Heterogeneity in Reported Side Effects Following Initiation of Elexacaftor‐Tezacaftor‐Ivacaftor: Experiences at a Quaternary CF Care Center

BACKGROUND: The benefits of Elexecaftor-Tezacaftor-Ivacaftor (ETI) therapy on the health and wellbeing of people with CF (pwCF) are well documented. Since approval, however, a growing number of potential side effects have emerged in reports from clinical practice. With current understanding of ETI tolerability limited to data from clinical trials, the prevalence of side effects and their impact on care decision making remains poorly categorized. METHODS: A 10-question survey was developed and distributed to patients 18 years or older who were treated at the Massachusetts General Hospital CF centers. Reports of side effects were measured across 12 distinct categories, and dose adjustments and discontinuation due to side effects were collected. If a patient reported no side effects, they did not have to complete the entire survey. RESULTS: Among 92 respondents initiated on ETI, 51 respondents (55.4%) reported potential side effects and 41 (44.5%) respondents reported no adverse events. The most commonly reported side effects were mental health, changes in appearance, and gastrointestinal complaints, which were reported by 22.8%, 30.4%, and 21.7% of patients, respectively. Eighteen (19.6%) respondents modified their dosing in response to side effects, and six discontinued treatment permanently (6.52%) due to persistent side effects. CONCLUSIONS: Responses demonstrated marked heterogeneity, with most respondents reporting at least one side effect following initiation. Dose modification was commonly utilized to mitigate adverse effects, however few respondents had to discontinue treatment. These findings demonstrate the importance of monitoring for potential drug-related side effects of ETI in clinical settings.