Hagenauer B, Salamon A, Thalhammer T, Kunert O, Haslinger E, Klingler P, Senderowicz A M, Sausville E A, Jäger W
Institute of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria.
Drug Metab Dispos. 2001 Apr;29(4 Pt 1):407-14.
The metabolism of flavopiridol (FLAP), a novel anticancer drug currently undergoing clinical development, was investigated in rat and human liver microsomes. In the presence of uridine 5'-diphosphoglucuronic acid, two biotransformation products (M1 and M2) could be detected. Formation of metabolite M1 and M2 in terms of enzymatic efficacy (Vmax/K(M)) was about 50- and 5-fold higher in rat (1.58 +/- 2.23 and 7.22 +/- 1.17 microl/min/mg) as compared with human liver microsomes (0.032 +/- 0.016 and 1.52 +/- 0.93 microl/min/mg), indicating species-related differences in FLAP glucuronidation. Incubation in the presence of human recombinant UDP-glucuronosyltransferases (UGTs) demonstrated that M1 is almost exclusively catalyzed by UGT1A1, whereas M2 is formed by UGT1A9 and only to a minor extent by UGT1A1 and UGT1A10. Chemical inhibition experiments further prove the involvement of UGT1A1 and UGT1A9 in the formation of M1 and M2, as the UGT1A1 substrate bilirubin preferably inhibited M1 over M2 (K(i): 36 and 258 microM, respectively), whereas the UGT1A9 substrate propofol showed a more pronounced decrease in M2 but not in M1 formation (K(i): 47 and 142 microM, respectively). Both conjugates were purified from rat liver microsomes and analyzed by mass spectrometry, NMR, and UV experiments. On the basis of these results, M1 was identified as 5-O-beta-glucopyranuronosyl-flavopiridol and M2 as 7-O-beta-glucopyranuronosyl-flavopiridol. In conclusion, our results elucidate the enzymatic pathways of FLAP in rat and human liver, which must be considered during cancer therapy of patients.
对一种目前正在进行临床开发的新型抗癌药物黄酮哌啶醇（FLAP）在大鼠和人肝微粒体中的代谢情况进行了研究。在尿苷5'-二磷酸葡糖醛酸存在的情况下，可以检测到两种生物转化产物（M1和M2）。就酶促效力（Vmax/K(M)）而言，大鼠（1.58±2.23和7.22±1.17微升/分钟/毫克）中代谢物M1和M2的形成比人肝微粒体（0.032±0.016和1.52±0.93微升/分钟/毫克）高约50倍和5倍，表明FLAP葡糖醛酸化存在种属差异。在人重组UDP-葡糖醛酸基转移酶（UGT）存在下进行孵育表明，M1几乎完全由UGT1A1催化，而M2由UGT1A9形成，仅少量由UGT1A1和UGT1A10形成。化学抑制实验进一步证明了UGT1A1和UGT1A9参与了M1和M2的形成，因为UGT1A1底物胆红素对M1的抑制作用比对M2更强（抑制常数分别为36和258微摩尔），而UGT1A9底物丙泊酚对M2形成的降低作用更明显，但对M1形成没有影响（抑制常数分别为47和142微摩尔）。两种缀合物均从大鼠肝微粒体中纯化出来，并通过质谱、核磁共振和紫外实验进行分析。基于这些结果，M1被鉴定为5-O-β-吡喃葡糖醛酸基-黄酮哌啶醇，M2为7-O-β-吡喃葡糖醛酸基-黄酮哌啶醇。总之，我们的结果阐明了FLAP在大鼠和人肝脏中的酶促途径，在患者癌症治疗过程中必须予以考虑。
