bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitro Activity of a Novel Series of Polyoxosilicotungstates against Human Myxo-, Herpes- and Retroviruses
Authors: Ikeda S. , Neyts J. , Yamamoto N. , Murrer B. , Theobald B. , Bossard G. , Henson G. , Abrams M. , Picker D. , De Clercq E.
Published: May 2015

A series of silicon-containing polyoxotungstates belonging to the ‘Keggin-type’ (‘Keggin’, ‘Keggin sandwich’) were evaluated for their antiviral activity against enveloped viruses (myxo-, herpes- and retroviruses). The compounds exhibited antiviral activity against influenza virus type A, respiratory syncytial virus (RSV), herpes simplex virus type-1 (HSV-1), type-2 (HSV-2), thymidine kinase-deficient (TIC) HSV-1, human cytomegalovirus (HCMV), human immunodeficiency virus type-1 (HIV-1) and type-2 (HIV-2) at concentrations that were well below their cytotoxic threshold. The ‘Keggin’ compound JM2815 (K5[Si-(TiCp)W11O39].12H2O) and the ‘Keggin sandwich’ compound JM1590 (K13[Ce(SiW11O39)2].26H2O) resulted in the highest selectivity indices against HIV-1 and HIV-2, and compound JM2820 ([Me3NH]8.[Si2Nb6W18O77]) was the most potent inhibitor of HSV and HCMV replication. These compounds proved active against HCMV and HSV when present during virus adsorption, and against influenza virus A and RSV when present after virus adsorption. Polyoxosilicotungstates inhibited the binding of radiolabeled HCMV particles to the cells at concentrations that were antivirally active, and the compounds were able to displace HCMV particles that were bound to a heparin-Sepharose matrix. Presumably, the polyoxosilicotungstates interact with positively charged domains on the viral envelope site(s) involved in the attachment of the (HCMV) virions to the cell surface receptor heparan sulphate.
Cellular Metabolism and Anti-Influenza Activity of 1,3,4-Thiadiazol-2-Ylcyanamide (LY217896)
Authors: Colacino J. M. , Birch G. M. , Tang J. C.
Published: May 2015

LY217896 (1,3,4-thiadiazol-2-ylcyanamide) is a 2-substituted thiadiazole that is an effective inhibitor of influenza A and B viruses in vitro and in the mouse infection model. The in vitro anti-influenza activity of LY217896 is reversed by a 10-fold excess amount of guanine or guanosine. LY217896 (1 or 10μg ml−1) effected a selective 60% decrease in the levels of intracellular pools of GTP in MDCK cells. The extent of cytotoxicity of LY217896 is positively correlated with the amount of LY217896 metabolite formed intracellularly. A cell line, derived from parental MDCK cells, was selected for resistance to 50 ng of LY217896 per ml. Unlike parental MDCK cells, the resistant cells were able to undergo log phase replication in LY217896 (25 g ml−1) and were unable to metabolize the compound. Furthermore, LY217896 had no antiviral activity against influenza A/Ann Arbor (IC50 >200μg ml−1) or vaccinia virus (IC50 = 13 μg ml−1) in resistant cells. In contrast, LY217896 inhibited influenza A/Ann Arbor (IC50 = 0.5 μg ml−1) or vaccinia virus (IC50 = 0.13 μg ml−1) in the parental MDCK cells. A thiadiazole, with a guanidinyl group in the 2 position, and ribavirin were active in both the parental cells and resistant cells. Nicotinamide (up to 240-fold excess) did not reverse the anti-influenza activity of LY217896 in vitro or in the mouse infection model. A 10-fold excess of nicotinamide reversed the cytotoxicity of 2-aminothiadiazole but not that of LY217896.
Inhibition of Influenza A and B Viruses by 2′-Deoxy-2′-Fluororibosides
Authors: Tisdale M. , Appleyard G. , Tuttle J. V. , Nelson D. J. , Nusinoff-Lehrman S. , Nakib W. Al , Stables J. N. , Purifoy D. J. M. , Powell K. L. , Darby G.
Published: May 2015

A series of 2′-deoxy-2′-fluororibosides were evaluated for anti-influenza activity in cell culture and in the mouse pneumonia model. Many were found to be potent inhibitors of Influenza A, in chick embryo fibroblast cells (IC50's 0.1–2.9 μM), and in reducing mouse lung virus titres (1–3 log10 units).

Purine analogues proved the most effective, but their activity was an order of magnitude higher in MDCK cells. Anti-influenza activity correlated with intracellular triphosphate levels and with substrate specificity of 2′-deoxycytidine kinase. 2′-deoxy-2′-fluoroguanosine selected for further study was active against all influenza A and B strains tested, including one clinical isolate which proved extremely sensitive when assayed in human tracheal cultures. In vivo, 2′-deoxy-2′-fluoroguanosine (2′-fluorodGuo) was significantly more effective than amantadine or ribavirin in reducing mouse lung virus titre when treatment commenced after infection.
Characterization of HIV Reverse Transcriptases with Tyr181→Cys and Leu100→lle Mutations
Authors: Zhang H. , Vrang L. , Unge T. , Öberg B.
Published: May 2015

Two mutants of human immunodeficiency virus (HIV) reverse transcriptase (RT), Tyr181 to Cys and Leu100 to He, have been prepared and characterized by use of various inhibitors. As compared to wild type RT the mutant RT's had lower Kcat/Km values. The Km values were lower with heteropolymeric than with homopolymeric template-primers. Inhibition by phosphonoformate was of mixed type with both wild-type and mutant RT's and the mutants were less sensitive to phosphonoformate than the wild type RT. The non-nucleoside RT inhibitors 9-CI-TIBO and L-697,661 gave a non-competitive inhibition with respect to substrate of the wild type RT. The mutant RT's were inhibited at higher concentrations, showing a mixed type of inhibition with respect to substrate. ddGTP caused a competitive inhibition of wild type and mutant RT's with respect to substrate. RT preparations with different mutations are useful in rapidly characterizing the interaction between various inhibitors and HIV RT and thus facilitate the development of new inhibitors.
In vitro Inhibitory Activity of Soluble ICAM-1 for the Numbered Serotypes of Human Rhinovirus
Authors: Crump C. E. , Arruda E. , Hayden F. G.
Published: May 2015

