Impact of overweight on the burden of non-communicable diseases in Belgium: the WaIST project

Issue

Excess weight status is one of the main metabolic risk factors for non-communicable diseases. According to the Belgian health interview survey of 2018, 49.3% of the adult population suffered from overweight. Despite the great national burden, and apart from isolated actions, there is not anymore a comprehensive nutritional and physical activity health plan in Belgium. Consequentially, Belgium requires action-oriented research to support the implementation of evidence-based policies for the prevention of excessive weight gain.

Description of the Problem

The WaIST project aims to assess the contribution of excess weight status to the societal impact of non-communicable diseases, disability and multi-morbidity, and to model and compare the potential impact of internationally recommended health policies. The project also aims to support knowledge translation and policy transfer through a close interaction with national decision makers and stakeholders.

Results

The disease burden of diabetes, cardiovascular diseases, cancer and musculoskeletal disorders will be estimated in terms of disability-adjusted life years (DALYs) and healthcare expenses from a societal perspective. For this purpose, survey, registry, health insurance, and hospital discharge data will be used. Subsequently, health interventions tackling overweight will be selected considering scientific evidence and stakeholder priorities. Health impact assessments will then be conducted projecting the future impact of the interventions on health outcomes and costs related to excess weight status.

Lessons

The use of national data for the computation of the burden of disease provides better estimates for DALYs and costs compared to European or global study results. Moreover, the results of the project will allow to explore the impact of health intervention specific for the Belgian case.

Key messages

Considering the burden associated with overweight-related diseases, preventing obesity is important from a public health and financial perspective. Integrating these results into evidence-based policies could provide governments and partners with a key tool for effective health interventions.

Laryngeal hemiplegia in the horse: an update

Laryngeal hemiplegia is a progressive upper airway dysfunction in the horse. It is not only seen in thoroughbred racehorses but also in warmblood horses, draft horses and in ponies. The condition is most frequently seen on the left side. The left laryngeal recurrent nerve gradually loses function and the function of the left cricoarythenoideus dorsalis muscle is compromised. This condition is most often idiopathic. It possibly leads to exercise intolerance but a respiratory noise is often the primary complaint of the owner. Right sided laryngeal hemiplegia is almost always related to other pathologies causing the nerve to malfunction. The diagnosis is not always easy because of the restricted availability of endoscopy in the field. A better understanding of laryngeal ultrasound examination might offer a new possibility in diagnosing laryngeal hemiplegia. If abnormal inspiratory sound is the only problem, laser treatment alone can be satisfactory. If the horse shows clear signs of exercise intolerance, further treatment is needed. If correctly executed, the outcome of laryngoplasty is good. Other techniques, like nerve grafting and pacemakers, are being explored and might even be regarded as better alternative treatments in the future, as these are more physiologic compared to laryngoplasty. In sporthorses presented with idiopathic laryngeal neuropathy without postoperative complications, the prognosis is good.

Inhibitory Effects of Acyclic Nucleoside Phosphonate Analogues on Hepatitis B Virus DNA Synthesis in HB611 Cells

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.

Phosphoramidates as Potent Prodrugs of anti-HIV Nucleotides: Studies in the Amino Region

Novel phosphoramidate derivatives of the anti-HIV nucleoside analogues AZT and d4T have been prepared by phosphorochloridate chemistry. These materials are designed to act as labile membrane-soluble prodrugs of the bio-active free nucleotides. All compounds were fully characterised by a range of methods and were subjected to evaluation in vitro of their anti-HIV efficacy. A notable feature of the current study was that any attempt to replace the amino acid moiety of the phosphoramidate with a simple amine lead to a marked, virtually total loss of activity. Such simple phenyl alkylamino phosphate derivatives of either d4T or AZT inhibit HIV replication at cytotoxic concentrations and have no detectable antiviral selectivity. This clearly highlights the vital role played by the amino acid in the antiviral efficacy of the blocked phosphoramidates.

Structural Features and Anti-Human Immunodeficiency Virus (HIV) Activity of the Isomers of 1-(2′,6′-Difluorophenyl)-1H,3H-Thiazolo[3,4-a]Benzimidazole, a Potent Non-Nucleoside HIV-1 Reverse Transcriptase Inhibitor

The structural features, including the absolute configuration, of the enantiomers of 1-(2′,6′-difluorophenyl)-1 H,3 H-thiazolo[3,4- a]benzimidazole (TBZ; NSC 625487), the lead compound of a new class of human immunodeficiency virus type 1 (HIV-1) non-nucleoside reverse transcriptase inhibitors (NNRTIs), are described. Diffractometric analysis revealed that TBZ, like other NNRTIs, assumes a butterfly-like conformation in which the phenyl ring at C1 is in an orthogonal orientation relative to the thiazolobenzimidazole system, and the 2′,6′-fluorine atoms form two intramolecular hydrogen bonds with H1 and one of the methylene protons at C3, respectively. The stereochemistry in solution, as confirmed by lanthanide shift reagent-assisted ‘H NMR, paralleled the situation present in the solid state. The in vitro anti-HIV activity of the two enantiomers was also evaluated and the results obtained showed that the R-(+) is more active than the S-(−) isomer in inhibiting HIV-1 replication. Resistance and cross-resistance to other NNRTIs as well as inhibitory effects on HIV-1 reverse transcriptase activity are also reported.

Modified Cyclodextrin Sulphates(mCDS11) have Potent Inhibitory Activity against HIV and High Oral Bioavailability

Modified cyclodextrin sulphate (mCDS) in which lipophilic groups were introduced to cyclodextrin sulphate (CDS) was synthesized and proved more inhibitory to the replication of HIV-1 and HIV-2 than CDS or dextran sulphate (DS). The anti-coagulant activity of mCDS was lower than that of DS. Cyclodextrin phosphate (CDP) showed anti-HIV activity similar to that of CDS, and its anti-coagulant activity was even lower than that of mCDS. Flow cytometric analysis suggested that the mechanism of the anti-HIV-1 action of CDS, mCDS, and CDP is based on inhibition of HIV-1 binding to the cells. The peak blood concentration after oral administration of mCDS11(potassium tris[6-benzylthio-6-deoxy]-β-cyclodextrin hexadecasulphate) to rabbits was about 1000 times higher than the concentration showing anti-HIV activity. The retention time in the blood was also long (blood half-life: 4 h). These results point to the potential usefulness of oral mCDS administration in the prophylaxis and/or therapy of HIV infections.

