Department of Pharmacy & Pharmacology, Antoni van Leeuwenhoek Hospital - The Netherlands Cancer Institute and MC Slotervaart, Louwesweg, 6, 1066, EC, Amsterdam, The Netherlands.
Department of Clinical Pharmacology and Pharmacy, VU University Medical Center, De Boelelaan 1117, 1081, HV, Amsterdam, The Netherlands.
Br J Clin Pharmacol. 2018 Jun;84(6):1279-1289. doi: 10.1111/bcp.13557. Epub 2018 Apr 16.
Gemcitabine (2',2'-difluoro-2'-deoxycytidine; dFdC) is a prodrug that has to be phosphorylated within the tumour cell to become active. Intracellularly formed gemcitabine diphosphate (dFdCDP) and triphosphate (dFdCTP) are considered responsible for the antineoplastic effects of gemcitabine. However, a major part of gemcitabine is converted into 2',2'-difluoro-2'-deoxyuridine (dFdU) by deamination. In the cell, dFdU can also be phosphorylated to its monophosphate (dFdUMP), diphosphate (dFdUDP) and triphosphate (dFdUTP). In vitro data suggest that these dFdU nucleotides might also contribute to the antitumour effects, although little is known about their intracellular pharmacokinetics (PK). Therefore, the objective of the present study was to gain insight into the intracellular PK of all dFdC and dFdU nucleotides formed during gemcitabine treatment.
Peripheral blood mononuclear cell (PBMC) samples were collected from 38 patients receiving gemcitabine, at multiple time points after infusion. Gemcitabine, dFdU and their nucleotides were quantified in PBMCs. In addition, gemcitabine and dFdU plasma concentrations were monitored. The individual PK parameters in plasma and in PBMCs were determined.
Both in plasma and in PBMCs, dFdU was present in higher concentrations than gemcitabine [mean intracellular area under the concentration-time curve from time zero to 24 h (AUC ) 1650 vs. 95 μMh]. However, the dFdUMP, dFdUDP and dFdUTP concentrations in PBMCs were much lower than the dFdCDP and dFdCTP concentrations. The mean AUC for dFdUTP was 312 μMh vs. 2640 μM*h for dFdCTP.
The study provides the first complete picture of all nucleotides that are formed intracellularly during gemcitabine treatment. Low intracellular dFdU nucleotide concentrations were found, which calls into question the relevance of these nucleotides for the cytotoxic effects of gemcitabine.
吉西他滨（2'，2'-二氟-2'-脱氧胞苷；dFdC）是一种前体药物，必须在肿瘤细胞内磷酸化才能发挥活性。细胞内形成的吉西他滨二磷酸（dFdCDP）和三磷酸（dFdCTP）被认为是吉西他滨抗肿瘤作用的原因。然而，吉西他滨的很大一部分通过脱氨作用转化为 2'，2'-二氟-2'-脱氧尿苷（dFdU）。在细胞内，dFdU 也可以被磷酸化为其单磷酸（dFdUMP）、二磷酸（dFdUDP）和三磷酸（dFdUTP）。体外数据表明，这些 dFdU 核苷酸也可能有助于抗肿瘤作用，尽管关于它们的细胞内药代动力学（PK）知之甚少。因此，本研究的目的是深入了解吉西他滨治疗过程中形成的所有 dFdC 和 dFdU 核苷酸的细胞内 PK。
从 38 名接受吉西他滨治疗的患者中采集外周血单核细胞（PBMC）样本，在输注后多个时间点采集。在 PBMC 中定量检测吉西他滨、dFdU 及其核苷酸。此外，监测吉西他滨和 dFdU 的血浆浓度。确定血浆和 PBMC 中的个体 PK 参数。
无论是在血浆中还是在 PBMC 中，dFdU 的浓度都高于吉西他滨[零至 24 小时的细胞内浓度-时间曲线下面积（AUC）1650 与 95 μMh]。然而，PBMC 中的 dFdUMP、dFdUDP 和 dFdUTP 浓度远低于 dFdCDP 和 dFdCTP 浓度。dFdUTP 的平均 AUC 为 312 μMh，而 dFdCTP 为 2640 μM*h。
该研究首次提供了吉西他滨治疗过程中细胞内形成的所有核苷酸的完整图像。发现细胞内的 dFdU 核苷酸浓度较低，这使人质疑这些核苷酸与吉西他滨的细胞毒性作用的相关性。
