Population pharmacokinetics of erlotinib and its pharmacokinetic/pharmacodynamic relationships in head and neck squamous cell carcinoma

A clinical study was conducted to determine the safety and efficacy of neoadjuvant erlotinib treatment in patients with head and neck squamous cell carcinoma [Thomas F, Rochaix P, Benlyazid A, et al. Pilot study of neoadjuvant treatment with erlotinib in non-metastatic head and neck squamous cell carcinoma. Clin Cancer Res 2007;13:7086–92]. The aim of the present analysis was to explore the impact of several covariates on the pharmacokinetics of erlotinib and its main metabolite (OSI-420) and to determine PK/PD relationships.Patients and methodsPlasma concentrations of erlotinib and OSI-420 of 42 patients were analysed using the NONMEM program to evaluate the impact of patients’ covariates on erlotinib pharmacokinetics. The presence of single nucleotide polymorphisms (SNP) in ABCB1 (2677G > T/A and 3435C > T), ABCG2 (421C > A) and CYP3A5 (6986G > A) was investigated. Pharmacokinetic/pharmacodynamic relationships between plasma drug exposure (AUC) and early drug response or toxicity were also studied.ResultsThe covariates retained to predict erlotinib clearance were ALAT (alanine amino transferase), age and ABCG2 polymorphism. A significant link between drug exposure and the grade of skin rash was observed but early response to treatment was not correlated to the erlotinib AUC.ConclusionsErlotinib treatment may present criteria justifying dose individualisation but further studies, including more patients, are necessary to define the modalities of this adaptation.