Acyclovir phosphonate [9-(3-phosphono-propyloxymethyl)guanine; SR3722] and the S enantiomer (SR3772), R enantiomer (SR3773), and R,S enantiomeric mixture (SR3745A) of ganciclovir phosphonate {9-[((-'-)-1-hydroxymethyl-3-phosphono)propyloxymethyl]guanine} were evaluated for their antiviral activities against murine cytomegalovirus. In severe combined immunodeficient mice infected with murine cytomegalovirus, SR3773 and SR3745A (12.5, 25, and 50 mg/kg of body weight per day) were superior to ganciclovir in extending the mean time to death, whereas SR3722 and SR3772 was less potent than ganciclovir. In normal BALB/c mice, SR3773 and ganciclovir were approximately equally active in preventing death. SR3773 caused renal tubular damage when administered at 50 mg/kgday for 15 days. These results suggest that SR3773 may have potential for use in the treatment of human cytomegalovirus infections, but it may also exhibit renal toxicity.Two antiviral drugs are approved for the treatment of human cytomegalovirus (HCMV) disease, ganciclovir (GCV) and foscarnet. Both compounds have toxic side effects which limit their usefulness (3,19), and the emergence of drugresistant viruses is a concern (6, 7). Thus, the need for safer and more effective anti-HCMV agents is apparent. Newer anti-HCMV compounds still in preclinical development include acyclic phosphonate derivatives of nucleosides such as (S)-1-[3-hydroxy-2-(phosphonylmethoxy)propyl]cytosine (HPMPC) (18).We and others reported that phosphonate derivatives of acyclovir and GCV inhibited HCMV and other animal CMVs (1, 5, 12, 13). Many of these nucleotide analogs were approximately as active as GCV in inhibiting HCMV in cell culture (causing 50% inhibition of viral plaques or cytopathology when used at between S and 20 ,uM, depending on the virus strain). Until recently, the most potent of these agents, {9-[((±)-1-hydroxymethyl-3-phosphono)propyloxymethyl]guanine; SR3745A or ganciclovir homophosphonate [5]} was available only as a mixture of R and S enantiomers. One of the two enantiomers (the R enantiomer) was believed to be responsible for the anti-HCMV activity and the other enantiomer (the S enantiomer) was presumed to be inactive. This hypothesis was based on earlier studies of ganciclovir homophosphonate phosphorylation (5). The R enantiomer approximates 2'-deoxyguanosine-5'-monophosphate in structure more closely than does the S enantiomer, and therefore should interact more readily with cellular enzymes. Methods have recently been devised to synthesize the chiral R (SR3773) and S (SR3772) enantiomers (11).This report describes antiviral evaluations of SR3745A, SR3772, and SR3773 in cell culture and in two murine CMV (MCMV) animal models (14, 17) of HCMV infection. Previously, SR3745A was shown to be beneficial against MCMV infection in mice (5), and so the likelihood that the chiral R

The effects of monoclonal antibody used in combination with ganciclovir (GCV) or (S)-1-[3-hydroxy-(2-phosphonylmethoxy)propyl]cytosine (HPMPC) against murine cytomegalovirus (MCMV) were determined in vitro and in vivo, in mice. The antibody and drug were added to cell cultures 24 h after MCMV adsorption so as not to affect the initial infection rate. The antibody (at 1.25-20 μg/ml) combined with GCV (0.3-5 μM) or HPMPC (0.008-0.125 μM)caused synergistic inhibition of virus yield in C127I cells. No toxic effect on cell growth in culture was observed at these antibody/drug combinations. The effects of antibody and GCV treatments were studied in MCMV-infected severe combined immunodeficient (SCID) mice. Antibody treatments (2.5 mg/kg/day) given by intraperitoneal injection every 3 days starting 24 h after virus inoculation extended survival time by 1 day relative to placebo-treated animals. Once daily, intraperitoneal treatments with GCV (25 and 50 mg/kg/day) for 7 days starting at 24 h after virus inoculation extended survival time 9-11 days. The combination of antibody plus GCV was only slightly better than GCV alone, indicating an additive interaction.

Bovine herpes mammillitis virus or bovine herpesvirus type 2 (BHV-2) causes ulcerative lesions on the teats and udders of infected cows. The authors investigated several nucleoside and nucleotide analogues as potential BHV-2 inhibitors. These included acyclovir, ganciclovir, 5-iodo-2′-deoxyuridine (IUdR), 1-(2-deoxy-2′-fluoro-β-D-arabinofuranosyl) derivatives of 5-iodocytosine (FIAC), 5-iodouracil (FIAU), and 5-methyluracil (FMAU), and various 3-hydroxyphospho-nylmethoxypropyl (HPMP) and 2-phosphonylme-thoxyethyl (PME) derivatives of adenine (A), guanine (G), 2,6-diaminopurine (DAP), and/or cytosine (C). Of these, FIAU and FMAU were the most potent in cell culture, inhibiting 50% of BHV-2 plaques at >0.05 μm. HPMPA and HPMPG were active at 0.3 μm; FIAC, IUdR, and HPMPC at 1.3-2.3 μm; PMEDAP and ganciclovir at 20-25 μm; acyclovir and PMEA at >100 μm. The two most potent agents, FIAU and FMAU, inhibited uninfected embryonic bovine tracheal cell growth by 50% at > 100 μm and 53 μm, respectively, resulting in selectivity indices (ratio of the 50% inhibitory concentration for cell growth to the 50% inhibitory concentration for plaque formation) of >2200 and 1100. Greater degrees of antiviral activity and selectivity were obtained in infected guinea pig embryo cells treated with FIAU, FMAU, and HPMPC. Infected cell extracts containing BHV-2-induced thymidine kinase activity phosphorylated FIAU, FMAU, and lUdR at nearly the same rate as thymidine, whereas FIAC, acyclovir, and ganciclovir were phosphorylated at ≤5% the rate of thymidine. Phosphorylation by this enzyme is required to generate the antivirally active nucleoside triphosphate in infected cells. In guinea pigs infected intravaginally with BHV-2, FMAU treatments of 1, 3.2, and 10 mg kg−1 per day for 5 days starting 1 day after virus challenge reduced vaginal lesion scores and virus titres in a dose-dependent manner. FIAU (10 μm) was as effective as 1 μm FMAU by the same regimen. A single treatment with 10 μm HPMPC was as active as daily treatments with 3.2 mg FMAU kg−1. These results indicate the potential of using antiviral agents to treat bovine herpes mammillitis virus infections in cattle, and the application of guinea pigs to study BHV-2 disease.