Biomedical subjects

J Balzarini

Publications and source records attributed to J Balzarini.

At least 253 records · Page 14Linked to original sources

PubMed1996

Marked inhibitory activity of non-nucleoside reverse transcriptase inhibitors against human immunodeficiency virus type 1 when combined with (-)2',3'-dideoxy-3'-thiacytidine.

Human immunodeficiency virus type 1 (HIV-1)-infected CEM cells were treated (as single agents or in combination) with (minus)-2', 3'-dideoxy-3'-thiacytidine (3TC) and the following HIV-1-specific non-nucleoside reverse transcriptase (RT) inhibitors (NNRTIs): 2', 5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5'-(4'-amino-1',2'-oxathi ole)-2',2'-dioxide derivative of 3-methylthymidine (TSAO-m3T), the thiocarboxanilides UC10 and UC42, bis(heteroaryl)piperazine (BHAP) derivative U90152, and the 1-(2-hydroxyethoxymethyl)-6-(phenylthio)thymine (HEPT) derivative 5-isopropyl-1-ethoxymethyl-6-benzyluracil (MKC-442). When used individually, the compounds led to the emergence of HIV-1 strains containing the following mutations in the RT: Glu138 to lysine for TSAO-m3T, Met184 to valine for 3TC, Lys103 to threonine/asparagine for the thiocarboxanilides, and Tyr181 to cysteine for BHAP and MKC-442. When 3TC was combined with TSAO-m3T, UC10, UC42, BHAP, or MKC-442, breakthrough of virus was markedly delayed or even suppressed. For these drug combinations, the concentrations of the individual drugs could be lowered by > or = 25-50-fold to suppress virus breakthrough compared with the individual use of the compounds. The concomitant presence of the Lys138 and Ile/Val184 mutations was found in the RT of the mutant viruses that emerged with combination therapy of the lowest concentrations of 3TC with either the lowest concentrations of TSAO-m3T or UC10 (approximately 0.5-3-fold the EC50 value). These virus strains retained high sensitivity to other NNRTIs such as BHAP or HEPT. The virus mutants that arose in the presence of combinations of the lowest concentrations of 3TC with either BHAP or HEPT predominantly contained the Cys181 mutation in the RT. In one case, the Ile181 mutation was found. The latter mutations, particularly the Ile181 mutation, resulted in markedly decreased sensitivity to the NNRTIs but not to 3'-azido-2', 3'-dideoxythymidine or 3TC.

Base Sequence↗

PubMed1996

Potent inhibition of human immunodeficiency virus and herpes simplex virus type 1 by 9-(2-phosphonylmethoxyethyl)adenine in primary macrophages is determined by drug metabolism, nucleotide pools, and cytokines.

The efficacy of 9-(2-phosphonylmethoxyethyl)adenine (PMEA) against the replication of human immunodeficiency virus (HIV) and herpes simplex virus type 1 (HSV-1) and its cellular metabolism were investigated in human primary macrophages from seronegative donors. PMEA potently inhibited the replication of both HIV and HSV-1 in macrophages, with similar EC50 values (0.025 and 0.032 microM, respectively), whereas the EC50 values of PMEA in lymphocytic C8166 cells and fibroblastoid Vero cells were 150-200-fold higher (3.5 and 7.9 microM, respectively). Granulocyte/macrophage colony-stimulating factor and macrophage colony-stimulating factor, two cytokine enhancers of the replication of HIV (and HSV-1), decreased the activity of PMEA against both viruses, yet EC50 values were still lower than in lymphocytes and fibroblasts. Thus, the selectivity index of PMEA in macrophages was > 2 orders of magnitude higher than that in lymphocytes and fibroblasts and still > 1 log higher under conditions of enhancement of virus replication in macrophages. The intracellular levels of 2'-deoxyadenosine-5'-triphosphate, the natural competitor of PMEA-diphosphate at the level of viral DNA polymerase (either RNA or DNA dependent), were 5-12-fold lower in macrophages than in other cells. Furthermore, intracellular concentrations of PMEA-diphosphate (the active metabolite of PMEA) were unusually much higher in macrophages (with or without cytokines) than in lymphocytes and fibroblasts. Consequently, the ratio of PMEA-diphosphate to 2'-deoxyadenosine-5'-triphosphate in monocytes/macrophages was approximately 2 orders of magnitude higher in macrophages than in the other cells and correlated closely with the pronounced antiviral potency of PMEA. The dual potent activity of PMEA against HIV and HSV-1 stresses the importance of clinical trials to assess the role of this drug in the therapy of HIV-related disease.

