Risk of thrombosis in adults with primary immune thrombocytopenia treated with eltrombopag vs romiplostim: a target trial emulation in the French Adult Immune Thrombocytopenia (FAITH) cohort

BACKGROUND: Thrombopoietin receptor agonists (TPO-RAs) have been identified as a risk factor for thrombosis in immune thrombocytopenia. A potential risk difference between eltrombopag and romiplostim (the only TPO-RAs available in France) is unknown and may be due to pharmacological differences. OBJECTIVES: We aimed to compare the risk of thrombosis between eltrombopag and romiplostim in adult patients with primary immune thrombocytopenia. METHODS: We performed a target trial emulation using the French national healthcare database. Patients exposed to first-line TPO-RAs were followed until the first hospitalization for thrombosis, discontinuation of TPO-RAs, death, or the end of follow-up at 1 year. We used inverse probability of treatment weighting and performed Cox proportional hazards models with time-varying adjustment. RESULTS: Between 2011 and 2022, 2761 and 949 patients were included in the eltrombopag and romiplostim groups, respectively. Patients in the romiplostim group were older and had more risk factors for thrombosis. The 1-year weighted cumulative incidence of thrombosis was 5.1% (95% CI, 3.6%-6.6%) with eltrombopag and 1.9% (95% CI, 1.0%-2.7%) with romiplostim. The adjusted hazard ratio for eltrombopag vs romiplostim was 1.93 (95% CI, 1.11-3.34) at 1 year. No significant difference was observed in the first 6 months, but emerged thereafter due to a few events. Results were similar for venous and arterial thrombosis when considered separately. The risk difference was the greatest in patients aged ≥75 years. CONCLUSION: Eltrombopag was associated with a greater risk of thrombosis than romiplostim after 6 months of exposure, particularly in elderly patients.