Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The myelotoxicities of three antiretroviral agents, 3'-azido-3'-deoxythymidine (AZT), carbovir (CBV) and 2',3'-didehydro-2',3'-dideoxythymidine (d4T), were evaluated in vitro with normal human and murine haematopoietic progenitor cells. These studies demonstrated that continuous AZT exposure was more inhibitory to human and murine colony formation than 1 h exposure, with murine and human progenitors similarly inhibited by continuous AZT exposure. These in vitro results on AZT's myelotoxicity correlate with both human and murine in vivo studies. CBV was only moderately toxic to human and murine cells following either 1 h or continuous exposure, with human and murine progenitors similarly suppressed by continuous CBV exposure. 1 h d4T exposure was less toxic to both human and murine marrow cells than continuous exposure and both species were equivalently inhibited when continuously exposed to d4T. In general, CBV was the least toxic agent to human and murine haematopoietic cells and AZT the most toxic. The study establishes CBV and d4T as less myelotoxic agents to human and murine haematopoietic progenitor cells in vitro than AZT which therefore could be considered as alternatives to AZT for the treatment of HIV infection.
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PMID:In vitro toxicity of 3'-azido-3'-deoxythymidine, carbovir and 2',3'-didehydro-2',3'-dideoxythymidine to human and murine haematopoietic progenitor cells. 131 40

The pharmacokinetics of stavudine (d4T; 2',3'-didehydro-3'-deoxythymidine) were studied in patients with AIDS-related complex or AIDS enrolled in a dose-ranging phase I/II study. Twenty-two patients were studied after the first oral dose of 0.67, 1.33, 2.67, or 4 mg/kg of body weight; 17 of them underwent an additional steady-state pharmacokinetic evaluation after thrice-daily dosing of the above doses. Stavudine absorption was rapid, with mean peak concentrations of 1.2-4.2 mg/L over the four dose levels studied. From 34% to 41% of an oral dose was excreted as unchanged drug in the urine. The mean values for plasma elimination half-life ranged from 1 to 1.6 h. The absolute bioavailability of a 4 mg/kg oral dose exceeded 80%. There was no change in pharmacokinetic parameters measured after the first dose and after chronic dosing. Stavudine is a new dideoxynucleoside with more complete and less variable oral absorption than existing nucleosides used for treatment of human immunodeficiency virus infection.
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PMID:Pharmacokinetics of stavudine in patients with AIDS or AIDS-related complex. 132 15

This study used DNA primer extension and sequencing gel analyses to evaluate the molecular action of 2',3'-didehydro-2',3'-dideoxythymidine triphosphate (D4TTP), in comparison with 3'-azido-2',3'-dideoxythymidine triphosphate (AZTTP), on DNA strand elongation by human immunodeficiency virus reverse transcriptases (HIV-RT) and human DNA polymerases alpha (pol alpha) and epsilon (pol epsilon) purified from T-lymphoblastoid CEM cells. D4TTP was preferentially incorporated into the T sites of the elongating DNA strand by HIV-RT and terminated DNA synthesis at the incorporation sites. The DNA chain termination activity of D4TTP was equipotent to that of AZTTP. In contrast, D4TTP was a poor substrate for pol alpha and pol epsilon. The analogue was incorporated into DNA by the human enzymes about 10,000- to 20,000-fold less efficiently than by HIV-RT, whereas the incorporation of AZTTP by pol alpha and pol epsilon was not detectable by the DNA primer extension assay. Pol epsilon, an enzyme with 3'----5'-exonuclease activity, was unable to remove the incorporated 2',3'-didehydro-2',3'-dideoxythymidine monophosphate (D4TMP) from the 3'-end of the DNA strand, whereas 3'-azido-2',3'-dideoxythymidine monophosphate was excised from DNA by pol epsilon at about 20% of the rate for normal deoxynucleotide excision. The preferential incorporation of D4TTP by HIV-RT appears to be a molecular basis for the selective anti-HIV activity of D4T, whereas the inability of pol epsilon to remove D4TMP from DNA may be related to the cytotoxicity of this compound.
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PMID:Selective action of 2',3'-didehydro-2',3'-dideoxythymidine triphosphate on human immunodeficiency virus reverse transcriptase and human DNA polymerases. 137 Aug 34

