CFTR Modulator Use Is Associated with Higher Hemoglobin Levels in Individuals with Cystic Fibrosis

Glycemia and Insulin Secretion in Cystic Fibrosis Two Years After Elexacaftor/Tezacaftor/Ivacaftor: PROMISE-ENDO

BACKGROUND

Elexacaftor/tezacaftor/ivacaftor (ETI) is a highly effective therapy that improves lung disease in people with cystic fibrosis (pwCF), but its effect on glucose tolerance and insulin secretion is unclear.

METHODS

PROMISE is a multicenter prospective, observational study of ETI in pwCF ≥12 years and at least one F508del allele. The PROMISE Endocrine sub-study (PROMISE-ENDO) enrolled participants at 10 CF Centers where hemoglobin A1c (HbA1c) was collected and 3-hour oral glucose tolerance tests (OGTT) conducted to examine glucose tolerance, glucose excursions, insulin secretory rates (deconvolution of C-peptide) and sensitivity (oral minimal model) prior to ETI and 12-18 months (mos) and 24-30 mos following ETI initiation. Longitudinal mixed effects models were used to test within-subject ETI effects.

RESULTS

At baseline, 79 participants completed OGTTs [39 (49%) male, median (IQR) age 19.6 (14.7, 27.3) years, BMI z-score 0.12 (-0.51, 0.65)]. At 12-18 mos n=68 and at 24-30 mos n=58 completed OGTTs. At 24-30 mos, fasting glucose (mg/dL) decreased [94 (92, 96) to 90 (88, 93), p=0.02] in the subset not on insulin therapy (n=61), but no differences in 1-hr or 2-hr glucose were found. HbA1c (%) decreased from 5.8 (5.6, 5.9) to 5.5 (5.4, 5.6), p<0.001 by 24-30 mos. Although insulin sensitivity (mU/L-1.min-1) decreased [8.4 (7.2, 9.5) vs. 6.8 (5.8, 7.9), p=0.03], no changes in oral disposition index were found, p=0.14.

CONCLUSIONS

After two years of ETI, fasting glucose and HbA1c showed modest decreases. Glucose tolerance varied, and overall measures of insulin secretion did not deteriorate.

Association between CFTR modulators and changes in iron deficiency markers in cystic fibrosis

BACKGROUND

Iron deficiency (ID) is a common extrapulmonary manifestation in cystic fibrosis (CF). CF transmembrane conductance regulator (CFTR) modulator therapies, particularly highly-effective modulator therapy (HEMT), have drastically improved health status in a majority of people with CF. We hypothesize that CFTR modulator use is associated with improved markers of ID.

METHODS

In a multicenter retrospective cohort study across 4 United States CF centers 2012-2022, the association between modulator therapies and ID laboratory outcomes was estimated using multivariable linear mixed effects models overall and by key subgroups. Summary statistics describe the prevalence and trends of ID, defined a priori as transferrin saturation (TSAT) <20 % or serum iron <60 μg/dL (<10.7 μmol/L).

RESULTS

A total of 568 patients with 2571 person-years of follow-up were included in analyses. Compared to off modulator therapy, HEMT was associated with +8.4 % TSAT (95 % confidence interval [CI], +6.3-10.6 %; p < 0.0001) and +34.4 μg/dL serum iron (95 % CI, +26.7-42.1 μg/dL; p < 0.0001) overall; +5.4 % TSAT (95 % CI, +2.8-8.0 %; p = 0.0001) and +22.1 μg/dL serum iron (95 % CI, +13.5-30.8 μg/dL; p < 0.0001) in females; and +11.4 % TSAT (95 % CI, +7.9-14.8 %; p < 0.0001) and +46.0 μg/dL serum iron (95 % CI, +33.3-58.8 μg/dL; p < 0.0001) in males. Ferritin was not different in those taking modulator therapy relative to off modulator therapy. Hemoglobin was overall higher with use of modulator therapy. The prevalence of ID was high throughout the study period (32.8 % in those treated with HEMT).

CONCLUSIONS

ID remains a prevalent comorbidity in CF, despite availability of HEMT. Modulator use, particularly of HEMT, is associated with improved markers for ID (TSAT, serum iron) and anemia (hemoglobin).