Selective Activity of Various Nucleoside and Nucleotide Analogues against Human Herpesvirus 6 and 7

We have developed a new sensitive enzyme immunoassay (EIA) and MTT (tetrazolium salt) assay for screening compounds against two variants of human herpesvirus 6 (HHV-6A, HHV-6B) and human herpesvirus 7 (HHV-7) and evaluated the anti-HHV-6 and HHV-7 activity of a series of anti-herpesvirus compounds and acyclic nucleoside phosphonate analogues. The results indicate that the pattern of activity of these compounds against these betaherpesviruses is similar to that for human cytomegalovirus (HCMV). The highest potency and selectivity against the two variants of HHV-6 and HHV-7 was demonstrated by S2242 (N7-isomer of 6-deoxy-ganciclovir). Also, ganciclovir (GCV), foscarnet, (phosphonoformic acid; PFA) and the acyclic nucleoside phosphonate analogues such as cidofovir (HPMPC) exhibited selective inhibitory activity against these viruses. Thymidine kinase (TK)-dependent drugs (acyclovir, ACV; brivudin, BVDU; and sorivudine, BVaraU) showed little, if any, activity. These results suggest a structural homology of the DNA polymerase and a lack of TK gene among these three betaherpesviruses (HHV-6, HHV-7 and HCMV). The finding that HHV-7 was highly sensitive to GCV also suggests that HHV-7 may have an HCMV-UL97-homologue gene for the phosphorylation of GCV. The present EIA method is more rapid and sensitive than the previously reported procedures and could be useful for the large-scale screening of compounds against HHV-6 and HHV-7.

Inhibitory Effects of Polycations on the Replication of Enveloped Viruses (HIV, HSV, CMV, RSV, Influenza A Virus and Togaviruses) in vitro

Polycationic compounds, i.e. poly-l-lysines and poly-d-lysines, were evaluated for their in vitro effect on the replication of various viruses. Poly-l-lysines of different molecular weight proved inhibitory to the replication of several enveloped viruses, such as human immunodeficiency virus type 1 and type 2 (HIV-1 and HIV-2), respiratory syncytial virus (RSV), influenza A virus, Sindbis virus, Semliki Forest virus, vesicular stomatitis virus (VSV), herpes simplex virus type 1 (HSV-1) and human cytomegalovirus (CMV). The mechanism of action of the polylysines against HIV-1, RSV and CMV could be attributed to an inhibitory effect on virus binding to the host cells, as demonstrated by an indirect immunofluorescence/laser flow cytofluorographic method, virus plaque reduction and measurement of radiolabelled virion association with the cells, respectively.

Human Brain Tumour Cell Lines as Cell Substrate to Demonstrate Sensitivity/Resistance of Herpes Simplex Virus Types 1 and 2 to Nucleoside Analogues

Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) grow in vitro in a broad range of human and animal cells. Here we describe the activity of several nucleoside and nucleotide analogues against HSV-1 and HSV-2 in human brain-tumour-derived cells. Of the compounds tested, ( E)-5-(2′-bromovinyl)-2′-deoxyuridine (BVDU) proved to be the most potent inhibitor of the wild-type, thymidine-kinase-positive (TK+) HSV-1. In contrast to BVDU, acyclovir and ganciclovir, which were virtually inactive against TK− HSV-1, the two acyclic nucleoside phosphonates ( S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) and ( S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) were equally active against TK+ and TK− HSV-1 strains. Depending on the brain tumour cell line used, differences in virus-drug sensitivity varied up to 30-fold. Upon passage of the virus in the brain tumour cell lines in the presence of the compounds, virus resistance developed rapidly to BVDU, acyclovir and foscarnet but not to HPMPC. Furthermore, the HSV-1 mutant that had become resistant to BVDU, acyclovir or foscarnet remained as sensitive to HPMPC and HPMPA as did the wild-type HSV-1 (KOS strain).

Synthesis and Biological Evaluation of New 5,6-dichlorobenzimidazole Nucleoside Derivatives

Novel 5,6-dichlorobenzimidazole nucleoside analogues structurally related to the well-known riboside DRB have been synthesized. The 1′,2′- trans nucleosides were prepared by condensation of peracylated sugars with 5,6-dichlorobenzimidazole, whereas the 1′,2′- cis β-D-arabinofuranosyl and β-D-lyxofuranosyl nucleosides were obtained by inversion of configuration on the sugar moiety. Chiral acyclic derivatives were stereospecifically prepared by ring-opening of furano- or pyrano-nucleosides by means of periodate oxidation, followed by borohydride reduction. The in vitro activities against a range of DNA and RNA viruses, as well as the cytotoxicities in human T-lymphocyte MT-4 cells, have been determined for these novel compounds and for DRB. No truly selective activity (i.e. clearly below the cytotoxic concentration) was observed against any of the viruses used. Some of the compounds, including DRB, were cytotoxic to MT-4 cells at CC50 values of less than 10 μg ml−1.

Anti-HIV and anti-HCMV Activities of New Aurintricarboxylic Acid Analogues

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

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.

Antiviral Activity of a Keggin Polyoxotungstate PM-19 against Herpes Simplex Virus in Mice

The in vivo activity of the Keggin polyoxotungstate PM-19 [K7(PTi2W10O40)·6H2O] was investigated against herpes simplex virus type 2 (HSV-2) in ddY mice. A single dose of PM-19 at 100mg kg−1administered intraperitoneally (i.p.) immediately after i.p. infection of ddY mice with HSV-2 offered 92% protection against an otherwise lethal HSV-2 infection. PM-19 was less or not effective if given by any route other than the i.p. route. When repeated doses of PM-19 were administered i.p. on day 0 (immediately after infection) and day 1 and 2 after infection, it proved protective over a dosage range of 0.1-50 mg kg−1day−1, its ED50 (50% effective dose, based on the number of survivors) being 0.25 mg kg−1day−1. Under these conditions, ACV was not effective even at doses up to 100 mg kg−1day−1.

