Biomedical subjects

Jan Balzarini

Publications and source records attributed to Jan Balzarini.

At least 163 records · Page 9Linked to original sources

PubMed2003

Thiosugars. X. Novel nucleoside analogues derived from 4-thio-L-lyxofuranose.

1-O-Acetyl-2,3,5-tri-O-benzyl-4-thio-L-lyxofuranose 1 was transformed into O-benzyl- and O-acetyl-protected 1-(4-thio-L-lyxofuranosyl) nucleoside derivatives by use of the TMSOTf method. Debenzylation with boron tribromide or deacetylation with sodium methoxide yielded the corresponding pyrimidine (7-11, 17, 18, 26 and 27) and purine (29 and 34) nucleoside analogues. The anomeric configurations were determined by NMR spectroscopy and, in the case of the 5-halo- (7-9) and nitrouridine derivative 11 and the 6-methylcytidine derivative 27, by X-ray structural analyses.--The unprotected nucleosides were not anti-virically inhibitory at 250 microM.

Antiviral Agents↗

PubMed2003

Non-nucleoside inhibitors of mitochondrial thymidine kinase (TK-2) differentially inhibit the closely related herpes simplex virus type 1 TK and Drosophila melanogaster multifunctional deoxynucleoside kinase.

5'-O-Trityl derivatives of thymidine (dThd), (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU), and their acyclic analogs 1-[(Z)-4-triphenylmethoxy-2-butenyl]thymine (KIN-12) and (E)-5-(2-bromovinyl)-1-[(Z)-4-triphenylmethoxy-2-butenyl]uracil (KIN-52) have been synthesized and evaluated for their inhibitory activity against the amino acid sequence related mitochondrial dThd kinase (TK-2), herpes simplex virus type 1 (HSV-1) TK, and Drosophila melanogaster multifunctional 2'-deoxynucleoside kinase (Dm-dNK). Several compounds proved markedly inhibitory to these enzymes and represent a new generation of nucleoside kinase inhibitors. KIN-52 was the most potent and selective inhibitor of TK-2 (IC(50), 1.3 microM; K(i), 0.50 microM; K(i)/K(m), 0.37) but was not inhibitory against HSV-1 TK and Dm-dNK at 100 microM. As found for the alternative substrate BVDU, the tritylated compounds competitively inhibited the three enzymes with respect to dThd. However, whereas BVDU behaved as a noncompetitive inhibitor (alternative substrate) of TK-2 and HSV-1 TK with respect to ATP as the varying substrate, the novel tritylated enzyme inhibitors emerged as reversible purely uncompetitive inhibitors of these enzymes. Computer-assisted modeling studies are in agreement with these findings. The tritylated compounds do not act as alternative substrates and they showed a type of kinetics against the nucleoside kinases different from that of BVDU. KIN-12, and particularly KIN-52, are the very first non-nucleoside specific inhibitors of TK-2 reported and may be useful for studying the physiological role of the mitochondrial TK-2 enzyme.

Adenosine Triphosphate↗

PubMed2003

Characterization of the transport of nucleoside analog drugs by the human multidrug resistance proteins MRP4 and MRP5.

The human multidrug resistance proteins MRP4 and MRP5 are organic anion transporters that have the unusual ability to transport cyclic nucleotides and some nucleoside monophosphate analogs. Base and nucleoside analogs used in the chemotherapy of cancer and viral infections are potential substrates. To assess the possible contribution of MRP4 and MRP5 to resistance against these drugs, we have investigated the transport mediated by MRP4 and MRP5. In cytotoxicity assays, MRP4 conferred resistance to the antiviral agent 9-(2-phosphonomethoxyethyl)adenine (PMEA) and high-performance liquid chromatography analysis showed that, like MRP5, MRP4 transported PMEA in an unmodified form. MRP4 also mediated substantial resistance against other acyclic nucleoside phosphonates, whereas MRP5 did not. Apart from low-level MRP4-mediated cladribine resistance, the cytotoxicity of clinically used anticancer nucleosides was not influenced by overexpression of MRP4 or MRP5. In contrast, MRP5 mediated efflux of the pyrimidine-based antiviral 2',3'-dideoxynucleoside 2',3'-didehydro-2',3'-dideoxythymidine 5'-monophosphate (d4TMP) and its phosphoramidate derivative alaninyl-d4TMP from cells loaded with the 2',3'-didehydro-2',3'-dideoxythymidine prodrugs cyclosaligenyl-d4TMP and aryloxyphosphoramidate d4TMP (So324), respectively. Moreover, only inside-out membrane vesicles derived from MRP5-overexpressing cells accumulated alaninyl-d4TMP. Cellular efflux and vesicular uptake studies were carried out to further compare transport mediated by MRP4 and MRP5 and showed that dipyridamole, dilazep, nitrobenzyl mercaptopurine riboside, sildenafil, trequinsin and MK571 inhibited MRP4 more than MRP5, whereas cyclic nucleotides and monophosphorylated nucleoside analogs were equally poor inhibitors of both pumps. These results strongly suggest that the affinity of MRP4 and MRP5 for nucleotide-based substrates is low.

