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Biomedical subjects

Jan Balzarini

Publications and source records attributed to Jan Balzarini.

At least 127 records · Page 7Linked to original sources
PubMed2004

Synthesis and antiviral activity of novel fluorinated 2',3'-dideoxynucleosides.

A series of 5-(trifluoroethoxymethyl)-2',3'-dideoxyuridines and 5-[bis(trifluoroethoxy)-methyl]-2',3'-dideoxyuridines have been prepared and screened for antiviral activity. The conformations of these compounds are discussed on the bases of NOE studies and the MO calculations. Modelling and NOE studies suggest both syn- and anti conformations for these 5-(2,2,2-trifluoroethoxymethyl)- and 5-[bis(2,2,2-trifluoroethoxy)-methyl]- derivatives. The NOE parameters are also suggested to be more attributable to the nature of the fluorine atom than to structural or conformational changes. Compounds 17, 26 and 30 showed some activity in anti-HIV-1 and anti-HIV-2 assays, but the compounds were devoid of activity against HSV and human rhinovirus. The compounds tested exhibited low cytotoxicity and were inactive against a bank of cancer cells in vitro.

Antiviral Agents↗
PubMed2004

How a modification (8-aza-3-deaza-2'-deoxyguanosine) influences the quadruplex structure of Hotoda's 6-mer TGGGAG with 5'- and 3'-end modifications.

We have synthesized a modified 6-mer using Hotoda's 6-mer TGGGAG with 5'- and 3'-end modifications as a template. We have replaced from one to all four 2'-deoxyguanosines by 8-aza-3-deaza-2'-deoxyguanosine (c3z8dG, 1) in order to investigate the anti-HIV structure activity relationship (SAR). ODN 4 (TGGG*AG) is the only one that exhibits a moderate anti-HIV-1 activity.

Anti-HIV Agents↗
PubMed2004

Second generation of cycloSal-pronucleotides with esterase-cleavable sites: the "lock-in"-concept.

A conceptual extension of the cycloSal-pronucleotide approach is presented. The characteristic feature of the new cycloSal-derivatives of the anti-HIV active nucleoside analogue d4T 1 is the incorporation of an enzymatically cleavable carboxylic ester moiety with the intention to trap the triesters inside cells ("lock-in"-concept). CycloSal-triesters bearing different ester groups in the 3-or 5-position of the cycloSal-moiety are described. Surprisingly, only acetyl-and levulinyl esters are cleaved readily in CEM cell extracts while alkyl esters were found to be stable. Nevertheless, in in-vitro anti-HIV assays most of the compounds achieve the thymidine-kinase bypass, thus proving that they act at least as nucleotide delivery systems.

Esterases↗
PubMed2004

Synthesis and biological evaluation of novel 1'-branched and spironucleoside analogues.

Novel anomeric spironucleosides and 1'-cyano-2',3'-didehydro-2',3'-dideoxyuridine, a structural analogue of known anti-HIV agents, were prepared by nucleophilic addition of organolithium reagents to 1'-cyano-2'-deoxy- and 1'-cyano-2'-deoxy-2'beta-bromo-uridine derivatives, respectively. The yield and distribution of products depended on the reaction conditions, which were studied in detail. Although none of the compounds exhibited antiviral activity, two compounds displayed cytostatic activity against both murine leukemia and human T-lymphocyte cells.

Antiviral Agents↗
PubMed2004

Thiosugars. XII. Synthesis of new 3'-O-substituted 2',5'-anhydro-2'-thio-alpha-D-pentofuranosyl nucleoside analogues.

Methyl 2,5-anhydro-3-O-(2-methoxyethyl)-2-thio-beta-D-arabinofuranoside and methyl 2,5-anhydro-3-O-(2-fluorobenzyl)-2-thio-alpha-D-lyxofuranoside were transformed into the corresponding uridine, thymidine, cytidine and adenosine analogues, which exclusively exhibited the alpha-configuration irrespective of the anomeric configuration of the donor. The structure, configuration, and conformation of the products was elucidated by X-ray structure analyses. The nucleoside analogues were tested for antiviral activities.

Antiviral Agents↗
PubMed2004

Synthesis and antiviral activity of 1-substituted 3-(3,5-dimethylbenzyl)uracil against HIV-1.

1,3-disubstituted uracils were obtained from uracil by the stepwise alkylation at N-1 and N-3 position with alkyl halide/alkali or alcohol under Mitsunobu conditions. The antiviral activity against HIV-1 of these compounds was examined to find that 1-cyanomethyl-3-(3,5-dimethylbenzyl)uracil and 1-phenyl-3-(3,5-dimethyl-benzyl)uracil showed powerful inhibition.

Antiviral Agents↗
PubMed2004

Susceptibility of feline immunodeficiency virus/human immunodeficiency virus type 1 reverse transcriptase chimeras to non-nucleoside RT inhibitors.