Pharmacokinetics of the anti-HIV Bicyclam SID791 (JM3100) in Rabbits, as Determined by both Analytical and Bio-Assay Methods

The serum levels of the bicyclam derivative 1,1′-[1,4-phenylenebis(methylene)]-bis-1,4,8,11-etraazacyclotetradecane octahydrochloride dihydrate [SID791 (JM3100)], a potent inhibitor of HIV replication (De Clercq et al., 1994) were determined in rabbits using two different methods. A method based on the UV-absorption of the Cu-complex of SID791 was used to analyse by HPLC the serum drug concentrations, and an antiviral activity bio-assay was performed to investigate whether the drug in the rabbit serum was in an available active form. After subcutaneous (sc) administration of SID791 to rabbits at 25 mg kg−1 of body weight, the compound was cleared from the serum in a bi-exponential manner (β1-half-lives: 67 and 69 min; β2-half-lives: 320 and 245 min; distribution volumes: 0.40 and 0.37 I; total body clearance: 0.30 and 0.29 I h−1; and AUC: 83.3 and 86.2 h μg ml−1, as determined by HPLC and bio-assay, respectively). Thus, very similar kinetic parameters were noted if serum drug concentrations were determined by HPLC analysis or bio-assay, suggesting that in the rabbit serum the drug is present as an antiviral active agent.

Sulphated Polymers are Potent and Selective Inhibitors of Various Enveloped Viruses, Including Herpes Simplex Virus, Cytomegalovirus, Vesicular Stomatitis Virus, Respiratory Syncytial Virus, and Toga-, Arena- and Retroviruses

The sulphated polymers, such as polyvinylalcohol sulphate (PVAS) and its co-polymer with acrylic acid (PAVAS), have proved to be potent inhibitors for herpes simplex virus, human cytomegalovirus, vesicular stomatitis virus, respiratory syncytial virus, Sindbis virus, Semliki Forest virus, Junin virus, Tacaribe virus, murine sarcoma virus and human immunodeficiency virus. They are not inhibitory to non-enveloped viruses, such as poliovirus and reovirus. The broad-spectrum antiviral effects of these compounds depend on their molecular weight and degree of sulphation. Pharmacokinetic studies in rabbits have indicated that after intravenous bolus injection the serum concentrations of these compounds decay biphasically, with an initial half-life of approximately 90–120 min.

In vitro Activity of a Novel Series of Polyoxosilicotungstates against Human Myxo-, Herpes- and Retroviruses

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.

Selective Inhibition of Myxovirus Replication by a Novel Series of Cholesterol-Naphthalenesulfonic Acid Hybrid Molecules

A novel series of hybrid molecules with cholesterol and naphthalenesulfonic acid have been synthesized and evaluated for their inhibitory activity against myxoviruses (respiratory syncytial virus [RSV], influenza A and B virus), Naphthalenesulfonic acids (compounds 1–3) and cholesterols (compounds 4 and 5) did not inhibit myxovirus-induced cytopathic-ity. However, hybrid molecules (compounds 6 and 7) proved active against RSV and influenza A virus but not influenza B virus. The antiviral effects of the hybrid compounds 6 and 7 were comparable to those of dextran sulfate. Mixtures of naphthalenesulfonic acid and cholesteryl chloroformate (compounds 1 and 5 molecules, corresponding to the hybrid molecule 6; and compounds 2 and 5, corresponding to the hybrid molecule 7) did not show antiviral activity. The mode of action of the cholesterol-linked naphthalenesulfonic acids can be attributed to inhibition of virus-cell fusion (influenza A virus) or inhibition of both virus-cell binding and fusion (RSV).

HPMPC (cidofovir), PMEA (adefovir) and Related Acyclic Nucleoside Phosphonate Analogues: A Review of their Pharmacology and Clinical Potential in the Treatment of Viral Infections

The acyclic nucleoside phosphonate (ANP) analogues are broad-spectrum antiviral agents, with potent and selective antiviral activity in vitro and in vivo. The prototype compounds are: ( S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC, cidofovir), which is active against a wide variety of DNA viruses; 9-(2-phosphonylmethoxyethyl)adenine (PMEA, adefovir), which is active against retro-, herpes- and hepadnaviruses, and ( R)-9-(2-phosphonylmethoxypropyl) adenine (PMPA), which is active against retro- and hepadnaviruses. The antiviral action of the ANP analogues is based on a specific interaction of the active diphosphorylated metabolite with the viral DNA polymerase. The long intracellular half-life of the active metabolite accounts for the optimal efficacy in infrequent dosing schedules. The potential of HPMPC as a broad-spectrum anti-DNA virus agent, as originally observed in vitro and in vivo, has been confirmed in clinical trials. HPMPC has recently been commercially released in the USA for the treatment of cytomegalovirus retinitis in AIDS patients. In addition, topical systemic HPMPC is being (or will be) explored for use against other herpesviruses (i.e. herpes simplex virus, Epstein-Barr virus, or varicella-zoster virus), by adenoviruses, or by human papilloma- or polyomaviruses. Intravenous HPMPC is associated with dose-dependent nephrotoxicity, that should be counteracted by prehydration and concomitant administration of probenecid, and by the application of an infrequent dosing schedule. The oral prodrug of PMEA, bis(pivaloyloxymethyl)-PMEA, is currently being evaluated in patients infected with human immunodeficiency virus (HIV) or hepatitis B virus. Finally, preclinical data on the efficacy of PMPA in animal retrovirus models point to its potential usefulness against HIV infections, when given either prophylactically or therapeutically in the treatment of established HIV infections.