Acrylates↗

PubMed2003

Novel human immunodeficiency virus (HIV) inhibitors that have a dual mode of anti-HIV action.

We have found that novel pyridine oxide derivatives are inhibitors of a wide range of human immunodeficiency virus (HIV) type 1 (HIV-1) and HIV-2 strains in CEM cell cultures. Some of the compounds showed inhibitory activities against recombinant HIV-1 reverse transcriptase (RT), whereas others were totally inactive against this viral protein in vitro. Partial retention of anti-HIV-1 activity against virus strains that contain a variety of mutations characteristic of those for resistance to nonnucleoside RT inhibitors and a lack of inhibitory activity against recombinant HIV-2 RT suggested that these pyridine oxide derivatives possess a mode of antiviral action independent from HIV RT inhibition. Time-of-addition experiments revealed that these pyridine oxide derivatives interact at a postintegration step in the replication cycle of HIV. Furthermore, it was shown that these compounds are active not only in acutely HIV-1-infected cells but also in chronically HIV-infected cells. A dose-dependent inhibition of virus particle release and viral protein expression was observed upon exposure to the pyridine oxide derivatives. Finally, inhibition of HIV-1 long terminal repeat-mediated green fluorescence protein expression in quantitative transactivation bioassays indicated that the additional target of action of the pyridine oxide derivatives may be located at the level of HIV gene expression.

Amino Acid Substitution↗

PubMed2003

Inhibition of human immunodeficiency virus by a new class of pyridine oxide derivatives.

A new class of pyridine oxide derivatives as inhibitors of human immunodeficiency virus type 1 (HIV-1) and/or HIV-2 replication in cell culture has been identified. The compounds, which specifically inhibit HIV-1, behave as typical nonnucleoside reverse transcriptase inhibitors (NNRTIs). The most active congener of this group, JPL-133 (UC-B3096), has a 50% effective concentration of 0.05 microg/ml for HIV-1(III(B)) with a selectivity index of approximately 760 in CEM cell cultures. However, the cytostatic activity of most pyridine oxide derivatives highly depended on the nature of the cell line. All compounds, including those pyridine oxide derivatives that inhibit both HIV-1 and HIV-2 replication, select for NNRTI-characteristic mutations in the HIV-1 reverse transcriptase of HIV-infected cell cultures (i.e., Lys103Asn, Val108Ile, Glu138Lys, Tyr181Cys and Tyr188His). These amino acid mutations emerged mostly through transition of guanine to adenine or adenine to guanine in the corresponding codons of the reverse transcriptase (RT) gene. The HIV-1-specific pyridine oxide derivatives lost their antiviral activity against HIV-1 strains containing these mutations in the RT. However, most compounds retained pronounced antiviral potency against virus strains that contained other NNRTI-characteristic RT mutations, such as Leu100Ile and Val179Asp. Furthermore, the complete lack of inhibitory activity of the pyridine oxide derivatives against recombinant HIV-2 RT and partial retention of anti-HIV-1 activity against HIV-1 strains that contain a variety of HIV-1-characteristic mutations suggest that the pyridine oxide derivatives must have a second target of antiviral action independent from HIV-1 RT.

Amino Acid Substitution↗

PubMed2003

Synthesis, solution conformation and anti-HIV activity of novel 3'-substituted-2',3'-dideoxy-5-hydroxymethyluridines and their 4,5-substituted analogues.

