neutrophil%, and inducible T-cell costimulator ligand (ICOSLG), but not clinical characteristics, correlated significantly with Δ%Bx. Evaluation of neutrophil%, NE, MPO, interleukin-8 (IL-8), ICOSLG, and hepatocyte growth factor (HGF), for predicting an increase of > 0.5% of Δ%Bx in two years, showed that IL-8 had the best sensitivity (82%) and specificity (73%). Neutrophil%, ICOSLG and HGF had sensitivities of 85, 82, and 82% and specificities of 59, 67 and 60%, respectively. The odds ratio for risk of >0.5% Δ%Bx was higher for IL-8 (12.4) than for neutrophil%, ICOSLG, and HGF (5.9, 5.3, and 6.7, respectively). Sensitivity and specificity were lower for NE and MPO).

CONCLUSIONS

High levels of IL-8, neutrophil%, ICOSGL and HGF in BALF may be good predictors for progression of bronchiectasis in young children with CF.

Effects of highly effective modulator therapy on the dynamics of the respiratory mucosal environment and inflammatory response in cystic fibrosis

BACKGROUND

While the widespread initiation of elexacaftor/tezacaftor/ivacaftor (ETI) has led to dramatic clinical improvements among persons with cystic fibrosis (pwCF), little is known about how ETI affects the respiratory mucosal inflammatory and physiochemical environment, or how these changes relate to lung function.

METHODS

We performed a prospective, longitudinal study of adults with CF and chronic rhinosinusitis (CF-CRS) followed at our CF center (n = 18). Endoscopic upper respiratory tract (paranasal sinus) aspirates from multiple visit dates, both pre- and post-ETI initiation, were collected and tested for cytokines, metals, pH, and lactate levels. Generalized estimating equations were used to identify relationships between ETI and upper respiratory tract (URT) biomarker levels, and between URT biomarkers and lung function or clinical sinus parameters.

RESULTS

ETI was associated with decreased upper respiratory mucosal cytokines B-cell activating factor (BAFF), IL-12p40, IL-32, IL-8, IL-22 and soluble tumor necrosis factor-1 (sTNFR1), and an increase in a proliferation-inducing ligand (APRIL) and IL-19. ETI was also associated with decreased URT levels of copper, manganese, and zinc. In turn, lower URT levels of BAFF, IL-8, lactate, and potassium were each associated with ~1.5% to 4.3% improved forced expiratory volume in 1 s (FEV1), while higher levels of IFNγ, iron, and selenium were associated with ~2% to 10% higher FEV1.

CONCLUSIONS

Our observations suggest a dampening of inflammatory signals and restriction in microbial nutrients in the upper respiratory tract with ETI. These findings improve our understanding of how ETI impacts the mucosal environment in the respiratory tract, and may give insight into the improved infectious and inflammatory status and the resulting clinical improvements seen in pwCF.

CFTR dysfunction leads to defective bacterial eradication on cystic fibrosis airways

Dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel by genetic mutations causes the inherited disease cystic fibrosis (CF). CF lung disease that involves multiple disorders of epithelial function likely results from loss of CFTR function as an anion channel conducting chloride and bicarbonate ions and its function as a cellular regulator modulating the activity of membrane and cytosol proteins. In the absence of CFTR activity, abundant mucus accumulation, bacterial infection and inflammation characterize CF airways, in which inflammation-associated tissue remodeling and damage gradually destroys the lung. Deciphering the link between CFTR dysfunction and bacterial infection in CF airways may reveal the pathogenesis of CF lung disease and guide the development of new treatments. Research efforts towards this goal, including high salt, low volume, airway surface liquid acidosis and abnormal mucus hypotheses are critically reviewed.