Oxathiin Carboxanilide Derivatives: A Class of Non-Nucleoside HIV-1-Specific Reverse Transcriptase Inhibitors (NNRTIs) that are Active against Mutant HIV-1 Strains Resistant to other NNRTIs

The HIV-1-specific oxathiin carboxanilide derivative 1-methylethyl 2-chloro-5-[[(5,6-dihydro-2-methyl-1,4-oxathiin-3-yl)carbonyl]amino]benzoate (NSC 615985) (designated UC84) has potent activity against HIV-1(IIIB) (50% effective concentration: 0.015 μg ml−1). UC84 was found to select for a 138-Lys mutant virus strain in HIV-1-infected CEM cell cultures. When the 138-Lys mutation was introduced solely in the p51 subunit of the p51/p66 reverse transcriptase (RT) heterodimer by site-directed mutagenesis, the enzyme proved 10-fold more resistant to UC84 than when the amino acid mutation was introduced solely in the p66 subunit of the p51/p66 RT heterodimer. These data provided clear evidence for a structural and functional role of the p51 subunit in the sensitivity/resistance of the enzyme to UC84. UC84 also proved to be virtually inactive against mutant HIV-1 strains containing the 100-lle, 106-Ala, 138-Lys or 181-Cys mutation in their RT. However, minor structural changes in the molecule, such as replacement of the oxygen of the amide moiety by sulfur, or the isopropyl ester moiety by cyclopentyl or a secondary butyl, or the methyl group of the oxathiin part by ethyl, made the compound markedly more inhibitory to one or several HIV-1 mutant strains. For example, compound 131 (1-methylethyl 2-chloro-5-[[(5,6-dihydro-2-methyl-1,4-oxathiin-3-yl)thioxomethyl]amino]benzoate was only 2-fold more active than the parent compound UC84 against wild-type HIV-1, but 30- to 100-fold more inhibitory to HIV-1 mutant strains that contained the 100-11e, 106-A1a, 138-Lys or 181-Cys in their RT. These findings should be taken into account when selecting suitable drug candidates for the treatment of HIV-1 infections, particularly those that have developed resistance to other non-nucleoside RT inhibitors (NNRTIs).

Synthesis and anti-HIV Evaluation of Alkyl and Alkoxyethyl Phosphodiester AZT Derivatives

A series of new AZT conjugates with alkyl and oxyalkyl ether phospholipids was synthesized and evaluated for inhibitory activities against HIV-1 and HIV-2. The alkoxyethyl derivatives 6a-c proved 3- to 5-fold more active against HIV-1 and HIV-2 than the alkyl analogues 6d-f. A trend for higher activity with longer alkyl side-chains was observed. However, the analogues with the shortest chain possessed the most favourable therapeutic index.

Antiviral Activity of N4-Aminocytidine Derivatives Related to AZT

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.

Comparative Anti-Retrovirus and Anti-Hepadnavirus Activity of Three Different Classes of Nucleoside Phosphonate Derivatives

The prototype compounds of three different classes of nucleoside phosphonates [i.e. 9-(2-phosphonomethoxyethyl)adenine (PMEA), 9-(2-phosphonomethoxyethoxy)adenine (PMEoA) and 9-[(2R,5R)-2,5-dihydro-5-(phosphonomethoxy)-2-furanyl]adenine (D4API)] were investigated and compared for their antiviral activities. The three test compounds showed a marked inhibition of human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) in CEW and MT-4 cell cultures [50% effective concentration (EC50): 0.8-14μm]. D4API was 2- and 15-fold more inhibitory than PMEA and PMEoA, respectively. In contrast, the activity of PMEA against human hepatitis B virus (HHBV) in human hepatoma Hep G2 2.2.15 cells was 5- and 10-fold more pronounced than the activities of PMEoA and D4API, respectively (EC50 1.2μm versus 10 and 6 μm, respectively). The inhibitory activity of D4API against Moloney murine sarcoma virus (MSV)-induced C3H/3T3 cell transformation was superior to the activities of PMEA and PMEoA by at least one order of magnitude (EC50 for D4API 1.3μM, versus 2.8 and 14 μM for PMEA and PMEoA, respectively). The markedly greater inhibitory effect of D4API on MSV in vitro was in agreement with our In vivo findings that D4API inhibited MSV-induced tumour formation in newborn mice and delayed the MSV-associated animal death at a lower dose than PMEA or PMEoA. Both PMEA and D4API emerged as promising compounds that warrant further investigation for their anti-retrovirus and anti-hepadnavirus activities in vivo.

Phenotypic Resistance of Herpes Simplex Virus Type 1 Strains Selected in Vitro with Antiviral Compounds and Combinations Thereof

Several drug-resistant herpes simplex virus type 1 (HSV-1) strains were obtained under the selective pressure of various antiherpetic drugs used alone or in combination. Their susceptibility to a wide range of antiviral compounds was determined. Strains selected under the pressure of brivudin (BVDU) or 1-β-D-arabinofuranosyl-( E)-5-(2-bromovinyl)uracil (BVaraU) alone were composed of two virus populations: (1) virus resistant to BVDU and BVaraU but not to acyclovir (ACV) or ganciclovir (GCV), which is suggestive of an alteration in the thymidylate kinase activity associated with the viral thymidine kinase (TK) (responsible for the phosphorylation of BVDU-monophosphate to BVDU-diphosphate); and (2) virus resistant to BVDU, BVaraU, ACV and GCV, which is indicative of an alteration in the viral TK activity that converts BVDU, BVaraU and other nucleoside analogues such as ACV and GCV to their monophosphate derivatives. Strains resistant to TK-dependent drugs (i.e. ACV, GCV, BVDU and BVaraU) as well as double-mutant strains with decreased sensitivity to both TK-dependent compounds and the pyrophosphate analogues foscarnet (PFA) and phosphonoacetic acid (PAA) (suggestive of mutations at the level of the DNA polymerase) were recovered under the selective pressure of ACV alone or in combination with BVDU or BVaraU. Combinations of BVDU or BVaraU with PFA or PAA led to strains resistant only to BVDU and BVaraU or double-mutant strains resistant to BVDU, BVaraU and the pyrophosphate analogues, but not to strains resistant to other TK-dependent drugs. Interestingly, strains resistant to ACV, BVDU, GCV and/or the pyrophosphate analogues PFA and PAA remained sensitive to the (S)-3-hydroxy-2-phosphonylmethoxypropyl (HPMP) derivatives of cytosine (HPMPC) and adenine (HPMPA).

