Population pharmacokinetics of roxadustat in Japanese dialysis-dependent chronic kidney disease patients with anaemia

Influencing factors of clinical efficacy of roxadustat among hemodialysis patients

OBJECTIVE

To explore independent influencing factors for clinical efficacy of roxadustat in hemodialysis patients.

METHODS

Hemodialysis patients treated with roxadustat were enrolled. The plasma trough concentrations of roxadustat were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A multiple logistic regression model was established to determine the factors that affect clinical efficacy of roxadustat in patients undergoing hemodialysis.

RESULTS

A total of 67 hemodialysis patients were enrolled in the study. The results showed that age, blood trough concentration of roxadustat, and baseline hemoglobin (Hb) level were independent factors of clinical efficacy of roxadustat (OR = 1.06, p = .025 for age; OR = 1.001, p = .037 for plasma concentration; and OR = 0.941, p = .003 for baseline Hb), with an AUC score of 0.859.

CONCLUSIONS

Age, blood trough concentration of roxadustat, and baseline Hb level were independent influencing factors of the response to roxadustat in hemodialysis patients.

Optimizing the dosing regimen of roxadustat in kidney transplant recipients with early post-transplant anemia

INTRODUCTION

Roxadustat, an oral inhibitor of hypoxia-inducible factor prolyl hydroxylase domain enzymes, has been approved for the treatment of renal anemia. However, there is a lack of study on its pharmacokinetics in kidney transplant recipients (KTRs) with early posttransplant anemia (PTA). Therefore, the aim of this study is to elucidate the pharmacokinetic characteristics of roxadustat in KTRs with early PTA and optimize the dosing regimen.

METHODS

A population pharmacokinetic (PopPK) analysis was performed based on 72-hour full concentration-time profiles collected from 52 Chinese KTRs. Covariates influencing exposure were assessed using stepwise covariate modelling. Monte Carlo simulations were conducted to recommend the dosing regimen for patients with different levels of covariates.

RESULTS

PopPK analysis showed that the concentration-time data can be fully described by a two-compartment model. Body weight (BW) and direct bilirubin (DBIL) levels significant affected the apparent clearance of roxadustat. Based on the established model and the estimated exposures of roxadustat by Monte Carlo simulations, a recommended dosing regimen for KTRs with early PTA at varying BW and DBIL levels were developed. Roxadustat at 100 mg three times weekly were suitable for the majority of KTRs with a DBIL level around 3 μmol/L and BW between 50 and 75 kg. The required dose may need to be increased with higher BW and lower DBIL levels, while decreased with lower BW and higher DBIL levels.

CONCLUSIONS

It was the first PopPK analysis of roxadustat in KTRs with early PTA, which provide a research basis for optimizing the dosing regimen.

Correlation between blood concentration of roxadustat and clinical efficacy in patients with anemia of chronic kidney disease

Roxadustat has been associated with the efficacy and safety in patients with chronic kidney disease-related anemia. However, the relationship between roxadustat blood concentration and clinical efficacy is lacking. To explore of the correlation between clinical efficacy and blood concentration of roxadustat in patients with renal anemia of chronic kidney diseases, so as to provide reference for rational clinical drug use. A total of 46 patients were selected with a diagnosis of renal anemia who were prescribed roxadustat at the department of nephrology of the First Hospital of Hebei Medical University from December 2019 to March 2020. The roxadustat blood concentration was determined at 12 weeks of treatment, according to the cumulative response rate, patients were divided into the response group and the nonresponse group, and the relationship between roxadustat blood concentration and treatment effect was analyzed. We also explored the correlation between various factors and the blood concentration. The patients in the response group had higher roxadustat blood concentrations than the nonresponse group (P < .05), and there was no correlation between blood concentration and clinical characteristics such as age, gender, and dosage (P > .05). The blood concentration of roxadustat was correlated with clinical efficacy. The higher the blood concentration, the better the clinical efficacy, meaning it might be a predictor of efficacy.

Clinical Pharmacokinetics and Pharmacodynamics of Roxadustat

The pharmacokinetics of roxadustat are well characterized, with an apparent volume of distribution after oral administration of 22–57 L, apparent clearance of 1.2–2.65 L/h, and renal clearance of 0.030–0.026 L/h in healthy volunteers; the elimination half-life is 9.6–16 h. Plasma binding is 99% and the fraction eliminated by hemodialysis is 2.34%. As an interpretation of the pharmacodynamics of roxadustat, we proposed a concept with a hypothetical cascade of two subsequent effects, first on erythropoetin (EPO) and second on hemoglobin (delta Hb). The primary effect on EPO is observed within a few hours after roxadustat administration and can be modeled using the sigmoidal Hill equation. The concentration at half-maximum effect can be inferred at 10–36 µg/mL, the Hill coefficient at 3.3, and the effect bisection time at 10–17 h, corresponding to EPO half-life. The subsequent effect on hemoglobin (delta Hb) is observed after several weeks and can be interpreted as an irreversible, dose proportional, unsaturable effect, continuing in agreement with the lifespan of red blood cells of 63–112 days.