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This is the third paper in the series providing updated information and recommendations for people with cystic fibrosis transmembrane conductance regulator (CFTR)-related disorder (CFTR-RD). This paper covers the individual disorders, including the established conditions - congenital absence of the vas deferens (CAVD), diffuse bronchiectasis and chronic or acute recurrent pancreatitis - and also other conditions which might be considered a CFTR-RD, including allergic bronchopulmonary aspergillosis, chronic rhinosinusitis, primary sclerosing cholangitis and aquagenic wrinkling. The CFTR functional and genetic evidence in support of the condition being a CFTR-RD are discussed and guidance for reaching the diagnosis, including alternative conditions to consider and management recommendations, is provided. Gaps in our knowledge, particularly of the emerging conditions, and future areas of research, including the role of CFTR modulators, are highlighted., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: NJS reports consulting fees and/or honoraria from Vertex, Chiesi, Gilead and Menarini. KDB reports consulting fees and/or honoraria from Vertex, ELoxx, Splisense and Arcturus. JGM reports honoraria from Vertex, Chiesi, Abbvie and Viatris. PGM reports consulting fees and/or honoraria from Vertex, AstraZenica, Limbic and MedEd. CS reports consulting fees and/or honoraria from Vertex, Chiesi, TFF and Pfizer. JC reports consulting fees for Astrazeneca, Boehringer Ingelheim, Grifols, Gilead sciences, Insmed, Genentech, Glaxosmithkline, Antabio, Zambon and Trudell. OCY reports consulting fees and honoraria from Vertex. DGD reports consulting fees and/or honoraria from Chiesi, Insmed and Vertex. DP reports payments for educational talks. DVD reports consulting fees for Arcturus, Arrevus, BiomX, Clarametyx, CFF, Enbiotix, Microbion, Pyros, Respirion and Zambon. ISG reports honoraria from Vertex. KWS, FB, VV, EDW, MW, EB, DD, PE, EG, GH, AK, DN, JAN, CR, IS, MDW report no personal fees/honoraria, (Copyright © 2024. Published by Elsevier B.V.)

Background: The forskolin-induced swelling (FIS) assay measures CFTR function on patient-derived intestinal organoids (PDIOs) and may guide treatment selection for individuals with Cystic Fibrosis (CF). The aim of this study is to demonstrate the repeatability and reproducibility of the FIS assay following a detailed Standard Operating Procedure (SOP), thus advancing the validation of the assay for precision medicine (theranostic) applications., Methods: Over a 2-year period, FIS responses to CFTR modulators were measured in four European labs. PDIOs from six subjects with CF carrying different CFTR genotypes were used to assess the repeatability and reproducibility across the dynamic range of the assay., Results: Technical, intra-assay repeatability was high (Lin's concordance correlation coefficient (CCC) 0.95-0.98). Experimental, within-subject repeatability was also high within each lab (CCCs all >0.9). Longer-term repeatability (>1 year) showed more variability (CCCs from 0.67 to 0.95). The reproducibility between labs was also high (CCC ranging from 0.92 to 0.97). Exploratory analysis also found that between-lab percentage of agreement of dichotomized CFTR modulator outcomes for predefined FIS thresholds ranged between 78 and 100 %., Conclusions: The observed repeatability and reproducibility of the FIS assay within and across different labs is high and support the use of FIS as biomarker of CFTR function in the presence or absence of CFTR modulators., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

After three publications defining an updated guidance on the diagnostic criteria for people with cystic fibrosis transmembrane conductance regulator (CFTR)-related disorders (pwCFTR-RDs), establishing its relationship to CFTR-dysfunction and describing the individual disorders, this fourth and last paper in the series addresses some critical challenges facing health care providers and pwCFTR-RD. Topics included are: 1) benefits and obstacles to collect data from pwCFTR-RD are discussed, together with the opportunity to integrate them into established CF-registries; 2) the potential of infants designated CRMS/CFSPID to develop a CFTR-RD and how to communicate this information; 3) a description of the challenges in genetic counseling, with particular regard to phenotypic variability, unknown long-term evolution, CFTR testing and pregnancy termination 4) a proposal for the assessment of potential barriers to the implementation and dissemination of the produced documents to health care professionals involved in the care of pwCFTR-RD and a process to monitor the implementation of the CFTR-RD recommendations; 5) clinical trials investigating the efficacy of CFTR modulators in CFTR-RD and how endpoints and outcomes might be adapted to the heterogeneity of these disorders., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

This paper is the first in a series providing updated guidance on the definition, evaluation and management of people with a Cystic Fibrosis Transmembrane conductance Regulator (CFTR)-Related Disorder (CFTR-RD). The need for this update relates to more precise characterisation of CFTR gene variants and improved assessment of CFTR protein dysfunction. The exercise is co-ordinated by the European CF Society Standards of Care Committee and Diagnostic Network Working Group and involves stakeholder engagement. This first paper was produced by a core group using an extensive literature review and papers graded for their quality. Subsequent wider stakeholder agreement was achieved. The definition of a CFTR-RD remains "a clinical condition with evidence of CFTR protein dysfunction that does not fulfil the diagnostic criteria for CF". Clearer guidance on CFTR dysfunction and relevant CFTR variants will be provided. Thresholds for clinical presentations are presented and the paradigm that pathobiological processes may be evident in more than one organ is agreed. In this paper we reflect on the early patient journey, highlighting that CF specialists as well as other relevant specialists should be involved in the care of people with a CFTR-RD., Competing Interests: Declaration of Competing Interest Carlo Castellani reports payments of honoraria for presentations from Vertex Pharmaceuticals and Chiesi and participation to Advisory Boards of Vertex Pharmaceuticals. Mylan, Actelion and Chiesi. Kris De Boeck reports consulting fees from Vertex Pharmaceuticals, Arcturus, Splisense, Translate Bio and Chiesi and honoraria for lectures from Vertex Pharmaceuticals. Elke De Wachter reports that her Institution received fundings from Vertex for her participation in an Advisory Board and for a presentation. Isabelle Sermet-Gaudelus reports funding for academic research from Vertex Therapeutics and participation to Scientific Boards of Vertex Therapeutics and Eliox; support for attending conferences by Vertex Therapeutics. Nicholas Simmonds reports payment of honoraria for lectures from Vertex, Chiesi, Gilead and Teva; participation to Advisory Boards of Vertex, Chiesi, Gilead and Menarini. Kevin Southern reports no competing interests, (Copyright © 2022. Published by Elsevier B.V.)

