Tezacaftor/ivacaftor in people with cystic fibrosis heterozygous for minimal function CFTR mutations

Real-world effectiveness of elexacaftor/tezacaftor/ivacaftor on the burden of illness in adolescents and adults with cystic fibrosis

Background

Elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) has been shown to be safe and efficacious in people with cystic fibrosis (CF) aged ≥2 years. Here, we describe results from an observational study assessing change in burden of illness following initiating ELX/TEZ/IVA in real-world settings.

Methods

This US-based, multicenter, observational study used data from electronic medical records to evaluate real-world burden of illness before and after ELX/TEZ/IVA initiation in people with CF aged ≥12 years heterozygous for F508del and a minimal function mutation (F/MF) or an uncharacterized CFTR mutation. Endpoints included absolute change from baseline in percent predicted forced expiratory volume in 1 s (ppFEV1), body mass index (BMI) and BMI-for-age z-score, glycated hemoglobin (HbA1c), and numbers of pulmonary exacerbations (PEx).

Results

Overall, 206 people with CF were enrolled (mean [SD] age 22.5 [11.1] years; 192 [93.2%] with F/MF genotype). Mean follow-up was 15.6 (SD, 1.6) months. Improvements in ppFEV1 (7.3 [95% CI: 5.7, 8.8] percentage points) were observed from baseline through follow-up. Increases in BMI (1.40 [95% CI: 1.07, 1.77] kg/m2) and BMI-for-age z-score (0.14 [95% CI: 0.00, 0.28]) were also observed from baseline at 12 months. The estimated annualized rate of any PEx was 1.31 at baseline and 0.61 over follow-up (rate ratio 0.47 [95% CI: 0.39, 0.55]), with annualized rates of PEx requiring antibiotics and hospitalizations of 0.55 and 0.88 in the baseline period and 0.12 and 0.36 over follow-up (rate ratios 0.22 [95% CI: 0.15, 0.31] and 0.41 [95% CI: 0.32, 0.51]), respectively. Absolute change in HbA1c was -0.22 (95% CI: -0.38, -0.06) from baseline through follow-up.

Conclusions

ELX/TEZ/IVA treatment was associated with improved lung function, increased BMI, reduced frequency of PEx, and improved (i.e., reduced) HbA1c. These results confirm the broad clinical benefits of ELX/TEZ/IVA seen in clinical trials and show the potential for ELX/TEZ/IVA to improve markers of glucose metabolism.

Corrector therapies (with or without potentiators) for people with cystic fibrosis with class II CFTR gene variants (most commonly F508del)

BACKGROUND

Cystic fibrosis (CF) is a common life-shortening genetic condition caused by a variant in the cystic fibrosis transmembrane conductance regulator (CFTR) protein. A class II CFTR variant F508del is the commonest CF-causing variant (found in up to 90% of people with CF (pwCF)). The F508del variant lacks meaningful CFTR function - faulty protein is degraded before reaching the cell membrane, where it needs to be to effect transepithelial salt transport. Corrective therapy could benefit many pwCF. This review evaluates single correctors (monotherapy) and any combination of correctors (most commonly lumacaftor, tezacaftor, elexacaftor, VX-659, VX-440 or VX-152) and a potentiator (e.g. ivacaftor) (dual and triple therapies).

OBJECTIVES

To evaluate the effects of CFTR correctors (with or without potentiators) on clinically important benefits and harms in pwCF of any age with class II CFTR mutations (most commonly F508del).

SEARCH METHODS

We searched the Cochrane CF Trials Register (28 November 2022), reference lists of relevant articles and online trials registries (3 December 2022).

SELECTION CRITERIA

Randomised controlled trials (RCTs) (parallel design) comparing CFTR correctors to control in pwCF with class II mutations.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data, assessed risk of bias and judged evidence certainty (GRADE); we contacted investigators for additional data.

