Beumer Jan H, Parise Robert A, Newman Edward M, Doroshow James H, Synold Timothy W, Lenz Heinz-Josef, Egorin Merrill J
Molecular Therapeutics/Drug Discovery Program, University of Pittsburgh Cancer Institute, Pittsburgh, PA, 15213, USA.
Cancer Chemother Pharmacol. 2008 Jul;62(2):363-8. doi: 10.1007/s00280-007-0603-8. Epub 2007 Sep 26.
Although the DNA methyltransferase inhibitor 5-fluoro-2'-deoxycytidine (FdCyd), is being evaluated clinically, it must be combined with the cytidine deaminase inhibitor tetrahydrouridine (THU) to prevent rapid metabolism of FdCyd to the pharmacologically active, yet unwanted, metabolites 5-fluoro-2'-deoxyuridine (FdUrd), 5-fluorouracil (FU), and 5-fluorouridine (FUrd). We assessed plasma concentrations of FdCyd and metabolites in patients receiving FdCyd and THU.
We validated an LC-MS/MS assay, developed for a preclinical study, to quantitate FdCyd and metabolites in human plasma. Patients were treated with five daily, 3-h infusions of FdCyd at doses of 5-80 mg/m(2) with 350 mg/m(2) THU. Plasma was obtained during, and before the end of infusions on days 1 and 5.
The lower limits of quantitation for FU, FdUrd, FUrd, FC and FdCyd were 1, 1.5, 10, 3, and 10 ng/ml, respectively. Plasma FdCyd increased with dose, from 19-96 ng/ml at 5 mg/m(2) to 1,600-1,728 ng/ml at 80 mg/m(2). FdUrd was undetectable in patients treated with FdCyd doses <20 mg/m(2), and increased from 2.3 ng/ml at 20 mg/m(2) to 3.5-5.7 ng/ml at 80 mg/m(2). FU increased from 1.2-5.5 ng/ml at 5 mg/m(2) to 6.0-12 ng/ml at 80 mg/m(2).
By co-administering FdCyd with THU, FdCyd plasma concentrations were achieved that are known to inhibit DNA methylation in vitro. The accompanying plasma FU and FdUrd concentrations are <10% those observed after therapeutic infusions of FU or FdUrd, while FdCyd levels are well above those required to inhibit methylation in vitro. Therefore, inhibition of DNA methylation with FdCyd and THU appears feasible.
尽管DNA甲基转移酶抑制剂5-氟-2'-脱氧胞苷（FdCyd）正在进行临床评估，但它必须与胞苷脱氨酶抑制剂四氢尿苷（THU）联合使用，以防止FdCyd快速代谢为具有药理活性但不需要的代谢产物5-氟-2'-脱氧尿苷（FdUrd）、5-氟尿嘧啶（FU）和5-氟尿苷（FUrd）。我们评估了接受FdCyd和THU治疗的患者血浆中FdCyd及其代谢产物的浓度。
我们验证了一种为临床前研究开发的液相色谱-串联质谱（LC-MS/MS）测定法，用于定量人血浆中的FdCyd及其代谢产物。患者接受为期5天、每天3小时的FdCyd输注，剂量为5-80mg/m²，同时给予350mg/m²的THU。在第1天和第5天输注期间及输注结束前采集血浆。
FU、FdUrd、FUrd、FC和FdCyd的定量下限分别为1、1.5、10、3和10ng/ml。血浆FdCyd浓度随剂量增加，从5mg/m²时的19-96ng/ml增加到80mg/m²时的1600-1728ng/ml。在接受FdCyd剂量<20mg/m²治疗的患者中未检测到FdUrd，其浓度从20mg/m²时的2.3ng/ml增加到80mg/m²时的3.5-5.7ng/ml。FU浓度从5mg/m²时的1.2-5.5ng/ml增加到80mg/m²时的6.0-12ng/ml。
通过将FdCyd与THU联合给药，可达到已知在体外能抑制DNA甲基化的FdCyd血浆浓度。同时出现的血浆FU和FdUrd浓度低于治疗性输注FU或FdUrd后观察到的浓度的10%，而FdCyd水平远高于体外抑制甲基化所需的水平。因此，用FdCyd和THU抑制DNA甲基化似乎是可行的。