Background: In cystic fibrosis (CF), genotype-phenotype correlation is complicated by the large number of CFTR variants, the influence of modifier genes, environmental effects, and the existence of complex alleles. We document the importance of complex alleles, in particular the F508C variant present in cis with the S1251N disease-causing variant, by detailed analysis of a patient with CF, with the [S1251N;F508]/G542X genotype and a very mild phenotype, contrasting it to that of four subjects with the [S1251N;F508C]/F508del genotype and classical CF presentation., Methods: Genetic differences were identified by Sanger sequencing and CFTR function was quantified using rectal organoids in rectal organoid morphology analysis (ROMA) and forskolin-induced swelling (FIS) assays. CFTR variants were further characterised in CF bronchial epithelial (CFBE) cell lines. The impact of involved amino acid changes in the CFTR 3D protein structure was evaluated., Results: Organoids of the patient [S1251N;F508] with mild CF phenotype confirmed the CF diagnosis but showed higher residual CFTR function compared to the four others [S1251N;F508C]. CFBE cell lines showed a decrease in [S1251N;F508C]-CFTR function but not in processing when compared to [S1251N;F508]-CFTR. Analysis of the 3D CFTR structure suggested an additive deleterious effect of the combined presence of S1251N and F508C with respect to NBD1-2 dimerisation., Conclusions: In vitro and in silico data show that the presence of F508C in cis with S1251N decreases CFTR function without affecting processing. Complex CFTR alleles play a role in clinical phenotype and their identification is relevant in the context of personalised medicine for each patient with CF., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

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., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In previous work, participants with a G970R mutation in cystic fibrosis transmembrane conductance regulator (CFTR) (c.2908G>C) had numerically lower sweat chloride responses during ivacaftor treatment than participants with other CFTR gating mutations. The objective of this substudy was to characterize the molecular defect of the G970R mutation in vitro and assess the benefit of ivacaftor in participants with this mutation. This substudy assessed sweat chloride, spirometry findings, and nasal potential difference on and off ivacaftor treatment in three participants with a G970R/F508del genotype. Intestinal organoids derived from rectal biopsy specimens were used to assess ivacaftor response ex vivo and conduct messenger RNA splice and protein analyses. No consistent or meaningful trends were observed between on-treatment and off-treatment clinical assessments. Organoids did not respond to ivacaftor in forskolin-induced swelling assays; no mature CFTR protein was detected in Western blots. Organoid RNA analysis demonstrated that 3 novel splice variants were created by G970R-CFTR: exon 17 truncation, exons 13-15 and 17 skipping, and intron 17 retention. Functional and molecular analyses indicated that the c.2908G>C mutation caused a cryptic splicing defect. Organoids lacked an ex vivo response with ivacaftor and supported identification of the mechanism underlying the CFTR defect caused by c.2908G>C. Analysis of CFTR mutations indicated that cryptic splicing was a rare cause of mutation misclassification in engineered cell lines. This substudy used organoids as an alternative in vitro model for mutations, such as cryptic splice mutations that cannot be fully assessed using cDNA expressed in recombinant cell systems., (© 2020 The Authors. Clinical and Translational Science published by Wiley Periodicals LLC on behalf of the American Society for Clinical Pharmacology and Therapeutics.)

CFTR modulators associated with substantial clinical benefit are expected to rapidly improve the baseline condition of people with cystic fibrosis (PWCF) as well as decrease the rate of lung function decline, the occurrence of pulmonary exacerbations and likely even other disease complications. These changes in clinical status of PWCF introduced by clinically effective modulator therapy will have major repercussions on modalities of future CF drug development. As part of its 'Strategic Plan to speed up Access to new Drugs', the European Cystic Fibrosis Society (ECFS) convened a meeting in Brussels on November 27 th 2019 with relevant stakeholders (CF researchers and clinicians, patient organization and pharmaceutical company representatives, regulators, health technology assessors; see Acknowledgments for list of attendees) to discuss the future of clinical trials in cystic fibrosis (CF) in the context of HEMT entering the clinical arena. The following is the conclusion of the presentations and discussions. It is hoped that these concepts will be considered in future regulatory guidelines and may provide rationale and support for alternative trial designs., (Copyright © 2020. Published by Elsevier B.V.)

As CFTR modulator therapy transforms the landscape of cystic fibrosis (CF) care, its lack of uniform access across the globe combined with the shift towards a new standard of care creates unique challenges for the development of future CF therapies. The advancement of a full and promising CF therapeutics pipeline remains a necessary priority to ensure maximal clinical benefits for all people with CF. It is through collaboration across the global CF community that we can optimize the evaluation and approval process of new therapies. To this end, we must identify areas for which harmonization is lacking and for which efficiencies can be gained to promote ethical, feasible, and credible study designs amidst the changing CF care landscape. This article summarizes the counsel from core advisors across multiple international regions and clinical trial networks, developed during a one-day workshop in October 2019. The goal of the workshop was to identify, in consideration of the highly transitional era of CFTR modulator availability, the drug development areas for which global alignment is currently uncertain, and paths forward that will enable advancement of CF therapeutic development., Competing Interests: Declaration of Competing Interest NMH serves as a consultant through her institution in her role as Executive Director of the CF Therapeutics Development Network Coordinating Center (CF TDNCC) and has received personal consulting fees from Kala Pharmaceuticals and Calithera. She has received grant funding from the Cystic Fibrosis Foundation (CFF) and National Institutes of Health (NIH). SvKR has received personal consulting fees from Antabio, Proteostasis Therapeutics (PTI), and Vertex Pharmaceuticals (VRTX). She has received grant support to her institution for her participation in the European Union HORIZON 2020 work. DPN serves as a consultant through his institution in his role as Medical Director of CF TDNCC. He has received grant support to his Institution from the CFF and Gilead Sciences. DRV has received personal consulting fees from AbbVie, Albumedix, AN2, Aradigm, Armata, Arrevus, Calithera, Chiesi USA, Cipla, Corbus, CFF, Eloxx, Enbiotix, Eveo, Galephar, Horizon, IBF, ICON clinical sciences, Ionis, Kala, Merck, Microbion, NDA, Protalix, PTC, Pulmocide, Recida, Savara, Vast, and VRTX. JCD has received other support from Aligipharma AS, Bayer AG, BI, Galapagos NV, ImevaX GmbH, Nivalis Therapeutics, ProQR Therapeutics, PTI, Raptor Pharamceuticals, VRTX, Enterprise, Novartis, Pulmocide, Flately and Teva for advisory board and educational activities. She has received grant support from the CF Trust. TL has received personal fees from Alan Boyd Consultants, Ltd for his participation in DSMB activities. FAR has received personal consulting fees from Novartis, Bayer, Roche, and Genentech for participation in CF related consulting activities. He has received grant support to his institution from VRTX for his participation as site PI in multicenter trials which they have funded as well as personal consulting fees. MWK has received personal consulting fees for advisory board participation, grant support to his institution for clinical trial participation, and non-financial support from VRTX, Savara, Laurent, Corbus Pharmaceuticals, PTC, and AzurRx. He has received personal consulting fees and non-financial support from Chiesi, Celtaxsys, Merck, and Kala. Personal consulting fees were received from Albumedix, Paranta, Protalix, Santhera, pH Pharma, Novartis, Ionis, the Italian Cystic Fibrosis Foundation, and the Food and Drug Administration. Grant support was provided to his Institution by NIH. Grant support was provided to his Institution by Anthera as well as personal consulting fees. SCB has received support from VRTX, Galapagos, and AbbVie for his participation in advisory boards and as site PI in multicenter trials which they have funded. JLTC has received personal consulting fees from Gilead Sciences, Protalix, and Santhera for participation in advisory board activities. She has received grant support to her institution from PTI, Celtaxsys, and VRTX as well as personal consulting fees for advisory activities. Grant support to her institution for her participation as site PI in a multicenter trial which they have funded from Eloxx. KDB has received consulting fees from Boehringer-Ingelheim (BI), Protalix Biotherapeutics, Raptor Pharmaceuticals, Novabiotics, Eloxx Pharmaceutics, Galapagos, and Chiesi. She has received speaker fees from Teva Pharmaceutical Industries and serves on the Steering Committee and Advisory Board for VRTX. DGD has received consulting fees from VRTX and consulting fees as well as grant support from PTI and Chiesi. PAF has received personal consulting fees from the Food and Drug Administration, Polyphor, and Santhera. He has received personal consulting fees and grant support from CFF, PTI, Savara, and VRTX. He has received grant support from NIH, Novartis, Novoteris, and Sound Pharmaceuticals. PD has received personal consulting fees from VRTX, PTI, and Actelion Pharmaceuticals. He has also received support for his participation as site PI in multicenter trials funded by Corbus Pharmaceuticals and VRTX. CHG has received grant funding from CFF, NIH, the European Commission and the Food and Drug Administration. He has also received honoraria from Gilead Sciences for grant reviews, honoraria from VRTX and Mylan for invited talks, and BI for participation as a PI in a multicenter trial in CF that they have funded. IF has received consulting fees and support from PTI, VRTX and BI for her participation in advisory boards as well as site PI in multicenter trials which they have funded. She has received support from Corbus Pharmaceuticals for participation as site PI in multicenter trials which they have funded ASM has received grant support to her Institution from CFF. BSQ has received grant support to his institution from the Cystic Fibrosis Canada, CFF, Michael Smith Foundation for Health Research, BC Lung Association, and Gilead Sciences. GZRB's institution has received support from the CFF, NIH and VRTX. for his participation as site PI in multicenter trials which they have funded. AGD, KP, JPC, SHD, SMS, and JMVD have nothing to disclose., (Copyright © 2020. Published by Elsevier B.V.)

