Effect of genetic polymorphisms on erlotinib pharmacokinetics and toxicity in patients with non-small-cell lung cancer

Abstract

Introduction: Aiming to develop a dose regimen that would maintain the clinical benefits of erlotinib while minimizing its adverse effects, we analyzed single nucleotide polymorphisms (SNPs) of PK‐related genes and investigated the relationships between genotypes and interindividual variabilities in the PK and adverse effects. Methods: We performed a multicenter study of 50 patients treated with 150 mg erlotinib as a second‐line or later treatment. PK and toxicity were assessed. For PK analyses, blood samples were collected from 28 patients at 5 to 18 time points, and trough blood samples were collected from 20 patients at 1 time point. SNPs in genes encoding metabolizing enzymes or efflux transporters (CYP1A1, CYP1A2, CYP2D6, CYP3A4, CYP3A5, UGT1A1, UGT2B7, GSTM1, GSTT1, ABCB1, and ABCG2) were analyzed. Population PK analyses were carried out using NONMEM. SNPs were tested as covariates in a population PK model. The effects of these SNPs and erlotinib exposure on toxicity were evaluated. Results and discussion: A 2‐compartment model with first order absorption and linear elimination described the erlotinib PK. Only the ABCB1 1236C > T polymorphism was a statically significant covariate for CL/F, showing a 29.4% decrease in CL/F for the TT genotype as compared with the CC and the CT genotypes. The interindividual variability in CL/F decreased by 10.6% after inclusion of the TT genotype as a covariate in the model. This result indicates that a dose reduction to 100 mg for the TT genotype group could equalize the erlotinib exposure between each genotype group. A higher incidence of adverse effects (mainly diarrhea) was observed in the TT genotype group. Conclusions: Only ABCB1 1236C > T influenced the exposure of erlotinib. This SNP was suggested to be related to the risk of adverse events. Individual dosing based on ABCB1 genotype might reduce the adverse effects. Further clinical trials are needed to investigate the toxicity and the clinical outcome of this dose regimen.