Background: As the first-line treatment of gastrointestinal stromal tumor (GIST), the pharmacokinetic and pharmacodynamic of imatinib (IM) were characterized by marked interindividual variability. Pharmacogenetics of IM involved metabolic enzymes and transporters have been extensively reported, but the results remained inconsistent. This study investigated the effect of genetic variants in hepatocyte nuclear factor 4 alpha (HNF4α, encoded by gene NR2A1), a pivotal transcriptional regulator of drug disposition genes, on dose-adjusted IM-free plasma levels and related adverse reactions in Chinese GIST patients.
Methods: Five common polymorphisms of NR2A1 (rs3818247, rs1884613, rs2071197, rs2425640, and rs736824) were genotyped in 70 Chinese GIST patients who had been administered IM 300-600 mg/d. The free IM trough plasma levels were determined based on a method of ultrafiltration coupled with high performance liquid chromatography-tandem mass spectrometry.
Results: There were wide interpatient variations in free plasma levels of IM (range, 9.50-67.50 ng/mL), in which significant sex differences were observed (P < 0.01). The dose-adjusted IM-free plasma levels showed a significant negative correlation with body surface area (r = -0.302, P = 0.012). Although there were no significant effects of NR2A1 polymorphisms on dose-adjusted IM-free plasma levels among the study population, polymorphism in rs736824 was found to be significantly associated with dose-adjusted IM-free plasma levels in male subjects (P = 0.031). For the IM-related adverse reaction, polymorphisms in rs3818247 were found to be significantly associated with periorbital edema (P = 0.032). In addition, no significant correlations were found between IM-free plasma levels and IM-related adverse reactions, except for the correlation of IM-free plasma levels with periorbital edema among male patients (P = 0.013).
Conclusions: The research demonstrated that NR2A1 polymorphisms may act as contributors of IM pharmacokinetics and responses in Chinese GIST patients. This represents an attractive opportunity for IM therapy optimization, worth testing in clinical trials.