Inhibitory Effect of Pyridobenzoazoles on Orthomyxo-and Paramyxovirus Replication in vitro

Among thirteen newly synthesized pyridobenzoazole derivatives which have been examined for anti-myxovirus and antiherpesvirus activities, three benzimidazoles emerged as potent anti-orthomyxo- or paramyxovirus compounds. 4-Cyano-2-benzamide-1-oxo-1,5-dihydropyrido[1,2a]benzimidazole (CBO-PB) showed broad antiviral activities against paramyxo-and orthomyxoviruses with EC50 of 0.1–2.0 μg ml−1, and 2-cyano-1-amino derivatives of CBO-PB (CCI-PB) were inhibitory to paramyxoviruses at 1.4–8.5 (μg ml−1 by a plaque reduction method. The third compound, 2-ethoxycarbonyl derivatives of CCI-PB was inhibitory only to respiratory syncytial virus (RSV) at 15–28 μg ml−1. Selectivity indexes of these 3 compounds for RSV in HeLa cells were 60, 86, and >13, respectively. All three compounds inhibited syncytium formation of RSV and Parainfluenzavirus (PFLUV) type 3 at comparable concentrations with EC50 for plaque formation. They inhibited antigen production of RSV and PFLUV at the concentrations that were 4 to 20-fold higher than those needed for plaque reduction, but they did not inhibit adsorption of virus to cells at all. All three compounds inhibited the growth of RSV in HeLa cells at 4-fold higher concentrations than their EC50 for plaque reduction.

Novel Nucleoside Phosphoramidates as Inhibitors of HIV: Studies on the Stereochemical Requirements of the Phosphoramidate Amino Acid

Novel phosphoramidate derivatives of the anti-HIV nucleoside analogue d4T were designed to act as labile membrane-soluble prodrugs of the bio-active free nucleotide d4TMP. We herein reveal the very marked dependence of the antiviral activity of these phosphoramidates upon the stereochemistry of the amino acid attached to the phosphate centre; with a strong preference for the L-stereochemistry. These phosphate triesters were shown to liberate amino acid derivatives of the nucleotide intracellularly. These novel analogues, typified by alaninyl d4T monophosphate, may act as intracellular sources of the free nucleotides. The alaninyl d4T adducts themselves exert an antiviral effect when administered extracellularly, but again with clear distinctions between the L- and D-series. This evidence indicates that extracellularly administered blocked triesters derived from L-amino acids can generate d4TMP intracellularly, by a new pathway which is highly dependent on the amino acid stereochemistry.

Antiviral Activity of low-MW Dextran Sulphate (Derived from dextran MW 1000) Compared to Dextran Sulphate Samples of Higher MW

Dextran sulphate inhibits the replication of enveloped viruses (such as retro-, herpes-, toga, arena-, rhabdo-, orthomyxo- and paramyxoviruses), but is inactive against non-enveloped viruses (such as polio, Coxsackie and reovirus). Within the molecular weight (MW) range of 10000–50000, not much variation was observed in the antiviral potencies of different dextran sulphate (DS) samples, irrespective of the virus examined. However, in contrast with the higher MW samples, the low MW DS sample (prepared from dextran with a MW of 1000) was virtually inactive against herpes simplex virus type 1 and type 2, vesicular stomatitis virus, vaccinia virus, influenza A virus, respiratory syncytial virus and togaviruses (Sindbis, Semliki Forest). It was 10–20-fold less active than the higher MW samples against cytomegalovirus and arenaviruses (Junin, Tacaribe). The inhibitory potency of the 1000 MW DS sample against human immunodeficiency virus (HIV) varied considerably depending on the virus strain and cell type. When examined in MT-4 cells, the 1000 MW DS sample was 7000-, 1000-, 200- or 10-fold more inhibitory to HIV-1HE than HIV-2EHO, HTLV-IIIB, HTLV-IIIRF and LAV-2ROD, respectively. In CEM cells, however, HIV-1HE was less sensitive to the inhibitory effect of the 1000 MW DS sample than HIV-2EHO, equally sensitive as HTLV-IIIB and fivefold more sensitive than LAV-2ROD.

New Polyacetal Polysulphate Active against Human Immunodeficiency Virus and other Enveloped Viruses

A new polyacetal polysulphate, termed PAPS, was synthesized starting from dextran through oxidation, reduction, and subsequent sulphation. PAPS inhibited HIV-1- and HIV-2-induced cytopathicity in MT-4 cells at concentrations comparable to those required for dextran sulphate (MW5000) to inhibit the cytopathicity of these viruses (50% inhibitory concentration: 0.4–0.04 μg ml−1). At these concentrations PAPS had no anticoagulant activity. PAPS suppressed syncytium formation between MOLT-4 cells and persistently HIV-1- or HIV-2-infected HUT-78 cells at a concentration of 1 μg ml−1, that is 25- to 30-fold lower than that required for dextran sulphate to inhibit syncytium formation. Like dextran sulphate, PAPS inhibited HIV-1 binding to the cells and anti-gp120 mAb binding to HIV-1 gp120. Also, PAPS proved equally active as dextran sulphate against herpes simplex virus, cytomegalovirus and the arenaviruses Junin and Tacaribe, and 10-fold more active than dextran sulphate against vaccinia, Sindbis, influenza A, and vesicular stomatitis virus. Neither PAPS nor dextran sulphate proved inhibitory to the non-enveloped viruses polio, Coxsackie and reovirus. Pharmacokinetic studies in rabbits revealed that after intravenous bolus injection the serum concentrations of PAPS decayed biphasically, with an initial half-life of approximately 45–60 min. Twenty-four hours following their intraperitoneal administration to mice, PAPS as well as dextran sulphate generated low titres of an antiviral principle that was at least partially interferon-like.

Screening of Compounds for Activity against HIV: A Collaborative Study

The collaborative study was undertaken to examine the sensitivity of a range of tests used in assessing the antiviral activities of compounds against human immunodeficiency virus (HIV). A panel of 20 compounds with diverse antiviral activities against HIV were tested under code at three antiviral testing centres supported by the Medical Research Council's AIDS Directed Programme and at the European Community Centralised Facility (ECCF) for New Antiviral Compounds against AIDS in Belgium. Compounds known to have major anti-HIV activity ranked high in all assays, with the exception of the glucosidase inhibitors and certain nucleoside analogues. Results of two assays based on MT4 cells (centre IV) showed a high degree of similarity, despite the use of distinct HIV-1 (HTLV-IIIB) and HIV-2 (ROD) viruses. Considerable similarity was also observed between the assays based on HTLV-IIIRF in C8166 cells (centres I and II). Other assays performed at centre II and at centre III had enhanced sensitivity for glycosidase inhibitors. The differences in anti-HIV activity that were observed may be attributable to specific properties of the cell lines used and particular testing methodologies. The use of more than one type of assay is advisable in order not to miss compounds with low to moderate activity against HIV.