Glycemia and β-cell function before and after elexacaftor/tezacaftor/ivacaftor in youth and adults with cystic fibrosis

Background

Diabetes is prevalent among people with CF (PwCF) and associated with worse clinical outcomes. CFTR modulators are highly effective in improving the disease course of CF. However, the effects of elexacaftor/tezacaftor/ivacaftor (ETI) on glucose metabolism in PwCF are unclear.

Methods

Twenty youth and adults with CF underwent frequently sampled oral glucose tolerance tests (fsOGTT) before and after ETI initiation. Glucose, insulin, and C-peptide were collected at 0, 10, 30, 60, 90, and 120 min after 1.75 g/kg (max 75 g) of dextrose. HbA1c and continuous glucose monitoring (CGM) were collected in a subset. Estimates of insulin secretion (C-peptide index), insulin resistance (HOMA2 IR and IS(OGTT Cpep)), and β-cell function (C-peptide oral disposition index, oDIcoeo), were compared before and after ETI.

Results

Participants were a median (IQR) of 20.4 (14.1, 28.6) years old, 75 % male. Follow-up occurred 10.5 (10.0, 12.3) months after ETI initiation. BMI z-score increased from 0.3 (-0.3, 0.8) to 0.8 (0.4, 1.5), p = 0.013 between visits. No significant differences were observed in glucose tolerance, glucose area under the curve, nor fsOGTT glucose concentrations before and after ETI. Median (IQR) C-peptide index increased from 5.7 (4.1, 8.3) to 8.8 (5.5, 10.8) p = 0.013 and HOMA2 IR increased (p < 0.001), while oDIcoeo was unchanged (p = 0.67). HbA1c decreased from 5.5 % (5.5, 5.8) to 5.4 % (5.2, 5.6) (p = 0.003) while CGM variables did not change.

Conclusions

BMI z-score and measures of both insulin resistance and insulin secretion increased within the first year of ETI initiation. β-cell function adjusted for insulin sensitivity (oDIcoeo) did not change.

Use of elexacaftor/tezacaftor/ivacaftor among cystic fibrosis lung transplant recipients

BACKGROUND

Cystic fibrosis (CF) lung transplant (LT) recipients may warrant treatment with elexacaftor/tezacaftor/ivacaftor (ETI) to improve extrapulmonary manifestations of CF. Our objectives were to identify reasons for prescribing ETI after LT and evaluate changes in body mass index (BMI), hemoglobin A1c, hemoglobin, and liver enzymes.

METHODS

This was an electronic health record-based cohort study, October 2019-September 2020, at 14 CF LT Consortium sites in North America. The study included CF LT recipients prescribed ETI after transplant. Differences in BMI, A1c, and hemoglobin were assessed with paired t-tests.

RESULTS

There were 94 patients prescribed ETI; indications included sinus disease (68%), GI symptoms (39%), or low BMI (19%). Prescriptions were written by CF physicians (34%), LT physicians (27%), or physicians who practice both CF and LT (39%). Forty patients (42%) stopped ETI at a median of 56 days [IQR 26, 139] after start/prescription date. ETI was not associated with a significant change in BMI (0.2 kg/m2, 95% CI [-0.1, 0.6], p = 0.150), but was associated with decreased A1c (0.4%, 95% CI 0.2, 0.7, p = 0.003), and increased hemoglobin for patients with anemia (0.6 g/dL, 95% CI 0.2, 1.0, p = 0.007). Three people (3%) stopped ETI due to elevated transaminases.

CONCLUSIONS

ETI is rarely prescribed for non-pulmonary indications after LT for CF. Further study is needed to determine the risks and benefits of ETI in the CF lung transplant population given the potential for drug interactions, side effects leading to discontinuation of ETI, and the possible mechanisms for ETI to positively impact long-term post-transplant outcomes.