HIV inhibitors targeted at the virus-associated reverse transcriptase (RT) can be divided into two groups, depending on whether they are targeted at the substrate or nonsubstrate binding site. To the first group belong the 2',3'-dideoxynucleosides (i.e., DDC, DDI), 3'-azido-2',3'-dideoxynucleosides (i.e., AZT), 3'-fluoro-2',3'-dideoxynucleosides (i.e., FLT), 2',3'-didehydro-2',3'-dideoxynucleosides (i.e., D4C, D4T) and carbocyclic derivatives thereof (i.e., carbovir), 2'-fluoro-ara-2',3'-dideoxynucleosides, 1,3-dioxolane derivatives (i.e., 2',3'-dideoxyl-3'-thiacytidine), oxetanocin analogues and carbocyclic derivatives thereof (i.e., cyclobut-G) and the 9-(2-phosphonylmethoxyethyl)adenine (PMEA) and 9-(3-fluoro-2-phosphonylmethoxypropyl)adenine (FPMPA) derivatives. These compounds need to be phosphorylated intracellularly to their triphosphate forms before they act as competitive inhibitors or alternate substrates (chain terminators) of HIV RT. The second group includes the tetrahydro-imidazo[4,5,l-jk][1,4]-benzodiazepin-2(1H)one (TIBO), 1-[(2-hydroxyethoxy)-methyl]-6-(phenylthio)thymine (HEPT), dipyrido[3,2-b:2',3'-e]-[1,4]diazepin-6-one (nevirapine) and pyridin-2(1H)one derivatives, which interact as such, noncompetitively, with a specific allosteric binding site of HIV-1 RT. Compounds belonging to the two different groups may give rise to synergism which combined, and, likewise, viral resistance to the compounds may arise through different mutations, depending on the nature of the compounds and the group to which they belong.
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PMID:HIV inhibitors targeted at the reverse transcriptase. 137 90

The antiviral mechanism of action and intracellular metabolism of 2',3'-dideoxycytidine (ddCyd), 3'-azido-2',3'-dideoxythymidine (AZT) and 2',3'-didehydro-2',3'-dideoxythymidine (D4T) has been investigated. Marked differences in the affinity of these anti-HIV compounds for their activating (phosphorylating) enzymes, and the eventual intracellular levels of their active 5'-triphosphate metabolites were discovered. Moreover, new approaches were developed to manipulate the metabolism of these products in such a way that combination of ddCyd with thymidine, and 2',3'-dideoxynosine with ribavirin resulted in an enhanced antiretroviral effect of the test compounds in vitro and/or in vivo. Several metabolic and kinetic properties of AZT and D4T proved highly relevant to perform or modify the treatment modalities of AIDS patients with these chemotherapeutics. A novel class of acyclic purine nucleotide phosphonate derivatives endowed with potent and selective anti-HIV activity has been developed. The prototype compound is 9-(2-phosphonylmethoxyethyl)adenine (PMEA). PMEA proved to have a potent antiretroviral activity in a number of retrovirus models in vivo. Furthermore, a unique administration schedule of PMEA in retrovirus infections has been proposed, in which the antiretroviral properties of PMEA are clearly superior and distinguished from those of other chemotherapeutics such as AZT. The metabolic and kinetic properties of PMEA and its phosphorylated metabolites have been investigated. Our data provide a better and profound insight in the antiretroviral activity and the molecular and biochemical bases for the mechanism or action of the drug.
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PMID:[Anti-retroviral activity and molecular-biochemical action mechanism of 2',3'-dideoxynucleoside analogs and 9-(2-phosphonylmethoxyethyl) purine derivatives]. 164 85

Three analogs of thymidine, D4T [2',3'-didehydro-2',3'-dideoxythymidine; 1-(2,3-dideoxy-beta-D-glyceropent-2-enofuranosyl)thymine], FddT (3'-fluoro-3'-deoxythymidine), and AZT (3'-azido-3'-deoxythymidine), were compared in biological tests designed to assess their potential utility as anti-human immunodeficiency virus (HIV) agents. The in vitro potencies of these compounds against HIV infection in CEM cells were measured, with FddT and AZT being more potent than D4T. The cytotoxicities of D4T, FddT, and AZT for CEM cells were comparable. The triphosphates of these three derivatives inhibited purified HIV reverse transcriptase, and their affinities for this polymerase were found to be 1 or 2 orders of magnitude greater than that for the normal substrate, dTTP. D4T was less toxic than FddT or AZT for cultured human and mouse bone marrow cells (granulocyte-macrophage CFU). The three compounds had similar toxicities for human progenitor erythrocyte burst-forming units. In a 30-day mouse toxicity study, AZT and FddT produced a similar spectrum of hematopoietic toxicities. These toxic effects occurred at much lower doses of FddT than of AZT. At the higher doses of FddT, a significant incidence of lethality occurred. By contrast, D4T was considerably less toxic than both AZT and FddT in this study. The dose-limiting toxicity of D4T in mice was hepatotoxicity. The very different phosphorylation patterns of D4T, its lower toxicity, and its comparable potency relative to FddT and AZT suggest that the potential of D4T as an anti-HIV agent should be further explored.
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PMID:Comparison of in vitro biological properties and mouse toxicities of three thymidine analogs active against human immunodeficiency virus. 169 57

An x-ray crystallographic analysis of the potent anti-HIV agent D4T revealed two independent conformations (conformers a and b) with different glycosyl bonds and furanose geometries. Conformer a exhibits the unusual O4' exo configuration and chi (C2, N1, C1', O4') of -118 degrees. Conformer b exhibits a nearly planar furanose geometry and chi of -174 degrees. The reduced form of D4T, ddT, is poorly active against HIV and also exists in two independent conformations. Chi of forms a and b (-129 and -170.9 degrees) are similar to that found with D4T. However, the furanoses exhibit the classical C2' endo and C3' endo geometries, respectively. These observed differences are not sufficient to account for the differing potencies of D4T versus ddT.
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PMID:Structural studies of the anti-HIV agent 2',3'-didehydro-2',3'-dideoxythymidine (D4T). 184 8