Mechanism of the Antiviral Activity of New Aurintricarboxylic Acid Analogues

Various new aurintricarboxylic acid (ATA) polymer analogues have been evaluated for their antiviral activity against a wide array of DNA and RNA viruses, and their mechanism of action against human cytomegalovirus (HCMV) and human immunodeficiency virus type 1 (HIV-1). Most of the polymers exhibited marked antiviral activity against a variety of enveloped viruses, but not against non-enveloped viruses. The ATA polymers displayed the most pronounced activity against HIV-1, HCMV and human herpesvirus type 6 (HHV-6). Their action against HCMV and HIV could be ascribed to inhibition of the initial attachment of virus particles to the cells. Using radiolabelled virus, we proved that the polymers inhibit the binding of HCMV to HEL fibroblasts. By flow cytometric analysis, we demonstrated that these new polymers interfere with (i) the binding of OKT4A monoclonal antibody (mAb) to the cellular CD4 receptor, (ii) the binding of anti-gp120 mAb to HIV-1 glycoprotein (gp) 120, and (iii) the adsorption of HIV-1 virions and recombinant HIV-1gp120 (rgp120) to MT-4 cells. The presence of a salicylic acid substituent on the central bridging carbon in the parent compound ATA seems to play an important role in the anti-HIV activity of these ATA related polymer analogues.

Activity of a Sulfated Polysaccharide Extracted from the Red Seaweed Aghardhiella Tenera against Human Immunodeficiency Virus and Other Enveloped Viruses

A galactan sulfate (GS) was isolated from an aqueous extract of the red seaweed Aghardhiella tenera and partially purified. GS inhibited the cytopathic effect of human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) in MT-4 cells at concentrations 10-fold higher than those required for the inhibition by dextran sulfate (MW 5000) of the cytopathic effect of HIV-1 and HIV-2 (50% inhibitory concentrations: 0.5 and 0.05 μg ml−1, respectively). GS suppressed syncytium formation between MOLT-4 cells and persistently HIV-1- or HIV-2-infected HUT-78 cells at concentrations higher than 5 μg ml−1. Like dextran sulfate (DS) and aurintricarboxylic acid (ATA), GS inhibited the binding of HIV-1 to the cells and the binding of anti-gp120 mAb to HIV-1 gp120. Like DS and ATA, GS proved active not only against HIV-1 and HIV-2 but also against other enveloped viruses, i.e. herpes-, toga-, arena-, myxo- and rhabdoviruses. GS represents a natural polysaccharide with broad-spectrum activity against a number of important viral pathogens.

Sulphated Cyclodextrins are Potent anti-HIV Agents Acting Synergistically with 2′,3′-dideoxynucleoside Analogues

Sulphated cyclodextrins proved to be potent inhibitors of human immunodeficiency virus (HIV), cytomegalovirus (CMV) and herpes simplex virus (HSV) but not other enveloped viruses (i.e. Sindbis virus, respiratory syncytial virus, Tacaribe virus, vesicular stomatitis virus or vaccinia virus). Their mechanism of action against HIV can be attributed to an inhibition of the binding of HIV-1 virions to the cells, as demonstrated by flow cytometric analysis. The sulphated cyclodextrins enhanced the anti-HIV-1 activity of pyrimidine 2′,3′-dideoxyribosides (i.e. azidothymidine, dideoxycytidine, didehydro-dideoxythymidine, fluorodide-oxychlorouridine), in a subsynergistic manner, and the anti-HIV-1 activity of purine 2′,3′-dideoxyribosides (dideoxyadenosine, dideoxyinosine, 2,6-diaminopurine dideoxyriboside) and 9-(2-phosphonylmethoxyethyl)adenine in a synergistic manner. Following intravenous administration of the sulphated cyclodextrins to rabbits, drug serum concentrations were obtained that were 100- to 1000-fold above the minimum inhibitory concentration for HIV or CMV.

Antiviral Portrait Series: 4. Polysuifates as Inhibitors of HIV and Other Enveloped Viruses

Polysulfates are highly potent and selective inhibitors of the in vitro replication of HIV and other enveloped viruses. They not only inhibit the cytopathic effect of HIV, but also prevent HIV-induced syncytium (giant cell) formation. They also act synergistically with other anti-HIV drugs. The anti-HIV activity of polysulfates is a result of their shielding of the positively charged sites in the V3 loop of the viral envelope glycoprotein gp120. When polysulfates were administered intravenously to rabbits, their half-life was approximately 2h. Although they are very poorly absorbed following oral administration, they can be made orally bioavailable with the appropriate chemical modifications. Also, polysulfates may lose (much of) their anticoagulant activity upon chemical modification without giving up their anti-HIV activity. Their efficacy in the therapy and/or prophylaxis of retroviral infections remains to be demonstrated both in animal models and in humans.

Side-Chain Derivatives of Biologically Active Nucleosides. Part 2: Synthesis and anti-HIV Activity of 5′-C-Methyl Derivatives of 3′-Fluoro-3′-Deoxythymidine

1-(3′-Fluoro-2′,3′,6′-trideoxy-β-D-allofuranosyl)thymine [7] and 1-(3′-fluoro-2′,3′,6′-trideoxy-α-L-talofuranosyl) thymine [8] were synthesized starting from the corresponding 2,3′-anhydro nucleoside derivatives. The fluorine was introduced stereoselectively by opening of the anhydro bridge in the presence of HF/AIF3. The 5′-C-methyl derivatives, [7] and [8], of 3′-fluoro-3′-deoxythymidine (FLT) were evaluated for their inhibitory effect against human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2). The compounds [7] and [8] had antiviral activity which was three orders of magnitude lower than the reference compound 3′-fluoro-3′-deoxythymidine. None of the compounds showed appreciable activity against other RNA or DNA viruses at subtoxic concentrations.