Background: 5T polymorphism is a CFTR mutation with unclear clinical consequences: the phenotype varies from healthy individuals to Cystic Fibrosis (CF). The aim of this study was to evaluate if nasal potential difference (NPD) and sweat testing correlate with symptoms and CF diagnosis in 5T patients., Methods: 86 patients with 5T who had undergone NPD measurement, were included (6 homozygous (5T/5T), 41 with a PI-CF causing mutation in trans (5T/PI-CF), 11 with a PS-CF causing mutation in trans (5T/PS-CF) and 28 without a known mutation in trans (5T/?). Data including age, phenotype, sweat chloride and follow up were collected., Results: 33% of the 5T/5T patients had abnormal NPD results, compared to 70% in 5T/PI-CF; 33% in 5T/PS-CF and 29% in 5T/?. The percentage of high or borderline sweat chloride was highest in 5T/PI-CF, and 5T/?, compared to 5T/5T and 5T/PS-CF (91, 96, 80, and 63%, respectively). TGm (number of TG repeats in intron 8) analysis was performed in 21 5T/PI-CF patients. TG11 was associated with lower sweat chloride, lower percentage of abnormal NPD and less progression of symptoms compared to TG12 and TG13., Conclusion: There is much variation in clinical status among 5T patients. All patients in this study with 5T/PS CF, all patients with both normal NPD and sweat test, and most patients with TG11 were stable or improving over time. Therefore, NPD measurement and TGm status aid to assess if a patient is at high risk for developing CF or CFTR-related disease and if specific follow up in a CF center is required., (Copyright © 2019 European Cystic Fibrosis Society. All rights reserved.)

Background: Ataluren was developed for potential treatment of nonsense-mutation cystic fibrosis (CF). A previous phase 3 ataluren study failed to meet its primary efficacy endpoint, but post-hoc analyses suggested that aminoglycosides may have interfered with ataluren's action. Thus, this subsequent trial (NCT02139306) was designed to assess the efficacy and safety of ataluren in patients with nonsense-mutation CF not receiving aminoglycosides., Methods: Eligible subjects with nonsense-mutation CF (aged ≥6 years; percent predicted (pp) FEV 1 ≥40 and ≤90) from 75 sites in 16 countries were randomly assigned in double-blinded fashion to receive oral ataluren or matching placebo thrice daily for 48 weeks. The primary endpoint was absolute change in average ppFEV 1 from baseline to the average of Weeks 40 and 48., Findings: 279 subjects were enrolled; 138 subjects in the ataluren arm and 136 in the placebo arm were evaluable for efficacy. Absolute ppFEV 1 change from baseline did not differ significantly between the ataluren and placebo groups at Week 40 (-0.8 vs -1.8) or Week 48 (-1.7 vs -2.4). Average ppFEV 1 treatment difference from baseline to Weeks 40 and 48 was 0.6 (95% CI -1.3, 2.5; p = 0.54). Pulmonary exacerbation rate per 48 weeks was not significantly different (ataluren 0.95 vs placebo 1.13; rate ratio p = 0.40). Safety was similar between groups. No life-threatening adverse events or deaths were reported., Interpretation: Neither ppFEV 1 change nor pulmonary exacerbation rate over 48 weeks were statistically different between ataluren and placebo groups. Development of a nonsense-mutation CF therapy remains elusive., Competing Interests: Declaration of Competing Interest JM is an employee of PTC Therapeutics, the funder of this clinical trial, and holds financial interests in the company. MWK, SMR, and DRV received compensation for consultant services from PTC Therapeutics prior to and/or during this study. EK, MW, IS-G, and KDB received compensation for travel expenses for meetings related to the study. All other authors declare no competing interests., (Copyright © 2020. Published by Elsevier B.V.)

Background. The most common CFTR mutation, F508del, presents with multiple cellular defects. However, the possible multiple defects caused by many rarer CFTR mutations are not well studied. We investigated four rare CFTR mutations E60K, G85E, E92K and A455E against well-characterized mutations, F508del and G551D, and their responses to corrector VX-809 and/or potentiator VX-770. Methods. Using complementary assays in HEK293T stable cell lines, we determined maturation by Western blotting, trafficking by flow cytometry using extracellular 3HA-tagged CFTR, and function by halide-sensitive YFP quenching. In the forskolin-induced swelling assay in intestinal organoids, we validated the effect of tagged versus endogenous CFTR. Results. Treatment with VX-809 significantly restored maturation, PM localization and function of both E60K and E92K. Mechanistically, VX-809 not only raised the total amount of CFTR, but significantly increased the traffic efficiency, which was not the case for A455E. G85E was refractory to VX-809 and VX-770 treatment. Conclusions. Since no single model or assay allows deciphering all defects at once, we propose a combination of phenotypic assays to collect rapid and early insights into the multiple defects of CFTR variants.