MAIN RESULTS

We included 34 RCTs (4781 participants), lasting between 1 day and 48 weeks; an extension of two lumacaftor-ivacaftor studies provided additional 96-week safety data (1029 participants). We assessed eight monotherapy RCTs (344 participants) (4PBA, CPX, lumacaftor, cavosonstat and FDL169), 16 dual-therapy RCTs (2627 participants) (lumacaftor-ivacaftor or tezacaftor-ivacaftor) and 11 triple-therapy RCTs (1804 participants) (elexacaftor-tezacaftor-ivacaftor/deutivacaftor; VX-659-tezacaftor-ivacaftor/deutivacaftor; VX-440-tezacaftor-ivacaftor; VX-152-tezacaftor-ivacaftor). Participants in 21 RCTs had the genotype F508del/F508del, in seven RCTs they had F508del/minimal function (MF), in one RCT F508del/gating genotypes, in one RCT either F508del/F508del genotypes or F508del/residual function genotypes, in one RCT either F508del/gating or F508del/residual function genotypes, and in three RCTs either F508del/F508del genotypes or F508del/MF genotypes. Risk of bias judgements varied across different comparisons. Results from 16 RCTs may not be applicable to all pwCF due to age limits (e.g. adults only) or non-standard designs (converting from monotherapy to combination therapy). Monotherapy Investigators reported no deaths or clinically relevant improvements in quality of life (QoL). There was insufficient evidence to determine effects on lung function. No placebo-controlled monotherapy RCT demonstrated differences in mild, moderate or severe adverse effects (AEs); the clinical relevance of these events is difficult to assess due to their variety and few participants (all F508del/F508del). Dual therapy In a tezacaftor-ivacaftor group there was one death (deemed unrelated to the study drug). QoL scores (respiratory domain) favoured both lumacaftor-ivacaftor and tezacaftor-ivacaftor therapy compared to placebo at all time points (moderate-certainty evidence). At six months, relative change in forced expiratory volume in one second (FEV1) % predicted improved with all dual combination therapies compared to placebo (high- to moderate-certainty evidence). More pwCF reported early transient breathlessness with lumacaftor-ivacaftor (odds ratio (OR) 2.05, 99% confidence interval (CI) 1.10 to 3.83; I2 = 0%; 2 studies, 739 participants; high-certainty evidence). Over 120 weeks (initial study period and follow-up), systolic blood pressure rose by 5.1 mmHg and diastolic blood pressure by 4.1 mmHg with twice-daily 400 mg lumacaftor-ivacaftor (80 participants). The tezacaftor-ivacaftor RCTs did not report these adverse effects. Pulmonary exacerbation rates decreased in pwCF receiving additional therapies to ivacaftor compared to placebo (all moderate-certainty evidence): lumacaftor 600 mg (hazard ratio (HR) 0.70, 95% CI 0.57 to 0.87; I2 = 0%; 2 studies, 739 participants); lumacaftor 400 mg (HR 0.61, 95% CI 0.49 to 0.76; I2 = 0%; 2 studies, 740 participants); and tezacaftor (HR 0.64, 95% CI 0.46 to 0.89; 1 study, 506 participants). Triple therapy No study reported any deaths (high-certainty evidence). All other evidence was low- to moderate-certainty. QoL respiratory domain scores probably improved with triple therapy compared to control at six months (six studies). There was probably a greater relative and absolute change in FEV1 % predicted with triple therapy (four studies each across all combinations). The absolute change in FEV1 % predicted was probably greater for F508del/MF participants taking elexacaftor-tezacaftor-ivacaftor compared to placebo (mean difference 14.30, 95% CI 12.76 to 15.84; 1 study, 403 participants; moderate-certainty evidence), with similar results for other drug combinations and genotypes. There was little or no difference in adverse events between triple therapy and control (10 studies). No study reported time to next pulmonary exacerbation, but fewer F508del/F508del participants experienced a pulmonary exacerbation with elexacaftor-tezacaftor-ivacaftor at four weeks (OR 0.17, 99% CI 0.06 to 0.45; 1 study, 175 participants) and 24 weeks (OR 0.29, 95% CI 0.14 to 0.60; 1 study, 405 participants); similar results were seen across other triple therapy and genotype combinations.

AUTHORS' CONCLUSIONS

There is insufficient evidence of clinically important effects from corrector monotherapy in pwCF with F508del/F508del. Additional data in this review reduced the evidence for efficacy of dual therapy; these agents can no longer be considered as standard therapy. Their use may be appropriate in exceptional circumstances (e.g. if triple therapy is not tolerated or due to age). Both dual therapies (lumacaftor-ivacaftor, tezacaftor-ivacaftor) result in similar small improvements in QoL and respiratory function with lower pulmonary exacerbation rates. While the effect sizes for QoL and FEV1 still favour treatment, they have reduced compared to our previous findings. Lumacaftor-ivacaftor was associated with an increase in early transient shortness of breath and longer-term increases in blood pressure (not observed for tezacaftor-ivacaftor). Tezacaftor-ivacaftor has a better safety profile, although data are lacking in children under 12 years. In this population, lumacaftor-ivacaftor had an important impact on respiratory function with no apparent immediate safety concerns, but this should be balanced against the blood pressure increase and shortness of breath seen in longer-term adult data when considering lumacaftor-ivacaftor. Data from triple therapy trials demonstrate improvements in several key outcomes, including FEV1 and QoL. There is probably little or no difference in adverse events for triple therapy (elexacaftor-tezacaftor-ivacaftor/deutivacaftor; VX-659-tezacaftor-ivacaftor/deutivacaftor; VX-440-tezacaftor-ivacaftor; VX-152-tezacaftor-ivacaftor) in pwCF with one or two F508del variants aged 12 years or older (moderate-certainty evidence). Further RCTs are required in children under 12 years and those with more severe lung disease.

Real-world safety and effectiveness of elexacaftor/tezacaftor/ivacaftor in people with cystic fibrosis: Interim results of a long-term registry-based study

BACKGROUND

Phase 3 clinical trials showed elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) was safe and efficacious in people with cystic fibrosis (CF) with ≥1 F508del-CFTR allele. To assess long-term effects of ELX/TEZ/IVA under real-world conditions of use, a 5-year observational registry-based study is being conducted. We report interim results from the first 2 years of follow-up.

METHODS

The study included people with CF in the US Cystic Fibrosis Foundation Patient Registry (CFFPR) who initiated ELX/TEZ/IVA between October 2019 and December 2020. Pulmonary exacerbations (PEx), percent predicted forced expiratory volume in 1 second (ppFEV1), hospitalizations, bacterial pathogens, body mass index (BMI), CF complications and comorbidities, and liver function tests (LFTs) after treatment initiation were compared with the 5-year pre-treatment period. Death and lung transplantation were assessed relative to 2019 CFFPR data.

