Correlation of the Plasma Concentration of Eltrombopag With Efficacy in the Treatment of Refractory Aplastic Anemia: A Single-Centre Study in China

Exploratory study on the individualized application of eltrombopag in paediatric immune thrombocytopaenia guided by therapeutic drug monitoring

There are variations in individual eltrombopag concentrations that may impact efficacy and adverse drug reactions (ADRs) in paediatric immune thrombocytopaenia (ITP). To solve this problem, we tailored the eltrombopag dosage refer to concentration, then followed up to assess concentration value in paediatric ITP. This is a single-centre, prospective, observational study. The eltrombopag dosage was adjusted, and children were divided into three groups: the maintenance, discontinuation, and increase groups. Concentration and other data were compared to explore concentration value in guiding the individualized treatment of paediatric ITP. Thirty-nine patients were enrolled, including 23 in the maintenance group, 3 in the discontinued group and 13 in the increase group. 3 patients discontinued eltrombopag due to ADRs, which was significantly higher than patients in the maintenance group (t = 3.606, p = 0.001). In all, 13 patients increased their dosage due to poor response, whose concentration and platelet count were significantly lower than patients in the maintenance group (t = 2.461, p = 0.019; t = 4.633, p < 0.001). Two months after the increase, the number of patients reaching CR and R respectively increased by 2 and 3, while the median platelet count was significantly raised (Z = -2.411, p = 0.016). Concentration could be used as a reference index for the individualized treatment of eltrombopag in paediatric ITP.

Spotlight on eltrombopag concentration in pediatric immune thrombocytopenia: A single-center observational study in China

Importance

Eltrombopag has been recommended for pediatric immune thrombocytopenia (ITP). Response and adverse drug reactions (ADRs) varied widely between individuals, even at the same dose of eltrombopag. The appropriate eltrombopag concentration in ITP has not been reported.

Objective

This study aims to explore the appropriate eltrombopag concentration in pediatric ITP.

Methods

This was a single-center, prospective cohort study. Children diagnosed with refractory persistent/chronic ITP and platelet count < 30×109/L were treated with eltrombopag and followed up for at least 2 months. Concentration was detected by high-performance liquid chromatography-mass spectrometry at least 2 weeks after eltrombopag. The clinical characteristics-concentration, concentration-response, and concentration-ADRs were analyzed.

Results

A total of 30 patients were enrolled, comprising 13 males and 17 females, with a median age of 72 (45‒94) months. The median dose and concentration were 1.39 (1.09‒1.56) mg/kg and 2.70 (2.25‒4.13) mg/L, respectively. Of the enrolled patients, 14 responded to treatment, whereas 16 did not. Additionally, five experienced adverse drug reactions. No linear correlation was observed between eltrombopag concentration and clinical characteristics. The concentration was lower in the response group than in the nonresponse group, but there was no significant difference (t = 0.755, P = 0.457). Patients who experienced ADRs had a higher concentration than those without ADRs (t = 2.538, P = 0.017). The area under the receiver operating characteristic curve of ADRs was 0.78 (95% confidence interval: 0.56‒1.00). Youden's index identified the cutoff point as 4.33 mg/L, with a sensitivity of 88% and a specificity of 60%. Logistic regression analysis demonstrated that a higher platelet count before eltrombopag predicted a favorable response.

Interpretation

Eltrombopag proves efficacious and well-tolerated for treating pediatric ITP. However, prolonged and high-dose administration may increase the likelihood of ADRs. Thus, examining the appropriate eltrombopag concentration assists in directing individualized management of pediatric ITP.

Simultaneous analysis of avatrombopag, eltrombopag, and hetrombopag in human plasma by UPLC-MS/MS for therapeutic drug monitoring

Avatrombopag, eltrombopag, and hetrombopag are three oral thrombopoietin receptor agonists used to treat thrombocytopenia. To investigate the pharmacokinetic properties, a fast and robust UPLC-MS/MS method was developed and validated for simultaneous determination of avatrombopag, eltrombopag, and hetrombopag in human plasma. Chromatographically separation was achieved on an Acquity BEH C18 column using a gradient elution of methanol-water (20:80, v/v) and acetonitrile containing 0.1% formic acid at a flow rate of 0.4 mL/min within 4.5 min. The linearity was assessed over the range of 7.5-1500 ng/mL for avatrombopag, 50-10,000 ng/mL for eltrombopag, and 5-1000 ng/mL for hetrombopag. This method was validated with adequate results in terms of selectivity, precision (intra- and inter-day CV from 4.2% to 12.2%), accuracy (RE from -6.6% to 7.5%), dilution integrity, carryover, recovery, matrix effects, as well as stability of the analytes under various conditions. The developed approach has been successfully applied to the therapeutic drug monitoring of avatrombopag, eltrombopag, and hetrombopag in patients with immune thrombocytopenia.

Relationship between CYP2C8, UGT1A1, and ABCG2 gene polymorphisms and the exposure, efficacy, and toxicity of eltrombopag in the treatment of refractory aplastic anemia

PURPOSE

Eltrombopag (ELT) is an effective drug for relapsed/refractory aplastic anemia (AA). Our previous study showed that ELT concentration was correlated with the effects of ELT. However, the factors affecting ELT concentration in patients with relapsed/refractory AA were not clarified. Therefore, we aimed to evaluate correlations between drug disposition-related gene polymorphisms and the concentration, efficacy, and toxicity of ELT.

METHODS

Forty-five patients who underwent ELT administration from January 2018 to January 2019 at Peking Union Medical Colleague Hospital (PUMCH) were included. The corresponding clinical information was also collected. ELT plasma concentrations were detected by high-performance liquid chromatography-mass spectrometry (HPLC/MS). CYP2C8, (UGT)1A1, and ABCG21 were genotyped by polymerase chain reaction (PCR). The influence of gene polymorphisms on the plasma concentration, efficacy, and toxicity of ELT was analyzed.

RESULTS

The mean dose required to obtain the optimal effects was significantly lower in the UGT1A1*6 variant carriers than in the UGT1A1*6 WT carriers. There was a significant correlation between the (UGT)1A1*6 polymorphism and higher ELT plasma concentrations (> 11.2 μg/mL). By logistic regression analysis, the efficacy of ELT was related to plasma concentration and a combined genotype of (UGT)1A1*6 and ABCG2. There were no significant associations between genotypes and adverse drug reactions (ADRs) or ELT concentrations and ADRs.

CONCLUSION

UGT1A1*6 is a predictor of the ELT plasma concentration and may help to determine the initial therapeutic dose in relapsed/refractory AA patients. Both drug exposure and patient genotype should be considered for better responses to ELT.