Pharmacokinetics, bioavailability study in rats and tissue distribution in mice of enasidenib by UPLC-MS/MS

Enasidenib is a first-in-class, orally available inhibitor of mutant IDH2 and was approved by the US Food and Drug Administration (FDA) as a treatment of adult patients with relapsed/refractory (R/R) AML. Studies of enasidenib about pharmacokinetics and bioavailability after oral and intravenous administration and tissue distribution in animal model have not been reported. This limits basic research regarding this mutant IDH2 inhibitor drug. The ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was used to determine the enasidenib in rat plasma, and mouse tissues with dacomitinib used as internal standard (IS). The mobile phase, which is acetonitrile solution containing 0.1 % formic acid, was applied in chromatographic separation on a CORTECS C18 column (2.1 × 50 mm, 1.6 μm) by gradient elution. To quantify the enasidenib, positive-electrospray ionization mode was used for multiple reaction monitoring (MRM). Target fragment ions were 474.57→456.64 m/z for enasidenib and 471.21→128.1 m/z IS. Calibration curve has a lower limit of quantification (LLOQ) of at least 1 ng/mL and was linear within 2-2000 ng/mL for enasidenib in the rat plasma and mouse tissues. Inter-day and intra-day accuracy were within 87.53% to 105.58% with precision of the method both less than 15%. The mean recovery value of enasidenib was > 99.53%. Our study demonstrated that although blood brain barrier existed, there were still rapid absorption and wide distribution of enasidenib in various tissues. The order of enasidenib concentration level observed in liver was kidney, spleen, lung, heart in the sequence of descending.

恩西地平（Enasidenib）是首款靶向突变型异柠檬酸脱氢酶2（mutant IDH2）的口服抑制剂，已获美国食品药品监督管理局（FDA）批准，用于治疗复发/难治性（R/R）急性髓系白血病（AML）成人患者。目前尚无针对恩西地平经口与静脉给药后的药代动力学、生物利用度，以及其在动物模型中组织分布的相关研究报道，这限制了这款突变型IDH2抑制剂的基础研究工作。本研究采用以达可替尼（dacomitinib）为内标（internal standard, IS）的超高效液相色谱-串联质谱法（UPLC-MS/MS），对大鼠血浆及小鼠组织中的恩西地平进行定量检测。色谱分离采用CORTECS C18色谱柱（2.1 × 50 mm，1.6 μm），流动相为含0.1%甲酸的乙腈溶液，采用梯度洗脱方式。定量分析采用正电喷雾电离模式下的多反应监测（multiple reaction monitoring, MRM）技术，恩西地平的特征碎片离子对为474.57→456.64 m/z，内标的特征碎片离子对为471.21→128.1 m/z。校准曲线的定量下限（lower limit of quantification, LLOQ）不低于1 ng/mL，恩西地平在大鼠血浆及小鼠组织中的线性范围为2~2000 ng/mL。日内与日间准确度介于87.53%至105.58%之间，方法精密度均低于15%；恩西地平的平均回收率大于99.53%。本研究结果表明，尽管存在血脑屏障，恩西地平仍可被快速吸收并广泛分布于各组织中，各检测组织中恩西地平浓度的降序排列依次为肝脏、肾脏、脾脏、肺脏、心脏。