Category: Preclinical Development
Purpose: The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) gefitinib (Gef), erlotinib (Erl) and osimertinib (Osi) are recommended as first-line therapy for non-squamous lung cancer harboring EGFR mutations. EGFR-TKIs are primarily metabolized by cytochrome P450 (CYP) 3A4. Therefore, EGFR-TKIs have been reported to interact with several drugs and foods, including CYP3A4 inhibitors and inducers. In particular, grapefruit juice (GFJ) is known to alter the pharmacokinetics of several drugs by affecting bioavailability. The mechanism of this interaction includes the inhibition of intestinal CYP3A4 activity and increased systemic exposure of CYP3A4 substrates. Warning are included in the package inserts of EGFR-TKIs with regard to Gef and Erl use in combination with GFJ, as plasma concentrations may increase. Although drug interactions between EGFR-TKIs and GFJ are suggested, there are limited data available regarding the influence of GFJ on EGFR-TKI pharmacokinetics. The aim of this study was therefore to clarify the effects of GFJ on EGFR-TKI pharmacokinetics. We evaluated the pharmacokinetics of Gef, Erl and Osi in rats after GFJ administration in vivo and measured the remaining percentage of the drugs after incubation with human liver microsomes (HLM) in the presence and absence of GFJ in vitro.
Methods: The pharmacokinetics of EGFR-TKIs (Gef, Erl and Osi) were evaluated after oral and intravenous administration in rats. Male Sprague-Dawley rats aged 8 weeks were used for this study after overnight fasting. Rats administered GFJ (6 mL/kg, 100% grapefruit juice, Sunkist®; Morinaga Milk Industry Co., Ltd., Tokyo, Japan) orally 3 h before EGFR-TKI administration and control rats were administered water. Gef (5 mg/kg), Erl (5 mg/kg), or Osi (5 mg/kg) suspended in 0.5% carboxymethyl cellulose was orally administered and blood samples (0.2 mL) were collected from the subclavian vein 0.5–24 h after administration. For intravenous administration, rats were treated with Gef (1 mg/kg), Erl (1 mg/kg), or Osi (1 mg/kg) intravenously and blood samples (0.2 mL) were collected from the subclavian vein 0.17–8 h after administration. Plasma concentrations of EGFR-TKIs were determined via liquid chromatography-mass spectrometry. An in vitro metabolic study was performed using HLM (1.25 mg/mL) in the presence and absence of GFJ (0, 1%v/v final concentration). Gef, Erl and Osi (5 μM) metabolism was initiated by the addition of drugs after a 20-min preincubation period with a final volume of 400 μL at 37 °C. Aliquots (50 μL) were transferred to acetonitrile (100 μL) after 0, 15, 30, 45, and 60 min, and centrifuged. Gef, Erl and Osi concentrations in the supernatant were determined via high-performance liquid chromatography. The percentage drug remaining was then calculated.
Results: Plasma concentrations of Gef after oral administration in rats pre-treated with GFJ were higher at all sampling times compared with those in control rats (Fig. 1A). However, there were no significant differences in Erl and Osi plasma concentrations in rats pre-treated with GFJ and the control rats (Fig. 1B). The peak plasma concentration (Cmax) of Gef increased by 47.1% after GFJ administration compared with that in the control, although this difference was not significant. The elimination half-life (t1/2) and the time to Cmax (Tmax) of Gef were not significantly different between rats pre-treated with and without GFJ. The area under the plasma concentration-time curve from 0 h to infinity (AUC) of Gef in rats pre-treated with GFJ increased significantly by 41.9% compared with that in control rats. The pharmacokinetic parameters of Erl and Osi did not change significantly after pre-treatment with GFJ. The bioavailabilities of Gef, Erl, and Osi were calculated using the AUC after each intravenous administration and were 51.3, 89.1, and 46.4%, respectively. The bioavailability of Gef increased significantly by 21.5% after GFJ pre-treatment, although no significant changes in Erl and Osi bioavailabilities were observed. The in vitro metabolic study showed that the remaining percentages of Gef and Erl after 30–60 min and 15–60 min incubation, respectively, in the presence of GFJ (1%) were significantly higher than those in the absence of GFJ (Fig. 2A and 2B). There was no significant difference in the remaining percentage of Osi in the absence and presence of GFJ (Fig. 2C).
Conclusion: Plasma concentrations and bioavailabilities of Gef were increased by pre-treatment with GFJ as a result of CYP3A inhibition as suggested by the in vitro metabolic study results. The bioavailability of Erl did not change significantly after GFJ pre-treatment, although significant inhibition of Erl metabolism was observed. This may be a result of its high bioavailability in rats (89%). The pharmacokinetics of Osi did not change significantly after GFJ pre-treatment because of the small contribution of CYP3A metabolism. In conclusion, the effects of GFJ on the pharmacokinetics of EGFR-TKIs differ and are related to their pharmacokinetic characteristics.
Shinya Uchida– Associate professor, University of Shizuoka, Shizuoka, Shizuoka, Japan
Ayae Suzuki– Shizuoka, Shizuoka, Japan
Osamu Yasumuro– Kamogawa, Chiba, Japan
Shimako Tanaka– Assistant professor, University of Shizuoka, Shizuoka, Shizuoka, Japan
Yasuharu Kashiwagura– Assistant professor, University of Shizuoka, Shizuoka, Shizuoka, Japan
Noriyuki Namiki– Professor, University of Shizuoka, Shizuoka, Shizuoka, Japan