The Thiocarboxanilides UC-10 and UC-781 Have an Additive Inhibitory Effect against Human Immunodeficiency Virus Type 1 Reverse Transcriptase and Replication in Cell Culture When Combined with other Antiretroviral Drugs

The thiocarboxanilides represent a structural class of potent and selective human immunodeficiency virus type 1 (HIV-1)-specific reverse transcriptase (RT) inhibitors. Combinations of the clinical candidate thiocarboxanilides UC-10 (oxime ether derivative) and UC-781 (pentenyloxy ether derivative) with a variety of nucleoside RT inhibitors (NRTIs) and non-nucleoside RT inhibitors (NNRTIs), two HIV protease inhibitors and one fusion/uncoating inhibitor were evaluated for their inhibitory effects on HIV-1 RT activity and HIV-1 replication in CEM cell cultures. The inhibitory activity of the NNRTIs including UC-10, UC-781, nevirapine, BHAR α-APA, 8-chloro-TIBO, MKC-442 and the quinoxaline HBY 097 against HIV-1 RT was highly dependent on the nature of the template/primer used in the HIV-1 RT reaction. However, fractionary inhibitory concentration (FIC) indexes for all drug concentrations evaluated in the combination experiments of UC-781 and the other NNRTIs fell within the range 0.5–1.5. This points to a predominantly additive effect of the thiocarboxanilides and other NNRTIs in the inhibition of HIV-1 RT. Similar FIC indexes were observed for the combination of UC-781 with the NRTI triphosphates AZT-TP, d4T-TP, ddCTP, ddATP and 3TC-TP and the NRTI diphosphate PMEApp against HIV-1 RT. All these drug combinations showed similar additive inhibitory effects on HIV-1 replication in cell culture. Also, the combinations of UC-10 or UC-781 with the protease inhibitors Ro31–8959/008 and ABT 84538.0 and the fusion/uncoating inhibitor bicyclam JM 3100 showed an additive effect (FIC within the 0.5–1.5 range). Thus, irrespective of the nature of the drugs, their combination with the thiocarboxanilides proved merely additive. In no case were antagonistic anti-HIV activity or increased cytotoxicity observed. In conclusion, thiocarboxanilides combined with a variety of clinically used anti-HIV agents result in additive anti-HIV activity.

Inhibition of HIV-1-Induced Cytopathogenicity, Syncytium Formation, and Virus-Cell Binding by Naphthalenedisulphonic Acids through Interaction with the Viral Envelope gp120 Glycoprotein

Bis-naphthalenedisulphonic acid derivatives with a biphenyl spacer, 4,4′-[4,4′-biphenyldiylbis(sulphonyl-amino)]bis(5-hydroxy-2,7-naphthalenedisulphonic acid) and 3,3′-[4,4′-biphenyldiylbis(sulphonyl-amino)]bis(1,5-naphthalenedisulphonic acid), have previously been reported as potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) replication in cell culture. These compounds have also proved inhibitory to syncytium formation in cocultures of MOLT-4 cells with HIV-1-infected HUT-78 cells. They also inhibit the binding of HIV-1 virions to MT-4 cells as determined by a flow cytometric (FACS) method. Further studies on their mechanism of action by the FACS have revealed that the compounds inhibit the binding of anti-gp120 monoclonal antibody to the viral envelope glycoprotein gp120. Binding of OKT4A/Leu3a monoclonal antibody to the cellular CD4 receptor is not affected by the compounds. These results suggest that the anti-HIV-1 activity of the naphthalenedisulphonic acid derivatives can be attributed to inhibition of the gp120-CD4 interaction through binding of the compounds to the viral gp120 antigen.

Anti-HIV Activities of Anionic Metalloporphyrins and Related Compounds

Various water-soluble polysulphonated and polycarboxylated porphyrins and some of their metallated derivatives have been prepared and their antiviral properties against human immunodeficiency virus (HIV-1, HIV-2), simian immunodeficiency virus and other viruses are reported. Besides these polyanionic compounds, two new series of porphyrins were included and studied from the perspective of bio-availability modulation: (i) acefylsulphonamido derivatives endowed with weak acidity properties (deprotonation gives the corresponding anionic derivatives in a pH range 4.5-8.5) and (ii) compounds with the anionic charge transiently masked by esterification (acetoxymethyl- and pivaloyloxymethylesters). Among the more active compounds in inhibiting HIV-induced cytopathic effects, the sulphonated and carboxylated porphyrin complexes were found to interact directly with the HIV protein gp 120 and not with the CD4 cellular receptor.

Dipyridamole Potentiates the Activity of Various Acyclic Nucleoside Phosphonates against Varicella-Zoster Virus, Herpes Simplex Virus and Human Cytomegalovirus

Dypiridamole (DPM) is widely used in the treatment of cardiovascular diseases as a coronary vasodilator and inhibitor of platelet aggregation. Phosphonylmethoxyethyl (PME) and 3-hydroxy-2-phosphonylmethoxypropyl (HPMP) derivatives of purines and pyrimidines are potent and selective inhibitors of varicella-zoster virus (VZV), herpes simplex virus (HSV) and human cytomegalovirus (HCMV). We have found that DPM markedly potentiates the antiviral effects of the PME derivatives of adenine (PMEA) and 2,6-diaminopurine (PMEDAP), and of the HPMP derivatives of adenine (HPMPA), 3-deazaadenine (HPMPc3A) and cyclic HPMPA (cHPMPA). This was reflected by a significant decrease in the 50% inhibitory concentration of the acyclic nucleoside phosphonates for VZV-, HSV- and HCMV-induced cytopathic effect or plaque formation. DPM did not enhance the activity of vidarabine, acyclovir or ganciclovir. These results were confirmed by virus yield assays (for HSV and HCMV) and flow cytometry (for VZV).