We studied the antirhinovirus activity of soluble intercellular adhesion molecule-1 (sICAM-1) against all 100 numbered human rhinovirus (HRV) serotypes in human embryonic lung fibroblast (HEL) cells. sICAM-1 inhibited replication of 88 of 90 HRVs belonging to the major receptor group with 50% effective concentrations (EC50) ranging from 0.1 to 41.1 μg ml−1 (~0.002 to 0.8 μM). No inhibition at 100 μg ml−1 (~2 μM) was observed for HRV belonging to the minor receptor group, type 87, and two serotypes of the major receptor group (types 23 and 25). Yield reduction assays done with five HRV serotypes in human adenoid expiants found that sICAM-1 had concentration-dependent inhibitory effects that correlated closely with the activity observed in HEL cells ( r2 = 0.99, P < 0.001).
In vitro Resistance to an Inhibitor of HIV Proteinase (Ro 31-8959) Relative to Inhibitors of Reverse Transcriptase (AZT and TIBO)
Authors: Craig J. C. , Whittaker L. , Duncan I. B. , Roberts N. A.
Published: May 2015

Serial passage of cell-free human immunodeficiency virus type 1 (HIV-1) strain GB8 on CEM cells was carried out in the presence of increasing concentrations of the HIV proteinase inhibitor Ro 31-8959 in parallel with representative reverse transcriptase (RT) inhibitors (AZT and the TIBO compound, R82150). In all instances, a significant increase in the concentration of compound required to produce a 90% reduction of syncytium formation (IC90) was found after seven to nine passages of virus. Reduced sensitivity to Ro 31 −8959 was confirmed by p24 ELISA. Virus passaged in the presence of RT inhibitors did not show a significant change in either the ability to grow in culture supplemented with step-wise increments of inhibitor concentration or the rate of growth in the presence of compound. In contrast, virus passaged in the presence of Ro 31 −8959 required, on average, more than 2.5-times the normal passage time and often did not replicate when increases in inhibitor concentration were applied during the initial passages.

The results show that reduced sensitivity to an inhibitor of HIV proteinase, Ro 31–8959, can be generated, but it would seem to arise less readily than that found with either of the RT inhibitors studied. While this study indicates the potential for a reduction in sensitivity to proteinase inhibitors, it does not necessarily reflect the ability of mutant virus either to be selected for or to be propagated in the clinic.
8-Aza Derivatives of 3-Deazapurine Nucleosides. Synthesis and in vitro Evaluation of Antiviral and Antitumor Activity
Authors: Franchetti P. , Messini L. , Cappellacci L. , Grifantini M. , Nocentini G. , Guarracino P. , Marongiu M. E. , la Colla P.
Published: May 2015

The syntheses of 4-amino-1-(β-D-ribofuranosyl)-1 H-1,2,3-triazolo[4,5-c]pyridine (8-aza-3-deazaadenosine, 1), 4-amino-1-(2-deoxy-β-D- erythro-pentofuranosyl)-1 H-1,2,3-triazolo[4,5-c]pyridine (2′-deoxy-8-aza-3-deazaadenosine, 2), and their N8 and N7 glycosylated analogues (12,13, 21,22) and 4-amino-1-(2,3-dideoxy-β-D- erythro-pentof uranosyl)-1 H-1,2,3-triazolo [4,5-c]pyridine (2′,3′-dideoxy-8-aza-3-deazaadenosine, 3) were carried out by glycosylation of the 4-chloro-3 H-1,2,3-triazolo[4,5-c]pyridine anion. The anomeric configuration as well as the position of glycosylation were determined by 1H-, 13C-NMR, UV and N.O.E. difference spectroscopy. Nucleoside (2) and its parent compound 2′-deoxy-3-deazaadenosine were found active against ASFV and VSV. The 4-chloro-2-(β-D-ribofuranosyl)-2 H-1,2,3-triazolo[4,5-c] pyridine (9) was active against Coxsackie B1, whereas none of the 8-aza-3-deaza purine nucleosides, compound (3) included, was active against HIV-1. The 6-chloro derivatives of 8-aza-3-deazapurine ribo- and 2′-deoxyribonucleosides (11) and (20) showed some activity against LoVo human colon adenocarcinoma.
3,4-Dihydro-2-Alkoxy-6-Benzyl-4-Oxopyrimidines (DABOs): A New Class of Specific Inhibitors of Human Immunodeficiency Virus Type 1
Authors: Artico M. , Massa S. , Mai A. , Marongiu M. E. , Piras G. , Tramontano E. , la Colla P.
Published: May 2015

A series of novel 3,4-dihydro-6-benzyl-4-oxopyrimidines substituted at both the C-5 and the C-2 positions were synthesized as potential anti-HIV agents. Preparation of the title compounds was achieved by condensation of O-methylisourea with methyl 2-alkyl-4-phenylacetylacetate and subsequent displacement of the methoxy group by reaction with a series of linear, ramified and cyclic alkoxy groups containing from three to six carbon units. Methyl 2-alkyl-4-phenylacetylacetates were prepared by alkylation of methyl 4-phenylacetylacetate, which was obtained starting from Meldrum's acid and phenacetyl chloride. Acid hydrolysis of 3,4-dihydro-6-benzyl-2-methoxy-4-oxopyrimidines furnished the corresponding 1,2,3,4-tetrahydro-6-benzyl-2,4-dioxopyrimidines. In acutely infected MT-4 cells, compounds 3e, 3o, 3q and 3r showed an anti-HIV-1 activity as potent and/or selective as HEPT and ddl. Unlike HEPT, the replacement of a methyl for an hydrogen atom at position C-5 of 3,4-dihydro-2-alkoxy-6-benzyl-4-oxopyrimidines (DABOs) did not abolish the antiviral activity, as well as the substitution of the C-5 methyl for an ethyl group did not increase the potency. However, similarly to HEPT and its derivatives, DABOs targeted the HIV-1 reverse transcriptase and neither inhibited the multiplication of HIV-2 in acutely infected MT-4 cells, nor that of HIV-1 in chronically infected H9/IIIB cells.
The Mode of Action of Penciclovir
Authors: Hodge R. A. Vere , Cheng Y.-C.
Published: May 2015