To map the determinants of the lack of susceptibility of feline immunodeficiency virus (FIV) reverse transcriptase (RT) to anti human immunodeficiency virus type 1 (HIV-1) non-nucleoside RT inhibitors (NNRTIs), a variety of chimeric HIV-1/FIV RTs were constructed. The majority of chimeric RTs had an affinity (Km) for their natural substrates comparable with that of the wild-type HIV-1 and FIV RTs, but their catalytic efficacy was decreased. Whereas HIV-1 RT could be made entirely insensitive to NNRTIs by exchanging the amino acid sequence 97 through 205 of FIV RT, none of the reverse FIV/HIV-1 RT chimeras gained susceptibility to NNRTIs. The amino acids that are thought to be involved in NNRTI susceptibility and that are different from those in HIV-1 RT have also been introduced in FIV RT. These mutant RTs gained virtually no susceptibility to efavirenz or capravirine. Vice versa, when these HIV-1-specific amino acids were replaced by their FIV RT counterparts in HIV-1 RT, susceptibility to the NNRTIs was lost. Thus, replacing segments or substituting relevant amino acids in FIV RT by their HIV-1 RT counterparts did not suffice to make FIV RT sensitive toward NNRTIs and was often accompanied by a decrease or even total loss of polymerase activity. It is postulated that, in contrast to the results found for HIV-1/HIV-2 RT chimeras and supported by the crystal structure of HIV-2 RT, there exist significant differences in the structure and/or flexibility of FIV RTs that may prevent NNRTIs from interacting with the FIV RT.

Amino Acid Sequence↗
PubMed2004

Crystal structures of the mitochondrial deoxyribonucleotidase in complex with two specific inhibitors.

Monophosphate nucleotidases are enzymes that dephosphorylate nucleotides to their corresponding nucleosides. They play potentially important roles in controlling the activation of nucleotide-based drugs targeted against viral infections or cancer cells. The human mitochondrial deoxyribonucleotidase (dNT-2) dephosphorylates thymidine and deoxyuridine monophosphates. We describe the high resolution structures of the dNT-2 enzyme in complex with two potent nucleoside phosphonate inhibitors, (S)-1-[2'-deoxy-3',5'-O-(1-phosphono) benzylidene-beta-d-threo-pentofuranosyl]thymine (DPB-T) at 1.6-A resolution and (+/-)-1-trans-(2-phosphonomethoxycyclopentyl)uracil (PMcP-U) at 1.4-A resolution. The mixed competitive inhibitor DPB-T and the competitive inhibitor PMcP-U both bind in the active site of dNT-2 but in distinctly different binding modes, explaining their different kinetics of inhibition. The pyrimidine part of the inhibitors binds with very similar hydrogen bond interactions to the protein but with their phosphonate moieties in different binding sites compared with each other and to the previously determined position of phosphate bound to dNT-2. Together, these phosphate/phosphonate binding sites describe what might constitute a functionally relevant phosphate entrance tunnel to the active site. The structures of the inhibitors in complex with dNT-2, being the first such complexes of any nucleotidase, might provide important information for the design of more specific inhibitors to control the activation of nucleotide-based drugs.

5'-Nucleotidase↗
PubMed2004

In vitro evaluation of nonnucleoside reverse transcriptase inhibitors UC-781 and TMC120-R147681 as human immunodeficiency virus microbicides.

The nonnucleoside reverse transcriptase inhibitors UC-781 and TMC120-R147681 (Dapivirine) effectively prevented human immunodeficiency virus (HIV) infection in cocultures of monocyte-derived dendritic cells and T cells, representing primary targets in sexual transmission. Both drugs had a favorable therapeutic index. A 24-h treatment with 1,000 nM UC-781 or 100 nM TMC120-R147681 prevented cell-free HIV infection, whereas 10-fold-higher concentrations blocked cell-associated HIV.

Anilides↗
PubMed2004

Mannose-specific plant lectins from the Amaryllidaceae family qualify as efficient microbicides for prevention of human immunodeficiency virus infection.