Adenine↗

PubMed1996

Highly favorable antiviral activity and resistance profile of the novel thiocarboxanilide pentenyloxy ether derivatives UC-781 and UC-82 as inhibitors of human immunodeficiency virus type 1 replication.

The novel human immunodeficiency virus type 1-specific thiocarboxanilide derivatives that contain either a substituted furanyl (UC-781) or thienyl (UC-82) ring linked to the thiocarboxy group and a pentenyloxyether chain linked to the 4-chlorophenyl ring in meta position show highly favorable antiviral properties. Compounds UC-781 and UC-82 discovered by scientists at Uniroyal Chemical Ltd. proved to be > or = 5-10-fold more inhibitory to wild-type human immunodeficiency virus type 1 strains (EC50 approximately 0.002 microgram/ml) than the thiocarboxanilide oxime ether UC-10 and other non-nucleoside reverse transcriptase inhibitors such as nevirapine, bis(heteroaryl)piperazine, and tetrahydroimidazo[4,5,l-jk][1,4]-benzodiazepin-2(1H)-one. In addition, the compounds were able to knock out virus replication in cell culture at concentrations that were 20-50-fold lower than those of nevirapine or bis(heteroaryl)piperazine. They were also highly efficient (EC50 < or = 0.02 microgram/ml) in suppressing the replication of mutant virus strains that contained mutations in their reverse transcriptase that conferred resistance to other non-nucleoside reverse transcriptase inhibitors (i.e., Tyr181 to Cys, Lys103 to Asn, Val106 to Ala, and Leu100 to Ile). The compounds selected for virus mutants that were only marginally resistant to the thiocarboxanilides ( < 10-20-fold). The antiviral activity of the compounds was only slightly affected by the presence of high concentrations of human serum, and the compounds were shown to be highly stable in the presence of human serum for at least 24 hr at room temperature.

Anilides↗

PubMed1996

Differences in the inhibition of human immunodeficiency virus type 1 reverse transcriptase DNA polymerase activity by analogs of nevirapine and [2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5"-(4"-amino-1", 2"-oxathiole-2",2"-dioxide] (TSAO).

We compared the inhibition of HIV-1 reverse transcriptase (RT) by 1-[2',5'-bis-O-(t-butyldimethylsilyl)-beta-D-ribofuranosyl]-3'- spiro-5"-(4"-amino-1", 2"-oxathiole-2",2"-dioxide)-3-ethylthymine (TSAOe3T) and the nonnucleoside RT inhibitor (NNRTI) 9-aminonevirapine (9-NH2N). Both compounds were equally effective against p51/p66 heterodimeric RT RNA-dependent DNA polymerase activity, although TSAOe3T was a much better inhibitor of the p51/p51 and p66/p66 RT homodimers. Inhibition by TSAOe3T and 9-NH2N combinations was essentially additive. TSAOe3T did not protect either free RT or the RT-template/ primer-deoxynucleoside triphosphate ternary complex from irreversible inactivation by the photolabel 9-azidonevirapine. Slight protection of the RT-template/primer binary complex was noted, but only at high TSAOe3T/photolabel ratios. Analysis of RT polymerization product profiles under both continuous- and single-processive cycle conditions showed that 9-NH2N prevented the formation of full-length product with a corresponding accumulation of smaller polymerization products. In contrast, all products formed in the absence of inhibitor, including full-length product, were noted in TSAOe3T-inhibited reactions, albeit at reduced levels. TSAOe3T thus inhibits HIV-1 RT by a different mechanism than NNRTI such as nevirapine. Our data suggest that TSAOe3T and 9-NH2N interact differently with HIV-1 RT, perhaps by binding to distinct sites on the enzyme.

Antiviral Agents↗

PubMed1996

Antiretrovirus specificity and intracellular metabolism of 2',3' -didehydro-2',3'-dideoxythymidine (stavudine) and its 5'-monophosphate triester prodrug So324.