Background: Eluforsen is an antisense oligonucleotide designed to bind to the mRNA region around the F508-encoding deletion and restore the cystic fibrosis transmembrane conductance regulator (CFTR) protein function in the airway epithelium. We assessed the safety and tolerability, pharmacokinetics and exploratory measures of efficacy of inhaled eluforsen in cystic fibrosis (CF) patients homozygous for the F508del-CFTR mutation., Methods: This randomised, double-blind, placebo-controlled, dose escalation 1b study recruited adult CF subjects with a FEV 1  > 70% predicted in four single ascending dose cohorts and four multiple ascending dose cohorts. Primary objectives were safety and tolerability. Secondary endpoints included pharmacokinetics, percent predicted forced expiratory volume in 1 s (ppFEV 1 ), and Cystic Fibrosis Questionnaire-Revised (CFQ-R) Respiratory Symptom Score (RSS)., Results: Single and multiple doses of inhaled eluforsen up to 50 mg were safe and well tolerated. A maximum tolerated dose was not established. Systemic exposure was low in all cohorts and lung function remained stable throughout the study. Three of four eluforsen-treated groups in the MAD study demonstrated an improvement in CFQ-R RSS at end of treatment with adjusted mean change from baseline values ranging from 6.4 to 12.7 points. In comparison, there was a mean decrease of 6.5 points in the placebo group from baseline to end of treatment., Conclusions: Inhaled eluforsen up to 50 mg dosed 3 times per week for 4 weeks was safe and well tolerated, showed low systemic exposure, and demonstrated improvement in CFQ-R RSS, a relevant measure of clinical benefit in CF patients., Competing Interests: Conflict of interest statement WdH, JP and NT are full-time employees of ProQR Therapeutics. NP-L and NH were full-time employees of ProQR Therapeutics during design development, execution and reporting of this study, and SM was full-time employee of ProQR Therapeutics during execution and reporting of this study. FB and MB are or were statistical consultants paid by ProQR Therapeutics. KDB report grants related to the submitted work. KDB and JSE report grants outside the submitted work. KDB and JSE report activity on advisory boards during the conduct of the study and outside the submitted work. PD, KDB and JSE received fees for consultancy. CS, MC and TP have no disclosures., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Detailed knowledge of how mutations in the cystic fibrosis transmembrane conductance regulator ( CFTR ) gene disturb the trafficking or function of the CFTR protein and the use of high-throughput drug screens have allowed novel therapeutic strategies for cystic fibrosis (CF). The main goal of treatment is slowly but surely shifting from symptomatic management to targeting the underlying CFTR defect to halt disease progression and even to prevent occurrence of CF complications. CFTR potentiators for patients with class III mutations, mutation R117H (and in United States also for patients with specific residual function mutations) and the combination of a CFTR modulator plus a potentiator for patients homozygous for F508del, are the two classes of modulators that are in use in the clinic. Approval of these therapeutics has progressively expanded to include both younger patients and a wider range of CFTR mutations. For a significant proportion of patients with CF, current treatment is however still insufficient or unavailable.This review provides an overview of the clinical trial results and the real-life efficacy data of approved CFTR modulators. In addition, we discuss the entire pipeline of CFTR modulators: novel potentiators and correctors, amplifiers, stabilizers, and read-through agents. Furthermore, we discuss other strategies to improve CFTR function like nonsense-mediated decay inhibitors, modified transfer ribonucleic acids, antisense oligonucleotides, and genetic therapies.CFTR modulators are already changing the face of CF and the pipeline of new therapies continues to be exciting., Competing Interests: None declared., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

The last decade has witnessed developments in the CF drug pipeline which are both exciting and unprecedented, bringing with them previously unconsidered challenges. The Task Force group came together to consider these challenges and possible strategies to address them. Over the last 18 months, we have discussed internally and gathered views from a broad range of individuals representing patient organizations, clinical and research teams, the pharmaceutical industry and regulatory agencies. In this and the accompanying article, we discuss two main areas of focus: i) optimising trial design and delivery for speed/efficiency; ii) drug development for patients with rare CFTR mutations. We propose some strategies to tackle the challenges ahead and highlight areas where further thought is needed. We see this as the start of a process rather than the end and hope herewith to engage the wider community in seeking solutions to improved treatments for all patients with CF., (Copyright © 2019. Published by Elsevier B.V.)

Background: Several treatment approaches in cystic fibrosis (CF) aim to correct CF transmembrane conductance regulator (CFTR) function; the efficacy of each approach is dependent on the mutation(s) present. A need remains for more effective treatments to correct functional deficits caused by the F508del mutation., Methods: Two placebo-controlled, phase 2a studies evaluated GLPG2222, given orally once daily for 29 days, in subjects homozygous for F508del (FLAMINGO) or heterozygous for F508del and a gating mutation, receiving ivacaftor (ALBATROSS). The primary objective of both studies was to assess safety and tolerability. Secondary objectives included assessment of pharmacokinetics, and of the effect of GLPG2222 on sweat chloride concentrations, pulmonary function and respiratory symptoms., Results: Fifty-nine and 37 subjects were enrolled into FLAMINGO and ALBATROSS, respectively. Treatment-related treatment-emergent adverse events (TEAEs) were reported by 29.2% (14/48) of subjects in FLAMINGO and 40.0% (12/30) in ALBATROSS; most were mild to moderate in severity and comprised primarily respiratory, gastrointestinal, and infection events. There were no deaths or discontinuations due to TEAEs. Dose-dependent decreases in sweat chloride concentrations were seen in GLPG2222-treated subjects (maximum decrease in FLAMINGO: -17.6 mmol/L [GLPG2222 200 mg], p < 0.0001; ALBATROSS: -7.4 mmol/L [GLPG2222 300 mg], p < 0.05). No significant effects on pulmonary function or respiratory symptoms were reported. Plasma GLPG2222 concentrations in CF subjects were consistent with previous studies in healthy volunteers and CF subjects., Conclusions: GLPG2222 was well tolerated. Sweat chloride reductions support on-target enhancement of CFTR activity in subjects with F508del mutation(s). Significant improvements in clinical endpoints were not demonstrated. Observed safety results support further evaluation of GLPG2222, including in combination with other CFTR modulators., Funding: Galapagos NV. Clinical trial registration numbers FLAMINGO, NCT03119649; ALBATROSS, NCT03045523., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the CFTR gene. The 3272-26A>G and 3849+10kbC>T CFTR mutations alter the correct splicing of the CFTR gene, generating new acceptor and donor splice sites respectively. Here we develop a genome editing approach to permanently correct these genetic defects, using a single crRNA and the Acidaminococcus sp. BV3L6, AsCas12a. This genetic repair strategy is highly precise, showing very strong discrimination between the wild-type and mutant sequence and a complete absence of detectable off-targets. The efficacy of this gene correction strategy is verified in intestinal organoids and airway epithelial cells derived from CF patients carrying the 3272-26A>G or 3849+10kbC>T mutations, showing efficient repair and complete functional recovery of the CFTR channel. These results demonstrate that allele-specific genome editing with AsCas12a can correct aberrant CFTR splicing mutations, paving the way for a permanent splicing correction in genetic diseases.

Background: Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. In this study we assessed the effect of antisense oligonucleotide eluforsen on CFTR biological activity measured by Nasal Potential Difference (NPD) in patients with the most common mutation, F508del-CFTR., Methods: This multi-centre, exploratory, open-label study recruited adults with CF homozygous or compound heterozygous for the F508del-CFTR mutation. Subjects received intranasal eluforsen three times weekly for 4 weeks. The primary endpoint was the within-subject change from baseline in total chloride transport (Cl-free+iso), as assessed by NPD. Secondary endpoints included within-subject change from baseline in sodium transport., Results: In the homozygous cohort (n = 7; per-protocol population), mean change (90% confidence interval) in Cl-free+iso was -3.0 mV (-6.6; 0.6) at day 15, -4.1 mV (-7.8; -0.4, p = .04) at day 26 (end of treatment) and - 3.7 mV (-8.0; 0.6) at day 47. This was supported by improved sodium transport as assessed by an increase in average basal potential difference at day 26 of +9.4 mV (1.1; 17.7, p = .04). The compound heterozygous cohort (n = 7) did not show improved chloride or sodium transport NPD values. Eluforsen was well tolerated with a favourable safety profile., Conclusions: In F508del-CFTR homozygous subjects, repeated intranasal administration of eluforsen improved CFTR activity as measured by NPD, an encouraging indicator of biological activity., (Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: The diagnosis of Cystic Fibrosis (CF) is by consensus based on the same parameters in all patients, yet the influence of ethnicity has only scarcely been studied. We aimed at elucidating the impact of Asian descent on the diagnosis of CF., Methods: We performed a retrospective analysis of the CFTR2 and UK CF databases for clinical phenotype, sweat chloride values and CFTR mutations and compared the diagnostic characteristics of Asian to non-Asian patients with CF., Results: Asian patients with CF do not have a worse clinical phenotype. The repeatedly reported lower FEV 1 of Asian patients with CF is attributable to the influence of ethnicity on lung function in general. However, pancreatic sufficiency is more common in Asian patients with CF. The diagnosis of CF in people with Asian ancestry is heterogeneous as mean sweat chloride values are lower (92±26 versus 99±22mmol/L in controls) and 14% have sweat chloride values below 60mmol/L (versus 6% in non-Asians). Also, CFTR mutations differ from those in Caucasians: 55% of British Asian patients with CF do not have one mutation included in the routine newborn screening panel., Conclusions: Bringing together the largest cohort of patients with CF and Asian ethnicity, we demonstrate that Asian roots impact on all three CF diagnostic pillars. These findings have implications for clinical practice in the increasingly ethnically diverse Western population., (Copyright © 2017 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