Iron Deficiency in Cystic Fibrosis: A Cross-Sectional Single-Centre Study in a Referral Adult Centre

Iron deficiency (ID) diagnosis in cystic fibrosis (CF) is challenging because of frequent systemic inflammation. We aimed to determine the prevalence and risk factors of ID in adult patients with CF. We conducted a single-centre prospective study in a referral centre. ID was defined by transferrin saturation ≤16% or ferritin ≤20 (women) or 30 (men) μg/L, or ≤100 μg/L in the case of systemic inflammation. Apparent exacerbation was an exclusion criterion. We included 165 patients (78 women), mean age—31.1 ± 8.9 years. ID prevalence was 44.2%. ID was significantly associated with female gender (58.9% vs. 38%), lower age (29.4 ± 8.5 vs. 32.5 ± 9.1), lower body mass index (20.5 ± 2.2 vs. 21.3 ± 2.5), and Pseudomonas aeruginosa colonization (70.8% vs. 55.1%). Diabetes mellitus, antiacid drug use and low pulmonary function were more frequent in patients with ID with no statistical significance. The use of CFTR correctors was not associated with ID. In the multivariate analysis, ID was associated with female gender (OR 2.64, CI95% 1.31−5.31), age < 30 years (OR 2.30, CI95% 1.16−4.56), and P. aeruginosa (OR 2.09, CI95% 1.04−4.19).

Exercise intolerance in cystic fibrosis-the role of CFTR modulator therapies

Exercise intolerance is common in people with CF (pwCF), but not universal among all individuals. While associated with disease prognosis, exercise intolerance is not simply a reflection of the degree of lung disease. In people with severe CF, respiratory limitations may contribute more significantly to impaired exercise capacity than in those with mild-moderate CF. At all levels of disease severity, there are peripheral factors e.g., abnormal macro- and micro-vascular function that impair blood flow and reduce oxygen extraction, and mitochondrial defects that diminish metabolic efficiency. We discuss advances in understanding the central and peripheral mechanisms underlying exercise intolerance in pwCF. Exploring both the central and peripheral factors that contribute to exercise intolerance in CF can help inform the development of new therapeutic targets, as well as help define prognostic criteria.

Use of proton pump inhibitors is associated with lower hemoglobin levels in people with cystic fibrosis

BACKGROUND

Proton pump inhibitors (PPIs) and histamine H2-receptor antagonists (H2RAs) are commonly prescribed to people with cystic fibrosis (PwCF) to treat gastroesophageal reflux disease (GERD) and/or protect pancreatic enzymes from degradation in the stomach. Acid suppressive medications (ASMs) could theoretically reduce hemoglobin (Hgb) levels by restricting enteral iron absorption, but evidence of an association between use of ASMs and lower Hgb levels is lacking in PwCF.

METHODS

We used unadjusted and covariate-adjusted generalized linear mixed models (GLMMs) to estimate the fixed effects of using versus never using ASMs on annual Hgb levels of PwCF in the U.S. Cystic Fibrosis Foundation Patient Registry (CFFPR) from 2011 to 2017.

RESULTS

There were 9850 users and 9007 never-users of ASMs from 2011 to 2017 who met inclusion criteria. Not adjusting for covariates, Hgb estimates were lower for male and female H2RA and/or PPI users versus never-users. Adjusting for covariates, mean Hgb was 0.1 g/dl (95% CI: 0.03, 0.17) lower for males that exclusively used PPIs than it was for male never-users of ASMs (p = .008). Adjusting for covariates, mean Hgb levels were 0.11 g/dl (95% CI: 0.04, 0.18) lower for females that exclusively used PPIs and 0.16 g/dl (95% CI: 0.05, 0.27) lower for females that used PPIs and H2RAs concurrently than it was for female never-users of ASMs (p = .005 and p = .002 for respective comparisons).

CONCLUSIONS

Males and females with cystic fibrosis (CF) who used PPIs and females with CF who concurrently used PPIs and H2RAs had lower Hgb levels than never-users of ASMs of the same sex in the CFFPR from 2011 to 2017.