This review describes the studies that have been carried out to date to investigate the mode of action of penciclovir. Penciclovir is phosphorylated much more efficiently than acyclovir in herpesvirus-infected cells yet the host cell kinases phosphorylate both compounds to a small but comparable extent. This highly preferential metabolism in herpesvirus-infected cells is a major factor in its selective antiviral activity. ( S)-penciclovir-triphospate is the major enantiomer produced and it has a much longer half-life than acyclovir-triphosphate in HSV-1, HSV-2, and varicella-zoster virus (VZV)-infected cells after drug removal. ( S)-penciclovir-triphosphate was formed at sufficiently high concentrations to be an effective inhibitor of viral DNA polymerases. This work suggests that viral DNA polymerase is the key target and that virus replication is prevented by inhibition of viral DNA synthesis, though it does not preclude other modes of action. The long half-life of penciclovir-triphosphate leads to an efficient and prolonged entrapment of the active product in virus-infected cells. This can account for the markedly better antiviral activity of penciclovir than acyclovir when infected cell cultures were treated for a short time followed by further incubation during which time the antiviral effect of acyclovir was reversed quickly. It is proposed that such assays reflect more closely the dynamic changes in plasma concentrations after oral dosing than do standard assays in which the test compounds are kept at a constant concentration. The clinical implications of these findings concerning mode of action are discussed.
Inhibitory Effects of Acyclic Nucleoside Phosphonate Analogues on Hepatitis B Virus DNA Synthesis in HB611 Cells
Authors: Yokota T. , Konno K. , Shigeta S. , Holy A. , Balzarini J. , De Clercq E.
Published: May 2015

By using an assay system based on a human hepatoblastoma cell line (HB611) that continuously synthesizes hepatitis B virus (HBV) DNA, 56 acyclic nucleoside phosphonate analogues were examined for their inhibitory effects on HBV DNA synthesis. The following compounds were found to inhibit HBV DNA synthesis at concentrations that were significantly lower than their minimum cytotoxic concentrations; 9-(2-phosphonylmethoxyethyl)adenine (PMEA), 9-(2-phosphonylmethoxyethyl) guanine(PMEG), 9-(2-phosphonylmethoxyethyl) guanine ethyl ester (PMEGEE), 9 - (2 - phosphonylmethoxyethyl) - 1 - deazaadenine (PMEC1A), 9-(2-phosphonylmethoxyethyl)-2,6-diaminopurine (PMEDAP), ( S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA), 9-(3-isopropoxy-2-phosphonylmethoxypropyl)adenine (IPPMPA), 9-( RS)-(2-phosphonylmethoxypropyl)adenine (PMPA) and 9-(3-hydroxy-2-phosphonylmethoxypropyl)-2, 6-diaminopurine (HPMPDAP). The most selective compounds (with indexes greater than 100) were PMEDAP, PMEA, IPPMPA, and PMPA. Acyclic pyrimidine nucleoside phosphonate analogues did not prove markedly selective as anti-HBV agents. Diphosphoryl derivatives of some acyclic purine nucleoside phos-phonates (i.e. PMEA, PMEDAP, HPMPA) were prepared. They proved inhibitory to HBV DNA polymerase but not cellular DNA polymerase α.
Novel Carbohydrate Conjugates as Potential Prodrugs of Acyclovir
Authors: Chamberlain S. D. , Moorman A. R. , Burnette T. C. , de Miranda P. , Krenitsky T. A.
Published: May 2015

Fifteen novel carbohydrate conjugates of desciclovir {2-[(2-amino-9 H-purin-9-yl]-methoxy]ethanol} were synthesized and evaluated as potential double prodrugs for acyclovir. The compounds were prepared by an acid-catalyzed reaction between reducing sugars and the 2-amino group of desciclovir. Spectral data indicated that the carbohydrate moieties in the products were predominately in the pyranose form. The suitability of each analogue as a double prodrug of acyclovir was evaluated by the urinary recovery of acyclovir from rats after oral dosing. The results showed that these highly water-soluble conjugates were poor prodrugs. Similar results were obtained with the glucose conjugate of acyclovir itself. A comparison of intraperitoneal vs. oral administration for six of the conjugates suggested that the unsuitability of these conjugates as prodrugs results from poor gastrointestinal absorption as well as inefficient metabolic removal of the carbohydrate moieties.
5′-O-Alkyl and Acyl Prodrugs of 1-β-D-Arabinofuranosyl-E-5-(2-Bromovinyl)Uracil
Authors: Kano F. , Ijichi K. , Ashida N. , Watanabe Y. , Sakata S. , Machida H.
Published: May 2015

5′- O-Alkyl derivatives of 1-β-D-arabinofuranosyl- E-5-(2-bromovinyl)uracil (BV-araU) were synthesized by selective alkylation and deprotection of 2′,3′-bis- O-tetrahydropyranyl BV-araU to enhance metabolic stability and evaluated for efficacy as oral prodrugs of BV-araU. For comparison, their acyl congeners, and 3′- O- and 2′- O-ethyl BV-araU, were also prepared by direct acylation of BV-araU and by selective protection, alkylation, and deprotection, respectively. The 5′- O-alkyl prodrugs were stable in acidic solutions, whereas the 5′- O-acyl analogues were unstable under the same conditions. When incubated with enterobacteria, the 5′- O-acyl derivatives resulted in the formation of BV-uracil through non-enzymatic hydrolysis of BV-araU, but the 5′- O-alkyl prodrugs did not. 5′- O-Short-chain aliphatic alkyl (not longer than butyl) and generally acyl prodrugs gave higher blood concentrations of BV-araU than the aromatic derivatives. Plasma concentrations of BV-araU were equal or slightly higher than those after equivalent oral doses of BV-araU. 5′- O-Ethyl BV-araU was effective against intracerebral, intraperitoneal, and cutaneous infections with herpes simplex virus type 1 in mice. 5′- O-Short-chain aliphatic alkyl derivatives may prove to be useful oral prodrugs of BV-araU because of increased metabolic stability.
Sodium Deoxycholate Exerts a Direct Destructive Effect on HIV and Influenza Viruses in vitro and Inhibits Retrovirus-Induced Pathology in An Animal Model
Authors: Oxford J. S. , Zuckerman M. A. , Race E. , Dourmashkin R. , Broadhurst K. , Sutton P. M.
Published: May 2015