RESULTS

16,116 people with CF were included (mean treatment duration 20.4 months). Among those with 5 years of pre-treatment data, mean PEx/patient/year declined to 0.18 (95% CI: 0.17, 0.19) in Years 1 and 2 post-treatment from 0.86 (95% CI: 0.83, 0.88) in the baseline year (79% reduction), after a continued increase observed pre-treatment. Similarly, a decline in mean hospitalizations/patient/year was observed in Year 1 that was sustained in Year 2 (74% reduction from baseline year). The mean absolute change in ppFEV1 from baseline was +8.2 percentage points (95% CI: 8.0, 8.4) in Year 1 and +8.9 percentage points (95% CI: 8.7, 9.1) in Year 2, after a continued decline observed pre-treatment. Positive bacterial cultures decreased for all evaluated pathogens, and mean BMI increased by 1.6 kg/m2 (95% CI: 1.5, 1.6) by Year 2. No new safety concerns were identified based on evaluation of CF complications, comorbidities, and LFTs. The annualized rates of death (0.47% [95% CI: 0.39, 0.55]) and lung transplantation (0.16% [95% CI: 0.12, 0.22]) were considerably lower than reported in 2019 (1.65% and 1.08%, respectively).

CONCLUSIONS

ELX/TEZ/IVA treatment was associated with sustained improvements in lung function, reduced frequency of PEx and all-cause hospitalization, increased BMI, and lower prevalence of positive bacterial cultures. Additionally, there was a 72% lower rate of death and 85% lower rate of lung transplantation relative to the year before ELX/TEZ/IVA availability. These results, from the largest cohort of ELX/TEZ/IVA-treated people to date, extend our understanding of the broad clinical benefits of ELX/TEZ/IVA.

CFTR Modulators: Current Status and Evolving Knowledge

In the past decade, the medical management of people with cystic fibrosis (pwCF) has changed with the development of small molecules that partially restore the function of the defective CF transmembrane conductance regulator (CFTR) protein and are called CFTR modulators. Ivacaftor (IVA), a CFTR potentiator with a large effect on epithelial ion transport, was the first modulator approved in pwCF carrying gating mutations. Because IVA was unable to restore sufficient CFTR function in pwCF with other mutations, two CFTR correctors (lumacaftor and tezacaftor) were developed and used in combination with IVA in pwCF homozygous for F508del, the most common CFTR variant. However, LUM/IVA and TEZ/IVA were only moderately effective in F508del homozygous pwCF and had no efficacy in those with F508del and minimal function mutations. Elexacaftor, a second-generation corrector, was thus developed and combined to tezacaftor and ivacaftor (ELX/TEZ/IVA) to target pwCF with at least one F508del variant, corresponding to approximately 85% of pwCF. Both IVA and ELX/TEZ/IVA are considered highly effective modulator therapies (HEMTs) in eligible pwCF and are now approved for nearly 90% of the CF population over 6 years of age. HEMTs are responsible for rapid improvement in respiratory manifestations, including improvement in symptoms and lung function, and reduction in the rate of pulmonary exacerbations. The impact of HEMT on extrapulmonary manifestations of CF is less well established, although significant weight gain and improvement in quality of life have been demonstrated. Recent clinical trials and real-world studies suggest that benefits of HEMT could even prove greater when used earlier in life (i.e., in younger children and infants). This article shortly reviews the past 10 years of development and use of CFTR modulators. Effects of HEMT on extrapulmonary manifestations and on CF demographics are also discussed.

Elexacaftor-Tezacaftor-Ivacaftor: A Life-Changing Triple Combination of CFTR Modulator Drugs for Cystic Fibrosis

Cystic fibrosis (CF) is a potentially fatal monogenic disease that causes a progressive multisystemic pathology. Over the last decade, the introduction of CF transmembrane conductance regulator (CFTR) modulator drugs into clinical practice has profoundly modified the lives of many people with CF (PwCF) by targeting the fundamental cause of the disease. These drugs consist of the potentiator ivacaftor (VX-770) and the correctors lumacaftor (VX-809), tezacaftor (VX-661), and elexacaftor (VX-445). In particular, the triple combination of CFTR modulators composed of elexacaftor, tezacaftor, and ivacaftor (ETI) represents a life-changing therapy for the majority of PwCF worldwide. A growing number of clinical studies have demonstrated the safety and efficacy of ETI therapy in both short- and long-term (up to two years of follow-up to date) and its ability to significantly reduce pulmonary and gastrointestinal manifestations, sweat chloride concentration, exocrine pancreatic dysfunction, and infertility/subfertility, among other disease signs and symptoms. Nevertheless, ETI therapy-related adverse effects have also been reported, and close monitoring by a multidisciplinary healthcare team remains vital. This review aims to address and discuss the major therapeutic benefits and adverse effects reported by the clinical use of ETI therapy for PwCF.

Cystic Fibrosis Transmembrane Conductance Regulator Protein Modulators in Children and Adolescents with different CF Genotypes - Systematic Review and Meta-Analysis

OBJECTIVE

To determine the efficacy of the first triple CFTR protein modulators in children and adolescents with cystic fibrosis.

METHODS

Systematic review and meta-analysis were conducted, following PRISMA guidelines. The following databases were searched extensively: PubMed/Medline, Clinical trials.gov, Google Scholar, Scopus, Embase, and Europe PMC using the keywords: "Ivacaftor," "Elexacaftor," "Tezacaftor," VX_661", VX_770", "VX_445", "cystic fibrosis". A total of ten randomized clinical trials were included in our analysis. Primary outcomes included: Absolute change in predicted FEV1 from baseline, Absolute change in sweat chloride test from baseline, Absolute change in BMI from baseline, Absolute change in CF-QR from baseline, and Adverse Events.