The Extrapulmonary Effects of Cystic Fibrosis Transmembrane Conductance Regulator Modulators in Cystic Fibrosis

The effects of cystic fibrosis (CF) transmembrane conductance regulator (CFTR) modulators on lung function, pulmonary exacerbations, and quality of life have been well documented. However, CF is a multiorgan disease, and therefore an evidence base is emerging on the systemic effects of CFTR modulators beyond the pulmonary system. This is of great clinical importance, as many of these studies provide proof of concept that CFTR modulators might be used one day to prevent or treat extrapulmonary manifestations stemming from CFTR dysfunction. In this concise review of the literature, we summarize the results of key publications that have evaluated the effects of CFTR modulators on weight and growth, pancreatic function, the gastrointestinal and hepatobiliary systems, sinus disease, bone disease, exercise tolerance, fertility, mental health, and immunity. Although many of these studies have reported beneficial extrapulmonary effects related to the use of ivacaftor (IVA) in patients with CF with at least one gating mutation, most of the evidence is low or very low quality, given the limited number of patients evaluated and the lack of control groups. Based on an even smaller number of studies evaluating the extrapulmonary effects of lumacaftor-IVA, the benefits are less clear. Although limited, these studies may provide the basis for future clinical trials to evaluate CFTR modulators on the extrapulmonary manifestations of CF.

Phenotypes of CF rabbits generated by CRISPR/Cas9-mediated disruption of the CFTR gene

Existing animal models of cystic fibrosis (CF) have provided key insights into CF pathogenesis but have been limited by short lifespans, absence of key phenotypes, and/or high maintenance costs. Here, we report the CRISPR/Cas9-mediated generation of CF rabbits, a model with a relatively long lifespan and affordable maintenance and care costs. CF rabbits supplemented solely with oral osmotic laxative had a median survival of approximately 40 days and died of gastrointestinal disease, but therapeutic regimens directed toward restoring gastrointestinal transit extended median survival to approximately 80 days. Surrogate markers of exocrine pancreas disorders were found in CF rabbits with declining health. CFTR expression patterns in WT rabbit airways mimicked humans, with widespread distribution in nasal respiratory and olfactory epithelia, as well as proximal and distal lower airways. CF rabbits exhibited human CF–like abnormalities in the bioelectric properties of the nasal and tracheal epithelia. No spontaneous respiratory disease was detected in young CF rabbits. However, abnormal phenotypes were observed in surviving 1-year-old CF rabbits as compared with WT littermates, and these were especially evident in the nasal respiratory and olfactory epithelium. The CF rabbit model may serve as a useful tool for understanding gut and lung CF pathogenesis and for the practical development of CF therapeutics.

How Clinically Efficient Is Lumacaftor/Ivacaftor for Cystic Fibrosis Patients? An Updated Literature Review

Cystic fibrosis (CF) is an autosomal recessive illness caused by the defective cystic fibrosis transmembrane conductance regulator (CFTR) gene. These patients suffer from repeated chronic sinuses and lung infections, resulting in frequent hospital admissions and antibiotic (Abx) courses. These are the major contributing factors responsible for a low health-related quality of life (HRQoL) and increasing the disease burden. The introduction and approval of CFTR modulators-lumacaftor (LUM) and ivacaftor (IVA) in 2015 by the US Food and Drug Administration (FDA) reduced the mortality and morbidity rates associated with the disease. In 2018, the FDA approved these drugs from age two and five years with two copies of F5806 del. This literature review aims to present the studies centered on the clinical effects of LUM/IVA. We searched for the relevant articles, from 2016 to 2020, in PubMed Central (PMC), Google Scholars, and Journal of Cystic Fibrosis. LUM/IVA has a broader range of effects. They showed marked improvement in the reduction of pulmonary exacerbations (PEx), Hospitalization rates, Abx use, and modification in forced expiratory volume in one second (FEV1) status of pre-existing severe lung disease. Now, there is a need for an initiative to conduct more clinical trials and studies in the future to assess and evaluate the long-term clinical benefits and safety of LUM/IVA therapy in all age groups.

Cystic fibrosis year in review 2019: Section 1 CFTR modulators

During the year 2019, research and case reports/series in the field of cystic fibrosis (CF) were in abundance. To adequately address the large body of CF research published during 2019, the CF year in review will be divided into three sections. This report is the first section, focusing specifically on new research related to cystic fibrosis transmembrane conductance regulator modulator therapy. Additional sections will concentrate on pulmonary and infections research and the multisystem effects of CF. It is an exciting time to be providing care for patients and their families with CF with all the exciting new discoveries that will be shared in these reviews.

