Effect of iguratimod on diclofenac metabolism by CYP2C9 in rats and human recombinant CYP2C9 yeast cells

Iguratimod (IGU, also known as T-614), a novel disease modifying antirheumatic drug intended to cure patients with rheumatoid arthritis (RA). The purpose of this study is to evaluate the effect of IGU on the pharmacokinetics of CYP2C9 probe drug diclofenac and its metabolite 4′-hydroxy diclofenac in vivo and in vitro. In in vivo experiments, 24 rats were randomly assigned to three groups consisting of the control group (Normal saline), low dose IGU group (10 mg/kg) and high dose IGU group (30 mg/kg). Blood samples were collected from orbital sinuses vein before 1 hour and serial times of giving diclofenac (15 mg/kg) to all the rats. Plasma concentration of diclofenac and its metabolite 4´-hydroxy diclofenac were assayed by high performance liquid chromatography. Pharmacokinetic parameters were assessed by Winnonlin 6.4 pharmacokinetic software. Moreover, in vitro studies were performed in recombinant human CYP2C9 yeast cell system. IGU at low dose showed no significant differences in the pharmacokinetic parameters of diclofenac and 4-hydroxy diclofenac in vivo when compared with control group (p>0.005). However, at the high dose of IGU, the pharmacokinetic parameters of 4´-hydroxy metabolite of diclofenac increase in half-life (T1/2) and mean area under the curve (AUC0→24), while a decrease in mean clearance (CL, mL/h/kg) and volume of distribution Vz (mL/kg). In addition, in in vitro study, high doses of IGU reduces the metabolism rate of diclofenac. IGU at high dose significantly increase the pharmacokinetics parameters of 4´-hydroxy diclofenac in rats. Additionally, it also showed the potent inhibitory effect on diclofenac metabolism in recombinant human CYP2C9 yeast cells.

艾拉莫德（Iguratimod，简称IGU，又称T-614）是一种新型改善病情抗风湿药（disease modifying antirheumatic drug），拟用于治疗类风湿关节炎（rheumatoid arthritis，RA）患者。本研究旨在评价IGU对CYP2C9探针药物（probe drug）双氯芬酸及其代谢产物4'-羟基双氯芬酸的体内外药代动力学（pharmacokinetics）影响。体内实验中，将24只大鼠随机分为3组，分别为对照组（生理盐水）、低剂量IGU组（10 mg/kg）与高剂量IGU组（30 mg/kg）；在给予双氯芬酸（15 mg/kg）前1小时及给药后各时间点，通过眶静脉丛采集所有大鼠的血液样本。采用高效液相色谱法（high performance liquid chromatography）测定双氯芬酸及其代谢产物4'-羟基双氯芬酸的血浆浓度，并通过Winnonlin 6.4药代动力学软件计算相关药代动力学参数。此外，本研究采用重组人CYP2C9酵母细胞体系开展体外实验。与对照组相比，低剂量IGU组大鼠体内双氯芬酸及4'-羟基双氯芬酸的药代动力学参数无显著差异（p>0.005）；但高剂量IGU可使双氯芬酸的4'-羟基代谢产物的半衰期（half-life，T₁/₂）、曲线下面积均值（AUC₀→₂₄）升高，同时使平均清除率（mean clearance，CL，mL/h/kg）及分布容积（volume of distribution，Vz，mL/kg）降低。此外，体外实验中高剂量IGU可降低双氯芬酸的代谢速率；高剂量IGU可显著升高大鼠体内4'-羟基双氯芬酸的药代动力学参数，同时对重组人CYP2C9酵母细胞中的双氯芬酸代谢产生强效抑制作用。