Elexacaftor/tezacaftor/ivacaftor (E/T/I) therapy has resulted in substantial improvements in health status for many with cystic fibrosis. Monitoring of liver tests is recommended due to observed rises in transaminases in trials and cases of hepatotoxicity. Comprehensive data in large populations of unselected individuals and those with established CF related liver disease (CFLD) is lacking.

Patients prescribed E/T/I at a large, adult centre had liver tests monitored at least 3 monthly for 12 months. Changes in individual liver tests were analysed and abnormalities were compared in those with and without CFLD.

255 of 267 eligible patients were included. Mild rises in median ALT, AST and bilirubin from baseline to 3 months (all p < 0.001) within normal limits were noted which were sustained. There were no differences in changes in liver tests between those with or without CFLD. There was a significant difference in alkaline phosphatase for those with raised levels at baseline versus those with normal baseline level (-18.5 vs +2.0 IU/L, p = 0.002). Clinically significant rises in ALT and AST occurred in 8 (3.1%) and 6 (2.4%) cases respectively, with derangements in 2 individuals attributed to therapy.

E/T/I leads to a mild, likely clinically insignificant increase in ALT, AST and bilirubin after 3 months which is sustained but does not appear to increase further in the vast majority. Underlying CFLD should not be a barrier to treatment. Although there was a reduction in ALP when elevated at baseline, this was not unique to those with pre-existing CFLD.