Airway Inflammation and Host Responses in the Era of CFTR Modulators

The arrival of cystic fibrosis transmembrane conductance regulator (CFTR) modulators as a new class of treatment for cystic fibrosis (CF) in 2012 represented a pivotal advance in disease management, as these small molecules directly target the upstream underlying protein defect. Further advancements in the development and scope of these genotype-specific therapies have been transformative for an increasing number of people with CF (PWCF). Despite clear improvements in CFTR function and clinical endpoints such as lung function, body mass index (BMI), and frequency of pulmonary exacerbations, current evidence suggests that CFTR modulators do not prevent continued decline in lung function, halt disease progression, or ameliorate pathogenic organisms in those with established lung disease. Furthermore, it remains unknown whether their restorative effects extend to dysfunctional CFTR expressed in phagocytes and other immune cells, which could modulate airway inflammation. In this review, we explore the effects of CFTR modulators on airway inflammation, infection, and their influence on the impaired pulmonary host defences associated with CF lung disease. We also consider the role of inflammation-directed therapies in light of the widespread clinical use of CFTR modulators and identify key areas for future research.

Answering the call to address cystic fibrosis treatment burden in the era of highly effective CFTR modulator therapy

BACKGROUND

We recognize an unprecedented opportunity to study the effects of withdrawing one or more chronic treatments in people with CF (PwCF) who benefit greatly from CFTR modulator therapy, but feasibility and acceptance of such a study within the community is unknown.

METHODS

We surveyed PwCF, their families, and their acquaintances between November 16, 2018, and December 2, 2018, and CF clinicians between December 19, 2018, and January 2, 2019, about treatment withdrawal research. We sought feedback from these groups about their level of interest in this research, the consistency with which they were taking modulator and non-modulator treatments, the ways in which they conceptualized health changes, and what chronic non-modulator treatments they were most interested in stopping. We also asked for stakeholder perspectives on the design of a treatment withdrawal trial, but we intend to report these perspectives elsewhere.

RESULTS

Eighty percent (541/675) of CF community respondents and 95% (206/218) of CF clinicians said that a trial of treatment simplification should be performed in the context of highly effective modulator therapy. Most current CFTR modulator users (292/359, 81%) have not stopped another chronic treatment. Worsening lung function by spirometry or increased daily symptoms were important health indicators. PwCF, their families, and/or their acquaintances ranked airway clearance techniques and inhaled antibiotics as the most burdensome treatments.

CONCLUSIONS

There is considerable support among the CF community and CF clinicians in the U.S. for controlled trials to assess the safety and impact of treatment simplification in patients taking highly effective modulator therapy.

Exercise Physiology Across the Lifespan in Cystic Fibrosis

Cystic fibrosis (CF), a severe life-limiting disease, is associated with multi-organ pathologies that contribute to a reduced exercise capacity. At present, the impact of, and interaction between, disease progression and other age-related physiological changes in CF on exercise capacity from child- to adult-hood is poorly understood. Indeed, the influences of disease progression and aging are inherently linked, leading to increasingly complex interactions. Thus, when interpreting age-related differences in exercise tolerance and devising exercise-based therapies for those with CF, it is critical to consider age-specific factors. Specifically, changes in lung function, chronic airway colonization by increasingly pathogenic and drug-resistant bacteria, the frequency and severity of pulmonary exacerbations, endocrine comorbidities, nutrition-related factors, and CFTR (cystic fibrosis transmembrane conductance regulator protein) modulator therapy, duration, and age of onset are important to consider. Accounting for how these factors ultimately influence the ability to exercise is central to understanding exercise impairments in individuals with CF, especially as the expected lifespan with CF continues to increase with advancements in therapies. Further studies are required that account for these factors and the changing landscape of CF in order to better understand how the evolution of CF disease impacts exercise (in)tolerance across the lifespan and thereby identify appropriate intervention targets and strategies.

Cystic fibrosis year in review 2018, part 1

Cystic fibrosis research and case reports were robust in the year 2018. This report summarizes research and cases related to Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) modulator therapies, inflammation and infection, epidemiology and the physiologic, and imaging assessment of disease.