2',3'-Didehydro-2',3'-dideoxythymidine (d4T) and its lipophilic 5'-monophosphate triester prodrug, So324, were evaluated for their antiretroviral and metabolic properties in four different animal species cell lines. The antiretrovirus activity of So324 was approximately 4-10-fold greater than that of d4T against human immunodeficiency virus types 1 and 2 and simian immunodeficiency virus in human T lymphocyte CEM and MT-4 cells and against feline immunodeficiency virus in feline Crandell kidney cells, 50-fold greater against visna virus in sheep choroid plexus cells, but 5-fold inferior against murine (Moloney) sarcoma virus in murine embryo fibroblast (C3H) cells. Although the administration of both d4T and So324 resulted in the formation of the 5'-monophosphate (d4T-MP), 5'-diphosphate, and 5'-triphosphate in the different cell lines, a new d4T metabolite markedly accumulated in So324-treated cells and exceeded d4T-TP levels by 13-242-fold depending on the cell line used. This metabolite could be identified as alaninyl d4T-MP. Alanyl d4T-MP may be considered to be an intracellular depot form of d4T and/or d4T-MP, which may account for the superior antiretroviral activity of the lipophilic d4T-MP triester So324 compared with d4T.

3T3 Cells↗

PubMed1996

Evidence for distinction of the differentiation-inducing activities and cytostatic properties of 9-(2-phosphonylmethoxyethyl)adenine and a variety of differentiation-inducing agents in human erythroleukemia K562 cells.

The acyclic nucleoside phosphonate derivative 9-(2-phosphonylmethoxyethyl) adenine (PMEA) is a strong inducer of differentiation in several tumor cell lines, including human erythroleukemia K562 cells. A PMEA-resistant K562 cell line (designated K562/PMEA-1) was selected in the presence of escalating PMEA concentrations. This cell line proved to be insensitive to the induction of erythroid differentiation by PMEA. It also was 108-fold resistant to the cytostatic effects of PMEA. The K562/PMEA-1 cells showed reduced sensitivity to the differentiation-inducing capacity and cytostatic activity of several closely related PMEA analogs. Furthermore, the mutant cells exhibited a decreased sensitivity to the differentiation-inducing activity of a wide variety of structurally nonrelated antimetabolites targeted at different enzymes of nucleotide biosynthesis. A 5-25-fold higher concentration of each of these compounds was required to obtain the same level of differentiation in the K562/PMEA-1 cells as in the wild-type cells. However, unlike the PMEA derivatives, the antimetabolites remained equally cytostatic for the mutant K562 cells and for the wild-type cells. Our results reveal two unique features of the K562/PMEA-1 cells: (i) specific resistance to both the differentiation-inducing and cytostatic effects of several acyclic nucleoside phosphonate analogs (which can be accounted for by a diminished cellular uptake and subsequent metabolism of the compounds) and (ii) nonspecific resistance to antimetabolites with regard to their differentiation-inducing, but not cytostatic, properties (which must reside in an unspecified alteration of a common site of the differentiation process that is shared by all of these antimetabolites).

Adenine↗

PubMed1995

The cytostatic activity of 5-(1-azidovinyl)-2'-deoxyuridine (AzVDU) against herpes simplex virus thymidine kinase gene-transfected FM3A cells is due to inhibition of thymidylate synthase and enhanced by UV light (lambda = 254 nm) exposure.

5-(1-Azidovinyl)-2'-deoxyuridine (AzVDU) and a series of 5-[1-azido-2-halogenoethyl]-derivatives of beta-D-arabinofuranosyluracil (AU) proved markedly inhibitory to the replication of herpes simplex virus type 1 (HSV-1) and varicella zoster virus (VZV), but not thymidine kinase (TK)-deficient HSV-1 and VZV strains. None of the compounds were cytostatic. However, AzVDU, but not the 5-[1-azido-2-halogenoethyl]-AU derivatives became highly cytostatic against HSV-1 and HSV-2 TK gene-transfected FM3A tumor cells. The molecular target for the cytostatic effect of AzVDU proved to be thymidylate synthase. Short exposure of AzVDU-treated FM3A TK-/HSV-1 TK+ cells to irradiation at lambda = 254 nm enhanced the cytostatic activity of AzVDU by 5-fold.

