Clinical Effectiveness of Elexacaftor/Tezacaftor/Ivacaftor in 6- to 11-Year-Olds with Cystic Fibrosis: An Observational Study

Abstract

Rationale: Elexacaftor/tezacaftor/ivacaftor (ETI) provided substantial health benefits to children with cystic fibrosis (CF) in clinical trials; there is less information about its effectiveness in a "real world" setting. Objectives: The aim of the PROMISE (A Prospective Study to Evaluate Biological and Clinical Effects of Significantly Corrected CFTR Function) Pediatric substudy is to determine the long-term (four years) impact of clinically prescribed ETI among children 6-11 years of age at enrollment. The primary outcome measure is the lung clearance index at a 2.5% (LCI_2.5). Methods: The PROMISE Pediatric substudy enrolled children with CF 6 to <12 years of age starting ETI. Outcomes measured at baseline (before ETI) and 1, 3, 6, and 12 months after ETI initiation included LCI_2.5, percentage predicted forced expiratory volume in 1 second, Cystic Fibrosis Questionnaire-Revised (CFQ-R) respiratory domain symptom score, height, weight, oropharyngeal cultures, and culture and deoxyribonucleic acid-based analysis of sputum microbiology (when sputum was available). Sweat chloride was assessed at baseline and at 1 and 6 months. Results: One hundred twenty-five participants were enrolled at 20 U.S. CF centers. Lung function improvement after ETI initiation was rapid and sustained through 12 months, with a mean decrease in LCI_2.5 of -0.79 (95% confidence interval [CI], -1.04 to 0.55) and a mean increase in percentage predicted forced expiratory volume in 1 second of 5.6% (95% CI, 3.4% to 7.7%). Respiratory symptoms also diminished significantly (mean change in CFQ-R respiratory domain symptom score, 4.1 [95% CI, 1.94 to 6.24]). Sweat chloride decreased significantly at 6 months (mean change, -47.2 mmol/L [95% CI, -51.99 to -43.8 mmol/L]). Weight, body mass index, and height z-scores were not different from baseline at 12 months. Staphylococcus aureus prevalence in oropharyngeal or sputum cultures did not change, but its density in sputum cultures decreased a mean of 1.47 log₁₀ colony-forming units/g (95% CI, -2.37 to -0.58 colony-forming units/g) at 12 months. Conclusions: Initiation of ETI in a real-world setting was associated with clinically significant improvements in lung function and symptoms and decreased S. aureus sputum density at one year; lung function improvements were smaller than those reported in clinical trials. Clinical trial registered with www.clinicaltrials.gov (NCT04038047).

Keywords: bacterial infection; cystic fibrosis; cystic fibrosis transmembrane conductance regulator modulator; lung function.