Rationale:The cystic fibrosis (CF) modulator drug elexacaftor/tezacaftor/ivacaftor (ETI) proved highly effective in controlled clinical trials for individuals with ≥1 F508del allele, which occurs in at least 85% of people with CF (PwCF). Objective: PROMISE is a post-approval study to understand the broad effects of ETI through 30 months clinical use in a more diverse US patient population with planned analyses after 6 months. Methods: Prospective, observational study in 487 PwCF age ≥12 years with ≥1 F508del allele starting ETI for the first time. Assessments occurred before and 1, 3, and 6 months into ETI therapy. Outcomes included change in ppFEV 1 , sweat chloride concentration, body mass index, and selfreported respiratory symptoms. Results: average age was 25.1 years. 44.1% entered the study using tezacaftor/ivacaftor or lumacaftor/ivacaftor while 6.7% were using ivacaftor, consistent with F508del homozygosity and G551D allele, respectively. At 6 months into ETI therapy, ppFEV 1 improved 9.76 percentage points (95% CI 8.76, 10.76) from baseline, CFQ-R Respiratory Domain score improved 20.4 points (95% CI 18.3, 22.5), and sweat chloride decreased -41.7 mmol/L (95% ). BMI also significantly increased.Changes were larger in those naïve to modulators but substantial in all groups, including those treated with ivacaftor at baseline. Conclusions: ETI by clinical prescription provided large improvements in lung function, respiratory symptoms, and BMI in a diverse population naïve to modulator drug therapy, using existing two-drug combinations, or using ivacaftor alone. Each group also experienced significant reductions in sweat chloride concentration, which correlated with improved ppFEV 1 in the overall study population.

Objectives:A defect in bicarbonate secretion contributes to the pathophysiology of gastrointestinal complications in patients with cystic fibrosis (CF). We measured gastrointestinal pH, clinical outcomes, and intestinal transit profiles in patients with the G551D mutation before and after treatment with ivacaftor, a CF transmembrane regulator channel (CFTR) potentiator.Methods:Observational studies of ivacaftor effectiveness were conducted in the United States and Canada. A subset of subjects ingested a wireless motility capsule (n=10) that measures in vivo pH, both before therapy with ivacaftor and 1 month after treatment; values obtained were compared for mean pH and area under the pH curve, and regional intestinal motility. We also queried subjects about abdominal pain and recorded body weight before and after treatment.Results:One month after administering ivacaftor, a significant increase in mean pH was observed after gastric emptying (P<0.05). Area under the pH curve analyses indicate increased bicarbonate mass (P<0.05 for select 5 min intervals and all segments >30 min); mean weight gain was 1.1 kg (P=0.08). No difference in abdominal pain or regional transit times was seen.Conclusions:CFTR modulation improves the proximal small intestinal pH profile in patients with the G551D CFTR mutation and we observed clinically relevant, contemporaneous weight gain, although it did not reach statistical significance. These data provide in vivo evidence that CFTR is an important regulator of bicarbonate secretion, which may be a translational link between CFTR function and clinical improvement.

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