RESULTS

Among primary findings, significant absolute change in predictive FEV1 from baseline through 4 weeks favoured the triple CFTR protein modulators. [MD=11.80,95%CI=8.47_15.12, p value=<0.00001]; as well as CF_QR score [MD=0.00,95%CI=-2.50_2.50, p value=1.00], and BMI kg/m² change [MD=16.90,95%CI=12.73_21.06, p value=<0.00001]. No significant change was noted for CFTR channels activity in the treatment group when compared to placebo or VX_770/VX_661 [MD= -12.57,95%CI=-94.46_69.32, p value=0.76].

CONCLUSION

In children aged ≥ 6 y old and adolescents with F508del_CFTR mutation, Elexacaftor-Tezacaftor-Ivacaftor tend to be more effective than first-generation therapy, demonstrating promising results by exhibiting significant improvement in lung function, body weight, and respiratory-related quality of life.

Cystic Fibrosis Patients with F508del/Minimal Function Genotype: Laboratory and Nutritional Evaluations after One Year of Elexacaftor/Tezacaftor/Ivacaftor Treatment

The last ten years have been characterized by an enormous step forward in the therapy and management of patients with Cystic Fibrosis (CF), thanks to the development and combination of Cystic Fibrosis Transmembrane Receptor (CFTR) correctors and potentiators. Specifically, the last approved triple combination elexacaftor/tezacaftor/ivacaftor has been demonstrated to improve lung function in CF patients with both homozygous Phe508del and Phe508del/minimal function genotypes. Here we have assessed the effect of elexacaftor/tezacaftor/ivacaftor in patients carrying the Phe508del/minimal function genotype (n = 20) after one year of treatments on liver function and nutrient absorption with a focus on lipid metabolism. We show that weight, BMI, and albumin significantly increase, suggesting a positive impact of the treatment on nutrient absorption. Furthermore, cholesterol levels as a biomarker of lipid metabolism increased significantly after one year of treatment. Most importantly, we suggest that these results were not dependent on the diet composition, possibly indicating that the drug improves the hepatic synthesis and secretion of proteins and cholesterol.

CFTR Modulators in People with Cystic Fibrosis: Real-World Evidence in France

Cystic fibrosis (CF) is a rare genetic multisystemic disease, the manifestations of which are due to mutations in the gene encoding the CF transmembrane conductance regulator (CFTR) protein and can lead to respiratory insufficiency and premature death. CFTR modulators, which were developed in the past decade, partially restore CFTR protein function. Their clinical efficacy has been demonstrated in phase 3 clinical trials, particularly in terms of lung function and pulmonary exacerbations, nutritional status, and quality of life in people with gating mutations (ivacaftor), homozygous for the F508del mutation (lumacaftor/ivacaftor and tezacaftor/ivacaftor), and in those with at least one F508del mutation (elexacaftor/tezacaftor/ivacaftor). However, many questions remain regarding their long-term safety and effectiveness, particularly in patients with advanced lung disease, liver disease, renal insufficiency, or problematic bacterial colonization. The impact of CFTR modulators on other important outcomes such as concurrent treatments, lung transplantation, chest imaging, or pregnancies also warrants further investigation. The French CF Reference Network includes 47 CF centers that contribute patient data to the comprehensive French CF Registry and have conducted nationwide real-world studies on CFTR modulators. This review seeks to summarize the results of these real-world studies and examine their findings against those of randomized control trials.

The impact of FDA and EMA regulatory decision-making process on the access to CFTR modulators for the treatment of cystic fibrosis

Background

Over the past decade, a new class of drugs called CFTR (cystic fibrosis transmembrane conductance regulator) modulators have shown to be able to improve clinical outcomes in patient with Cystic Fibrosis. In this analysis, we have extensively reviewed the regulatory pathways and decisions adopted by FDA and EMA to speed up the development, the review and the approval of these drugs, with the aim of identifying possible clinical and public health implications associated with differences.

Results

CFTR modulators have been developed towards addressing three main genetic domains: (1) F508del homozygous (F508del/F508del), (2) F508del heterozygous, and (3) genotypes not carrying F508del mutation; and expanded from adult to paediatric population. Programs to expedite the reviewing and licensing of CFTR modulators were extensively adopted by FDA and EMA. All CFTR modulators have been licensed in the US as orphan drugs, but in the EU the orphan status for LUM/IVA was not confirmed at the time of marketing authorization as results from the pivotal trial were not considered clinically significant. While FDA and EMA approved CFTR modulators on the basis of results from phase III double-blind RCTs, main differences were found on the extension of indications: FDA accepted non-clinical evidence considering a recovery of the CFTR function ≥ 10% based on chloride transport, a reliable indicator to correlate with improvement in clinical outcomes. By contrast, EMA did not deem preclinical data sufficient to expand the label of CFTR modulators without confirmatory clinical data.

Conclusions

Regulators played an important role in fostering the development and approval of CFTR modulators. However, differences were found between FDA and EMA in the way of reviewing and licensing CFTR modulators, which extended beyond semantics affecting patients’ eligibility and access: FDA’s approach was more mechanistic/biology-driven while the EMA’s one was more oriented by clinical evidence. This might refer to the connection between the EMA and the Member States, which tends to base decisions on pricing and reimbursement on clinical data rather than pre-clinical ones. Here we have proposed a two-step personalized-based model to merge the ethical commitment of ensuring larger access to all potential eligible patients (including those harboring very rare mutations) with the one of ensuring access to clinically assessed and effective medicines through Real World Data.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02350-5.