The bile salt sodium deoxycholate had a virucidal effect on influenza, Rauscher leukaemia and HIV-1 viruses, reducing virus infectivity by a maximum of 6 logs TCID50 ml−1 after 1 h incubation at 37 °C with 50 μg ml−1 of the compound. Electron microscopy demonstrated directly that sodium deoxycholate and other bile salts perturbed influenza virus structure causing partial or complete disruption of the virion lipid membrane, thus allowing entry of phosphotungstate dye to the virion interior. Parenteral administration of sodium deoxycholate (14 mg kg−1) to Balb/C mice abrogated pathology caused by Rauscher leukaemia virus replicating in the spleen and influenza virus replicating in the lung. Bile salts may also have clinical potential as topical virucidal agents at the point of entry of enveloped viruses and particularly against HIV.
Effect of Inhibitors of Protein Myristoylation on Varicella-Zoster Virus Replication
Authors: Gilbert R. L. , Blunt C. J. , Harper D. R. , Jeffries D. J. , Mcllhinney R. A. J.
Published: May 2015

Inhibitors of N-myristoyltransferase (NMT) have been shown to inhibit retrovirus replication, notably that of the human immunodeficiency virus (HIV), where the absence of protein myristoylation inhibits viral replication. The authors have assayed 14 compounds derived from myristic acid for activity against varicella-zoster virus (human herpesvirus 3; VZV) by plaque reduction assay. Seven showed cytotoxicity and of the others, two failed to inhibit VZV replication. One of these was N-myristoylglycinaldiethylacetal (GoA), which has been reported to be active against HIV. 12-(methoxy) dodecanoic acid (13-oxamyristic acid), which has also been reported to inhibit HIV replication, was found to inhibit VZV replication but was cytotoxic at high concentrations. The greatest inhibitory effect without apparent toxicity was induced by 2-hydroxytetradecanoic acid and its enantiomers. The results of these assays provide further evidence that inhibitors of NMT have potential as antiviral agents against the many viruses with myristoylated proteins.
Multi-Branched Peptide Constructs (MBPC) of the V3 Loop of Envelope Glycoprotein gp120 Inhibit Human Immunodeficiency Virus-Induced Syncytium Formation
Authors: Benjouad A. , Fenouillet E. , Gluckman J.-C. , Sabatier J.-M.
Published: May 2015

The principle neutralizing domain of human immunodeficiency virus type-1 (HIV-1) envelope glycoprotein, the V3 region, is likely to be involved in HIV-mediated membrane fusion. While V3-derived monomeric peptides enhance HIV-1 infection through a CD4-dependent mechanism (DeRossi et al., 1991), the authors observed that multi-branched peptide constructs (MBPC) based on the V3 consensus sequence of European/North American isolates inhibited both HIV-1 and HIV-2 mediated syncytia at concentrations that did not alter cell viability nor blood lymphocyte allogeneic, antigen- or mitogen-induced proliferations. V3 MBPC bound to CD4+ cells and their binding was inhibited by soluble CD4 and by a benzylated peptide derived from its CDR3 region. These data indicate that V3-based MBPC may be used for delineating HIV entry mechanisms and might behave as antiviral agents of broad specificity.
Long-Term Treatment of HIV-Infected MT-4 Cells in Culture with HIV Proteinase Inhibitor RO 31-8959 Leads to Complete Cure of Infection
Authors: Nitschko H. , Lindhofer H. , Schätzl H. , Eberle J. , Deby G. , Kranz B. , von der Helm K.
Published: May 2015

An HIV-infected cell culture was treated with the specific HIV proteinase inhibitor Ro 31-8959 for three months to analyse the antiviral effect and possible cytotoxicity of the drug in long-term treatment. The drug was added 1 h after HIV infection with 0.002 m.o.i. and maintained for 87 days in the cell culture. There was no detectable cell death nor any evidence of HIV production in this time. Cells were proven to be initially infected, since premature drug removal led to a re-emergence of infectious HIV and cell death. However, after 87 days of treatment the drug could be removed safely and HIV was cleared demonstrably from the culture. These data suggest that long-term dosage may be advantageous to the clinical treatment of HIV infection by HIV proteinase inhibitors.
Alkyl Hydrogen Phosphonate Derivatives of the anti-HIV Agent AZT may be Less Toxic than the Parent Nucleoside Analogue
Authors: McGuigan C. , Bellevergue P. , Jones B. C. N. M. , Mahmood N. , Hay A. J. , Petrik J. , Karpas A.
Published: May 2015

Novel alkyl hydrogen phosphonate derivatives of the anti-HIV nucleoside analogue AZT have been prepared by phosphorochloridite chemistry. These materials are designed to act as labile membrane-soluble prodrugs of the bioactive free nucleotides. In vitro evaluation has revealed the compounds to have a pronounced and selective antiviral action. Short-chain (C1-C7) alkyl derivatives are more potent than the parent hydrogen phosphonate, whilst one long-chain (C18) compound is less active. In an assay that demonstrates the toxicity of the parent drug AZT, the alkyl H-phosphonates appear to be less cytotoxic, whilst retaining full antiviral activity. Lastly, the compounds are all poorly active in a cell line (JM) that is poorly responsive to AZT, indicating that they act as depot forms of the nucleoside rather than of the free nucleotide.
Antiherpesvirus Activity of the Combination of 5-iodo-2′-deoxycytidine with methotrexate: An in vitro and in vivo Study
Authors: Cremonesi C. , Scarpini C. , Bianchi R. , Radaelli A. , Gimelli M. , De Giuli Morghen C.
Published: May 2015