To decrease the toxicity of potent anti-HIV nucleosides 3'-azido-2',3'-dideoxythymidine (AZT) and 2',3'-dideoxy-3'-fluorothymidine (3'-FddThd, FLT), their new analogues, 3'-azido-2',3'-dideoxy-5-hydroxymethyluridine (3'-Az5HmddUrd) and 2',3'-dideoxy-3'-fluoro-5-hydroxymethyluridine (3'-F5HmddUrd), were synthesized. The reaction of 3'-azido-2',3'-dideoxyuridine (3'-AzddUrd) and 2',3'-dideoxy-3'-fluorouridine (3'-FddUrd) with formaldehyde, under strongly alkaline conditions and at elevated temperature, proceeded after 4 days to completion to afford the corresponding 5-hydroxymethyl derivatives 3'-Az5HmddUrd and 3'-F5HmddUrd in good yield. These compounds were also prepared by oxidation of AZT and FLT with the use of K2S2O8. 1H NMR analyses were subjected to the series of 3', 4 and 5-substituted pyrimidine 2'-deoxy- and 2',3'-dideoxynucleosides involving 3'-Az5HmddUrd and 3'-F5HmddUrd. Analysis of the sugar furanose ring puckering demonstrated that all 3'-fluorine derivatives exhibited strong domination of the S conformation (approximately 100%) while 3'-substitution by electron-donating groups, such as NH2, increased population of the N conformation. Experimentally observed substituent effect on the furanose ring puckering equilibrium was reconstructed in the 100 ps molecular dynamic trajectories obtained for AZT, FLT, dThd, 2',3'-ddThd and 3'-amino-2',3'-ddThd. It may be concluded that anti-HIV activity is linked to a direct interaction of the 3'-substituent with reverse transcriptase (RT) binding site. Anti-HIV activities of 3'-Az5HmddUrd and 3'-F5HmddUrd are lower than activity of AZT and FLT; however, 3'-Az5HmddUrd and 3'-F5HmddUrd are less toxic than AZT and FLT.

Anti-HIV Agents↗

PubMed2003

Synthesis and antiviral activity of some 5'-N-phthaloyl-3'-azido-2',3'-dideoxythymidine analogues.

A variety of substituted 5'-N-phthaloyl-3'-azido-2',3'-dideoxythymidine derivatives has been evaluated for their activity against HIV-1, HIV-2 and Moloney murine sarcoma virus (MSV) in cell culture. Most of the 3'-azido-2',3'-dideoxythymidine (AZT, zidovudine) derivatives showed antiviral activity in the lower micromolar concentration range and there was a close correlation between their anti-HIV and anti-MSV activity (r = 0.99). The adamantyl phthaloyl derivative was active at submicromolar concentrations. None of the compounds showed marked cytostatic activity. They did not inhibit recombinant HIV-1 reverse transcriptase. All compounds were inactive against HIV in thymidine kinase-deficient cells, pointing to the compounds' requirement to release free AZT to afford antiviral efficacy.

Animals↗

PubMed2003

Halophenyl furanopyrimidines as potent and selective anti-VZV agents.

Bicyclic furano pyrimidines have been previously reported by us to be highly potent and selective inhibitors of varicella zoster virus (VZV). p-Alkyl phenyl analogues are particularly potent with EC50 values below 1 nM. In this article we report the synthesis and anti-VZV activity of a series of halophenyl analogues, with variation in the nature (F, Cl, Br) and location (o, m, p) of the halogen substituent. The compounds show a range of activities from ca. 10 nM to > 50 microM. In most cases, ortho substitution leads to greatest activity, meta substitution is in general poor, and the effect of p-substitution shows a marked dependence on the halogen atom. The p-fluorophenyl compound is unique amongst compounds of this class in being inactive as an antiviral. The possible origins of these marked SARs are discussed.

Antiviral Agents↗

PubMed2003

Synthesis and antiviral activities of 3-aralkylthiomethylimidazo[1,2-b]pyridazine derivatives.

The synthesis of novel substituted 3-aralkylthiomethylimidazo[1,2-b]pyridazines is reported. All of the synthesized compounds are devoid of antiviral activity against the replication of human immunodeficiency virus. However, compounds 6-chloro-8-methyl-3-phenethylthioimidazo[1,2-b]pyridazine and 6-chloro-2-methyl-3-phenethylthioimidazo[1,2-b]pyridazine are potent inhibitors of the replication of human cytomegalovirus in vitro, while compounds 6-chloro-2-methyl-3-benzylthiomethylimidazo[1,2-b]pyridazine and 6-chloro-2-methyl-3-phenethyl-thioimidazo[1,2-b]pyridazineare inhibitors of the replication of varicella-zoster virus. The results presented here suggest that compound 10 should be considered as a new lead in the development of antiviral agents.

Antiviral Agents↗

PubMed2003

Design and synthesis of phosphonoacetic acid (PPA) ester and amide bioisosters of ribofuranosylnucleoside diphosphates as potential ribonucleotide reductase inhibitors and evaluation of their enzyme inhibitory, cytostatic and antiviral activity.

