Inhibition of experimental deoxyribonucleic acid virus-induced encephalitis by 9-beta-D-arabinofuranosylhypoxanthine 5'-monophosphate

A review of compounds exhibiting anti-orthopoxvirus activity in animal models

Several animal models using mice (most frequently), rabbits, or monkeys have been used to identify compounds active against orthopoxvirus infections. The treatment of vaccinia virus infections has been well studied in models involving infection of scarified skin or eyes, or resulting from intravenous, intraperitoneal, intracerebral, or intranasal virus inoculation. Cowpox virus has been used in intranasal or aerosol infection studies to evaluate the treatment of lethal respiratory infections. Rabbitpox, monkeypox, and variola viruses have been employed to a lesser extent than the other viruses in chemotherapy experiments. A review of the literature over the past 50 years has identified a number of compounds effective in treating one or more of these infections, which include thiosemicarbazones, nucleoside and nucleotide analogs, interferon, interferon inducers, and other unrelated compounds. Substances that appear to have the greatest potential as anti-orthopoxvirus agents are the acyclic nucleotides, (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (cidofovir, HPMPC) and 1-[((S)-2-hydroxy-2-oxo-1,4,2-dioxaphosphorinan-5-yl)methyl]cytosine (cyclic HPMPC), and the acyclic nucleoside analog, 2-amino-7-[(1,3-dihydroxy-2-propoxy)methyl]purine (S2242). Other classes of compounds that have not been sufficiently studied in lethal infection models and deserve further consideration are thiosemicarbazones related to methisazone, and analogs of adenosine-N(1)-oxide and 1-(benzyloxy)adenosine.

Comparison of the in vitro and in vivo anti-herpes activities of 1-beta-D-arabinofuranosylthymine and its 5'-monophosphate

In vitro and in vivo anti-herpes activities of 1-beta-D-arabinofuranosylthymine 5'-monophosphate (ara-TMP) were compared with those of 1-beta-D-arabinofuranosylthymine (ara-T). On a molar basis ara-TMP was almost as active as ara-T against six strains of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) as monitored by a cytopathogenicity-inhibition and a plaque reduction assay in human embryonic lung fibroblast cells. When tested against experimental encephalitis in mice inoculated intracerebrally with HSV-1, intraperitoneal or intravenous treatment with 150 mg/kg/day of ara-TMP or 100 mg/kg/day of ara-T, for 5 days was effective in increasing in the mean survival time of mice. For a single dose of ara-TMP, intravenous administration was more effective than intraperitoneal or oral administration. However, oral administration of ara-T was the most effective of the treatment regimens used. Substantial plasma levels of ara-T were detected for a longer time after oral administration of ara-T than after intravenous administration of ara-TMP or ara-T, suggesting that the efficacy of oral administration of ara-T may be correlated with the maintenance of the substantial blood drug levels.

Viral keratitis-inhibitory effect of 9-beta-D-arabinofuranosylhypoxanthine 5'-monophosphate

Topical application of 9-beta-d-arabinofuranosylhypoxanthine 5'-monophosphate (ara-HxMP) significantly inhibited the development of keratitis induced by types 1 and 2 herpes simplex virus and vaccinia virus in the eyes of rabbits. Parameters for evaluation of efficacy were infectivity (corneal opacity, lesion size, and type), Draize (erythema, conjunctival swelling, and discharge), and reduction in titer of recoverable virus from the eye. When the relative efficacy of the related compounds 9-beta-d-arabinofuranosyladenine (ara-A), ara-A 5'-monophosphate (ara-AMP), and ara-Hx was determined against type 1 herpes simplex virus in a parallel experiment, the more water-soluble compounds (ara-HxMP, ara-AMP) were the most effective. The relative efficacy of ara-A was also determined against type 2 herpes and vaccinia virus-induced keratitis. Mortality in rabbits due to central nervous system involvement caused by types 1 and 2 herpes simplex virus was inhibited. Ara-HxMP was not discernibly toxic to the eye at concentrations of at least 20%; efficacy was still discernible with a 0.1% solution.