We evaluated the in vitro and in vivo antiviral activity of the deoxyribonucleoside analogue 5-iodo-2′-deoxycytidine (IDC) combined with the dihydrofolate reductase inhibitor methotrexate (MTX) on herpes simplex virus types 1 and 2 (HSV-1, HSV-2). The IDC-MTX combination synergistically inhibited HSV-1 and HSV-2 replication in vitro at concentrations that did not reduce cellular viability and was very effective in reducing the severity of cutaneous lesions in the experimental guinea pig model in vivo. The antiviral activity of the IDC-MTX combination in guinea pigs was also compared with that of acyclovir and was demonstrated to be higher.
Brain Targeting of anti-HIV Nucleosides: in vitro and in vivo Evaluation of 6-chloro-2′,3′-dideoxypurine, a Lipophilic Prodrug of 2′,3′-dideoxyinosine
Authors: Doshi K. J. , Boudinot F. D. , Gallo J. M. , Schinazi R. F. , Chu C. K.
Published: May 2015

Lipophilic 6-halo-2′,3′-dideoxypurine nucleosides may be useful prodrugs for the targeting of 2′,3′-dideoxyinosine (ddl) to the central nervous system. The purpose of this study was to evaluate the potential effectiveness of 6-chloro-2′,3′-dideoxypurine (6-CI-ddP) for the targeting of ddl to the brain. In vitro studies indicated that the adenosine deaminase-mediated biotransformation of 6-CI-ddP to ddl was more rapid in mouse brain homogenate than in mouse serum. The brain distribution of 6-CI-ddP and ddl was assessed in vivo in mice following intravenous and oral administration of the prodrug or parent drug. Brain concentrations of ddl were similar after intravenous administration of 6-CI-ddP or ddl. However, after oral administration of the 6-CI-ddP prodrug, significantly greater concentrations of ddl were seen in the brain compared to those found after oral administration of ddl. The brain:serum AUG ratio (expressed as a percentage) of ddl after intravenous administration of 50 mg kg−1 of the active nucleoside was 3%. Following oral administration of 250 mg kg−1 ddl, low concentrations of ddl were detected in the brain. Brain:serum AUC ratios following intravenous and oral administration of the prodrug 6-CI-ddP were 19–25%. Thus, brain:serum AUC ratios were 6- to 8-fold higher after prodrug administration than those obtained after administration of the parent nucleoside. Oral administration of 6-CI-ddP yielded concentrations of ddl in the brain similar to those obtained following intravenous administration. The results of this study provide further evidence that 6-CI-ddP may be a useful prodrug for delivering ddl to the central nervous system, particularly after oral administration.
Antiviral Activities of Mizoribine and other Inosine Monophosphate Dehydrogenase Inhibitors against Several Ortho- and Paramyxoviruses
Authors: Kosugi Y. , Saito Y. , Mori S. , Watanabe J. , Baba M. , Shigeta S.
Published: May 2015

Mizoribine (4-carbamoyl-1-β-D-ribofuranosylimidazo-lelium-5-olate), EICAR (5-ethynyl-1-β-D-ribofuranosylimi-dazole-4-carboxamide), mycophenolic acid and ribavirin are antiviral agents targeted for inosine monophosphate (IMP) dehydrogenase. These compounds have been examined for their activities against orthomyxoviruses [influenza viruses (FluV)] and paramyxoviruses [parainfluenza viruses (PFIuV), mumps virus, measles virus (MLSV) and respiratory syncytial virus (RSV)] in vitro. Mizoribine was 1- to 9-fold more active than ribavirin against RSV, PFIuV and MLSV. EICAR and mycophenolic acid showed higher potency than mizoribine and ribavirin against all myxoviruses examined. None of the four compounds examined proved cytotoxic to stationary host cells (HeLa, Vero and MDCK) at a concentration of 200 μg ml−1 or more. On the other hand, EICAR and mycophenolic acid were toxic to rapidly growing cells at concentrations of 2.2-9 and 0.1-1.1 μg ml−1, respectively. Mizoribine and ribavirin showed cytotoxicity to the growing cells at higher concentrations (12-51 μg ml−1). The antiviral activities of mizoribine against FluV and RSV were reversed by 25-100 μm of each of guanosine and guanosine monophosphate (GMP). The antiviral activity of ribavirin against FluV was reversed by 25 μg of each of guanosine and GMP, while its activity against RSV was reversed by ≥ 100 μm of each of these compounds. Neither xanthosine nor xanthosine monophosphate (XMP) reversed the antiviral effects of mizoribine and ribavirin at concentrations of 300 μM. Concentrations 9 times higher than the median effective doses (EC50) of mizoribine and ribavirin inhibited the growth of RSV in HeLa cells as determined in an assay of infectious virus yield. Mizoribin should be further pursued as a candidate drug for the treatment of ortho- and paramyxovirus infections.
Antiviral Activity of N4-Aminocytidine Derivatives Related to AZT
Authors: Loakes D. , Brown D. M. , Mahmood N. , Balzarini J. , De Clercq E.
Published: May 2015

A number of N4-hydroxy and N4-amino derivatives of 3′-azido-2′,3′-dideoxy-5-methylcytidine have been synthesized and tested for antiviral activity against HIV-1 and HIV-2. The N4-phenylamino and N4-dimethylamino analogues show marked anti-HIV activity which is comparable to that of AZT.
Peptides Containing 2-, 3- or 4-Fluorophenylalanine or 2,2- or 3,3-Difluorophenylalanine as Potential Inhibitors of HIV Protease
Authors: Viani S. , Condom R. , Frogier P. R. T. , Guedj R.
Published: May 2015

A series of peptide mimetic substrates of the HIV-1 protease, corresponding substantially to the amino acid sequence of the Tyr-Pro cleavage site contained in the gag polyprotein, in which the tyrosine amino acid of the scissile bond was replaced by 2-, 3- or 4-fluorophenylalanine or 2,2- or 3,3-difluorophenylalanine, has been developed. The synthesis of these compounds and the results of inhibition studies are described.
Isolation and Characterization of Human Immunodeficiency Virus Type-1 Mutants Resistant to the Non-Nucleotide Reverse Transcriptase Inhibitor MKC-442
Authors: Seki M. , Sadakata Y. , Yuasa S. , Baba M.
Published: May 2015