The anti-human immunodeficiency virus (-HIV) nucleoside analogs azidothymidine (AZT), dideoxycytidine (ddC), dideoxyinosine (ddl), dideoxydidehydrothymidine (D4T), and dideoxydidehydrocytidine (D4C) and the anticancer drug cytosine arabinoside (AraC) were compared for their effects on the mitochondrial DNA (mtDNA) content in a human lymphoblastoid cell line, CEM. The potency of these compounds in reducing mtDNA content was in the order of ddC greater than D4C greater than D4T greater than AZT greater than ddl. AraC did not have a significant effect on mtDNA content. All of the compounds tested, except AraC, stimulated lactic acid production at concentrations that inhibited mtDNA synthesis. The action of ddC and ddl occurred at concentrations that did not affect cell growth significantly in 4 days but retarded cell growth by day 6. D4T and D4C decreased mtDNA content by 50% at doses lower than those that inhibited cell growth by 50% in 4 days (ID50). However, AZT required a dose higher than the ID50 to exert similar effects on mtDNA content. The decrease of mtDNA content caused by ddC also occurred in nerve growth factor-treated PC12 cells, which differentiate to neuron-like cells upon treatment with nerve growth factor. The preferential inhibition of mtDNA, compared with cell growth, by some of these anti-HIV nucleoside analogs correlates well with their ability to cause drug-limiting delayed toxicity, such as peripheral neuropathy, in patients. These data suggest that the selective mitochondrial toxicity could be responsible for the delayed toxicity caused by these anti-HIV analogs.
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PMID:Effect of anti-human immunodeficiency virus nucleoside analogs on mitochondrial DNA and its implication for delayed toxicity. 185 60

The inhibitory effects of a series of antiviral compounds on human immunodeficiency virus type 1 (HIV-1) were evaluated in a plaque assay (PA) in MT-4 cells and a focal immunoassay (FIA) in CD4+ HeLa cells. Similar 50% inhibitory concentrations (IC50) were obtained for the sulfated polysaccharides when measured by PA or FIA: the IC50 values of dextran sulfate and pentosan polysulfate were 0.8 microgram/ml and 0.35 microgram/ml, respectively. Also, comparable IC50 values (ranging from 1.42 to 2.71 microM) were obtained for purine 2',3'-dideoxyribosides (i.e. DDA, DDI and DDG) when evaluated by PA or FIA. In contrast, the IC50 values of pyrimidine 2',3'-dideoxyribosides were invariably 4- to 10-fold lower when monitored by PA than FIA: the IC50s of AZT, D4T and DDC in the PA were 0.015, 0.094 and 0.038 microM, respectively, and in the FIA were 0.062 microM, 0.29 microM and 0.46 microM, respectively. The differential anti-HIV-1 activities found with AZT, D4T and DDC in the PA and FIA systems may at least be related in part to differences in the metabolism of the compounds (i.e. phosphorylation by thymidine kinase or 2'-deoxycytidine kinase) between MT-4 and CD4+ HeLa cells. The novel anti-HIV-1 compounds tetrahydro-imidazo[4,5,1-jk][1,4]-benzodiazepin-2(1H)-thione (TIBO) derivatives, R82150 and R82913, and the acyclouridine derivative 1-[(2-hydroxyethoxy)methyl]-6-phenylthiothymine (HEPT) were also more inhibitory to HIV-1 in the PA than FIA system. The IC50 values of R82150, R82913 and HEPT, as based on PA, were 0.005, 0.003 and 0.79 microM, respectively. Their IC50 values, as based on FIA, were 0.020 microM, 0.015 microM and 3.77 microM, respectively. The TIBO derivatives emerged as the most effective HIV-1 inhibitors of the compounds tested whether assayed by PA or FIA.
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PMID:Anti-HIV-1 activity of antiviral compounds, as quantitated by a focal immunoassay in CD4+ HeLa cells and a plaque assay in MT-4 cells. 198 Jan 26

In order to obtain agents with therapeutic indices superior to those of AZT, FLT, or D4T, several analogues of anti-HIV-1 nucleosides were synthesized. These include 2',3'-dideoxy-2',3' -difluoro-5-methyluridine (13), its arabino analogue 19, arabino-5-methylcytosine analogue 21, 3'-deoxy-2',3'-didehydro-2' -fluorothymidine (25), 3'-azido-2',3'-dideoxy-2'-fluoro-5-methyluridine (29), 2'-azido-3'-fluoro-2',3'-dideoxy-5-methyluridine (31), and 2'3'-dideoxy-2' -fluoro-5-methyluridine (37). These new nucleosides were screened for their activity against HIV and feline TLV in vitro. None of the compounds showed significant activity. It is interesting to note that such a small modification in the sugar moiety of active anti-HIV nucleosides (i.e., displacement of hydrogen by fluorine) almost completely inactivate the agents.
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PMID:Fluorinated sugar analogues of potential anti-HIV-1 nucleosides. 203 90


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