Effects of Lumacaftor/Ivacaftor on Cystic Fibrosis Disease Progression in Children 2 through 5 Years of Age Homozygous for F508del-CFTR: A Phase 2 Placebo-controlled Clinical Trial.

Rationale: Lumacaftor/ivacaftor (LUM/IVA) was shown to be safe and well tolerated in children 2 through 5 years of age with cystic fibrosis (CF) homozygous for F508del-CFTR in a Phase 3 open-label study. Improvements in sweat chloride concentration, markers of pancreatic function, and lung clearance index2.5 (LCI2.5), along with increases in growth parameters, suggested the potential for early disease modification with LUM/IVA treatment. Objective: To further assess the effects of LUM/IVA on CF disease progression in children 2 through 5 years of age using chest magnetic resonance imaging (MRI). Methods: This Phase 2 study had two parts: a 48-week, randomized, double-blind, placebo-controlled treatment period in which children 2 through 5 years of age with CF homozygous for F508del-CFTR received either LUM/IVA or placebo (Part 1) followed by an open-label period in which all children received LUM/IVA for an additional 48 weeks (Part 2). The results from Part 1 are reported. The primary endpoint was absolute change from baseline in chest MRI global score at Week 48. Secondary endpoints included absolute change in LCI2.5 through Week 48 and absolute changes in weight-for-age, stature-for-age, and body mass index-for-age z-scores at Week 48. Additional endpoints included absolute changes in sweat chloride concentration, fecal elastase-1 levels, serum immunoreactive trypsinogen, and fecal calprotectin through Week 48. The primary endpoint was analyzed using Bayesian methods, where the actual Bayesian posterior probability of LUM/IVA being superior to placebo in the chest MRI global score at Week 48 was calculated using a vague normal prior distribution; secondary and additional endpoints were analyzed using descriptive summary statistics. Results: Fifty-one children were enrolled and received LUM/IVA (n = 35) or placebo (n = 16). For the change in chest MRI global score at Week 48, the Bayesian posterior probability of LUM/IVA being better than placebo (treatment difference, <0; higher score indicates greater abnormality) was 76%; the mean treatment difference was -1.5 (95% credible interval, -5.5 to 2.6). Treatment with LUM/IVA also led to within-group numerical improvements in LCI2.5, growth parameters, and biomarkers of pancreatic function as well as greater decreases in sweat chloride concentration compared with placebo from baseline through Week 48. Safety data were consistent with the established safety profile of LUM/IVA. Conclusions: This placebo-controlled study suggests the potential for early disease modification with LUM/IVA treatment, including that assessed by chest MRI, in children as young as 2 years of age. Clinical trial registered with www.clinicaltrials.gov (NCT03625466).

Rate of Lung Function Decline in People with Cystic Fibrosis Having a Residual Function Gene Mutation.

INTRODUCTION: Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. Approximately 5% of people with CF have residual function (RF) CFTR mutations that result in partially retained CFTR activity. Published literature on disease trajectory among those with RF mutations is limited. In this retrospective study, we characterized lung function decline across different age groups in CFTR modulator-untreated people with CF heterozygous for F508del and an RF mutation (F/RF). METHODS: Rate of decline in percent predicted forced expiratory volume in 1 s (ppFEV1) was analyzed using data from the US CF Foundation Patient Registry (2006-2014) in F/RF (all), F/RF (excluding R117H), and F508del homozygous (F/F) cohorts. Annual rates of ppFEV1 decline were estimated over 2-year periods based on calendar year. Subgroup analyses by age [6-12 (children), 13-17 (adolescents), 18-24 (young adults), and ≥ 25 years (adults)] were performed. RESULTS: The estimated annualized rate of ppFEV1 decline was - 0.70 percentage points per year (95% CI -1.09, -0.30) in the F/RF (all) cohort (N = 1242) versus -1.91 percentage points per year (95% CI -2.01, -1.80) in the F/F cohort (N = 11,916) [difference, 1.29 percentage points per year (95% CI 0.88, 1.70); P < 0.001]. In the F/RF (all) cohort, all age groups demonstrated lung function decline ranging from -0.30 to -1.38. In the F/RF (excluding R117H) cohort, the rate of decline was -1.05 percentage points per year (95% CI -1.51, -0.60) [difference versus F/F cohort, 0.95 percentage points per year (95% CI 0.48, 1.41; P < 0.001); not statistically significant in children and young adults]. CONCLUSION: Progressive lung function decline was observed in people with F/RF genotypes across all assessed age groups, reinforcing the importance of early intervention and clinical monitoring to preserve lung function in all people with CF.

In people with cystic fibrosis, lung function typically decreases over time and is linked to the severity of the disease. How fast lung function decreases (referred to as the rate of lung function decline) in cystic fibrosis depends on the specific mutations (changes) in the CFTR gene (which causes the disease). Lung function decline has been well studied in some mutation groups, but not many previous studies have looked at lung function decline in people with one copy of the F508del-CFTR mutation (which is the most common CFTR mutation and results in little to no functional CFTR protein) and another CFTR mutation called a residual function mutation (referred to as people with F/RF genotypes). We used data from the US Cystic Fibrosis Foundation Patient Registry (which collects information on the health of people in the USA who have cystic fibrosis), to look at the rate of lung function decline in people with F/RF genotypes. We found that people with cystic fibrosis who have F/RF genotypes experience lung function loss over time. We also found that this lung function loss occurred in people of all ages with F/RF genotypes. This finding supports the importance of early treatment to help prevent lung function loss in all people with cystic fibrosis, including people with F/RF genotypes.

Tezacaftor/ivacaftor in people with cystic fibrosis who stopped lumacaftor/ivacaftor due to respiratory adverse events.

BACKGROUND: Increased rates of respiratory adverse events have been observed in people ≥12 years of age with cystic fibrosis homozygous for the Phe508del-CFTR mutation treated with lumacaftor/ivacaftor, particularly in those with percent predicted forced expiratory volume in 1 s (ppFEV1) of <40%. We evaluated the safety, tolerability, and efficacy of tezacaftor/ivacaftor in people with cystic fibrosis homozygous for Phe508del-CFTR who discontinued lumacaftor/ivacaftor due to treatment-related respiratory signs or symptoms. METHODS: Participants ≥12 years of age with cystic fibrosis homozygous for Phe508del-CFTR with ppFEV1 of ≥25% and ≤90% were randomized 1:1 and treated with tezacaftor/ivacaftor or placebo for 56 days. RESULTS: Of 97 participants, 94 (96.9%) completed the study. The primary endpoint was incidence of predefined respiratory adverse events of special interest (chest discomfort, dyspnea, respiration abnormal, asthma, bronchial hyperreactivity, bronchospasm, and wheezing): tezacaftor/ivacaftor, 14.0%; placebo, 21.3%. The adverse events were mild or moderate in severity. None were serious or led to treatment interruption or discontinuation. Overall, the discontinuation rate was similar between groups. The mean (SD) ppFEV1 at baseline was 44.6% (16.1%) with tezacaftor/ivacaftor and 48.0% (18.1%) with placebo. The posterior mean difference in absolute change in ppFEV1 from baseline to the average value of days 28 and 56 was 2.7 percentage points with tezacaftor/ivacaftor vs placebo. CONCLUSIONS: Tezacaftor/ivacaftor was generally safe, well tolerated, and efficacious in people ≥12 years of age with cystic fibrosis homozygous for Phe508del-CFTR with ppFEV1 of ≥25% and ≤90% who previously discontinued lumacaftor/ivacaftor due to treatment-related respiratory signs or symptoms.