Precision Medicine Based on CFTR Genotype for People with Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal recessive genetic condition that is caused by variants in the cystic fibrosis transmembrane conductance regulator gene. This causes multisystem disease due to dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) ion channel at the apical surface of epithelia. Until recently, treatment was directed at managing the downstream effects in affected organs, principally improving airway clearance and treating infection in the lungs and improving malabsorption in the gastrointestinal tract. Care delivered by multidisciplinary teams has yielded incremental improvements in outcomes. However, the development of small-molecule CFTR modulator drugs over the last decade has heralded a new era of CF therapeutics. Modulators target the underlying defect and improve CFTR function. Either monotherapy or a combination of modulators is used depending on the specific genotype and class of CFTR disease-causing variants that an individual has. Both ivacaftor and the ivacaftor/tezacaftor/elexacaftor combination have been demonstrated to be associated with clinically very significant benefits in randomised trials and have rapidly been made available as part of standard care in many countries. CFTR modulators represent one of the best examples of precision medicine to date. They are expensive, however, and equity of access to them worldwide remains an issue. Studies and approvals are also ongoing for children under the age of 6 years for ivacaftor/tezacaftor/elexacaftor. Furthermore, no modulators are available for around 10% of the people with CF. In this review, we firstly summarise the genetics, pathophysiology and clinical problems associated with CF. We then discuss the development of CFTR modulators and key clinical trials to support their use along with other potential future therapeutic approaches.

Progress in precision medicine in cystic fibrosis: a focus on CFTR modulator therapy

The genetic multisystem condition cystic fibrosis (CF) has seen a paradigm shift in therapeutic approaches within the past decade. Since the first clinical descriptions in the 1930s, treatment advances had focused on the downstream consequences of a dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) chloride ion channel. The discovery of the gene that codes for CFTR and an understanding of the way in which different genetic mutations lead to disruption of normal CFTR function have led to the creation and subsequent licensing of drugs that target this process. This marks an important move towards precision medicine in CF and results from clinical trials and real-world clinical practice have been impressive. In this review we outline how CFTR modulator drugs restore function to the CFTR protein and the progress that is being made in this field. We also describe the real-world impact of CFTR modulators on both pulmonary and multisystem complications of CF and what this will mean for the future of CF care.

CFTR modulator drugs target the underlying cellular defect in cystic fibrosis. They have a range of pulmonary and multisystem effects and are leading to a transformation of care for a majority of people with cystic fibrosis.https://bit.ly/3nfEt8i

Review of CFTR modulators 2020

Cystic fibrosis transmembrane conductance regulator (CFTR) modulators are small molecules that directly impact the CFTR protein, improving the function of the CFTR chloride and bicarbonate channel. Beginning in 2012 with the Food and Drug Administration approval of the first CFTR modulator, ivacaftor, this class of medications has had largely positive effects on many outcomes in people with cystic fibrosis (PwCF), including lung function, growth, and other clinical parameters. There have been continued exciting developments in the current research on CFTR modulators, expanding beyond original studies. This first part of a three-part cystic fibrosis (CF) year in review 2020 will focus on research on CFTR modulators. In addition to reviewing new clinical insights, we describe work done on novel outcomes, adverse effects, issues related to cost, and next steps for clinical trials. The review focuses on articles from Pediatric Pulmonology published in 2020, but it includes articles from other journals that are of particular interest to clinicians. New developments in CF research continue to be brought forth to the CF community, deepening the understanding of this disease and improving clinical care.

Elexacaftor is a CFTR potentiator and acts synergistically with ivacaftor during acute and chronic treatment

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), which lead to early death due to progressive lung disease. The development of small-molecule modulators that directly interact with CFTR to aid in protein folding (“correctors”) and/or increase channel function (“potentiators”) have proven to be highly effective in the therapeutic treatment of CF. Notably, incorporation of the next-generation CFTR corrector, elexacaftor, into a triple combination therapeutic (marketed as Trikafta) has shown tremendous clinical promise in treating CF caused by F508del-CFTR. Here, we report on a newly-described role of elexacaftor as a CFTR potentiator. We explore the acute and chronic actions, pharmacology, and efficacy of elexacaftor as a CFTR potentiator in restoring function to multiple classes of CFTR mutations. We demonstrate that the potentiating action of elexacaftor exhibits multiplicative synergy with the established CFTR potentiator ivacaftor in rescuing multiple CFTR class defects, indicating that a new combination therapeutic of ivacaftor and elexacaftor could have broad impact on CF therapies.

Disease characterization of people with cystic fibrosis and a minimal function mutation: Data from the Italian registry

BACKGROUND

People with cystic fibrosis (pwCF) and a minimal function (MF) mutation are poorly characterized. The aim of this study was to evaluate the disease characteristics of adult and pediatric pwCF with a genotype including an MF mutation on the basis of 2018 data from the Italian CF Registry (ICFR).

METHODS

This cross-sectional, descriptive analysis of CF disease characteristics included all of the pwCF with at least one MF mutation or two F508del (F) mutations, and at least one 2018 entry in the ICFR. Data concerning the disease characteristics of pwCF with an F/F genotype are provided for reference.