Airway inflammation accelerates pulmonary exacerbations in cystic fibrosis

Airway inflammation underlies cystic fibrosis (CF) pulmonary exacerbations. In a prospective multicenter study of randomly selected, clinically stable adolescents and adults, we assessed relationships between 24 inflammation-associated molecules and the future occurrence of CF pulmonary exacerbation using proportional hazards models. We explored relationships for potential confounding or mediation by clinical factors and assessed sensitivities to treatments including CF transmembrane regulator (CFTR) protein synthesis modulators. Results from 114 participants, including seven on ivacaftor or lumacaftor-ivacaftor, representative of the US CF population during the study period, identified 10 biomarkers associated with future exacerbations mediated by percent predicted forced expiratory volume in 1 s. The findings were not sensitive to anti-inflammatory, antibiotic, and CFTR modulator treatments. The analyses suggest that combination treatments addressing RAGE-axis inflammation, protease-mediated injury, and oxidative stress might prevent pulmonary exacerbations. Our work may apply to other airway inflammatory diseases such as bronchiectasis and the acute respiratory distress syndrome.

Influence of highly effective modulator therapy on the sputum proteome in cystic fibrosis

BACKGROUND

There have been dramatic clinical improvements in people with cystic fibrosis (PwCF) commenced on the cystic fibrosis conductance regulator (CFTR) modulator elexacaftor/tezacaftor/ivacaftor (ETI). Sputum proteomics is a powerful research technique capable of identifying important airway disease mechanisms. Using this technique, we evaluated how ETI changes the sputum proteome in PwCF.

METHODS

Sputum samples from 21 CF subjects pre- and post- ETI, 6 CF controls ineligible for ETI, and 15 healthy controls were analysed by liquid chromatography mass spectrometry.

RESULTS

Post-ETI, mean FEV1 % increased by 13.7 % (SD 7.9). Principal component and hierarchical clustering analysis revealed that the post-ETI proteome shifted to an intermediate state that was distinct from pre-ETI and healthy controls, even for those achieving normal lung function. Functional analysis showed incomplete resolution of neutrophilic inflammation. The CF control sputum proteome did not alter. At the protein-level many more proteins increased in abundance than decreased following ETI therapy (80 vs 30; adjusted p value <0.05), including many that have anti-inflammatory properties. Of those proteins that reduced in abundance many were pro-inflammatory neutrophil-derived proteins. Several important respiratory proteases were unchanged.

CONCLUSIONS

Sputum proteomics can provide insights into CF lung disease mechanisms and how they are modified by therapeutic intervention, in this case ETI. This study identifies imbalances in pro- and anti- inflammatory proteins in sputum that partially resolve with ETI even in those achieving normal spirometry values. This post-ETI intermediate state could contribute to ongoing airway damage and therefore its relevance to clinical outcomes needs to be established.

Use of elexacaftor/tezacaftor/ivacaftor leads to changes in detection frequencies of Staphylococcus aureus and Pseudomonas aeruginosa dependent on age and lung function in people with cystic fibrosis

OBJECTIVES

The impressive improvements of cystic fibrosis (CF) transmembrane conductance regulator (CFTR) function by elexacaftor/tezacaftor/ivacaftor (ETI) result in changes in the detection frequencies of Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA). We assessed determinants of the response to ETI with regards to SA and PA detection frequencies as documented in the German CF registry for people with CF (pwCF) ≥12 years.

METHODS

We evaluated changes in the detection frequencies of SA and PA for 21 months before and after initiation of ETI and used different statistical tests to identify determinants of detection changes.

RESULTS

We included data from 1092 pwCF with results from culture-dependent diagnostics for SA and PA detection from 7944 microbiological samples before and 6.845 microbiological samples after initiation of ETI. Detections of SA decreased from 54.3% to 44.3% and 40.2% and those of PA from 39.9% to 31.9% and 22.6% 3 and 21 months after initiation of therapy, respectively (all P <0.001). Reduction of SA and PA were observed in throat swabs and sputa, associated significantly with age, previous lung function, and were dependent on pre-ETI colonization status.

CONCLUSIONS

The different patterns of reductions of SA and PA suggest that pathogen-specific biological processes govern the responsiveness of microbiological colonization towards ETI in pwCF.

Diminished airway host innate response in people with cystic fibrosis who experience frequent pulmonary exacerbations

RATIONALE

Pulmonary exacerbations are clinically impactful events that accelerate cystic fibrosis (CF) lung disease progression. The pathophysiological mechanisms underlying an increased frequency of pulmonary exacerbations have not been explored.

