Cystic fibrosis (CF) is a disease caused by an error in a person’s genetics, which contain the instructions for how our body grows, functions, and looks. This is unique for each individual. The error, causing cystic fibrosis, leads to a thickening of mucus in several organs such as lungs, pancreas, intestine… In the first place, this leads to problems in the lungs which is also the most frequent cause of death. Additionally, the pancreas can become blocked, preventing the release of essential factors to digest food, which can lead to malnutrition. After years of research, scientists succeeded to develop a medication to repair the genetic defect focusing on improvement in lung function. This medication is called cystic fibrosis transmembrane conductance regulator (CFTR) modulators. In this master’s thesis, we focused on one specific type of CFTR modulators, which was elexacaftor/tezacaftor/ivacaftor (ETI). In Belgium, the product is known as Kaftrio. It has been proven to be very effective on lung function and body mass index (BMI), but previous studies have demonstrated a change in parameters that may indicate potential liver damage. Cystic fibrosis is defined as a rare disease; however, numbers prove its important relevance. In Belgium, according to a report of Sciensano in 2021, 1379 people are diagnosed with CF. These patients have a reduced quality of life and life expectancy. Linked to CF, 5.1% of the adults had liver disease. Based on the specific error in genetics, 85% of the patients with CF (PwCF) are eligible for ETI. Patients in the trials are being treated for longer and longer, giving us a better idea of the possible long-term effects. Given it is a lifetime treatment, it is important to get a better understanding of the long-term impact of ETI on other organs, here with focus on the liver, and the general health of the patients.