FINDINGS

A total of 5501 pwCF had at least one entry in the 2018 ICFR, including 2867 whose genotype included an MF mutation; in particular, 1432 had an MF/F genotype and 1148 the F/F genotype. The most frequent F/MF genotypes were F/N1303K (n = 247, 8.6%) and F/G542X (n = 193, 6.7%). The MF/no-F patients generally had a milder phenotype (a later diagnosis, lower sweat chloride levels, better nutrition, better lung function [starting from adolescence], and a lower prevalence of chronic infections and CF-related complications) than the MF/F or F/F patients.

INTERPRETATION

The findings of this descriptive analysis highlight the disease characteristics of pwCF with an MF-including genotype in Italy. The considered clinical outcomes of the pwCF with an F/MF genotype were not generally different from those of pwCF with an F/F genotype, but the patients with an MF/no-F genotype generally had a milder phenotype.

State of the Art on Approved Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Modulators and Triple-Combination Therapy

Cystic fibrosis (CF) is the most common life-limiting inherited disease in Caucasian populations, affecting approximately 80,000 people worldwide. CF is a complex multi-organ monogenic autosomal recessive disorder caused by a mutation in cystic fibrosis transmembrane conductance regulator (CFTR) gene. Since the discovery of the CFTR gene in 1989, more than 2000 mutations have been identified so far and about 240 can cause CF. Until recently, the treatment for CF was aimed to prevent and manage the manifestations of CFTR dysfunction, primarily recurrent pulmonary infections and pancreatic exocrine failure. Over the past few decades, the therapeutic approach to CF has been revolutionized by the development of a new class of small molecules called CFTR modulators that target specific defects caused by mutations in the CFTR gene. CFTR modulators have been shown to change profoundly the clinical course of the CF, leading to meaningful improvements in the lives of a large proportion of people of CF heterozygous for F508del, especially if started in young children. Further studies are needed to extend the use of triple CFTR modulation therapy also for young children in order to prevent the irreversible effects of the disease and for patients with very rare mutations with a personalized approach to treatment.

New Therapies to Correct the Cystic Fibrosis Basic Defect

Rare diseases affect 400 million individuals worldwide and cause significant morbidity and mortality. Finding solutions for rare diseases can be very challenging for physicians and researchers. Cystic fibrosis (CF), a genetic, autosomal recessive, multisystemic, life-limiting disease does not escape this sad reality. Despite phenomenal progress in our understanding of this disease, treatment remains difficult. Until recently, therapies for CF individuals were focused on symptom management. The discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene and its product, a protein present at the apical surface of epithelial cells regulating ion transport, allowed the scientific community to learn about the basic defect in CF and to study potential therapies targeting the dysfunctional protein. In the past few years, promising therapies with the goal to restore CFTR function became available and changed the lives of several CF patients. These medications, called CFTR modulators, aim to correct, potentialize, stabilize or amplify CFTR function. Furthermore, research is ongoing to develop other targeted therapies that could be more efficient and benefit a larger proportion of the CF community. The purpose of this review is to summarize our current knowledge of CF genetics and therapies restoring CFTR function, particularly CFTR modulators and gene therapy.

Development of elexacaftor - tezacaftor - ivacaftor: Highly effective CFTR modulation for the majority of people with Cystic Fibrosis

Introduction: Cystic fibrosis (CF), the most common life-shortening inherited disorder in people of European descent, also occurs in other ethnicities. The identification of the disease, the isolation of the causative gene, termed the cystic fibrosis transmembrane conductance regulator (CFTR) and the improved survival from comprehensive multidisciplinary treatment is one of the success stories of modern medicine. Survival has increased dramatically over the last 50 years, from 10 years in the 1960s to 30 years in the 1990s and approximately 50 years currently.Areas covered: This review will examine the development of highly effective modulators for CF which will revolutionize therapy for more than 90% of the people with CF. This review summarizes the development of triple combination CFTR modulator elexacaftor-tezacaftor-ivacaftor.Expert opinion: The development of this highly effective CFTR modulator for the majority of people with CF will likely change the landscape of CF care. The challenge is to now find highly effective therapy for the remaining 10% of the people with CF who may need other therapeutic agents to correct their primary defect.

Long-term safety and efficacy of tezacaftor-ivacaftor in individuals with cystic fibrosis aged 12 years or older who are homozygous or heterozygous for Phe508del CFTR (EXTEND): an open-label extension study

BACKGROUND

Tezacaftor-ivacaftor is an approved cystic fibrosis transmembrane conductance regulator (CFTR) modulator shown to be efficacious and generally safe and well tolerated over 8-24 weeks in phase 3 clinical studies in participants aged 12 years or older with cystic fibrosis homozygous for the Phe508del CFTR mutation (F/F; study 661-106 [EVOLVE]) or heterozygous for the Phe508del CFTR mutation and a residual function mutation (F/RF; study 661-108 [EXPAND]). Longer-term (>24 weeks) safety and efficacy of tezacaftor-ivacaftor has not been assessed in clinical studies. Here, we present results of study 661-110 (EXTEND), a 96-week open-label extension study that assessed long-term safety, tolerability, and efficacy of tezacaftor-ivacaftor in participants aged 12 years or older with cystic fibrosis who were homozygous or heterozygous for the Phe508del CFTR mutation.