OBJECTIVES

To compare host immune response during intravenous antibiotic treatment of pulmonary exacerbations in people with CF who have a history of frequent versus infrequent exacerbations.

METHODS

Adults with CF were recruited at onset of antibiotic treatment of a pulmonary exacerbation and were categorised as infrequent or frequent exacerbators based on their pulmonary exacerbation frequency in the previous 12 months. Clinical parameters, sputum bacterial load and sputum inflammatory markers were measured on day 0, day 5 and at the end of treatment. Shotgun proteomic analysis was performed on sputum using liquid chromatography-mass spectrometry.

MEASUREMENTS AND MAIN RESULTS

Many sputum proteins were differentially enriched between infrequent and frequent exacerbators (day 0 n=23 and day 5 n=31). The majority of these proteins had a higher abundance in infrequent exacerbators and were secreted innate host defence proteins with antimicrobial, antiprotease and immunomodulatory functions. Several differentially enriched proteins were validated using ELISA and Western blot including secretory leukocyte protease inhibitor (SLPI), lipocalin-1 and cystatin SA. Sputum from frequent exacerbators demonstrated potent ability to cleave exogenous recombinant SLPI in a neutrophil elastase dependent manner. Frequent exacerbators had increased sputum inflammatory markers (interleukin (IL)-1β and IL-8) and total bacterial load compared to infrequent exacerbators.

CONCLUSIONS

A diminished innate host protein defence may play a role in the pathophysiological mechanisms of frequent CF pulmonary exacerbations. Frequent exacerbators may benefit from therapies targeting this dysregulated host immune response.

Plasma levels of chemokines decrease during elexacaftor/tezacaftor/ivacaftor therapy in adults with cystic fibrosis

Background

Cystic fibrosis (CF) is associated with dysregulated immune responses, exaggerated inflammation and chronic infection. CF transmembrane conductance regulator (CFTR) modulator therapies directly target the underlying protein defects and resulted in significant clinical benefits for people with CF (pwCF). This study analysed the effects of triple CFTR modulator therapy elexacaftor/tezacaftor/ivacaftor (ETI) on CF-associated inflammation, especially systemic chemokines.

Methods

A bead-based immunoassay was used to quantify proinflammatory chemokines (IL-8, IP-10, Eotaxin, TARC, RANTES, MIP-1α, MIP-1β, MIP-3α, MIG, ENA-78, GROα, I-TAC) in plasma samples from pwCF collected before, at three, and at six months after starting ETI therapy.

Results

Fifty-one pwCF (47 % female; mean age 32 ± 10.4 years) were included. At baseline, 67 % were already receiving CFTR modulator therapy with tezacaftor/ivacaftor or lumacaftor/ivacaftor. After initiation of ETI therapy there was a significant improvement in percent predicted forced expiratory volume in 1 s (+12.7 points, p < 0.001) and a significant decrease in sweat chloride levels (-53.6 %, p < 0.001). After 6 months' treatment with ETI therapy there were significant decreases in plasma levels of MIP-3α (-68.2 %, p = 0.018), GROα (-17.7 %, p = 0.013), ENA-78 (-16.3 %, p = 0.034) and I-TAC (-3.4 %, p = 0.032). IL-8 exhibited a reduction that did not reach statistical significance (-17.8 %, p = 0.057); levels of other assessed cytokines did not change significantly from baseline.

Conclusions

ETI appears to affect a distinct group of chemokines that are predominately associated with neutrophilic inflammation, demonstrating the anti-inflammatory properties of ETI therapy.

