Shaw T, Mok S S, Locarnini S A
Victorian Infectious Diseases Reference Laboratory, Fairfield Hospital, Australia.
Hepatology. 1996 Nov;24(5):996-1002. doi: 10.1002/hep.510240504.
The deoxyguanosine analog penciclovir (PCV; 9-[4-hydroxy-3-hydroxymethyl-but-1-yl]guanine), has shown potent antiviral activity against herpes viruses and hepadnaviruses. Efficacy against chronic hepatitis B virus (HBV) infection has been demonstrated in an animal model and in recent clinical trials of famciclovir, the oral form of PCV. The antiviral activity of PCV is believed to be dependent on the intracellular formation of PCV-triphosphate (PCV-TP) which is presumed to inhibit HBV replication by interfering with viral DNA polymerase activity. The (S)-enantiomer is preferentially formed in herpes virus-infected cells, and is the more active against the herpes simplex virus; however, little is known about the biochemical mechanisms of PCV phosphorylation or of interference with viral replication in HBV-infected cells. Here, we report that in contrast with herpes simplex virus, the (R)-enantiomer of PCV-TP is a more potent inhibitor of HBV DNA polymerase-reverse transcriptase (pol-RT) in vitro than the (S)-enantiomer. In assays for HBV DNA pol-RT activity, in which purified viral core particles were the enzyme source, the IC50s for (R)- and (S)-enantiomers of PCV-TP were 2.5 micromol/L and 11 micromol/L, respectively. The estimated Kis for (R)- and (S)- PCV-TP were approximately 0.03 micromol/L and approximately .04 micromol/L, respectively, about 3-fold lower than the Km for deoxyguanosine triphosphate (dGTP) in the same system. In addition, we report that PCV metabolism is similar in both control (HepG2) and in HBV-transfected (2.2.15) hepatoblastoma cells in vitro, indicating that cellular enzyme(s) catalyze PCV phosphorylation. Peak PCV-TP concentrations of about .4 micromol/L were reached in both cell types in less than 12 hours, and intracellular PCV-TP was exceptionally stable with a half-life of about 18 hours. These observations provide a mechanistic basis for the potent activity of PCV against HBV.
脱氧鸟苷类似物喷昔洛韦（PCV；9-[4-羟基-3-羟甲基丁-1-基]鸟嘌呤）对疱疹病毒和嗜肝DNA病毒显示出强大的抗病毒活性。在动物模型以及喷昔洛韦（PCV的口服形式）的近期临床试验中，已证明其对慢性乙型肝炎病毒（HBV）感染有效。据信PCV的抗病毒活性取决于细胞内三磷酸喷昔洛韦（PCV-TP）的形成，推测其通过干扰病毒DNA聚合酶活性来抑制HBV复制。（S）-对映体在疱疹病毒感染的细胞中优先形成，并且对单纯疱疹病毒更具活性；然而，关于PCV磷酸化或其在HBV感染细胞中干扰病毒复制的生化机制知之甚少。在此，我们报告，与单纯疱疹病毒相反，在体外，PCV-TP的（R）-对映体比（S）-对映体是更有效的HBV DNA聚合酶-逆转录酶（pol-RT）抑制剂。在以纯化的病毒核心颗粒作为酶源的HBV DNA pol-RT活性测定中，PCV-TP的（R）-和（S）-对映体的IC50分别为2.5微摩尔/升和11微摩尔/升。（R）-和（S）-PCV-TP的估计Kis分别约为0.03微摩尔/升和约0.04微摩尔/升，比同一系统中三磷酸脱氧鸟苷（dGTP）的Km低约3倍。此外，我们报告在体外对照（HepG2）和HBV转染（2.2.15）的肝癌细胞中PCV代谢相似，表明细胞酶催化PCV磷酸化。两种细胞类型在不到12小时内均达到约0.4微摩尔/升的PCV-TP峰值浓度，并且细胞内PCV-TP异常稳定，半衰期约为18小时。这些观察结果为PCV对HBV的强大活性提供了机制基础。
