Inhibition of HIV-1 reverse transcriptase by 5'-triphosphates of 5-substituted uridine analogs

An adenosine nucleoside analogue NITD008 inhibits EV71 proliferation

Enterovirus 71 (EV71), one of the major causative agents of Hand-Foot-Mouth Disease (HFMD), causes severe pandemics and hundreds of deaths in the Asia-Pacific region annually and is an enormous public health threat. However, effective therapeutic antiviral drugs against EV71 are rare. Nucleoside analogues have been successfully used in the clinic for the treatment of various viral infections. We evaluated a total of 27 nucleoside analogues and discovered that an adenosine nucleoside analogue NITD008, which has been reported to be an antiviral reagent that specifically inhibits flaviviruses, effectively suppressed the propagation of different strains of EV71 in RD, 293T and Vero cells with a relatively high selectivity index. Triphosphorylated NITD008 (ppp-NITD008) functions as a chain terminator to directly inhibit the RNA-dependent RNA polymerase activity of EV71, and it does not affect the EV71 VPg uridylylation process. A significant synergistic anti-EV71 effect of NITD008 with rupintrivir (AG7088) (a protease inhibitor) was documented, supporting the potential combination therapy of NITD008 with other inhibitors for the treatment of EV71 infections.

Bioactive triterpenoids from Kadsura heteroclita

A phytochemical study of Kadsura heteroclita led to the isolation of eight triterpenoids, including two new compounds, named kadheterilactone A (1) and kadheterilactone B (2), as well as six known compounds, longipedlactone H (3), longipedlactone A (4), longipedlactone F (5), kadsuranic acid A (6), nigranoic acid (7), and schisandronic acid (8). Their structures were elucidated on the basis of spectroscopic methods, including 2D NMR techniques. The cytotoxic activities of 1-8 were tested against several tumor cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium hydrobromide (MTT) assay in vitro. As a result, 4 and 5 turned out to be significantly cytotoxic against Hep-G2 and Bel-7402 tumor cell lines. All compounds were also tested for inhibition on HIV-1 protease (PR) and reverse transcriptase (RT). Compounds 6 and 7 showed strong inhibition on HIV-1 PR, while 8 exhibited moderate activity, others were only weakly active. No compounds were active against HIV-1 RT.

Comparative inhibition of hepatitis B virus DNA polymerase and cellular DNA polymerases by triphosphates of sugar-modified 5-methyldeoxycytidines and of other nucleoside analogs

Of a series of 14 nucleoside 5'-triphosphates, those of 2',3'-dideoxy-3'-fluoro-5-methylcytidine, 3'-azido-2',3'-dideoxy-5-methylcytidine, 2',3'-dideoxy-3'-fluoroguanosine, 2',3'-didehydro-2',3'-dideoxy-5-methylcytidine, 2',3'-dideoxy-3'-fluoro-5-ethylcytidine, and 2',3'-dideoxy-3'-fluoroadenosine emerged as the most potent inhibitors of hepatitis B virus DNA polymerase (50% inhibitory dose, 0.03 to 0.35 microM). In contrast, cellular DNA polymerases proved to be resistant to (alpha) or partially affected by (beta) these analogs. These compounds are among the most effective and selective inhibitors of endogenous hepatitis B virus DNA polymerase recognized to date.