Impact of Elexacaftor/Tezacaftor/Ivacaftor on Fat-Soluble Vitamin Status in 2 to 5 Year-Old Children Using a Cystic Fibrosis-Specific Multivitamin Formulation.

Background: Young children with Cystic Fibrosis (CwCF) are at risk of fat-soluble vitamin (FSV) deficiencies due to pancreatic insufficiency, despite pancreatic enzyme supplementation. CFTR modulator therapy such as elexacaftor/tezacaftor/ivacaftor (ETI) may improve pancreatic function, but its impact on FSV levels in this age group remains unclear. We evaluated changes in FSV serum levels in a cohort transitioning to ETI, taking a CF-specific, multivitamin formulation with beta-carotene as the primary source of vitamin A (DEKAs Plus Liquid, DPL). Methods: Retrospective data with paired analysis from 23 CwCF (2-5 years old) were analyzed. Serum FSV levels (D, E, A) and fecal elastase-1 (FE-1) were measured at baseline and 12 months post-ETI initiation. Daily FSV doses and covariates (FE-1, naive of CFTR modulators and ETI dose) were documented. Statistical analyses included Wilcoxon signed-rank tests and general linear models. Results: No significant changes were observed in serum FSV levels, while FSV dosing and formulation remained unchanged. Covariates did not influence serum level changes. Interestingly, ETI significantly improved FE-1 (p = 0.018), with 6/18 children achieving pancreatic sufficiency (FE-1 > 200 µg/g). Conclusions: In young CwCF initiating ETI, FSV levels were unchanged while pancreatic function improved. The use of provitamin A (beta-carotene) as in DPL resulted in no change in vitamin A levels and aligns with consensus guidance to prioritize provitamin A in ETI-treated children. Further validation in larger cohorts is warranted.