In patients with cystic fibrosis, most treatments addressing the underlying basic defect are mutation or mutation class specific. These treatments are disease modifying if they lower the year to year change in lung function. We therefore calculated the current loss of lung function, measured by year to year change in forced expired volume in 1s in 11,417 patients included in the European Cystic Fibrosis Society Patient Registry. Whereas patients with at least one mutation of class IV or V have on average a lower year to year change, we did not find a difference between patients with a stop codon mutation, homozygous for F508del or at least one class III mutation. These data are useful background information to discuss the impact of different disease modifying treatments., (Copyright © 2016 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

Cystic fibrosis is an inherited multi-system disease associated with chronic lung infection, malabsorption, salt loss syndromes, male infertility and leading to numerous comorbidities. The landscape in cystic fibrosis care has changed markedly with currently more adult patients than children in many countries. Over 2000 different mutations in the CFTR gene have been reported and the majority are extremely rare. Understanding how CFTR mutations translate to disturbed synthesis or function of the CFTR protein has opened the way to 'personalized' treatments to correct the basic defect. The first 2 drugs have reached the clinic: a CFTR potentiator to augment CFTR channel function, and the combination of this potentiator with a corrector to increase CFTR expression at the cell membrane. To obtain robust correction of CFTR expression at the cell membrane, combinations of correctors with additive efficacy are under investigation. Other mutation type-specific treatments under clinical investigation are premature stop codon-read through drugs and antisense oligonucleotides that correct the basic defect at the mRNA level. Restoring the defective gene by gene editing can already be achieved ex vivo. Mutation agnostic treatments are explored as well: stabilizing CFTR expression at the cell membrane, circumventing the CFTR channel by blocking or activating other ion channels, and gene therapy. Combinations of these therapies can be anticipated. The pipeline of corrective strategies under clinical investigation is increasing continuously and a rising number of pharmaceutical companies are entering the field., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Introduction: Sweat chloride concentration, a biomarker of CFTR function, is an appropriate outcome parameter in clinical trials aimed at correcting the basic CF defect. Although there is consensus on a cut-off value to diagnose CF, we have only limited information on the within subject variability of sweat chloride over time. Such information would be useful for sample size calculations in clinical trials. Therefore, we retrospectively analyzed repeated sweat chloride values obtained in patients with G551D mutation(s) assigned to placebo in an ivacaftor interventional trial., Methods: In subjects with G551D at least 12years of age, a pilocarpine sweat test using Macroduct collector was taken on both arms at 8 time points over 48weeks. We explored 1062 pilocarpine sweat test values obtained in 78 placebo patients of the VX08-770-102 trial., Results: Mean overall sweat chloride value (all patients, all tests, n=1062) was 100.8mmol/L (SD 12.7mmol/L). Using a multilevel mixed model, the between-subject standard deviation (SD) for sweat chloride was 8.9mmol/L (95% CI 7.4-10.6) and within-subject SD was 8.1mmol/L (95% CI 7.5-8.7). Limits of repeatability for repeat measurements were -19.7 to +21.6mmol/L using values from one arm, and -13.3 to 11.8mmol/L using mean of values obtained at 4 test occasions. Sample size calculations showed that the minimal treatment effect on sweat chloride concentration that can be demonstrated for a group of 5 patients is around 15mmol/L, using a cross-over design and combinations of 4 tests for each phase of the trial., Conclusion: Although the sweat test is considered a robust measure, sweat chloride measurements in patients with CF and a G551D mutation had an inherent biological variability that is higher than commonly considered. Further analyses of placebo group data are crucial to learn more about the natural variability of this outcome parameter., (Copyright © 2016 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

The use of 3 novel tools available for the diagnosis and treatment in cystic fibrosis are described here. 1) The lung clearance index is a sensitive method which can detect functional impairment in the first months after birth. 2) Detailed morphological analyses of the lung can be performed with the new MRI sequences, without any contrast medium or risk of radiation. The analysis of functional MRI data (perfusion, diffusion, ventilation, inflammation) will be possible, and these data will be correlated to morphological data. The exploration of other organs such as the sinuses, liver and abdomen during the same examination represents another definite advantage. 3) Organoïds are a good example of personalized medicine. This tool explores CFTR function and treatment response in each of the 2000 or so known CFTR mutations. These tests are limited to specialized centers, mostly within a research context. However, their generalization after standardization is expected in the near future., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

CFTR mutations are grouped according to disease-causing mechanism. Several studies demonstrated that patients having at least one mutation of class IV/V, present with a milder phenotype, but little is known about their relative treatment burden. We compared treatment burden between patients with two class I, II, or III mutations and patients with at least one mutation of class IV/V in the 2010 database of the Belgian CF Registry. We calculated a "Treatment Burden Index" (TBI) by assigning long term therapies to categories low, medium and high intensity, for differential weighing in the total score. There were 779 patients with two known class I/II/III mutations and 94 patients with at least one class IV/V mutation. Compared to class I/II/III, class IV/V patients had a lower median number of clinic visits (4 vs. 5; P < 0.001), a lower risk of hospitalization (24.7% vs. 50.8%; P < 0.001) and intravenous antibiotic treatment (23.5% vs. 46.0%; P < 0.001) and a lower median TBI (6 vs. 9; P < 0.001). These differences remained significant when only class IV/V patients with pancreatic insufficiency (n = 31) were considered. This study clearly demonstrates the significantly lower treatment burden in patients with CF and at least one class IV/V mutation compared to patients with two class I/II/III mutations and contributes to providing better individual counseling at time of diagnosis., (© 2015 Wiley Periodicals, Inc.)

