Exposure-response analysis of oral and intravenous imatinib in critically ill patients with COVID-19 acute respiratory distress syndrome

Introduction: Imatinib, initially approved for chronic myeloid leukemia (CML) and gastrointestinal stromal tumors (GIST), was investigated in two randomized placebo-controlled trials for its potential effect on COVID-19-related ARDS (C-ARDS). A known relationship between imatinib concentrations and effectiveness exists in CML and GIST, but this is uncharacterized in critically ill C-ARDS patients, where standard dosing may not be suitable. Aims: This study aims to explore the association between unbound imatinib, total imatinib, and total N-desmethyl-imatinib exposure with clinical outcomes in critically ill C-ARDS patients. Methods: This post-hoc analysis included C-ARDS patients from the CounterCOVID and InventCOVID trials, all requiring invasive ventilation. In the CounterCOVID trial, patients received 800 mg imatinib on day 1, followed by 400 mg once daily for 9 days. In InventCOVID, the dose was 200 mg intravenously twice daily for 7 days or until ICU discharge. A pharmacokinetic (PK) model simulated the concentration-time profiles of total imatinib (T), unbound imatinib (U), and the sum of total imatinib plus its metabolite desmethyl-imatinib (PM). PK samples were used to estimate individual PK parameters, after which associations with clinical outcomes (WHO score, P/F ratio, ICU stay, ventilator-free days, and mortality) were tested using linear mixed models and regression analysis. Results: Data from 53 patients revealed that critically ill patients reached higher total imatinib exposure but similar unbound imatinib exposure compared to others. Critical illness and concurrent treatments influenced imatinib exposure. No clear exposure-response relationship was found between imatinib exposure and clinical outcomes. Conclusion: Although critical illness was linked to higher imatinib exposure, no exposure-response relationship was found. Disease severity may have also impacted the drug's effectiveness, suggesting that ICU patients may require adjusted dosing. Future clinical studies of repurposed drugs should focus on exposure-response relationships to better understand optimal dosing in new patient populations, particularly for highly protein-bound drugs. Trial Registration: ClinicalTrials.gov Identifier: NCT04794088, registered 11 March 2021. European Clinical Trials Database (EudraCT number: 2020-005447-23).