Metabolism, Pharmacokinetics, Tissue Distribution, and Stability Studies of the Prodrug Analog of an Anti-Hepatitis B Virus Dinucleoside Phosphorothioate
作者:John E. Coughlin、Rajendra K. Pandey、Seetharamaiyer Padmanabhan、Kathleen G. O'Loughlin、Judith Marquis、Carol E. Green、Jon C. Mirsalis、Radhakrishnan P. Iyer
DOI:10.1124/dmd.111.044446
日期:2012.5
The alkoxycarbonyloxy dinucleotide prodrug R p, S p-2 is an orally bioavailable anti-hepatitis B virus agent. The compound is efficiently metabolized to the active dinucleoside phosphorothioate R p, S p-1 by human liver microsomes and S9 fraction without cytochrome P450-mediated oxidation or conjugation. The conversion of R p, S p-2 to R p, S p-1 appears to be mediated by liver esterases, occurs in a stereospecific manner, and is consistent with our earlier reported studies of serum-mediated hydrolytic conversion of R p, S p-2 to R p, S p-1. However, further metabolism of R p, S p-1 does not occur. The presence of a minor metabolite, the desulfurized product 10 was noted. The prodrug R p, S p-2 was quite stable in simulated gastric fluid, whereas the active R p, S p-1 had a half-life of <15 min. In simulated intestinal fluid, the prodrug 2 was fully converted to 1 in approximately 3 h, whereas 1 remained stable. To ascertain the tissue distribution of the prodrug 2 in rats, the synthesis of 35S-labeled R p, S p-2 was undertaken. Tissue distribution studies of orally and intravenously administered radiolabeled [35S]2 demonstrated that the radioactivity concentrates in the liver, with the highest liver/plasma ratio in the intravenous group at 1 h being 3.89 (females) and in the oral group at 1 h being 2.86 (males). The preferential distribution of the dinucleotide 1 and its prodrug 2 into liver may be attributed to the presence of nucleoside phosphorothioate backbone because phosphorothioate oligonucleotides also reveal a similar tissue distribution profile upon intravenous administration.
烷氧基羰基氧基二核苷酸原药 R p, S p-2 是一种可口服的抗乙型肝炎病毒药物。该化合物可通过人体肝脏微粒体和 S9 产物高效代谢为活性二核苷硫代磷酸酯 R p, S p-1,而无需细胞色素 P450 介导的氧化或共轭作用。R p、S p-2 向 R p、S p-1 的转化似乎是由肝脏酯酶介导的,以立体特异性的方式发生,与我们早先报道的由血清介导的 R p、S p-2 向 R p、S p-1 的水解转化研究一致。然而,R p, S p-1 并未发生进一步代谢。我们注意到存在一种次要代谢产物,即脱硫产物 10。原药 R p, S p-2 在模拟胃液中相当稳定,而活性 R p, S p-1 的半衰期小于 15 分钟。在模拟肠液中,原药 2 在大约 3 小时内完全转化为 1,而 1 则保持稳定。为了确定原药 2 在大鼠体内的组织分布,我们合成了 35S 标记的 R p、S p-2。口服和静脉注射放射性标记 [35S]2 的组织分布研究表明,放射性集中在肝脏,静脉注射组在 1 小时内的肝脏/血浆比率最高,为 3.89(雌性),口服组在 1 小时内的肝脏/血浆比率最高,为 2.86(雄性)。二核苷酸 1 及其原药 2 优先分布于肝脏可能是由于存在硫代磷酸核苷骨架,因为硫代磷酸寡核苷酸在静脉注射后也显示出类似的组织分布特征。