Eltrombopag Combined With Cyclosporine A in the Treatment of Pediatric Patients With SAA: Establishing the Range for Eltrombopag Concentrations

Eltrombopag (ELT), as an oral thrombopoietin receptor agonist, in combination with cyclosporine A (CsA) provides a novel therapeutic option for pediatric severe aplastic anemia (SAA). However, current clinical protocols predominantly adopt fixed-dose regimens without adequate consideration of pediatric pharmacokinetic characteristics and drug-drug interactions, resulting in interindividual variability in efficacy and safety, as well as a lack of standardized therapeutic drug monitoring criteria for personalized treatment. This retrospective study analyzed treatment data from 83 pediatric patients with SAA (diagnosed at Kunming Children's Hospital between January 2020 and May 2025) to evaluate dose-concentration, concentration-efficacy, and concentration-adverse effects (ADRs) relationships, aiming to establish ELT concentration thresholds and reference ranges associated with therapeutic efficacy and ADRs. Results demonstrated a significant positive correlation between dosage and concentration (Pearson analysis). The study identified an efficacy threshold of 2.5 μg/mL (AUC = 0.85) and an ADRs threshold of 4.0 μg/mL (AUC = 0.82). Kaplan-Meier analysis revealed significant differences in time-to-response and time-to-adverse events among different concentration groups (4.0 μg/mL). The study confirms that ELT concentrations are closely associated with clinical efficacy and ADRs, and the established reference range of 2.5-4.0 μg/mL can serve as a basis for individualized pediatric treatment.