Animals↗

PubMed1995

Synthesis and antiviral activity of benzyl-substituted imidazo [1,5-a]-1,3,5-triazine (5,8-diaza-7,9-dideazapurine) derivatives.

A variety of imidazo[1,5-a]-1,3,5-triazine derivatives carrying C-, O-, and S-benzyl and/or 4-methylbenzyl groups were synthesized and examined for their inhibitory effects on the replication of ortho- and paramyxoviruses. The key compounds 8-R-2-thioxo-2,3-dihydroimidazo [1,5-a]-1,3,5-triazin-4(1H)-ones 3a,b,d were synthesized by chlorotrimethylsilane/HMDS-effected cyclization--rearrangement of the corresponding 6-amino-5-(formylamino)-5-R-2-mercaptopyrimidin-4(5H)-ones 2a,b,d (R = benzyl, 4-methylbenzyl and 5-(benzyloxy)pentyl). Compounds 3a,b were further transformed into 4-thiones 5a,b and 4-dimethylamino derivatives 7a,b. Preparation of S-methyl, S-benzyl, and S-(4-methylbenzyl) derivatives 12-19 was carried out by the treatment of thioxo compounds 3b,d, 5b, and 8b in an alcohol/potassium carbonate system with methyl iodide or the appropriate aralkyl bromide. Simultaneous presence of the benzyl and thio structural units was found to be indispensable for any selective biological activity. Some 2-thio substituted compounds were specifically inhibitory to some viruses, e.g., 8-(4-methylbenzyl)-2-[(4-methylbenzyl) thio]imidazo[1,5-a]-1,3,5-triazin-4-one (13) and 8-[5-(benzyloxy)pentyl]-2-[(4-methylbenzyl)thio]imidazo [1,5-a]-1,3,5-triazin-4-one (15) inhibited influenza A virus at a concentration of 4.1 and 5.3 microM, and 2-(benzylthio)-6, 8-dimethylimidazo[1,5-a]-1,3,5-triazin-4-one (16) and 6, 8-dimethyl-2-[(4-methylbenzyl)thio]imidazo[1,5-a]1,3, 5-triazin-4-one (17) inhibited respiratory syncytial virus at a concentration of 21.9 and 15.7 microM, respectively, that is, at concentrations that were 20-50-fold lower than the cytotoxic concentrations. Compound 13 was inhibitory to respiratory syncytial virus at a concentration of 1.4 microM, that is, at a concentration that was 180-fold lower than the cytotoxic concentration to MDCK or Vero cells but only 7-fold lower than the cytotoxic concentration to HeLa cells. The 4-thiones 5a,b were nonselectively inhibitory to ortho-and paramyxoviruses at concentrations that coincided with their cytotoxic concentrations.

Animals↗

PubMed1995

Sensitivity/resistance profile of a simian immunodeficiency virus containing the reverse transcriptase gene of human immunodeficiency virus type 1 (HIV-1) toward the HIV-1-specific non-nucleoside reverse transcriptase inhibitors.

To develop an animal model for the therapy of AIDS with human immunodeficiency virus type 1 (HIV-1)-specific reverse transcriptase (RT) inhibitors, we recently constructed a hybrid simian immunodeficiency virus (SIV)/HIV-1 in which the RT gene of SIV was replaced by the RT gene of HIV-1. This chimaeric virus, designated RT-SHIV, was found to be markedly sensitive to the inhibitory effects of both nucleoside (ddN) and non-nucleoside RT inhibitors (NNRTIs). In contrast, SIV was inhibited only by ddNs (i.e., 3TC and AZT), but not NNRTIs. When RT-SHIV was grown in the presence of 3TC, nevirapine, TSAO-m3T or the thiocarboxanilide UC-42 drug-resistant mutant virus strains emerged in cell culture as rapid as for HIV-1(IIIB). The antiviral sensitivity/resistance spectrum of the mutant RT-SHIV strains against NNRTIs and ddNs, and the nature of the mutations that appeared in their RT were similar to those of the mutant HIV-1 strains that were selected under identical experimental conditions. Infection of macaques with RT-SHIV may be a useful tool for studying the mechanism of NNRTI-resistance development and the therapy of NNRTI-resistant viruses in an animal model.

