Factors associated with prescription of elexacaftor/tezacaftor/ivacaftor among people with cystic fibrosis aged 12 years or older with at least one F508del allele

Background: This study aims to characterize the uptake of elexacaftor/tezacaftor/ivacaftor (ETI) following Food and Drug Administration (FDA) approval in October 2019. Methods: People with cystic fibrosis (PwCF) ≥12 years enrolled in the CF Foundation Patient Registry (CFFPR) from 2019–2022 with at least one copy of F508del were included. We calculated summary statistics according to ETI prescription status. We used a Kaplan-Meier estimator to determine median days to ETI prescription to identify differences in prescription uptake by lung function, race, and ethnicity and a Cox proportional hazards model to identify risk factors associated with timing of first ETI prescription. Results: A total of 17,183 people (91 %) were prescribed ETI. The median time to prescription was 121 days (95 % CI: 119, 122), with 75 % prescribed within 311 days (95 % CI: 301, 325). PwCF prescribed ETI were younger, had lower lung function, more pulmonary exacerbations in the prior year, earlier age of diagnosis, and were more likely to have been prescribed another CFTR modulator (if eligible). Public health insurance, ppFEV₁ >90, Black race and Hispanic ethnicity were associated with lower hazards (e.g., later) of ETI prescription whereas prior modulator prescription, pancreatic insufficiency, increased exacerbation frequency and prior infections were associated with a higher hazard (earlier) of prescription. Conclusions: While over 90 % of eligible individuals were prescribed ETI within three years, time of first prescription was associated with demographic factors and disease severity. Further research should investigate the reasons for this delay and approaches to reduce time to initiation for ETI and future therapies.