METHODS

Study 661-110 was a 96-week, phase 3, multicentre, open-label study at 170 clinical research sites in Australia, Europe, Israel, and North America. Participants were aged 12 years or older, had cystic fibrosis, were homozygous or heterozygous for Phe508del CFTR, and completed one of six parent studies of tezacaftor-ivacaftor: studies 661-103, 661-106, 661-107, 661-108, 661-109, and 661-111. Participants received oral tezacaftor 100 mg once daily and oral ivacaftor 150 mg once every 12 h for up to 96 weeks. The primary endpoint was safety and tolerability. Secondary endpoints were changes in lung function, nutritional parameters, and respiratory symptom scores; pulmonary exacerbations; and pharmacokinetic parameters. A post-hoc analysis assessed the rate of lung function decline in F/F participants who received up to 120 weeks of tezacaftor-ivacaftor in studies 661-106 (F/F) and/or 661-110 compared with a matched cohort of CFTR modulator-untreated historical F/F controls from the Cystic Fibrosis Foundation Patient Registry. Primary safety analyses were done in all participants from all six parent studies who received at least one dose of study drug during this study. This study was registered at ClinicalTrials.gov (NCT02565914).

FINDINGS

Between Aug 31, 2015, to May 31, 2019, 1044 participants were enrolled in study 661-110 from the six parent studies of whom 1042 participants received at least one dose of study drug and were included in the safety set. 995 (95%) participants had at least one TEAE; 22 (2%) had TEAEs leading to discontinuation; and 351 (34%) had serious TEAEs. No deaths occurred during the treatment-emergent period; after the treatment-emergent period, two deaths occurred, which were both deemed unrelated to study drug. F/F (106/110; n=459) and F/RF (108/110; n=226) participants beginning tezacaftor-ivacaftor in study 661-110 had improvements in efficacy endpoints consistent with parent studies; improvements in lung function and nutritional parameters and reductions in pulmonary exacerbations observed in the tezacaftor-ivacaftor groups in the parent studies were generally maintained in study 661-110 for an additional 96 weeks. Pharmacokinetic parameters were also similar to those in the parent studies. The annualised rate of lung function decline was 61·5% (95% CI 35·8 to 86·1) lower in tezacaftor-ivacaftor-treated F/F participants versus untreated matched historical controls.

INTERPRETATION

Tezacaftor-ivacaftor was generally safe, well tolerated, and efficacious for up to 120 weeks, and the safety profile of tezacaftor-ivacaftor in study 661-110 was consistent with cystic fibrosis manifestations and with the safety profiles of the parent studies. The rate of lung function decline was significantly reduced in F/F participants, consistent with cystic fibrosis disease modification. Our results support the clinical benefit of long-term tezacaftor-ivacaftor treatment for people aged 12 years or older with cystic fibrosis with F/F or F/RF genotypes.

FUNDING

Vertex Pharmaceuticals Incorporated.

Current and novel therapeutic strategies for the management of cystic fibrosis

Introduction: Cystic fibrosis (CF), is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and affects thousands of people throughout the world. Lung disease is the leading cause of death in CF patients. Despite the advances in treatments, the management of CF mainly targets symptoms. Recent CFTR modulators however target common mutations in patients, alleviating symptoms of CF. Unfortunately, there is still no approved treatments for patients with rare mutations to date.Areas covered: This paper reviews current treatments of CF that mitigate symptoms and target genetic defects. The use of gene and drug delivery systems such as viral or non-viral vectors and nano-compounds to enhance CFTR expression and the activity of antimicrobials against chronic pulmonary infections respectively, will also be discussed.Expert opinion: Nano-compounds tackle biological barriers to drug delivery and revitalize antimicrobials, anti-inflammatory drugs and even genes delivery to CF patients. Gene therapy and gene editing are of particular interest because they have the potential to directly target genetic defects. Nanoparticles should be formulated to more specifically target epithelial cells, and biofilms. Finally, the development of more potent gene vectors to increase the duration of gene expression and reduce inflammation is a promising strategy to eventually cure CF.

Corrector therapies (with or without potentiators) for people with cystic fibrosis with class II CFTR gene variants (most commonly F508del)

BACKGROUND

Cystic fibrosis (CF) is a common life-shortening genetic condition caused by a variant in the cystic fibrosis transmembrane conductance regulator (CFTR) protein. A class II CFTR variant F508del (found in up to 90% of people with CF (pwCF)) is the commonest CF-causing variant. The faulty protein is degraded before reaching the cell membrane, where it needs to be to effect transepithelial salt transport. The F508del variant lacks meaningful CFTR function and corrective therapy could benefit many pwCF. Therapies in this review include single correctors and any combination of correctors and potentiators.

OBJECTIVES

To evaluate the effects of CFTR correctors (with or without potentiators) on clinically important benefits and harms in pwCF of any age with class II CFTR mutations (most commonly F508del).

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Cystic Fibrosis Trials Register, reference lists of relevant articles and online trials registries. Most recent search: 14 October 2020.

SELECTION CRITERIA

Randomised controlled trials (RCTs) (parallel design) comparing CFTR correctors to control in pwCF with class II mutations.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data, assessed risk of bias and evidence quality (GRADE); we contacted investigators for additional data.