Differential Activity of Polyanionic Compounds and Castanospermine against HIV Replication and HIV-Induced Syncytium Formation Depending on Virus Strain and Cell Type

Polyanionic compounds [i.e. pentosan polysulphate, dextran sulphate, heparin, suramin, and aurintricarboxylic acid (ATA)] and castanospermine were examined for their inhibitory effect on human immunodeficiency virus (HIV) strains (HIV-1IIIB, HIV-1RF, HIV-2ROD and HIV-2EHO) in two different assays (HIV cytopathicity in MT-4 cells and HIV antigen expression in CEM cells). In the MT-4 assay dextran sulphate and pentosan polysulphate were more active against HIV-2ROD, suramin was more active against HIV-1RF, and ATA more active against HIV-2EHO-Heparin was less, but castanospermine was more, active against the two HIV-2 strains. In the CEM assay dextran sulphate and suramin were equally active against all HIV strains, pentosan polysulphate was more active against both HIV-2 strains, whereas heparin was less active against HIV-2ROD and ATA again was more active against HIV-2EHO. The compounds and soluble CD4 (sCD4) were also tested in the HIV-induced syncytium formation assay, where chronically infected HUT-78 cells were mixed with uninfected MOLT-4 or CEM cells. The inhibitory effect of suramin and ATA on syncytium formation was independent of the virus strain or cell type. For dextran sulphate and pentosan polysulphate, it was dependent on virus strain, and for heparin, castanospermine, and sCD4, it was dependent on both the virus strain and cell type.

Differential Susceptibility of Several Drug-Resistant Strains of Herpes Simplex Virus Type 2 to Various Antiviral Compounds

Drug-resistant herpes simplex virus type 2 (HSV-2) strains were obtained under the selective pressure of acyclovir, ganciclovir, brivudin, foscamet, 2-phosphonyl-methoxyethyl (PME) derivatives of adenine (PMEA) and 2,6-diaminopurine (PMEDAP), and 3-hydroxy-2-phosphonylmethoxypropyl (HPMP) derivatives of adenine (HPMPA) and cytosine (HPMPC; cidofovir). A significant degree of cross-resistance between HPMPC and HPMPA on the one hand, and between PMEA, PMEDAP and foscarnet on the other, was noted, suggesting a different mode of interaction of the PME and HPMP derivatives at the DNA polymerase level. The results described here with HSV-2 agree with the published results for HSV-1 and human cytomegalovirus.

A Comparative Study of 5-ethyl-2′-Deoxyuridine and Selected Lipophilic 5,6-Dihydro Double/Triple Prodrugs

(+)- Trans-(5R,6R)-5-bromo-5-ethyl-6-ethoxy-5,6-dihydro-5′-O-valeryl-2′-deoxyuridine (3) and (+)- trans-(5R,6R)-5-bromo-5-ethyl-6-ethoxy-5,6-dihydro-3′,5′-di-O-valery[-2′-deoxyuridine (4) were synthesized in 55% and 8.6% yield, respectively, by esterification of the 5′-hydroxyl group of (+)- trans-(5R,6R)-5-bromo-5-ethyl-6-ethoxy-5,6-dihydro-2′-deoxyuridine (2) using valeryl chloride. [4-14C]-3 and [4-14C]-4 were synthesized in 79% and 64% chemical and radiochemical yield, respectively, by similar esterifications of [4-14C]-2.

The double prodrug 3 was readily hydrolysed (> 95% in 8 min) to 5-ethyl-2′-deoxyuridine (EDU) by porcine liver esterase in vitro. The biotransformations of 2 and 3 were studied following i.v. injection of a 0.4 mmol/kg i.v. dose to male Balb/c mice. The single prodrug 2 was rapidly cleared (<10 min) from the blood. The area under the blood concentration-time curve (AUC) for EDU, as a metabolite of 2, was higher (2.1 ± 0.4 μmol.h.g−1) than the AUC observed when EDU itself was injected (1.7 ± 0.2 μmol.h.g−1). The double prodrug 3 provided a sustained high concentration of EDU in blood, with an AUC for EDU, as a metabolite of 3, of 1.8 ± 0.2 μmol.hr.g−1. 5′-O-Valeryl-5-ethyl-2′-deoxyuridine and 3 were both detected in blood samples collected up to 35 min post i.v. injection. 5-Ethyluracil and 5-(1-hydroxyethyl)-uracil were identified as secondary metabolites of EDU, 2 and 3. Compared to [4-14C]-EDU, i.v. injection of [4-14C]-3 or [4-14C]-4 provided significantly higher (P < 0.001) radioactivity levels in the brain, but neither EDU, 2 or 3 protected mice against intracerebral herpes simplex virus infection.

Hepatic uptakes of 2, 3 and 4, in mice, were similar to each other despite the respective substantial increases in both molecular weight and lipophilicity of this series. In rats, biliary excretion over the 0-4 h period after i.v. injection accounted for only 2.9-3.9% of the injected dose for these prodrugs.

Antiviral Activity of Bicyclic Pyrimidine Nucleosides

A number of pyrimidine nucleosides, which may show two hydrogen bonding modes, have been prepared and tested for antiviral activity against a series of viruses. Whilst none of the compounds described showed significant activity against human immunodeficiency virus (HIV), the bicyclic 2′-deoxynucleoside, [2], derived from the base 6H,8H-3,4-dihydropyrimido[4,5-c][1,2]oxazin-7-one, was shown to inhibit herpes simplex virus type 1 (HSV-1) at similar concentrations as BVDU1 and ACV. Compounds 13, 6-(2-deoxyribofuranosyl)-6H,8H-2-methyl-3,4-dihydropyrimido[4,5-c][1,2]oxazin-7-one, and 14, N4-hydroxy-5-(2-chloroethyl)-2′-deoxyuridine, were as active as ACV against varicella-zoster virus (VZV).

Public Health Triangulation to inform decision-making in Belgium

We assessed the impact of a nation-wide ambulatory care complex intervention (the "care trajectory program") on quality of care in Belgium. We used the three-step public health triangulation method described in this paper and data from four different data sources: a national reimbursement database, an electronic patient record-based general practitioner network, the Belgian general practitioner sentinel network, and a new national registry for care trajectory patients. By applying our method and using the available evidence, we identified key findings that have been accepted by experts and stakeholders. We also produced timely recommendations for the decision-making process, four years after the start of the care trajectory program.

EPR-based, quality-related process parameters: a nationwide assessment

The aim of the study was to determine whether or not primary care EPR-based data can be used to measure specific process parameters that can then, in turn, be used to assess the quality of care provided to chronic patients. We analysed data from a large research network that collects data from all Belgian GP practices through both manual and automatic extraction procedures. We built a number of quality-related process parameters and observed the concordance of our results with two external databases: a nationwide reimbursement database and a regional EPR-based network. We found that only the automatic data extraction method was suitable for building process parameters. The current research network may lead to an underestimation of the quality of care processes. We suggested ways to improve this network.