Background: Cystic fibrosis is a life-limiting disease that is caused by defective or deficient cystic fibrosis transmembrane conductance regulator (CFTR) protein activity. Phe508del is the most common CFTR mutation., Methods: We conducted two phase 3, randomized, double-blind, placebo-controlled studies that were designed to assess the effects of lumacaftor (VX-809), a CFTR corrector, in combination with ivacaftor (VX-770), a CFTR potentiator, in patients 12 years of age or older who had cystic fibrosis and were homozygous for the Phe508del CFTR mutation. In both studies, patients were randomly assigned to receive either lumacaftor (600 mg once daily or 400 mg every 12 hours) in combination with ivacaftor (250 mg every 12 hours) or matched placebo for 24 weeks. The primary end point was the absolute change from baseline in the percentage of predicted forced expiratory volume in 1 second (FEV1) at week 24., Results: A total of 1108 patients underwent randomization and received study drug. The mean baseline FEV1 was 61% of the predicted value. In both studies, there were significant improvements in the primary end point in both lumacaftor-ivacaftor dose groups; the difference between active treatment and placebo with respect to the mean absolute improvement in the percentage of predicted FEV1 ranged from 2.6 to 4.0 percentage points (P<0.001), which corresponded to a mean relative treatment difference of 4.3 to 6.7% (P<0.001). Pooled analyses showed that the rate of pulmonary exacerbations was 30 to 39% lower in the lumacaftor-ivacaftor groups than in the placebo group; the rate of events leading to hospitalization or the use of intravenous antibiotics was lower in the lumacaftor-ivacaftor groups as well. The incidence of adverse events was generally similar in the lumacaftor-ivacaftor and placebo groups. The rate of discontinuation due to an adverse event was 4.2% among patients who received lumacaftor-ivacaftor versus 1.6% among those who received placebo., Conclusions: These data show that lumacaftor in combination with ivacaftor provided a benefit for patients with cystic fibrosis homozygous for the Phe508del CFTR mutation. (Funded by Vertex Pharmaceuticals and others; TRAFFIC and TRANSPORT ClinicalTrials.gov numbers, NCT01807923 and NCT01807949.).

Objective: To increase the power of nasal potential difference (NPD) as a biomarker of CFTR function, improvement of its repeatability is needed. We evaluated the improvement in repeatability resulting from measuring NPD (1) over a larger surface area and (2) at a fixed location., Methods: To assess repeatability, NPD was measured on two occasions with a new method using a larger surface catheter at fixed locations on the nasal floor (LSC-floor(5cm) and LSC-floor(3cm)) or at the most negative basal potential (LSC-floor(max)); with a sidehole catheter on the nasal floor at 5 cm) from the nasal margin (SHC-floor(5cm)) or at the most negative potential (SHC-floor(max)); and with an endhole catheter below the inferior surface of the lower turbinate at the most negative potential (EHC-turb(max))., Results: The within-subject standard deviation (S(w)) for repeated measurements of the total chloride response in the controls was smallest with the LSC-floor at a fixed location (LSC-floor(5cm) 3.1 mV; 95% CI 2.3-4.6 mV) and highest with the SHC-floor (SHC-floor(max) 14.6 mV; 95% CI 10.9-22.2 mV) or the EHC-turbinate (EHC-turb(max) 12.5 mV; 95% CI 10.7-23.0 mV) at the most negative basal potential. Measuring with the LSC-floor at the maximal potential increased the Sw (LSC-floor(max) 8.8 mV, 95% CI 6.0-16.1 mV, p=0.009 vs LSC-floor(5cm)), while measuring with the SHC-floor at a fixed location slightly decreased the Sw (SHC-floor(5cm) 9.8 mV, 95% CI 8.9-20.6 mV, p=0.06 vs SHC-floor(max)). In patients with cystic fibrosis, the S(w) was comparable, between 2.2 mV and 4.3 mV. Sample size calculations for trials using NPD to assess changes in ion transport showed that the number of subjects to be included could be approximately halved measuring with the larger surface catheter at a fixed location vs SHC or EHC at fixed locations., Conclusion: Measuring the NPD at a fixed location and over a larger surface resulted in increased repeatability and thereby also power as a biomarker of CFTR modulation., (Copyright © 2014 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

Background: Ivacaftor is used to treat patients with CF and a G551D gating mutation; the KONNECTION study assessed the efficacy and safety of ivacaftor in patients with CF and a non-G551D gating mutation., Methods: Patients with CF ≥6-years- old with non-G551D gating mutations received ivacaftor 150mg q12h or placebo for 8weeks in this 2-part, double-blind crossover study (Part 1) with a 16-week open-label extension (Part 2). The primary efficacy outcome was absolute change in FEV1 through 8 and 24weeks of ivacaftor treatment; secondary outcomes were changes in BMI, sweat chloride, and CFQ-R and safety through 8 and 24weeks of treatment., Results: Eight weeks of ivacaftor resulted in significant improvements in percent predicted FEV1, BMI, sweat chloride, and CFQ-R scores that were maintained through 24weeks. Ivacaftor was generally well tolerated., Conclusions: Ivacaftor was efficacious in a group of patients with CF who had selected non-G551D gating mutations., (Copyright © 2014 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

Background: Ataluren was developed to restore functional protein production in genetic disorders caused by nonsense mutations, which are the cause of cystic fibrosis in 10% of patients. This trial was designed to assess the efficacy and safety of ataluren in patients with nonsense-mutation cystic fibrosis., Methods: This randomised, double-blind, placebo-controlled, phase 3 study enrolled patients from 36 sites in 11 countries in North America and Europe. Eligible patients with nonsense-mutation cystic fibrosis (aged ≥ 6 years; abnormal nasal potential difference; sweat chloride >40 mmol/L; forced expiratory volume in 1 s [FEV1] ≥ 40% and ≤ 90%) were randomly assigned by interactive response technology to receive oral ataluren (10 mg/kg in morning, 10 mg/kg midday, and 20 mg/kg in evening) or matching placebo for 48 weeks. Randomisation used a block size of four, stratified by age, chronic inhaled antibiotic use, and percent-predicted FEV1. The primary endpoint was relative change in percent-predicted FEV1 from baseline to week 48, analysed in all patients with a post-baseline spirometry measurement. This study is registered with ClinicalTrials.gov, number NCT00803205., Findings: Between Sept 8, 2009, and Nov 30, 2010, 238 patients were randomly assigned, of whom 116 in each treatment group had a valid post-baseline spirometry measurement. Relative change from baseline in percent-predicted FEV1 did not differ significantly between ataluren and placebo at week 48 (-2.5% vs -5.5%; difference 3.0% [95% CI -0.8 to 6.3]; p=0.12). The number of pulmonary exacerbations did not differ significantly between treatment groups (rate ratio 0.77 [95% CI 0.57-1.05]; p=0.0992). However, post-hoc analysis of the subgroup of patients not using chronic inhaled tobramycin showed a 5.7% difference (95% CI 1.5-10.1) in relative change from baseline in percent-predicted FEV1 between the ataluren and placebo groups at week 48 (-0.7% [-4.0 to 2.1] vs -6.4% [-9.8 to -3.7]; nominal p=0.0082), and fewer pulmonary exacerbations in the ataluern group (1.42 events [0.9-1.9] vs 2.18 events [1.6-2.7]; rate ratio 0.60 [0.42-0.86]; nominal p=0.0061). Safety profiles were generally similar for ataluren and placebo, except for the occurrence of increased creatinine concentrations (ie, acute kidney injury), which occurred in 18 (15%) of 118 patients in the ataluren group compared with one (<1%) of 120 patients in the placebo group. No life-threatening adverse events or deaths were reported in either group., Interpretation: Although ataluren did not improve lung function in the overall population of nonsense-mutation cystic fibrosis patients who received this treatment, it might be beneficial for patients not taking chronic inhaled tobramycin., Funding: PTC Therapeutics, Cystic Fibrosis Foundation, US Food and Drug Administration's Office of Orphan Products Development, and the National Institutes of Health., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