Continuing our investigations on inhibitors of ribonucleotide reductase (RNR), the crucial enzyme that catalyses the reduction of ribonucleotides to deoxyribonucleotides, we have now prepared and evaluated 5'-phosphonoacetic acid, amide and ester analogues of adenosine, uridine and cytidine with the aim to verify both substrate specificity and contribution to biological activity of diphosphate mimic moieties. A molecular modelling study has been conducted on the RNR R1 subunit, in order to verify the possible interaction of the proposed bioisosteric moieties. The study compounds were finally tested on the recombinant murine RNR showing a degree of inhibition that ranged from 350 microM for the UDP analogue 5'-deoxy-5'-N-(phosphon-acetyl)uridine sodium salt (amide) to 600 microM for the CDP analogue 5'-O-[(diethyl-phosphon)acetyl]cytidine (ester). None of the tested compounds displayed noteworthy cytostatic activity at 100-500 microM concentrations, whereas ADP analogue 5'-N-[(diethyl-phosphon) acetyl]adenosine (amide) and 5'-deoxy-5'-N-(phosphon-acetyl)adenosine sodium salt (amide) showed a moderate inhibitory activity (EC50: 48 microM) against HSV-2 and a modest inhibitory activity (EC50: 110 microM) against HIV-1, respectively.

Amides↗

PubMed2003

Structure-activity relationship studies on a novel family of specific HIV-1 reverse transcriptase inhibitors.

We have previously reported the discovery and preliminary structure-activity relationships of a new class of specific HIV-1 reverse transcriptase (RT) inhibitors whose prototype compound is the 1-[2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3-N-[(carboxy) methyl]-thymine. In an attempt to increase the inhibitory efficacy against HIV-1 RT of this new class of nucleosides, and to further explore the structural features required for anti-HIV-1 activity, different types of modifications have been carried out on the prototype compound. These include substitution of the tert-butyldimethylsilyl groups by other liphophilic groups, replacement of the carboxy group at the N-3 position of the nucleobase by other functional groups, change in the length of the spacer between the thymine and the carboxylic acid residue and substitution of the thymine moiety by other pyrimidine (uracil, 5-ethyluracil) or purine (hypoxanthine) nucleobases. In addition, the most salient structural features of this new class of HIV-1-specific nucleosides have been incorporated into classical HIV RT nucleoside inhibitors such as ddl, AZT, d4T. Our studies demonstrate that both the carboxymethyl moiety at the nucleobase and tert-butyldimethylsilyl groups at the sugar are important structural components since deletion of either of them is detrimental to the antiviral activity.

Anti-HIV Agents↗

PubMed2003

Synthesis and antiviral activity of 1,3-disubstituted uracils against HIV-1 and HCMV.

The development of new non-nucleoside reverse transcriptase inhibitors (NNRTIs) is an efficient strategy for finding new therapeutic agents against human immunodeficiency virus (HIV). A large number of 6-substituted uracil derivatives have been prepared in order to explore new NNRTIs. However, there are few approaches to anti-HIV agents from 1,3-disubstituted uracil derivatives. Therefore, we tried to prepare several 1,3-disubstituted uracils, which were easily obtainable from uracil by preparation under alkali and Mitsunobu conditions, and examined their antiviral activity against HIV-1 and human cytomegalovirus (HCMV). We found that 1-benzyl-3-(3,5-dimethylbenzyl)uracil and 1-cyanomethyl-3-(3,5-dimethylbenzyl)-4-thiouracil showed powerful inhibition against HCMV and HIV-1, respectively.

Antiviral Agents↗

PubMed2003

Carbocyclic analogues of nucleosides from bis-(Hydroxymethyl)-cyclopentane: synthesis, antiviral and cytostatic activities of adenosine, inosine and uridine analogues.

Six new carbocyclic nucleosides were prepared by constructing a purine base (in compounds 9-11) or pyrimidine base (in 6-8) on the amino groups of (+/-)-(1 beta,2 alpha,4 beta)-4-amino-1,2-cyclopentanedimethanol (4) and (+/-)-(1 beta,3 alpha,4 beta)-4-amino-1,3-cyclopentanedimethanol (5), and their activities against a variety of viruses and tumour cell lines were determined.

Adenosine↗

PubMed2003

Nonnucleoside HIV-1 reverse transcriptase inhibitors: Part I. Synthesis and structure-activity relationship of 1-alkoxymethyl-5-alkyl-6-naphthylmethyl uracils as HEPT analogues.

