Abstract
A population pharmacokinetic model based on data from three phase I studies was to be developed including a covariate analysis to describe the concentration-time profiles of matuzumab, a novel humanised monoclonal antibody. Matuzumab was administered as multiple 1 h i.v. infusions with 11 different dosing regimens ranging from 400 to 2000 mg, q1w-q3w. For analysis, 90 patients with 1256 serum concentration-time data were simultaneously fitted using the software NONMEM. Data were best described using a two-compartment model with the parameters central (V1) and peripheral distribution volume (V2), intercompartmental (Q) and linear (CLL) clearance and an additional nonlinear elimination pathway (Km, Vmax). Structural parameters were in agreement with immunoglobulin characteristics. In total, interindividual variability on Vmax, CLL, V1 and V2 and interoccasion variability on CLL was 22-62% CV. A covariate analysis identified weight having an influence on V1 (+0.44% per kg) and CLL (+0.87% per kg). All parameters were estimated with good precision (RSE<39%). A robust population pharmacokinetic model for matuzumab was developed, including a nonlinear pharmacokinetic process. In addition, relevant and plausible covariates were identified and incorporated into the model. When correlated to efficacy, this model could serve as a tool to guide dose selection for this 'targeted' cancer therapy.