Influence of blood group and von Willebrand factor on population pharmacokinetics and dose individualization of recombinant factor VIII in Taiwanese patients with haemophilia A

Introduction: The large interpatient variability in the pharmacokinetic (PK) parameters of recombinant Factor VIII (rFVIII) observed in haemophilia A hinders efficient and cost-beneficial prophylactic regimen initiation. Identification of factors influencing the PK of rFVIII may shed more light on personalised treatment. Aim: This study aimed to develop a population PK model in the Taiwanese haemophilia A and evaluate the current national health insurance (NHI) reimbursement guidelines of Taiwan for haemophilia treatment. Methods: A population PK analysis was established based on 69 Taiwanese with moderate or severe haemophilia A. A nonlinear mixed-effects modelling (NONMEM^®) was used to estimate PK parameters and their variabilities. A Monte Carlo simulation was performed to evaluate different prophylactic regimens. Results: A two-compartment model with first-order elimination best described the rFVIII data. Weight-based allometric scaling was related to clearance and central volume of distribution. Blood type and baseline von Willebrand factor (VWF) were significant covariates for clearance. For single dose simulations, a time achieving target level (> 1 IU/dL) was associated with increasing rFVIII dose and VWF level. The multiple dose simulations showed that > 96.4% of patients with high VWF level (> 200%) had predicted trough level > 1 IU/dL for all dosing regimens (15-40 IU/kg, two to three times weekly). However, for twice weekly dosing, lower percentage (47.62-62.20%) of patients with blood group O and low VWF level (< 50%) achieved a predicted trough level > 1 IU/dL. Conclusion: The population PK of rFVIII was successfully developed. Dose adjustment based on blood type and VWF level should be considered.