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Influence of schisantherin A on the pharmacokinetics of lenvatinib in rats and its potential mechanism.

Background
Lenvatinib (LEN) is approved as first-line therapy for advanced hepatocellular carcinoma (HCC). Schisantherin A (STA) can exert hepatoprotective and anti-tumor effects. The clinical combination of LEN and STA is very common, especially for patients with advanced HCC, but the effect of STA on the pharmacokinetics of LEN is unclear. This study aimed to investigate the effects of STA on the pharmacokinetics of LEN in rats and explore its potential mechanism.


Methods
Male Sprague-Dawley (SD) rats were orally administered different doses of STA or vehicle control for 7 consecutive days, and 1.2 mg/kg of LEN was given on day 7. The messenger RNA (mRNA) and protein expression levels in the intestines and liver were investigated by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot.


Results
It was revealed that STA increased the oral bioavailability of LEN. The area under the curve from time 0 to infinity (AUC0-∞) and maximum plasma concentration (Cmax) of LEN after co-administration with STA (20 mg/kg) increased by 54.3% (3,396.73±989.35 vs. 5,240.03±815.49 µg/L/h) and 54.8% (490.64±124.20 vs. 759.66±152.75 µg/L), respectively. The clearance decreased from 0.38±0.12 to 0.23±0.04 L/h/kg, and the apparent volume of distribution (Vz) decreased from 10.83±3.19 to 6.35±1.38 L/kg in the presence of 20 mg/kg STA. In addition, the expression of P-glycoprotein (P-gp) mRNA and protein in the intestines was markedly decreased.


Conclusions
This study showed that STA increased the bioavailability of LEN, probably due to inhibition of P-gp in the intestine, thereby increasing systemic absorption of LEN. Thus, there is an interaction between the two drugs, and careful monitoring must be conducted when they are used in combination.