肝靶向核苷类逆转录酶抑制剂HepDirect前药的研究进展

靶向给药能够增加局部药物的浓度,提高疗效,减少不良反应。目前实现药物靶向性的重要策略是使用靶向载体,如抗体、肽、天然或人工合成的聚合物、糖或肽标记的毫微粒和脂质体等。但这些方法有很多不足,如难以通过内皮细胞到达血管外靶点、生产成本高、共轭物诱导免疫原反应、载药量有限及给药方式不便等。Erion等人发现了一类新的磷酸酯和膦酸酯前药,取名为HepDirect前药。该类前药可以特异性地被肝细胞CYP450同工酶CYP3A4酶氧化,释放活性形式的核苷酸或核苷膦酸。经动物和人体试验,HepDirect前药具有明显的肝靶向性,未发现与副产物相关的毒性。文中通过查阅近几年的相关文献,对核苷类HepDirect前药的原理、稳定性、副产物、代表药物等进行综述。     

Zidovudine and other reverse transcriptase inhibitors in the management of human immunodeficiency virus-related disease.

Licensed in 1987, zidovudine remains the only medication with proved efficacy for the treatment of disease caused by the human immunodeficiency virus (HIV). New information on the pharmacology (adults and children), effects of kidney and liver dysfunction on the disposition of the drug, and drug-drug interactions have improved the way we use and monitor this agent. The serious toxicity associated with zidovudine has led researchers to develop safer dosage regimens. Also, recognition that zidovudine slows but does not halt progression of disease has increased the search for effective alternatives. The best-studied agents are didanosine (2',3'-dideoxyinosine, ddl), zalcitabine (2',3'-dideoxycytidine, ddC), and foscarnet.     

光谱法研究核苷类逆转录酶抑制剂药物与DNA的相互作用

目的 研究核苷类逆转录酶抑制剂药物(阿德福韦、拉米夫定、恩去他滨)与小牛胸腺DNA(ct-DNA)的相互作用及其作用机制.方法 采用荧光光谱法和热力学理论进行研究.结果 确定核苷类逆转录酶抑制剂药物与ct-DNA间的猝灭过程是静态猝灭;求得27°C时,药物与ct-DNA间的结合常数(K)分别为3.41×103、2.63×103、1.02×103 L·mol-1,结合位点数n分别为1.05、0.958、1.03,猝灭速率常数(Kq)分别为2.07×1011、3.50×1010、7.80×1010 L·mol-1·s-1.结论 核苷类逆转录酶抑制剂药物与小牛胸腺DNA间的主要作用为嵌插作用,与DNA结合的作用机制相似.     

Interaction of fused-pyrimidine nucleoside analogs with human concentrative nucleoside transporters: High-affinity inhibitors of human concentrative nucleoside transporter 1

Human concentrative nucleoside transporters (hCNTs) mediate electrogenic secondary active transport of physiological nucleosides and nucleoside drugs into cells. Six fused-pyrimidine ribonucleosides and one 2′-deoxynucleoside were assessed for their abilities to inhibit [³H]uridine transport in the yeast Saccharomyces cerevisiae producing recombinant hCNT1, hCNT2 or hCNT3. Six of the analogs inhibited hCNT1 with K_i values < 1 μM whereas only two analogs inhibited hCNT3 with K_i values < 1 μM and none inhibited hCNT2. To assess if the inhibitory analogs were also permeants, currents evoked were measured in oocytes of Xenopus laevis producing recombinant hCNT1, hCNT2 or hCNT3. Significant inward currents, indicating permeant activity, were generated with (i) three of the analogs in hCNT1-producing oocytes, (ii) none of the analogs in hCNT2-producing oocytes and (iii) all of the analogs in hCNT3-producing oocytes. Four were not, or were only very weakly, transported by hCNT1. The thienopyrimidine 2′-deoxynucleoside (dMeThPmR, 3) and ribonucleoside (MeThPmR, 4) were the most active inhibitors of uridine transport in hCNT1-producing oocytes and were an order of magnitude more effective than adenosine, a known low-capacity transport inhibitor of hCNT1. Neither was toxic to cultured human leukemic CEM cells, and both protected CEM cell lines with hCNT1 but not with hENT1 against gemcitabine cytotoxicity. In summary, dMeThPmR (3) and MeThPmR (4) were potent inhibitors of hCNT1 with negligible transportability and little apparent cytotoxicity, suggesting that pending further evaluation for toxicity against normal cells, they may have utility in protecting normal hCNT1-producing tissues from toxicities resulting from anti-cancer nucleoside drugs that enter via hCNT1.     

Formaldehyde cytotoxicity in three human cell types assessed in three different assays.

International standards for preclinical screening of the cytotoxicity of dental materials so far recommend the use of established cell lines. The aim of this study was to assess the relative susceptibility of human dental pulp fibroblasts (HPF), human buccal epithelial cells (HBE) and HeLa cervix cancer cells exposed to identical cytotoxic challenges. Formaldehyde, which may be released from dental materials such as dental composites, glassionomer cements, and endodontic sealers, was used as test chemical. Cytotoxicity data including dose-response relations and TC(50) values were assessed in three different assays: BrdU incorporation, neutral red uptake and MTT assays. HBE and HPF demonstrated statistically significant lower TC(50) values in both the neutral red and the BrdU assay in comparison to HeLa cells. In the MTT assay no statistically significant differences were observed between the cell types. In the two target-tissue cell types (HPF and HBE) the Neutral Red assay revealed lower TC(50) values in comparison to the BrdU assay. In HeLa cells no statistically significant differences were observed between the assays. In conclusion, the present study confirms that cytotoxicity data obtained by cell culture studies are influenced by both cell culture model and choice of assay. Under identical experimental conditions, human target tissue cells appeared to be more sensitive to formaldehyde toxicity than human HeLa cancer cells.