Dataset Information

Population pharmacokinetics of clofarabine for allogeneic hematopoietic cell transplantation in paediatric patients.

ABSTRACT:

Aims

Clofarabine has recently been evaluated as part of the conditioning regimen for allogeneic hematopoietic stem cell transplantation (HCT) in children. Pharmacokinetic (PK) exposure of different agents commonly used in conditioning regimens is strongly related to HCT outcome. Consequently, the PK of clofarabine may be important for outcome. This report describes the population PK of clofarabine in paediatric patients and one adult.

Methods

From 80 paediatric (0.5-18 years) and 1 adult patient (37 years), 805 plasma concentrations were included in pharmacokinetic analyses using nonlinear mixed effects modelling.

Results

A two-compartment model adequately described the PK of clofarabine. Body weight and estimated glomerular filtration rate (eGFR) were included as covariates. Clearance was differentiated into nonrenal and renal clearance (approximately 55% of total clearance), resulting in population estimates of 24.0 L/h (95% confidence interval [CI] 13.7-34.4) and 29.8 L/h (95% CI 23.9-36.1) for a patient of 70 kg with normal renal function, respectively. Unexplained interindividual variability in clearance was 17.8% (95% CI 14.6-22.4). A high variability in exposure was observed (range area under the curve_T0-inf 1.8-6.0 mg/L*h) after body surface area (BSA) based dosing. Interestingly, children with low body weight had a lower exposure than children with a higher body weight, which indicates that the currently practised BSA-based dosing is not adequate for clofarabine.

Conclusion

A clofarabine dosing algorithm based on this PK model, using body weight and eGFR, results in a more predictable exposure than BSA-based dosing. However, the exact target exposure needs to be further investigated.

SUBMITTER: Nijstad AL

PROVIDER: S-EPMC8359279 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The primary objective of this work was to characterize the pharmacokinetics (PK) of systemic clofarabine (clo-fara) in pediatric allogeneic hematopoietic cell transplantation (HCT) recipients receiving either nucleoside monotherapy or a dual nucleoside analog preparative regimen. Fifty-one children (median age, 4.9 years; range, .25 to 14.9 years) undergoing allogeneic HCT for a variety of malignant and nonmalignant disorders underwent PK assessment. Plasma samples were collected over the 4 to 5 days of clo-fara treatment and quantified for clo-fara, using a validated liquid chromatography/tandem mass spectrometry assay. Nonlinear mixed-effects modeling was used to develop the population PK model, including identification of covariates that influenced drug disposition. In agreement with previously published models, a 2-compartment PK model with first-order elimination best described the PK of clo-fara. Final parameter estimates for clo-fara were consistent with previous reports and were as follows: clearance (CL), 23 L/h/15 kg; volume of the central compartment, 42 L/15 kg; volume of peripheral compartment, 47 L/15 kg; and intercompartmental CL, 9.8 L/h/15 kg. Unexplained variability was acceptable at 33%, and the additive residual error (reflective of the assay) was estimated to be 0.36 ng/mL. Patient-specific factors significantly impacting clo-fara CL included actual body weight and age. The covariate model was able to estimate clo-fara CL with good precision in children spanning a wide age range from infancy to early adulthood and demonstrates the need for variable dosing in children of different ages. For example, the dose required for a 6-month and 1-year old was approximately 43% and 17% lower, respectively, than the typical 40 mg/m2dose to achieve the median AUC0-24of 1.04 mg·h/L in the study population. Despite the known renal elimination of clo-fara, no significant clinical parameters for renal function were retained in the final model (P> .05). Coadministration of fludarabine with clo-fara did not alter the CL of clo-fara (P> .05). These results will help inform individualized dosing strategies for clo-fara to improve clinical outcomes and limit drug-related adverse events in children undergoing HCT.