MKC-442, 6-benzy 1-1-ethoxymethyl-5-isopropyIuraciI (l-EBU), is a potent and selective non-nucleoside inhibitor of human immunodeficiency virus type-1 (HIV-1) reverse transcriptase (RT). Nevirapine, another non-nucleoside RT inhibitor (NNRTI), is associated with rapid emergence of drug-resistant variants during in vitro passages of HIV-1. The emergence of resistant viruses to MKC-442 or nevirapine was examined in vitro. MT-4 cells infected with a clinical isolate (HE) of HIV-1 were cultivated in medium containing excess concentrations of these drugs, and the drug susceptibilities of the breakthrough viruses recovered from the medium were measured. Although nevirapine lost its antiviral activity after six passages, a delay in the emergence of fully resistant viruses was observed for MKC-442. Two resistant clones for each drug were isolated and nucleotide sequences within the RT region were analysed. An amino acid substitution at position 181 (Tyr to Cys) was found, with additional substitutions at positions 103 (Lys to Arg) and 108 (Val to lle) in the MKC-442-resistant viruses. These clones showed various susceptibilities to MKC-442, and cross-resistance to other NNRTIs but not to AZT. These results suggest that the major binding site of MKC-442 on the HIV-1 RT is the tyrosine residue common to these NNRTIs, and that drug resistance to NNRTIs is dependent on both the quality and the quantity of mutations within the HIV-1 RT gene.
Characterization of the Antiviral Activity of Highly Substituted Pyrroles: A Novel Class of Non-Nucleoside HIV-1 Reverse Transcriptase Inhibitor
Authors: Antonucci T. , Warmus J. S. , Hodges J. C. , Nickell D. G.
Published: May 2015

As a result of mass screening of the Parke-Davis Pharmaceutical compound library for inhibitors of HIV-1 reverse transcriptase (RT) activity, a novel class of inhibitor, the pyrroles, was identified. Subsequently, a series of analogues was screened for inhibitory activity against HIV-1 and some structure-activity relationships were identified. Further characterization of the most potent pyrrole involved comparing its effects in peripheral blood lymphocytes (PBLs) with its effects in transformed cell lines; the pyrrole had the same efficacy (EC50 = approximately 2 μM) but was less toxic in PBLs (IC50 = 175 μM) than in the cell lines CEM-SS and MT-2 (IC50 = 60-70 μM). The pyrrole was active against a strain of HIV-1 resistant to AZT (strain G9106) but lost activity against both HIV-2 (strain ROD) and a strain of HIV-1 resistant to a non-nucleoside reverse transcriptase inhibitor (the pyridinone-resistant strain A17). Moreover, in direct enzymatic testing against HIV-1 RT purified from virus particles and against RT expressed recombinantly, the pyrrole showed potent inhibitory activity. We conclude that the pyrroles present a novel class of HIV-1 non-nucleoside reverse transcriptase inhibitor.
In vitro Antimyxovirus and Anti-Human Immunodeficiency Virus Activities of Polyoxometalates
Authors: Shigeta S. , Mori S. , Watanabe J. , Baba M. , Khenkin A. M. , Hill C. L. , Schinazi R. F.
Published: May 2015

Polyoxometalates have been shown to inhibit the replication of retro-, toga-, paramyxo- and herpesviruses. The primary mechanism of the anti-human immunodeficiency virus type 1 (HIV-1) action of polyoxometalates seems to be inhibition of binding of virus to cells and inhibition of syncytium formation. Since myxoviruses and HIV-1 are known to interact with the cytoplasmic membrane by adsorption and penetration of virus and by fusion of infected and uninfected cells, 25 polyoxometalates were examined for anti-ortho-, anti-paramyxovirus and anti-HIV-1 activity in vitro. Of the 25 compounds evaluated, 24 showed antiviral effects against influenza virus A, 11 showed activity against respiratory syncytial virus, six showed activity against measles virus, and 23 were considered effective against HIV-1 at a lower concentration than that producing cytotoxicity. Four polyoxotungstates which had potent inhibitory effects were examined for inhibitory effects against additional ortho- and paramyxoviruses, and proved to have a broad spectrum of antimyxoviral activity. HS-058, the Keggin sandwich compound K10Fe4(H2O)2(PW9O34)2·nH2O, was inhibitory against influenza viruses A and B, respiratory syncytial virus, measles virus, and parainfluenza virus 2, with median effective concentrations of 1.4, 21.8, 7.4, 0.8 and 0.32 μ,M, respectively. However, HS-058 had no effect on parainfluenza virus 3 or mumps virus. The median cytotoxic concentration of HS-058 for Madin-Darby canine kidney (MDCK) and HEp-2 cells was more than 200 μM and that for HMV-2 and Vero cells was about 50 μM. When HS-058 was added at different times after influenza A and respiratory syncytial virus infection, it inhibited binding of the latter but not of the former to cells. However, at higher concentrations, HS-054 and HS-058 inhibited haemolysis of chick erythrocytes by influenza virus and syncytium formation involving respiratory syncytial virus-infected cells and uninfected cells. Four times the median effective antiviral concentration of HS-058 completely inhibited the growth of influenza virus A in MDCK cells when compound was added before virus adsorption. Furthermore, when HS-058 was added after virus adsorption, it inhibited the yield of virus in MDCK cells infected at low but not at high multiplicity of infection.
Anti-HIV and anti-HCMV Activities of New Aurintricarboxylic Acid Analogues
Authors: Cushman M. , Wang P. , Reymen D. , Esté J. , Witvrouw M. , Neyts J. , De Clercq E.
Published: May 2015