The plant lectins derived from Galanthus nivalis (Snowdrop) (GNA) and Hippeastrum hybrid (Amaryllis) (HHA) selectively inhibited a wide variety of human immunodeficiency virus type 1 (HIV-1) and HIV-2 strains and clinical (CXCR4- and CCR5-using) isolates in different cell types. They also efficiently inhibited infection of T lymphocytes by a variety of mutant virus strains. GNA and HHA markedly prevented syncytium formation between persistently infected HUT-78/HIV cells and uninfected T lymphocytes. The plant lectins did not measurably affect the antiviral activity of other clinically approved anti-HIV drugs used in the clinic when combined with these drugs. Short exposure of the lectins to cell-free virus particles or persistently HIV-infected HUT-78 cells markedly decreased HIV infectivity and increased the protective (microbicidal) activity of the plant lectins. Flow cytometric analysis and monoclonal antibody binding studies and a PCR-based assay revealed that GNA and HHA do not interfere with CD4, CXCR4, CCR5, and DC-SIGN and do not specifically bind with the membrane of uninfected cells. Instead, GNA and HHA likely interrupt the virus entry process by interfering with the virus envelope glycoprotein. HHA and GNA are odorless, colorless, and tasteless, and they are not cytotoxic, antimetabolically active, or mitogenic to human primary T lymphocytes at concentrations that exceed their antivirally active concentrations by 2 to 3 orders of magnitude. GNA and HHA proved stable at high temperature (50 degrees C) and low pH (5.0) for prolonged time periods and can be easily formulated in gel preparations for microbicidal use; they did not agglutinate human erythrocytes and were not toxic to mice when administered intravenously.

Agglutinins↗
PubMed2004

The phenylmethylthiazolylthiourea nonnucleoside reverse transcriptase (RT) inhibitor MSK-076 selects for a resistance mutation in the active site of human immunodeficiency virus type 2 RT.

The phenylmethylthiazolylthiourea (PETT) derivative MSK-076 shows, besides high potency against human immunodeficiency virus type 1 (HIV-1), marked activity against HIV-2 (50% effective concentration, 0.63 microM) in cell culture. Time-of-addition experiments pointed to HIV-2 reverse transcriptase (RT) as the target of action of MSK-076. Recombinant HIV-2 RT was inhibited by MSK-076 at 23 microM. As was also found for HIV-1 RT, MSK-076 inhibited HIV-2 RT in a noncompetitive manner with respect to dGTP and poly(rC).oligo(dG) as the substrate and template-primer, respectively. MSK-076 selected for A101P and G112E mutations in HIV-2 RT and for K101E, Y181C, and G190R mutations in HIV-1 RT. The selected mutated strains of HIV-2 were fully resistant to MSK-076, and the mutant HIV-2 RT enzymes into which the A101P and/or G112E mutation was introduced by site-directed mutagenesis showed more than 50-fold resistance to MSK-076. Mapping of the resistance mutations to the HIV-2 RT structure ascertained that A101P is located at a position equivalent to the nonnucleoside RT inhibitor (NNRTI)-binding site of HIV-1 RT. G112E, however, is distal to the putative NNRTI-binding site in HIV-2 RT but close to the active site, implying a novel molecular mode of action and mechanism of resistance. Our findings have important implications for the development of new NNRTIs with pronounced activity against a wider range of lentiviruses.

Amino Acid Sequence↗
PubMed2004

Profile of resistance of human immunodeficiency virus to mannose-specific plant lectins.

The mannose-specific plant lectins from the Amaryllidaceae family (e.g., Hippeastrum sp. hybrid and Galanthus nivalis) inhibit human immunodeficiency virus (HIV) infection of human lymphocytic cells in the higher nanogram per milliliter range and suppress syncytium formation between persistently HIV type 1 (HIV-1)-infected cells and uninfected CD4(+) T cells. These lectins inhibit virus entry. When exposed to escalating concentrations of G. nivalis and Hippeastrum sp. hybrid agglutinin, a variety of HIV-1(III(B)) strains were isolated after 20 to 40 subcultivations which showed a decreased sensitivity to the plant lectins. Several amino acid changes in the envelope glycoprotein gp120, but not in gp41, of the mutant virus isolates were observed. The vast majority of the amino acid changes occurred at the N glycosylation sites and at the S or T residues that are part of the N glycosylation motif. The degree of resistance to the plant lectins was invariably correlated with an increasing number of mutated glycosylation sites in gp120. The nature of these mutations was entirely different from that of mutations that are known to appear in HIV-1 gp120 under the pressure of other viral entry inhibitors such as dextran sulfate, bicyclams (i.e., AMD3100), and chicoric acid, which also explains the lack of cross-resistance of plant lectin-resistant viruses to any other HIV inhibitor including T-20 and the blue-green algae (cyanobacteria)-derived mannose-specific cyanovirin. The plant lectins represent a well-defined class of anti-HIV (microbicidal) drugs with a novel HIV drug resistance profile different from those of other existing anti-HIV drugs.

Amino Acid Substitution↗
PubMed2004

Bicyclic nucleoside inhibitors of varicella-zoster virus modified on the sugar moiety: 3' and 5' derivatives.