More than 1900 different mutations in the CFTR gene have been reported. These are grouped into classes according to their effect on the synthesis and/or function of the CFTR protein. CFTR repair therapies that are mutation or mutation class specific are under development. To progress efficiently in the clinical phase of drug development, knowledge of the relative frequency of CFTR mutation classes in different populations is useful. Therefore, we describe the mutation class spectrum in 25,394 subjects with CF from 23 European countries. In 18/23 countries, 80% or more of the patients had at least one class II mutation, explained by F508del being by far the most frequent mutation. Overall 16.4% of European patients had at least one class I mutation but this varied from 3 countries with more than 30% to 4 countries with less than 10% of subjects. Overall only respectively 3.9, 3.3 and 3.0% of European subjects had at least one mutation of classes III, IV and V with again great variability: 14% of Irish patients had at least one class III mutation, 7% of Portuguese patients had at least one class IV mutation, and in 6 countries more than 5% of patients had at least one class V mutation., (Copyright © 2013 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

Background: Cystic fibrosis (CF) spans a wide spectrum. Therefore, benchmarking between registries implies comparing similar cohorts., Objective and Methods: Explore patient characteristics in Belgian (B), French (F), German (G) and Dutch (NL) registries (total N=13,122) and determine whether they fulfill predefined diagnostic criteria., Results: Using as case definition sweat chloride >60mmol/L or 2 CFTR mutations identified, CF diagnosis was not documented in 2.8, 5.7, 6.5 and 21.6% of subjects in the F, B, NL, and G registries. Restricting CFTR mutation interpretation to 124 CF causing mutations in CFTR2, these numbers rose to 10.5, 10.4, 14.5 and 24.3% respectively. Excluding these subjects impacted on outcomes. The impact differed between countries; the largest changes seen were a decrease in % adults from 51.9 to 47.8% in G, a decrease in % pancreas sufficiency from 17.0 to 13.0 in F, an increase in % homozygous for F508del from 55.3 to 63.7 in NL and a decrease of % with sweat chloride ≤60mmol/L from 8.4 to 1.1 in B., Conclusion: CF diagnosis is not documented in 10 to 24% of patients included in CF registries. Excluding these patients for analyses leads to significant changes in outcomes., (© 2013.)

Cystic fibrosis is caused by dysfunction or deficiency of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, an epithelial chloride channel that has a key role in maintaining homoeostasis of the airway surface liquid layer in the lungs. More than 1900 CFTR mutations that might result in a disease phenotype have been identified; these can be grouped into classes on the basis of their effect on CFTR protein production, trafficking, function, and stability. In the past 2 years, landmark clinical trials have shown that correction of CFTR function leads to substantial clinical benefit for individuals with cystic fibrosis. These findings are ushering in a new era of cystic fibrosis treatments designed to correct the underlying CFTR defect caused by different mutation classes. With analysis of continuing trials and available patient registries, here we assess mutation types and the number and geographical distribution of patients who are likely to benefit from CFTR-correcting treatment., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

In patients with cystic fibrosis, cystic fibrosis transmembrane conductance regulator (CFTR) biomarkers, such as sweat chloride concentration and/or nasal potential difference, are used as end-points of efficacy in phase-III clinical trials with the disease modifying drugs ivacaftor (VX-770), VX809 and ataluren. The aim of this project was to review the literature on reliability, validity and responsiveness of nasal potential difference, sweat chloride and intestinal current measurement in patients with cystic fibrosis. Data on clinimetric properties were collected for each biomarker and reviewed by an international team of experts. Data on reliability, validity and responsiveness were tabulated. In addition, narrative answers to four key questions were discussed and agreed by the team of experts. The data collected demonstrated the reliability, validity and responsiveness of nasal potential difference. Fewer data were found on reliability of sweat chloride concentration; however, validity and responsiveness were demonstrated. Validity was demonstrated for intestinal current measurement, but further information is required on reliability and responsiveness. For all three end-points, normal values were collected and further research requirements were proposed. This body of work adds useful information to support the promotion of CFTR biomarkers to surrogate end-points and to guide further research in the area.

Background: VX-809, a cystic fibrosis transmembrane conductance regulator (CFTR) modulator, has been shown to increase the cell surface density of functional F508del-CFTR in vitro., Methods: A randomised, double-blind, placebo-controlled study evaluated the safety, tolerability and pharmacodynamics of VX-809 in adult patients with cystic fibrosis (n=89) who were homozygous for the F508del-CFTR mutation. Subjects were randomised to one of four VX-809 28 day dose groups (25, 50, 100 and 200 mg) or matching placebo., Results: The type and incidence of adverse events were similar among VX-809- and placebo-treated subjects. Respiratory events were the most commonly reported and led to discontinuation by one subject in each active treatment arm. Pharmacokinetic data supported a once-daily oral dosing regimen. Pharmacodynamic data suggested that VX-809 improved CFTR function in at least one organ (sweat gland). VX-809 reduced elevated sweat chloride values in a dose-dependent manner (p=0.0013) that was statistically significant in the 100 and 200 mg dose groups. There was no statistically significant improvement in CFTR function in the nasal epithelium as measured by nasal potential difference, nor were there statistically significant changes in lung function or patient-reported outcomes. No maturation of immature F508del-CFTR was detected in the subgroup that provided rectal biopsy specimens., Conclusions: In this study, VX-809 had a similar adverse event profile to placebo for 28 days in F508del-CFTR homozygous patients, and demonstrated biological activity with positive impact on CFTR function in the sweat gland. Additional data are needed to determine how improvements detected in CFTR function secondary to VX-809 in the sweat gland relate to those measurable in the respiratory tract and to long-term measures of clinical benefit., Clinical Trial Number: NCT00865904.

Several diseases have been clinically or genetically related to cystic fibrosis (CF), but a consensus definition is lacking. Here, we present a proposal for consensus guidelines on cystic fibrosis transmembrane conductance regulator (CFTR)-related disorders (CFTR-RDs), reached after expert discussion and two dedicated workshops. A CFTR-RD may be defined as "a clinical entity associated with CFTR dysfunction that does not fulfil diagnostic criteria for CF". The utility of sweat testing, mutation analysis, nasal potential difference, and/or intestinal current measurement for the differential diagnosis of CF and CFTR-RD is discussed. Algorithms which use genetic and functional diagnostic tests to distinguish CF and CFTR-RDs are presented. According to present knowledge, congenital bilateral absence of vas deferens (CBAVD), acute recurrent or chronic pancreatitis and disseminated bronchiectasis, all with CFTR dysfunction, are CFTR-RDs., (Copyright © 2011 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.)

The pilocarpine sweat test, and in vivo assessment of CFTR function via nasal potential difference or intestinal current measurement are important tools to confirm the diagnosis of CF in subjects with suggestive symptoms. Since these tests reflect CFTR function and thus relate to the basic disease process in CF, changes in these parameters are also being used to assess the pharmacologic effect of compounds aimed at restoring CFTR function. However, longitudinal data proving that changes in these measurements are associated with meaningful clinical improvements in the course of disease in CF patients are needed. Consequently, many CF clinical investigators need to be facile with these existing methods to measure CFTR-related outcomes. This introduction sets the stage for more in-depth discussion of existing strategies to measure changes in CFTR function generated by gene therapy or small molecule modulators of CFTR function such as correctors and potentiators. It is hoped that lessons learned through the use of these measures will inform the future development of other robust methods to assess novel therapeutic strategies uncovered by basic scientists.