A variety of aurintricarboxylic acid (ATA) polymer analogues were prepared by substituting certain salicylic acid derivatives and carbonyl compounds for salicylic acid and formaldehyde in the ATA polymerization reaction. The new polymers were evaluated for prevention of the cytopathic effects of human immunodeficiency virus (HIV-1 and HIV-2) in MT-4 cell culture, HIV-1 in CEM cell culture, and human cytomegalovirus (HCMV) in HEL cell culture. The abilities of the analogues to inhibit syncytium formation between HIV-1- or HIV-2-infected HUT-78 cells and uninfected MOLT-4 cells were also evaluated. Several of the new analogues were found to be equipotent with ATA and dextran sulfate against HIV-1, HIV-2 and HCMV. The anti-HIV potencies of the new substances paralleled their activities against HCMV. The antiviral activities of the new analogues probably result from inhibition of virion binding to the cell membrane.
2′-Deoxyuridines with a 5-Heteroaromatic Substituent: Synthesis and Biological Evaluation
Authors: Luyten I. , Jie L. , Van Aerschot A. , Pannecouque C. , Wigerinck P. , Rozenski J. , Hendrix C. , Wang C. , Wiebe L. , Balzarini J. , De Clercq E. , Herdewijn P.
Published: May 2015

A series of novel 2′-deoxyuridines with a thienyl substituent in the 5-position were synthesized as potential anti-HSV-1 agents. The brominated derivatives (1d, 1e and 3b) were obtained via halogenation reactions of the protected 5-(thien-2-yl)-2′-deoxyuridine and 5-(thien-3-yl)-2′-deoxyuridine, respectively. The palladium-catalysed cross-coupling reaction with stannylated thiophene was used for the synthesis of ( E)-5-(2-thienylvinyl)-2′-deoxyuridine and 5-(5,2′-dithien-2-yl)-2′-deoxyuridine. These compounds show moderate to good activity against herpes simplex virus type 1 (HSV-1) in the order of decreasing activity 1d>4>1e>3b∼5. Finally, two substituted 5-isoxazol derivatives of 2′-deoxyuridine (6a and 6b) were obtained via a 1,3-dipolar cycloaddition of the protected 5-ethynyl-2′-deoxyuridine. These new compounds demonstrated poor affinity for the virus-specific enzyme thymidine kinase.
Penciclovir-Resistance Mutations in the Herpes Simplex Virus DNA Polymerase Gene
Authors: Chiou Henry C. , Kumura Keiko , Hu André , Kerns Kelvin M. , Coen Donald M.
Published: May 2015

Penciclovir is the active form of the orally available prodrug famciclovir, which is entering clinical use for herpesvirus infections. Like aciclovir, penciclovir is an acyclic guanosine analogue that is phosphorylated by viral thymidine kinase and whose triphosphate can inhibit viral DNA polymerase. We tested several well-characterized herpes simplex virus mutants with aciclovir-resistance mutations in the viral DNA polymerase gene for altered sensitivity to penciclovir. The mutants varied in their susceptibilities to penciclovir with one exhibiting 2-fold hypersensitivity, one marginal resistance and three about 3-fold resistance. Marker rescue and DNA sequencing analyses mapped the penciclovir-resistance mutation of one mutant, AraA r7, to a single base change that alters a glycine to a cysteine at residue 841 within conserved region III of α-like DNA polymerases. The results have implications for the mechanism of selective action of penciclovir, for the potential for development of resistance in the clinic, and for the substrate recognition properties of herpes simplex virus DNA polymerase.
Inhibition of HIV-1 and LP-BM5 Replication in Macrophages by Dideoxycytidine and Dideoxycytidine 5′-Triphosphate
Authors: Magnani M. , Casabianca A. , Rossi L. , Fraternale A. , Brandi G. , Silvotti L. , Piedimonte G.
Published: May 2015

The antiviral agent 2′,3′-dideoxycytidine (ddC) has been shown to be active against HIV-1 infectivity. However, conflicting results have been reported concerning its efficacy in macrophages. Because macrophages possess low levels of the kinase(s) responsible for ddC phosphorylation, we investigated the ability of ddC and 2′,3′-dideoxycytidine 5′-trisphosphate (ddCTP) to suppress HIV-1 and LP-BM5 replication in these cells. Retrovirus replication was only partially inhibited in the two systems investigated by a high (1 μM) ddC concentration. The direct administration of ddCTP, using autologous red blood cells as a delivery system, was found to inhibit HIV-1 and LP-BM5 replication by more than 90% in macrophages without affecting major cell functions. These data, together with those already reported for FIV [Magnani et al. (1994) AIDS Res Hum Retroviruses 10: 1179-1186], suggest that the anabolic phosphorylation of ddC is an important determinant of its anti-HIV activity and that pharmacological interventions that modulate ddC metabolism may be useful for improving its antiretroviral activity in macrophages.
Dimeric Macrocyclic Polyamines with Potent Inhibitory Activity against Human Immunodeficiency Virus
Authors: Inouye Y. , Kanamori T. , Sugiyama M. , Yoshida T. , Koike T. , Shionoya M. , Enomoto K. , Suehiro K. , Kimura E.
Published: May 2015

The structure-activity relationships of monomeric and dimeric macrocyclic polyamines were studied in an attempt to find potent inhibitors of human immunodeficiency virus (HIV) types 1 and 2. In general, dimeric polyamines are superior as HIV inhibitors to their monomeric counterparts, and the activity of a dimer is proportional to that of its constituent monomers. For the monomeric compounds, the amount of positive charge on the monomer rings under physiological conditions was more important for anti-HIV activity than the ring size. On the basis of these findings, the 14-membered tetraamine cyclam was selected as the component of dimeric compounds with potentially high activity. Of the series of newly synthesized bicyclams, in which the monomeric cyclams were linked at each C-6 position, a compound with an aIkyI chain bridge three carbons in length was found to exhibit the maximum anti-HIV activity. For one particular strain (HIV-2GH-1), syncytium formation was inhibited by the bicyclams at a similar concentration to that required to inhibit the viral cytopathic effect.
Synthesis and anti-HIV-1 Activity of [1-[2′,5′-Bis-O-(Tert-Butyldimethylsilyl)-β-L-Ribofuranosyl]Thymine]-3′-Spiro-5″-(4″-Amino-1″,2″-Oxathiole-2″,2″-Dioxide) (L-TSAO-T), the L-enantiomer of the Highly Specific HIV-1 Reverse Transcriptase Inhibitor TSAO-T
Authors: Ingate S. T. , Camarasa M.-J. , De Clercq E. , Balzarini J.
Published: May 2015