Acquired Immunodeficiency Syndrome↗

PubMed1995

Suppression of the breakthrough of human immunodeficiency virus type 1 (HIV-1) in cell culture by thiocarboxanilide derivatives when used individually or in combination with other HIV-1-specific inhibitors (i.e., TSAO derivatives).

Five structurally related thiophene and furane analogues of the oxathiin carboxanilide derivative NSC 615985 (UC84) (designated UC10, UC68, UC81, UC42, and UC16) were identified as potent inhibitors of HIV-1 replication in cell culture and HIV-1 reverse transcriptase activity. These compounds were markedly active against a series of mutant HIV-1 strains, containing the Leu-100-->Ile, Val-106-->Ala, Glu-138-->Lys, or Tyr-181-->Cys mutations in their reverse transcriptase. However, the thiocarboxanilide derivatives selected for mutations at amino acid positions 100 (Leu-->Ile), 101 (Lys-->Ile/Glu), 103 (Lys-->Thr/Asp) and 141 (Gly-->Glu) in the HIV-1 reverse transcriptase. The compounds completely suppressed HIV-1 replication and prevented the emergence of resistant virus strains when used at 1.3-6.6 microM--that is, 10- to 25-fold lower than the concentration required for nevirapine and bis(heteroaryl)piperazine (BHAP) U90152 to do so. If UC42 was combined with the [2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5"-(4"-amino-1",2"- oxathiole-2",2"-dioxide)]-beta-D-pentofuranosyl (TSAO) derivative of N3-methylthymine (TSAO-m3T), virus breakthrough could be prevented for a much longer time, and at much lower concentrations, than if the compounds were used individually. Virus breakthrough could be suppressed for even longer, and at lower drug concentrations, if BHAP was added to the combination of UC42 with TSAO-m3T, which points to the feasibility of two- or three-drug combinations in preventing virus breakthrough and resistance development.

Antiviral Agents↗

PubMed1995

Synthesis and anti-HIV activity of [AZT]-[TSAO-T] and [AZT]-[HEPT] dimers as potential multifunctional inhibitors of HIV-1 reverse transcriptase.

In an attempt to combine the HIV-inhibitory capacity of 2',3'-dideoxynucleoside (ddN) analogues and non-nucleoside reverse transcriptase (RT) inhibitors (NNRTI), we have designed, synthesized, and evaluated for their anti-HIV activity several dimers of the general formula [ddN]-(CH2)n-[NNRTI]. These dimers combine in their structure a ddN such as AZT and a NNRTI such as TSAO-T and HEPT linked through an appropriate spacer between the N-3 of the thymine base of both compounds. The [TSAO-T]-(CH2)n-[AZT] dimers proved markedly inhibitory to HIV-1. Also, if AZT was replaced by thymidine in the dimer molecules, potent anti-HIV-1 activity was observed. However, although the compounds proved inhibitory to HIV-1, they were less potent inhibitors than the parent compounds from which they were derived. None of the dimers were endowed with anti-HIV-2 activity. In contrast with the TSAO-T monomers, none of the TSAO-T-containing dimers proved markedly cytotoxic to the cells. There was a clear trend toward decreased antiviral potency with lengthening the methylene spacer in the [TSAO-T]-(CH2)n-[AZT] dimers.

Antiviral Agents↗

PubMed1995

Inhibitory effect of 9-(2-phosphonylmethoxyethyl)adenine on visna virus infection in lambs: a model for in vivo testing of candidate anti-human immunodeficiency virus drugs.

