Pharmacokinetic modelling of intravenous immunoglobulin in children with primary immunodeficiencies and secondary antibody deficiencies – Research

Aims:

Children with primary immunodeficiency (PID) and secondary antibody deficiency (SAD) often require immunoglobulin replacement therapy due to low plasma immunoglobulin G (IgG) levels and recurrent infections. Existing pharmacokinetic models for immunoglobulin in PID patients predominantly focus on adults, with limited attention to secondary antibody deficiencies and a lesser emphasis on paediatric populations. This study aims to investigate the pharmacokinetic properties of IgG in paediatric patients with PID and SAD.

Methods:

Population pharmacokinetic analysis for PID and SAD children treated with intravenous immunoglobulin at a tertiary paediatric centre was conducted using NONMEM® (7.5.1). Dosing simulations to achieve therapeutic levels of 6 and 8 gL^-1 were performed.

Results:

A population pharmacokinetic analysis of 64 patients (median age 4.08 years, range 0.06-16.8) was performed. A two-compartment model with first-order elimination, incorporating both additive and proportional residual error, adequately described the data. Interindividual variability was modelled on clearance, volume of distribution and baseline IgG levels, with allometric scaling to a 70-kg body weight applied a priori. The estimated clearance was 0.308 L^-1 day^-1 70 kg^-1 (95% CI 0.23, 0.67), and the volume of distribution was 10.96 L^-1 70 kg^-1 (95% CI 5.97, 15.79). Patients with SAD exhibited a lower clearance rate of 54% compared with PID patients. Dosing simulations indicated that the recommended SAD dosing regimen maintained therapeutic IgG levels in the simulated population. However, only 44.8% to 51.9% of patients with PID achieved target IgG levels with the standard regimen.

Conclusions:

This study provides insights into immunoglobulin pharmacokinetics in paediatric PID and SAD patients, guiding optimised dosing strategies. Administering a loading dose would improve the probability of maintaining therapeutic IgG levels during the 4-week dosing interval.