The L-isomer of the potent HIV-1-RT inhibitor TSAO-T has been stereospecifically synthesized and tested for its ‘ in vitro’ antiretroviral activity against HIV-1. Unlike the D-isomer, the L-isomer did not show appreciable inhibition of HIV-1 replication. The cytotoxicity was comparable with the cytotoxicity of the D-enantiomer.
Antiviral Activities of Peptides with Sequences Related to the Cytoplasmic Domain of the Respiratory Syncytial Virus Glycoproteins
Authors: Ryan C. , Mo J. , Schlesinger M. J.
Published: May 2015

A set of peptides from 6–10 amino acids in length with sequences corresponding to the respiratory syncytial virus (RSV) attachment glycoprotein, G, has been found to inhibit secretion of virus particles from two human cell lines infected with RSV. Peptides of similar lengths with sequences related to the fusion (F) protein were not effective. A modified assay for syncytia formation was used to measure infectious particles and we found that cell-free infectious RSV was inhibited by those same peptides that blocked particle release. However, only about 5–20% of the total infectious virus formed in the cultured cells was released from the cells – the remaining was assayable only after lysis of the infected cells. Formation of this major fraction of infectious, cell-associated RSV was not affected by the peptides. The inhibitory peptides were ineffective in blocking release of infectious virus from cells infected with influenza, vesicular stomatitis and Semliki Forest viruses. Only a set of specific amino acids in these peptides were inhibitory and they consisted of a very hydrophobic sequence that also required a cysteine residue.
Current Issues in the Management of Genital Herpes
Authors: Barton S. E.
Published: May 2015

Genital infection by herpes simplex virus (HSV) produces a variety of clinical manifestations, patient presentations and management problems which differ in their severity and complexity. In the UK the currently available data for the incidence of genital HSV have been provided predominantly by the KC60 returns from diagnoses made in genitourinary (GU) medicine clinics. The increasing availability and recent publication of the first results, using HSV type-specific antibody tests within GU and non-GU patient populations, provide a tool to monitor trends in the epidemiology of HSV. It is, however, important to understand that the sexual behaviour which leads to this infection is variable and not necessarily general.

The clinical availability of type-specific HSV antibody tests also gives rise to the possibility of screening individuals and informing those who test positive of their, previously undiagnosed, condition. The practicalities and problems of this approach need to be fully assessed. The possibility of uncovering previously undiagnosed cases through general practitioners is being considered, first, in terms of surveys of the general practitioners' management of genital HSV and, secondly, because the funding of health care in the UK has put the cost-effectiveness in GU medicine clinics under the spotlight. This paper will explore the new developments in the management of genital HSV and suggests adherence to the clear principles of diagnosis and treatment that is in the patient's best interest. This has the clear aim of improving the patient's quality of life, a factor which must remain paramount as new technologies, healthcare strategies and therapies become available.
Parameters for the Successful Management of Cytomegalovirus
Authors: Griffiths P. D.
Published: May 2015

Cytomegalovirus (CMV) is a major pathogen for the neonate and the transplant recipient in both of whom the incidence of the disease and its severity are increased when the donor, or mother, has a primary infection. Many individuals with recurrent infection who experience the disease do so because they are being reinfected from an exogenous source, rather than reactivating their own strain, arguing that natural immunity can reduce, but not completely control, CMV disease. Antiviral therapy is thus needed to control CMV disease. There are four major strategies for the use of drugs against CMV - prophylaxis, suppression, pre-emptive therapy and treatment; significant benefit has been shown for some of these in some groups of transplant patients. The strategies must now be compared, and patient management regimes comparing the various approaches should be considered.
Some Fundamental Statistical Concepts in Clinical Trials and their Application in Herpes Zoster
Authors: Kay R.
Published: May 2015

The correct application of appropriate statistical methods in clinical trials is essential for deriving valid conclusions. This paper covers a number of the key principles, with particular relevance to studies in herpes zoster. The distinct roles of the P-value and the confidence interval are investigated and their use in the assessment of the equivalence of two treatments evaluated. The principle of intent-to-treat is discussed and is seen to be vitally important for obtaining correct conclusions. The definition of end-points in the assessment of pain in herpes zoster is controversial; it is argued here that the only valid approach is to consider the time from start of treatment to complete cessation of all pain. Finally, methods for the evaluation of time to event data are explained in general terms, and particular drawbacks relevant to herpes zoster are discussed.
Valaciclovir – An Improvement Over Aciclovir for the Treatment of Zoster
Authors: Murray A. B.
Published: May 2015

Aciclovir, the first effective antiviral with an acceptable safety profile for the treatment of herpesvirus infections, has shown some limitation in clinical usefulness because of its low oral bioavailability. The search for an improved agent resulted in development of the L-valyl ester of aciclovir, valaciclovir. Valaciclovir has a much improved oral bioavailability and exhibits the same favourable toxicity profile as aciclovir. Following absorption, valaciclovir is rapidly and almost completely converted to aciclovir and the essential amino acid, L-valine. In man, the bioavailability of aciclovir following oral administration of valaciclovir is approximately 54%, compared to only 12-20% for oral aciclovir.

A large multicentre study has compared the efficacy and safety of valaciclovir with aciclovir for the treatment of zoster, and has shown significantly improved clinical benefit for valaciclovir. In addition, by retaining the same mode of action and pre-clinical profile as aciclovir, and combined with a similar safety profile in humans, valaciclovir is set to become the new standard in the treatment and prevention of herpesvirus infections and diseases.
Synthesis and Anti-HSV-1 Activity of New 3-Amino-3-Arylpropionic Acid Esters
Authors: Guillon J. , Dallemagne P. , Rault S. , Amoros M. , Boustie J. , Robba M.
Published: May 2015

A number of 3-methylbut-2-enyl esters of various 3-amino-3-arylpropionic acids have been synthesized and tested for antiviral activity against HSV-1. Many of these compounds, analogues of the 3-methylbut-2-enyl caffeate, isolated from poplar buds, show marked anti-HSV-1 activity and are less toxic than the natural ester.