The acyclic nucleoside phosphonate analog 9-(2-phosphonylmethoxyethyl)adenine (PMEA) was recently found to be effective as an inhibitor of visna virus replication and cytopathic effect in sheep choroid plexus cultures. To study whether PMEA also affects visna virus infection in sheep, two groups of four lambs each were inoculated intracerebrally with 10(6.3) TCID50 of visna virus strain KV1772 and treated subcutaneously three times a week with PMEA at 10 and 25 mg/kg, respectively. The treatment was begun on the day of virus inoculation and continued for 6 weeks. A group of four lambs were infected in the same way but were not treated. The lambs were bled weekly or biweekly and the leukocytes were tested for virus. At 7 weeks after infection, the animals were sacrificed, and cerebrospinal fluid (CSF) and samples of tissue from various areas of the brain and from lungs, spleen, and lymph nodes were collected for isolation of virus and for histopathologic examination. The PMEA treatment had a striking effect on visna virus infection, which was similar for both doses of the drug. Thus, the frequency of virus isolations was much lower in PMEA-treated than in untreated lambs. The difference was particularly pronounced in the blood, CSF, and brain tissue. Furthermore, CSF cell counts were much lower and inflammatory lesions in the brain were much less severe in the treated lambs than in the untreated controls. The results indicate that PMEA inhibits the propagation and spread of visna virus in infected lambs and prevents brain lesions, at least during early infection. The drug caused no noticeable side effects during the 6 weeks of treatment.

Adenine↗

PubMed1995

The human immunodeficiency virus(HIV) inhibitor 9-(2-phosphonylmethoxyethyl)adenine (PMEA) is a strong inducer of differentiation of several tumor cell lines.

9-(2-phosphonylmethoxyethyl)adenine (PMEA) is the prototype compound of a series of acyclic nucleoside phosphonate derivatives endowed with potent and selective anti-retroviral activity in vitro and in vivo. We have now found that PMEA is also a potent inducer of differentiation of a number of tumor cells, including human erythroleukemia K562 cells, rat choriocarcinoma RCHO cells and human acute promyelocytic leukemic HL-60 cells. At 10 microM PMEA, rat RCHO cell cultures could be almost fully differentiated, and at 50 microM PMEA, approximately 50% of the K562 cells could be triggered to produce hemoglobin. The differentiating activity of butyric acid was at least partially additive to that of PMEA when both drugs were combined in K562 cell cultures. PMEA needs to be present for at least 2 or 3 days in the K562 cell cultures to achieve optimal differentiating activity. This suggests that either a PMEA metabolite and/or its anti-metabolic effects may be responsible for differentiation of the tumor cells.

Adenine↗

PubMed1995

3-deaza- and 7-deaza-5'-noraristeromycin and their antiviral properties.

An enantiospecific synthesis of 3-deaza-5'-noraristeromycin as its dihydrochloride ((-)-6) has been accomplished in six steps beginning with the reaction of (+)-(1R,4S)-4-hydroxy-2-cyclopenten-1-yl acetate with 4-chloro-1H-imidazo[4,5-c]pyridine. The preparation of 7-deaza-5'-noraristeromycin ((-)-7) was described previously. Compounds (-)-6 and (-)-7 were evaluated for antiviral activity against a large number of viruses. Compound (-)-6 produced an antiviral activity pattern similar to 5'-noraristeromycin but was less potent. Compound (-)-6 inhibited CEM cell proliferation at a 50% inhibitory concentration of 27 micrograms/mL but proved not inhibitory to HEL cell proliferation and not toxic to E6SM, HeLa, Vero, and MDCK cells at concentrations up to 200 micrograms/mL. While (-)-6 showed inhibition of S-adenosyl-L-homocysteine (AdoHcy) hydrolase, it was less inhibitory than 5'-noraristeromycin. Compound (-)-7 displayed no antiviral properties or inhibitory effects toward AdoHcy hydrolase.

Adenosine↗

PubMed1995

Cytotoxicity of 3'-azido-3'-deoxythymidine correlates with 3'-azidothymidine-5'-monophosphate (AZTMP) levels, whereas anti-human immunodeficiency virus (HIV) activity correlates with 3'-azidothymidine-5'-triphosphate (AZTTP) levels in cultured CEM T-lymphoblastoid cells.