Laboratory Tools to Predict CFTR Modulator Therapy Effectiveness and to Monitor Disease Severity in Cystic Fibrosis

The implementation of cystic fibrosis (CF) transmembrane conductance regulator (CFTR) modulator drugs into clinical practice has been attaining remarkable therapeutic outcomes for CF, a life-threatening autosomal recessive genetic disease. However, there is elevated CFTR allelic heterogeneity, and various individuals carrying (ultra)rare CF genotypes remain without any approved modulator therapy. Novel translational model systems based on individuals' own cells/tissue are now available and can be used to interrogate in vitro CFTR modulator responses and establish correlations of these assessments with clinical features, aiming to provide prediction of therapeutic effectiveness. Furthermore, because CF is a progressive disease, assessment of biomarkers in routine care is fundamental in monitoring treatment effectiveness and disease severity. In the first part of this review, we aimed to focus on the utility of individual-derived in vitro models (such as bronchial/nasal epithelial cells and airway/intestinal organoids) to identify potential responders and expand personalized CF care. Thereafter, we discussed the usage of CF inflammatory biomarkers derived from blood, bronchoalveolar lavage fluid, and sputum to routinely monitor treatment effectiveness and disease progression. Finally, we summarized the progress in investigating extracellular vesicles as a robust and reliable source of biomarkers and the identification of microRNAs related to CFTR regulation and CF inflammation as novel biomarkers, which may provide valuable information for disease prognosis.

Longitudinal microbial and molecular dynamics in the cystic fibrosis lung after Elexacaftor-Tezacaftor-Ivacaftor therapy

BACKGROUND

Cystic fibrosis (CF) is a genetic disorder causing poor mucociliary clearance in the airways and subsequent respiratory infection. The recently approved triple therapy Elexacaftor-Tezacaftor-Ivacaftor (ETI) has significantly improved lung function and decreased airway infection in persons with CF (pwCF). This improvement has been shown to occur rapidly, within the first few weeks of treatment. The effects of longer term ETI therapy on lung infection dynamics, however, remain mostly unknown.

RESULTS

Here, we applied 16S rRNA gene amplicon sequencing, untargeted metabolomics, and neutral models to high-resolution, longitudinally collected sputum samples from pwCF on ETI therapy (162 samples, 7 patients) and compared to similarly collected data set from pwCF not taking ETI (630 samples, 9 patients). Because ETI reduces sputum production, samples were collected in freezers provided in the subject's homes at least 3 months after first taking ETI, with those on ETI collecting a sample approximately weekly. The lung function (%ppFEV1) of those in our longitudinal cohort significantly improved after ETI (6.91, SD = 7.74), indicating our study cohort was responsive to ETI. The daily variation of alpha- and beta-diversity of both the microbiome and metabolome was higher for those on ETI, reflecting a more dynamic microbial community and chemical environment during treatment. Four of the seven subjects on ETI were persistently infected with Pseudomonas or Burkholderia in their sputum throughout the sampling period while the total bacterial load significantly decreased with time (R = - 0.42, p = 0.01) in only one subject. The microbiome and metabolome dynamics on ETI were personalized, where some subjects had a progressive change with time on therapy, whereas others had no association with time on treatment. To further classify the augmented variance of the CF microbiome under therapy, we fit the microbiome data to a Hubbell neutral dynamics model in a patient-stratified manner and found that the subjects on ETI had better fit to a neutral model.

CONCLUSION

This study shows that the longitudinal microbiology and chemistry in airway secretions from subjects on ETI has become more dynamic and neutral and that after the initial improvement in lung function, many are still persistently infected with CF pathogens.

Understanding and addressing the needs of people with cystic fibrosis in the era of CFTR modulator therapy

Cystic fibrosis is a multiorgan disease caused by impaired function of the cystic fibrosis transmembrane conductance regulator (CFTR). Since the introduction of the CFTR modulator combination elexacaftor-tezacaftor-ivacaftor (ETI), which acts directly on mutant CFTR to enhance its activity, most people with cystic fibrosis (pwCF) have seen pronounced reductions in symptoms, and studies project marked increases in life expectancy for pwCF who are eligible for ETI. However, modulator therapy has not cured cystic fibrosis and the success of CFTR modulators has resulted in immediate questions about the new state of cystic fibrosis disease and clinical challenges in the care of pwCF. In this Series paper, we summarise key questions about cystic fibrosis disease in the era of modulator therapy, highlighting state-of-the-art research and clinical practices, knowledge gaps, new challenges faced by pwCF and the potential for future health-care challenges, and the pressing need for additional therapies to treat the underlying genetic or molecular causes of cystic fibrosis.