Treatment effects of Elexacaftor/Tezacaftor/Ivacaftor in people with CF carrying non-F508del mutations

Background: In vitro studies have demonstrated rescue of CFTR function with Elexacaftor/Tezacaftor/Ivacaftor (ETI) in several mutations other than F508del. However, clinical efficacy was not tested in vivo in people with CF (pwCF) carrying mutations other than F508del. We report effects of treatment with ETI in pwCF with non-F508del mutations. Methods: We retrospectively analyzed pwCF with non-F508del mutations who received treatment with ETI. We evaluated sweat chloride, nutritional status, spirometry, antibiotic treatment, and pulmonary exacerbations (PEx), at baseline and 3-6 months after commencing treatment with ETI. Results: We included 16 pwCF, including eight without previous use of CFTR modulators. Median time on treatment was 5.3 (range, 1.8-7.7) months. Compared to baseline, in the “naïve” group sweat chloride concentration was reduced from 113.0 (98-129) to 64.0 (32-97) mEq/L (n=7; median (IQR), p=0.018), and rate of pulmonary exacerbations declined from a median of 1.5 (IQR 1, 2.75) in the previous year to 0 (0,0) (p= 0.019) with a significant decline in annualized days with antibiotics (oral + parenteral) per year: 36 (17.5; 42) in the year before to 0 (0,0) (median (IQR), p= 0.027). Mean FEV₁% changed from 66.3±25 to 72.4±29 % (mean ± SD, p=0.058). In the group of patients previously treated with Ivacaftor or Tezacaftor/Ivacaftor, we didn't observe significant improvements in any of the parameters. Conclusions: We demonstrate the clinical efficacy of ETI in pwCF carrying CFTR processing non-F508del mutations which are predicted to respond by in vitro studies. Our results support routine clinical use of ETI in this patient group.