Activation of the anti-human immunodeficiency virus (HIV) compound 3'-azido-3'-deoxythymidine (AZT) is dependent on its 5'-phosphorylation by cellular nucleoside and nucleotide kinases. Azidothymidine 5'-triphosphate (AZTTP) is considered to be the metabolite responsible for both the anti-HIV effect of AZT, via inhibition of reverse transcriptase, and cytoxicity by interference with cellular DNA polymerases. During the characterization of AZT metabolism in cultured human T-lymphoblastoid CEM cells, a spontaneously occurring variant cell line, CEM/Ag-1, was found that showed approximately 10-fold resistance to AZT growth inhibition as compared to wild type (wt) cells (EC50 = 2 mM as compared to 350 microM for wt cells). CEM/Ag-1 cells had a 3-fold reduced capacity to accumulate azidothymidine monophosphate (AZTMP) compared to wt cells whereas similar levels of AZTTP were found in both cell lines. The intracellular half-life of AZTMP was approximately 70 min in both wt and CEM/Ag-1 cells. A 3-fold lower specific activity of cytoplasmic thymidine kinase was observed in CEM/Ag-1 extracts as compared to wt. The reduced thymidine kinase activity was not correlated to a decreased level of thymidine kinase mRNA. Syncytium formation of CEM/Ag-1 cells infected with HIV-2 as well as HIV-1 antigen production was inhibited at the same concentrations of AZT (approx. 0.01 microM) as were HIV-1 and HIV-2 infected wt cells. Thus, minor decreases in cellular thymidine kinase levels may markedly affect the cytoxicity of AZT but have no major effect on the antiviral activity of AZT. Our results strongly suggest that AZTMP is responsible for a major part of the growth inhibitor effects, while AZTTP mainly mediates the antiviral activity of AZT.

Blotting, Northern↗

PubMed1995

Synthesis, biological evaluation, and structure analysis of a series of new 1,5-anhydrohexitol nucleosides.

In view of the selective anti-HSV activity of 1,5-anhydro-2,3-dideoxy-2- (5-iodouracil-1-yl)-D-arabino-hexitol, a series of novel 1,5-anhydrohexitol nucleosides were synthesized and evaluated for their inhibitory activity against several viruses. The 5-iodouracil 3 and the 5-ethyluracil 4 derivatives are highly selective TK-dependent inhibitors of HSV-1 and HSV-2. Broad anti-herpes virus activity was noticed for 5-fluorocytosine 6 and 2,6-diaminopurine 10 analogues. From a transport study of 3, using the thymidine influx competition method, one can conclude that intracellular uptake of this compound most probably occurs by passive diffusion. X-ray analysis of compounds 3 and 9 showed that the heterocyclic base of 1,5-anhydrohexitol pyrimidine and purine is placed in the axial position and that the sugar ring adopts a slightly distorted chair conformation.

Animals↗

PubMed1995

Synthesis and cytotoxic activity of 6-vinyl- and 6-ethynyluridine and 8-vinyl-and 8-ethynyladenosine.

It is well-known that the introduction of vinyl and ethynyl moieties into nucleosides is of crucial importance for cytostatic, antiviral, or other biological activities. In this study 6- and 8-vinyl-and -ethynyluridine and -adenosine were prepared by a general procedure involving the palladium-catalyzed cross-coupling of trimethylsilylacetylene or vinyltributyltin. The introduction of a vinyl group at C-6 of uridine or an ethynyl group at C-8 of adenosine resulted in nucleoside derivatives showing cytostatic activity against several murine and/or human tumor cell lines. Interestingly, 8-vinyladenosine had pronounced selective inhibitory effects on human (Molt/4F and MT-4) versus murine (L1210 and FM3A) tumor cell lines.

Adenosine↗

PubMed1995

Inhibition of visna virus replication and cytopathic effect in sheep choroid plexus cell cultures by selected anti-HIV agents.

Several anti-HIV agents were tested against visna virus replication and cytopathic effect (CPE) in sheep choroid plexus cell cultures. Sulphated polysaccharides (i.e., dextran sulphate, pentosan polysulphate and heparin) and plant lectins, which inhibit viral adsorption and fusion, were found to be 10- to 40-fold less active against visna virus than against HIV. Bicyclam derivatives were at least 250-fold less active against visna virus and the highly HIV-1 specific TIBO derivatives were without a significant inhibitory effect on visna virus at subtoxic concentrations. In contrast, several 2',3'-dideoxynucleosides and acyclic nucleoside phosphonate analogues, which inhibit reverse transcription, were found to be very effective inhibitors of visna virus replication and viral CPE in cell culture.

Animals↗