Objective: Pancreatitis is an infrequent complication among patients with cystic fibrosis (CF). It has mainly been reported for patients with pancreatic sufficiency (PS). Previous studies involved only a small number of patients because they contained data from single centers. The aim of this study was to evaluate the incidence of pancreatitis in a large heterogeneous CF population, to determine the relationship with pancreatic function, and to assess whether pancreatitis is associated with specific CFTR mutations., Methods: Physicians caring for patients with CF were approached through the CF Thematic Network or through the European Cystic Fibrosis Foundation newsletter. They were asked to provide data on their current patient cohort through a standardized questionnaire and to report how many patients they had ever diagnosed as having pancreatitis. A detailed questionnaire was then sent, to be filled out for all of their patients for whom pancreatitis had ever occurred. We defined pancreatitis as an episode of acute abdominal pain associated with serum amylase levels elevated above the ranges established by each participating center's laboratory. General clinical data included age, genotype, age at diagnosis of CF, sweat chloride concentrations, pancreatic status, biometric findings, and respiratory status. CFTR mutations were also reported according to the functional classification of classes I to V. Patients were categorized as having PS, pancreatic insufficiency (PI), or PI after an initial period of PS. PI was defined as a 72-hour stool fat loss of >7 g/day, fat absorption of <93%, or fecal elastase levels of <200 microg/g feces. Clinical data on pancreatitis included age at the first episode, amylase and lipase levels, possible triggers, and occurrence of relapses or complications., Results: A total of 10071 patients with CF, from 29 different countries, who were undergoing follow-up monitoring in 2002 were surveyed. Among this group, pancreatitis had ever been diagnosed for 125 patients (1.24%; 95% confidence interval [CI]: 1.02-1.46%). There was variability in the reported rates of pancreatitis for different countries. Twenty-six centers in 15 different countries sent detailed clinical data on their patients with pancreatitis and on their whole CF clinic. This involved 3306 patients with CF and 61 cases of pancreatitis, leading to a prevalence of 1.84% (95% CI: 1.39-2.30%). The mean age of the patients with pancreatitis ever was 24.4 years (SD: 10.8 years). The first episode of pancreatitis occurred at a mean age of 19.9 years (SD: 9.6 years). The median serum amylase level at the time of pancreatitis was 746 IU/L (interquartile range: 319-1630 IU/L), and the median lipase level was 577 IU/L (interquartile range: 229-1650 IU/L). The majority of patients had PS (34 of 61 patients, 56%; 95% CI: 43-68%). Pancreatitis occurred for 15 patients with PI (25%; 95% CI: 14-35%). Eight patients developed PI after initial PS. The occurrence of pancreatitis among patients with PS was 34 cases per 331 patients, ie, 10.27% (95% CI: 7.00-13.55%); the occurrence of pancreatitis among patients with PI was 15 cases per 2971 patients, ie, 0.5% (95% CI: 0.25-0.76%). The mean age (in 2002) of the CF cohort with pancreatitis did not differ between the PS and PI subgroups. The forced expiratory volume in 1 second was significantly lower among the patients with PI than among the patients with PS, ie, 65% (SEM: 7%) vs 79% (SEM: 4%). The mean age at the occurrence of pancreatitis and the amylase and lipase levels during pancreatitis were not different for patients with pancreatitis and PI versus PS. In the group with PS, 31 of 34 patients carried at least 1 class IV or V CFTR mutation. In the groups with PI and PI after PS, 5 of 15 patients and 3 of 8 patients, respectively, carried 2 class I, II, or III CFTR mutations. Relapses and/or evolution to chronic pancreatitis occurred for 42 patients. Pancreatitis preceded the diagnosis of CF in 18 of 61 cases. These patients were significantly older than the rest of the cohort, ie, age of 28.4 years (SEM: 3.4 years) vs 22.7 years (SEM: 1.3 years). Their median age at the diagnosis of CF was also significantly greater, ie, 21.5 years (interquartile range: 11.9-31 years) vs 7.6 years (interquartile range: 0.4-17.0 years). However, the ages at the occurrence of pancreatitis were similar, ie, 21.0 years (SEM: 3.0 years) vs 19.5 years (SEM: 1.2 years)., Conclusions: This study of 10071 patients with CF from 29 different countries revealed an estimated overall occurrence of pancreatitis among patients with CF of 1.24% (95% CI: 1.02-1.46%). The incidence of pancreatitis was much higher among patients with PS. However, pancreatitis was also reported for 15 patients with PI from 11 centers in 9 different countries. A correct diagnosis of pancreatitis for the reported patients with PI was supported by amylase and lipase levels increased above 500 IU/L, similar to those for patients with PS and pancreatitis. A correct diagnosis of PI for these patients with pancreatitis was supported by the adequacy of the methods used. We chose the cutoff values used to distinguish between patients with PI and control subjects without gastrointestinal disease. For one half of the patients, the diagnosis of PI was established on the basis of low levels of stool elastase (mean: 97 mug/g stool). With a cutoff value of 200 microg/g stool, this noninvasive test has high sensitivity (>95%) and high specificity (>90%) to differentiate patients with PI from control subjects with normal pancreatic function. For the other one half of the patients with PI in the cohort, the pancreatic status was determined on the basis of the 3-day fecal fat balance, with the widely used cutoff value of >7 g of fat loss per day. The most likely reason for pancreatitis occurring among patients with PI is that some residual pancreatic tissue is present among these patients. Pancreatitis is a rare complication among patients with CF. It occurred for 1.24% (95% CI: 1.02-1.46%) of a large CF cohort. Pancreatitis occurs mainly during adolescence and young adulthood. It is much more common among patients with CF and PS (10.3%), but it can occur among patients with PI (0.5%). Pancreatitis can be the first manifestation of CF. Pancreatitis was reported for patients carrying a wide range of mutations.

In this European study, the phenotype in 68 patients, homozygous or compound heterozygous for the G85E mutation, was investigated. Each index case was compared with two cystic fibrosis (CF) patients from the same clinic, matched for age and sex: one with pancreatic sufficiency (PS) and one with pancreatic insufficiency (PI). When comparing 31 G85E/F508del and F508del/F508del patients, there were no differences in median age at diagnosis, mean sweat chloride value, most recent weight for height, most recent forced expiratory volume in one second % predicted, prevalence of chronic Pseudomonas aeruginosa colonisation and typical CF complications. However, PI was less frequent in the G85E/F508del group. Comparison of 55 G85E patients (with second mutation known and not classified as mild) with PS controls (n=44) showed that the G85E patients had a significantly higher sweat chloride, more often failure to thrive at diagnosis, higher prevalence of PI, worse current weight for height, higher prevalence of chronic P. aeruginosa colonisation and liver cirrhosis. Pulse-chase experiments revealed that G85E cystic fibrosis transmembrane conductance regulator failed to mature on a M470 as well as on a V470 background. Therefore, G85E is a class II mutation. Although there is variability in its clinical presentation, G85E mutation results in a severe phenotype.

Abstract: The ECFS-CTN Standardisation Committee has undertaken this review of lung clearance index as part of the group's work on evaluation of clinical endpoints with regard to their use in multicentre clinical trials in CF. The aims were 1) to review the literature on reliability, validity and responsiveness of LCI in patients with CF, 2) to gain consensus of the group on feasibility of LCI and 3) to gain consensus on answers to key questions regarding the promotion of LCI to surrogate endpoint status. It was concluded that LCI has an attractive feasibility and clinimetric properties profile and is particularly indicated for multicentre trials in young children with CF and patients with early or mild CF lung disease. This is the first article to collate the literature in this manner and support the use of LCI in clinical trials in CF. [Copyright &y& Elsevier]