1-alkoxymethyl-5-alkyl-6-naphthylmethyl uracils, which are novel 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) analogues, were synthesized for evaluation as selective and potent nonnucleoside human immunodeficiency virus (HIV)-1 reverse transcriptase inhibitors. The anti-HIV-1 activity of these compounds was assayed in vitro using HIV-1 infected MT-4 and CEM bioassays. The EC50, CC50 and SI were recorded and calculated. The appropriate position, especially in the 1-position of the naphthyl ring, led to dramatic increases in potency, in both MT-4 and CEM cellular assays. The most important compounds in this series, 1-ethoxymethyl-5-isopropyl-6-(1-naphthylmethyl)thymine 8l (IC50=17 nM, CC50=38332 nM, SI=2229) and 1-benzyloxymethyl-5-ethyl-6-(1-naphthylmethyl)thymine 8n (IC50=17 nM, CC50=32560 nM, SI=1889) were significantly more potent than HEPT (EC50=7.0 microM, CD50=740 microM) in the anti-HIV-1 in vitro cellular assay.

Cell Line↗

PubMed2002

A thymidine phosphorylase-stable analogue of BVDU with significant antiviral activity.

(E)-5-(2-Bromovinyl)isodideoxyuridine (BVisoDDU), synthesized on the basis of molecular modeling, is selectively active against HSV-1 (three different strains) but inactive against HSV-2. Unlike BVDU, BVisoDDU is completely resistant to cleavage by thymidine phosphorylase. BVisoDDU is also the first nucleoside analogue lacking OH groups at both the 2'- and 3'-position that shows pronounced activity against HSV-1 replication.

Antiviral Agents↗

PubMed2002

Design, synthesis, structure-activity relationships, and molecular modeling studies of 2,3-diaryl-1,3-thiazolidin-4-ones as potent anti-HIV agents.

Starting from 1H,3H-thiazolo[3,4-a]benzimidazoles (TBZs), we performed the design, synthesis, and the structure-activity relationship studies of a series of 2,3-diaryl-1,3-thiazolidin-4-ones. Some derivatives proved to be highly effective in inhibiting HIV-1 replication at nanomolar concentrations with minimal cytotoxicity, thereby acting as nonnucleoside HIV-1 RT inhibitors (NNRTIs). Computational studies were used to delineate the ligand-RT interactions and to probe the binding of the ligands to HIV-1 RT.

Anti-HIV Agents↗

PubMed2002

Metabolic activation of nucleoside and nucleotide reverse transcriptase inhibitors in dendritic and Langerhans cells.

BACKGROUND: Langerhans cells and interstitial dendritic cells are the earliest targets for HIV infection through sexual transmission of HIV. Metabolism of nucleoside analogues markedly differs in proliferating T lymphocytes and resting monocyte/macrophages, and thus their antiviral efficacy can substantially differ between both cell types. METHODS: The metabolism of radio-labelled zidovudine (ZDV), lamivudine (3TC) and tenofovir (PMPA) to their antivirally active metabolites was studied in primary cells, representative of early in vivo targets of HIV [i.e. monocyte-derived dendritic cells (MO-DC), MO-derived Langerhans cells (MO-LC), PHA/IL-2-activated T-blast cells] as well as in a laboratory T-lymphocyte (CEM) cell line. RESULTS: Whereas lamivudine metabolism to its active triphosphate derivative (3TC-TP) did not markedly differ between T-cells and MO-derived LC and DC, zidovudine was much better converted to ZDV-TP in T-cells than in MO-LC and MO-DC. In contrast, tenofovir was markedly more abundantly converted to its antivirally active diphosphate metabolite PMPApp in MO-DC and MO-LC than zidovudine and lamivudine. CONCLUSION: Our metabolic data suggest that tenofovir may be superior to zidovudine and lamivudine for inhibition of HIV replication in dendritic/Langerhans cells, the first-line cell types targeted by a primary HIV infection.

Adenine↗

PubMed2002

Synthesis and biological activity of strongly fluorescent tricyclic analogues of acyclovir and ganciclovir.

In search of strongly fluorescent tricyclic analogues of acyclovir (ACV, 1) and ganciclovir (GCV, 2), derivatives of the 3,9-dihydro-9-oxo-5H-imidazo[1,2-a]purine system, several 6-[4-(acyloxy)phenyl], 6-[4-(acylamino)phenyl], and 6-[4-(phenoxycarbonyloxy)phenyl]-substituted TACV and TGCV analogues were synthesized and evaluated for their activity against herpes simplex virus types 1 and 2 in cell culture. All TACV and TGCV analogues showed strong fluorescence (quantum yield of 30-65% vs 2-aminopurine 100%). The 6-[4-(phenoxycarbonyloxy)phenyl]-substituted compounds 11 and 19 displayed the best combination of the fluorescence and antiviral potency.

Acyclovir↗