Bicyclic furanopyrimidine nucleoside analogues (BCNAs) have been previously reported as potent and selective anti-varicella-zoster virus (VZV) agents. Few modifications on the sugar moiety have been considered so far but some of them have shown interesting activity against human cytomegalovirus (HCMV) while losing activity against VZV. In addition, recent work has led to an entirely new series of anti-HCMV bicyclic furopyrimidine agents, acting through a non-nucleoside mechanism. In order to further investigate structure-activity relationship studies on the sugar moiety, some 3'- and 5'-chloro derivatives and 5'-deoxygenated derivatives have been synthesized. The lack of anti-VZV activity of the 5'-modified derivatives is further proof of a mechanism of action involving VZV thymidine kinase (TK)-mediated phosphorylation. Similarly, the replacement of the 3'-OH with chlorine showed a decrease of antiviral activity, which can be correlated to the lack of interaction with VZV TK as demonstrated by enzyme assays. These results confirm free 5'-OH and 3'-OH as necessary requirements for efficient recognition by VZV TK and for potent anti-VZV activity in cell culture.

Antiviral Agents↗
PubMed2004

Aryloxy phosphoramidate triesters as pro-tides.

We herein describe the development of aryloxy phosphoramidate triesters as an effective pro-tide motif for the intracellular delivery of charged bio-active antiviral nucleoside monophosphates. The review covers the discovery of such aryl phosphoramidates, their mechanism of action and structure-activity relationships. The application of this strategy to a range of antiviral nucleosides is highlighted.

Amides↗
PubMed2004

"Lock-in"-cycloSal-pronucleotides - a new generation of chemical Trojan Horses?

The cycloSal-concept is one example of a successful nucleotide delivering system (pronucleotide). For several nucleoside analogues, the cycloSal-approach improved the antiviral potency and the applicability of the nucleosides could be broadened. Here, a conceptional extension of the original design of the cycloSal-system will be discussed.

Antiviral Agents↗
PubMed2004

TSAO compounds: the comprehensive story of a unique family of HIV-1 specific inhibitors of reverse transcriptase.

Emergence of drug-resistant viral strains is one of the major milestones and the main cause for the failure of antiretroviral therapy. Combination of different anti-HIV agents has become the standard clinical practice to keep the viral load at low or even undetectable levels and to prevent emergence of virus-drug resistance. Among the human immunodeficiency virus (HIV) reverse transcriptase (RT) inhibitors, the so called nonnucleoside RT inhibitors (NNRTIs) have gained a definitive place in the treatment of HIV infections in combination with nucleoside analogue RT inhibitors (NRTIs) and HIV protease inhibitors (PIs). The virus can be markedly suppressed for a relatively long period of time when exposed to multiple drug combination therapy (highly active antiretroviral therapy, HAART). TSAO derivatives are a peculiar group of highly functionalized nucleosides that belong to the so-called nonnucleoside RT inhibitors (NNRTIs). They exert their unique selectivity for HIV-1 through a specific interaction with the p51 subunit of HIV-1 RT. They are the first small molecules that seem to interfere with the dimerization process of the enzyme. This review covers the work carried out with this unique class of specific inhibitors of HIV-1 reverse transcriptase, including structure activity relationship studies (SAR), its mechanism of action, resistance studies, model of interaction with the enzyme, etc.

Anti-HIV Agents↗
PubMed2003

Synthesis and biological evaluation of iodinated and fluorinated 9-(2-hydroxypropyl) and 9-(2-hydroxyethoxy)methyl purine nucleoside analogues.

The novel fluorinated and iodinated purine derivatives containing 9-(2-hydroxypropyl) (1a-7a and 9a-13a) and 9-(2-hydroxyethoxymethyl) (1b-3b, 5b, and 7b-12c) side chains were synthesized by a multistep synthetic route involving Baltz-Schiemann's fluorination and diazotation/iodination as key reactions. An unequivocal proof for the stereostructure of 5b was obtained by X-ray structure analysis. New compounds were evaluated for their cytostatic activity against murine leukemia (L1210); mammary carcinoma (FM3A); and human T-lymphocytes (Molt4/C8 and CEM), melanoma (HBL), cervical carcinoma (HeLa), colon carcinoma (HT29 and SW620), laryngeal carcinoma (Hep2), and pancreatic carcinoma (MiaPaCa2) as well as diploid fibroblasts (WI38). Of all the compounds, the 2-aminopurin-6-thione derivative 9a showed the most pronounced inhibitory activity against human SW620 cells. The 2-aminopurin-6-thione derivative 9b exhibited the most selective inhibitory activity against human HeLa, Hep2, SW620, and murine L1210 cell proliferation as compared to normal fibroblast (WI38) cell proliferation. None of the compounds showed inhibitory activities against HIV-1, HIV-2, HSV-1, and HSV-2, vaccinia, vesicular stomatitis, parainfluenza-3, reovirus-1, Sindbis, Coxsackie B4, or respiratory syncytial virus. The new purine derivatives, and particularly 9a and 9b, appear to demonstrate sufficient cytostatic potency and selectivity to justify further evaluation of their potential.

Animals↗