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Arabinogalactan (9kDa)-9-β-D-arabinofuranosyladenine-5'-monophosphate [AG (9kDa)-araAMP] was 25-fold more active than the parent compound 9-β-D-arabinofuranosyladenine (araA) in decreasing the amount of hepatitis B virus (HBV) DNA intracellular replicative intermediates in HBV-transfected 2.2.15 cells. The putative active 5'-triphosphate metabolite, araATP, exhibited a 50% inhibitory concentration (IC 50 ) of 5 μM toward woodchuck hepatitis virus DNA polymerase, consistent with the anti-HBV activity of these derivatives. AG (9kDa)-araAMP inhibited HepG2 cell proliferation by only 16% at a concentration as high as 822 μM (araA equivalents) and no effects were observed in the presence of 8.22 μM or 82.2 μM of the drug. Lactate production, mitochondrial DNA (mtDNA) content, and mitochondrial morphology were not affected by AG (9kDa)-araAMP at concentrations between 8.22 μM and 822 μM. In contrast, both araA and its in vivo metabolite, 9-β-D-arabinofuranosylhypoxanthine (araH), induced substantial dose-dependent effects on cell growth, lactate production and mtDNA steady-state levels at concentrations of 8.22 μM and 82.2 μM. Some loss of cristae within the mitochondria was also observed in cells incubated with araH. In , AG (9kDa)-araAMP exhibits a potent and selective anti-HBV activity and the lack of toxic effects on host cell mitochondrial functions supports its further development.

An arabinogalactan conjugate containing a 9 kDa fragment of arabinogalactan and adenine-9-beta-D-arabinofuranoside 5'-monophosphate (araAMP), denoted AG(9 kDa)-araAMP, has been synthesized and characterized. In 2.2.15 (human hepatoblastoma) cells, the attachment of araAMP to AG(9 kDa), a ligand of the asialoglycoprotein receptor, decreased the effective concentration for inhibiting extracellular hepatitis B virus (HBV) production by 90% (EC90) from 17 to 0.9 microM adenine arabinoside (araA) equivalents, and increased the cytotoxic concentration (CC50) from 188 to17 300 microM araA equivalents. Hence, the selectivity index (CC50/EC90) of araA was improved from 11 (188/17) to19200 (17 300/0.9) by conjugation with the 9 kDa fragment of arabinogalactan. AG(9 kDa)-araAMP did not affect the production of viral RNA or viral proteins. In the woodchuck hepatitis model, AG(9 kDa)-araAMP inhibited woodchuck hepatitis virus (WHV) DNA replication at a dose of 0.3 mg of araA equivalents per kg; in this case, AG(9 kDa)-araAMP was 20-30 times more potent than was unconjugated araA. AG(9 kDa)-araAMP was effective by intramuscular or subcutaneous administration. The reduction in HBV DNA levels obtained in 2.2.15 cells and of WHV DNA levels in woodchucks was sustained after treatment with AG(9 kDa)-araAMP ceased. In both cases, viral DNA gradually returned to pre-treatment levels.