K. De Boeck

Lumacaftor–Ivacaftor in Patients with Cystic Fibrosis Homozygous for Phe508del CFTR

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.).

Pulmonary exacerbation: towards a definition for use in clinical trials. Report from the EuroCareCF Working Group on outcome parameters in clinical trials.

Pulmonary exacerbations represent a key outcome variable in clinical trials of cystic fibrosis (CF). As there is variation in the trigger for use of intravenous antibiotics compared to the use of oral antibiotics or new nebulised therapy for treatment of exacerbations, the consensus view is that use of intravenous antibiotics cannot be regarded as the key defining character for an exacerbation on its own. The consensus view is that the clinical need for additional treatment as indicated by a recent change in clinical parameters provides the best definition of an exacerbation. Which parameters to include as well as the problems associated with the use of scoring systems and symptom clusters are being discussed.

New clinical diagnostic procedures for cystic fibrosis in Europe

In the majority of cases, there is no difficulty in diagnosing Cystic Fibrosis (CF). However, there may be wide variation in signs and symptoms between individuals which encourage the scientific community to constantly improve the diagnostic tests available and develop better methods to come to a final diagnosis in patients with milder phenotypes. This paper is the result of discussions held at meetings of the European Cystic Fibrosis Society Diagnostic Network supported by EuroCareCF. CFTR bioassays in the nasal epithelium (nasal potential difference measurements) and the rectal mucosa (intestinal current measurements) are discussed in detail including efforts to standardize the techniques across Europe. New approaches to evaluate the sweat gland, future of genetic testing and methods on the horizon like CFTR expression in human leucocytes and erythrocytes are discussed briefly.

CFTR biomarkers: time for promotion to surrogate end-point

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.

Lung clearance index: Evidence for use in clinical trials in cystic fibrosis

The ECFS-CTN Standardisation Committee has undertaken this review of lung clearance index as part of the groups 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.

Primary ciliary dyskinesia: Evolution of pulmonary function

Pulmonary function tests were obtained in 11 patients with primary ciliary dyskinesia. Their mean age was 15 years (range 6–32). Their pulmonary function was obstructive, with a vital capacity (mean ± SD) of 75% ± 20% predicted, a forced expiratory volume in 1s (FEV1) of 63% ± 20% predicted and a raised residual volume of 169% ± 50% predicted. After inhalation of 200 μg of salbutamol the mean change in FEV1 was + 13.2% ± 9.6% of the baseline value. In the 10 oldest patients, lung function had been measured at regular intervals during 3–20 years. Interestingly, during childhood and adolescence the evolution was not unfavourable: vital capacity increased by 8% ± 20% and FEV1 remained stable (mean change 0.3% ± 12%). Only 2 patients had an unfavourable evolution.ConclusionAt time of diagnosis, patients with primary ciliary dyskinesia have partially reversible obstructive airway disease. During regular follow up and therapy, there is no evidence of a further decline in lung function. Patients with associated immunodeficiency or important damage at the start of therapy may have a worse prognosis.

The relative frequency of CFTR mutation classes in European patients with cystic fibrosis

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.

Phenotypic characterisation of patients with intermediate sweat chloride values: towards validation of the European diagnostic algorithm for cystic fibrosis

Background: In patients with symptoms suggestive of cystic fibrosis (CF) and intermediate sweat chloride values (30–60 mmol/l), extensive CFTR gene mutation analysis and nasal potential difference (NPD) measurement are used as additional diagnostic tests and a positive result in either test provides evidence of CFTR dysfunction. To define the phenotype of such patients and confirm the validity of grouping them, patients with intermediate sweat chloride values in whom either additional CF diagnostic test was abnormal were compared with subjects in whom this was not the case and patients with classic CF. Methods: The phenotypic features of four groups were compared: 59 patients with CFTR dysfunction, 46 with an intermediate sweat chloride concentration but no evidence of CFTR dysfunction (CF unlikely), 103 patients with CF and pancreatic sufficiency (CF-PS) and 62 with CF and pancreatic insufficiency (CF-PI). Results: The CFTR dysfunction group had more lower respiratory tract infections (p = 0.01), more isolation of CF pathogens (p<0.001) and clubbing (p = 0.001) than the CF unlikely group, but less frequent respiratory tract infections with CF pathogens than the CF-PS group (p = 0.05). Patients in the CF-PS group had a milder phenotype than those with PI. Many features showed stepwise changes through the patient groups. Conclusion: Patients with intermediate sweat chloride values and two CFTR mutations or an abnormal NPD measurement have a CF-like phenotype compatible with CFTR dysfunction and, as a group, differ phenotypically from patients with intermediate sweat chloride values in whom further CF diagnostic tests are normal as well as from CF-PS and CF-PI patients.

Small-intestinal abnormalities in cystic fibrosis patients.

A survey is given of the pathophysiology of the main alterations in the small intestine of cystic fibrosis patients. Special attention is paid to the understanding of meconium ileus in the fetus and the newborn, the repercussion of duodenal acidity on the duodenal mucosa and the intraduodenal digestion, and primary and secondary biochemical alterations in the secretory-digestive-absorptive function of the small-intestinal mucosa. The meconium equivalent syndrome and its connection with the atypical course of intussusception and appendiceal perforation with silent pelvic abscess are also discussed.

Early referral to cystic fibrosis specialist centre impacts on respiratory outcome.

BACKGROUND Published studies concerning the impact of specialist care on lung disease in cystic fibrosis remain limited and most are either biased due to comparison with historical controls and/or underpowered. METHODS In this retrospective multicentric study, data from all CF children fulfilling the following criteria were collected: 1) Age 6-<18 at the end of 2003; 2) diagnosis before 8 y; 3) follow-up in an accredited CF Belgian centre; 4) at least 1 spirometry and respiratory culture available for 2003. Group A included children referred > or =2 years after the diagnosis. Patients from Group A were then matched with a single early referred patient on the basis of 2 criteria: same centre, as closest age as possible (Group B). RESULTS Data from 217 children were collected (Group A: 67/217). Late referred patients had a lower FEV(1) (77.2%+/-22.4 vs 86.7% pred.+/-19.4, p=0.01) and a higher prevalence of Pseudomonas aeruginosa (38.6 vs 17.5%, p<0.05). CONCLUSION In this population of CF children, a delay of 6.1 y (vs 0.1 y) between diagnosis and referral to a specialist clinic resulted in poorer respiratory outcome at age 13.