MAIN RESULTS

We included 19 RCTs (2959 participants), lasting between 1 day and 24 weeks; an extension of two lumacaftor-ivacaftor studies provided additional 96-week safety data (1029 participants). We assessed eight monotherapy RCTs (344 participants) (4PBA, CPX, lumacaftor, cavosonstat and FDL169), six dual-therapy RCTs (1840 participants) (lumacaftor-ivacaftor or tezacaftor-ivacaftor) and five triple-therapy RCTs (775 participants) (elexacaftor-tezacaftor-ivacaftor or VX-659-tezacaftor-ivacaftor); below we report only the data from elexacaftor-tezacaftor-ivacaftor combination which proceeded to Phase 3 trials. In 14 RCTs participants had F508del/F508del genotypes, in three RCTs F508del/minimal function (MF) genotypes and in two RCTs both genotypes. Risk of bias judgements varied across different comparisons. Results from 11 RCTs may not be applicable to all pwCF due to age limits (e.g. adults only) or non-standard design (converting from monotherapy to combination therapy). Monotherapy Investigators reported no deaths or clinically-relevant improvements in quality of life (QoL). There was insufficient evidence to determine any important effects on lung function. No placebo-controlled monotherapy RCT demonstrated differences in mild, moderate or severe adverse effects (AEs); the clinical relevance of these events is difficult to assess with their variety and small number of participants (all F508del/F508del). Dual therapy Investigators reported no deaths (moderate- to high-quality evidence). QoL scores (respiratory domain) favoured both lumacaftor-ivacaftor and tezacaftor-ivacaftor therapy compared to placebo at all time points. At six months lumacaftor 600 mg or 400 mg (both once daily) plus ivacaftor improved Cystic Fibrosis Questionnaire (CFQ) scores slightly compared with placebo (mean difference (MD) 2.62 points (95% confidence interval (CI) 0.64 to 4.59); 1061 participants; high-quality evidence). A similar effect was observed for twice-daily lumacaftor (200 mg) plus ivacaftor (250 mg), but with low-quality evidence (MD 2.50 points (95% CI 0.10 to 5.10)). The mean increase in CFQ scores with twice-daily tezacaftor (100 mg) and ivacaftor (150 mg) was approximately five points (95% CI 3.20 to 7.00; 504 participants; moderate-quality evidence). At six months, the relative change in forced expiratory volume in one second (FEV1) % predicted improved with combination therapies compared to placebo by: 5.21% with once-daily lumacaftor-ivacaftor (95% CI 3.61% to 6.80%; 504 participants; high-quality evidence); 2.40% with twice-daily lumacaftor-ivacaftor (95% CI 0.40% to 4.40%; 204 participants; low-quality evidence); and 6.80% with tezacaftor-ivacaftor (95% CI 5.30 to 8.30%; 520 participants; moderate-quality evidence). More pwCF reported early transient breathlessness with lumacaftor-ivacaftor, odds ratio 2.05 (99% CI 1.10 to 3.83; 739 participants; high-quality evidence). Over 120 weeks (initial study period and follow-up) systolic blood pressure rose by 5.1 mmHg and diastolic blood pressure by 4.1 mmHg with twice-daily 400 mg lumacaftor-ivacaftor (80 participants; high-quality evidence). The tezacaftor-ivacaftor RCTs did not report these adverse effects. Pulmonary exacerbation rates decreased in pwCF receiving additional therapies to ivacaftor compared to placebo: lumacaftor 600 mg hazard ratio (HR) 0.70 (95% CI 0.57 to 0.87; 739 participants); lumacaftor 400 mg, HR 0.61 (95% CI 0.49 to 0.76; 740 participants); and tezacaftor, HR 0.64 (95% CI, 0.46 to 0.89; 506 participants) (moderate-quality evidence). Triple therapy Three RCTs of elexacaftor to tezacaftor-ivacaftor in pwCF (aged 12 years and older with either one or two F508del variants) reported no deaths (high-quality evidence). All other evidence was graded as moderate quality. In 403 participants with F508del/minimal function (MF) elexacaftor-tezacaftor-ivacaftor improved QoL respiratory scores (MD 20.2 points (95% CI 16.2 to 24.2)) and absolute change in FEV1 (MD 14.3% predicted (95% CI 12.7 to 15.8)) compared to placebo at 24 weeks. At four weeks in 107 F508del/F508del participants, elexacaftor-tezacaftor-ivacaftor improved QoL respiratory scores (17.4 points (95% CI 11.9 to 22.9)) and absolute change in FEV1 (MD 10.0% predicted (95% CI 7.5 to 12.5)) compared to tezacaftor-ivacaftor. There was probably little or no difference in the number or severity of AEs between elexacaftor-tezacaftor-ivacaftor and placebo or control (moderate-quality evidence). In 403 F508del/F508del participants, there was a longer time to protocol-defined pulmonary exacerbation with elexacaftor-tezacaftor-ivacaftor over 24 weeks (moderate-quality evidence).

AUTHORS' CONCLUSIONS

There is insufficient evidence that corrector monotherapy has clinically important effects in pwCF with F508del/F508del. Both dual therapies (lumacaftor-ivacaftor, tezacaftor-ivacaftor) result in similar improvements in QoL and respiratory function with lower pulmonary exacerbation rates. Lumacaftor-ivacaftor was associated with an increase in early transient shortness of breath and longer-term increases in blood pressure (not observed for tezacaftor-ivacaftor). Tezacaftor-ivacaftor has a better safety profile, although data are lacking in children under 12 years. In this population, lumacaftor-ivacaftor had an important impact on respiratory function with no apparent immediate safety concerns; but this should be balanced against the blood pressure increase and shortness of breath seen in longer-term adult data when considering lumacaftor-ivacaftor. There is high-quality evidence of clinical efficacy with probably little or no difference in AEs for triple (elexacaftor-tezacaftor-ivacaftor) therapy in pwCF with one or two F508del variants aged 12 years or older. Further RCTs are required in children (under 12 years) and those with more severe respiratory function.