UMLS:C0019693 - FACTA Search

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Query: UMLS:C0019693 (HIV)
170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a set of 42 antiretroviral naive HIV-1 infected persons who were treated with either Zidovudine (AZT) monotherapy, or a combination of AZT + ddC (Zalcitabine) or AZT + ddI (Didanosine), the HIV-1 DNA load was measured by competitive polymerase chain reaction (PCR) and related to the HIV-1 RNA load in plasma, the CD4+ counts and to clinical markers. The question was whether a reduction in the cellular HIV-1 DNA level contributes to clinical benefit, as predicted by a lasting response in HIV-1 RNA levels in plasma. No significant decline relative to baseline in HIV-1 DNA load was found in the AZT monotherapy arm. In this arm the differences from baseline for both HIV-1 RNA load and CD4+ T cell counts were small and transient. In both combination therapy arms, the maximum mean decline in HIV-1 DNA load was 0.6 log and it never differed significantly from baseline. This is in contrast to plasma HIV-1 RNA load that declined earlier and steeper (mean of 1.5 and 1.9 log for AZT + ddC and AZT + ddI, respectively) and that remained significantly below baseline for 80 weeks. Although 9 of 42 (32%) of the patients under combination therapy had prolonged decreased plasma RNA levels, the proviral HIV-1 DNA remained present in the cells throughout the total follow-up of 144 weeks. In conclusion, combination therapy showed better laboratory parameter responses than AZT monotherapy, in agreement with the clinical data. The HIV-1 DNA sequences did not disappear in any of the patients, heralding renewed active infection after cessation of therapy.
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PMID:Cellular proviral HIV type 1 DNA load persists after long-term RT-inhibitor therapy in HIV type 1 infected persons. 971 20

Therapy with two nucleoside reverse transcriptase inhibitors (NRTI), the backbone of triple combinations, is still widely used in early stages of HIV-1 disease. However, factors influencing virologic response need to be further analyzed, to test the hypothesis that the reduction of plasma RNA viremia with NRTI may be greater in patients with higher baseline viral load (BVL) and to analyze the predictive factors of viral load drop below detection (200 HIV RNA copies/ml of plasma). Selected for the study were 169 HIV-1-infected antiretroviral therapy-naive patients with CD4+ T-lymphocyte counts ranging from 6 to 1040/microl coming from three randomized studies comparing the efficacy of monotherapy (zidovudine [ZDV], 250 mg every 12 hours; N=40) versus two-drug therapy consisting of ZDV (250 mg every 12 hours) with dideoxycytidine (ddC, 0.75 mg every 8 hours) or didanosine (ddI, 200 mg every 12 hours; N=129). Viral load was measured at 1, 3, and 6 months by polymerase chain reaction (PCR). A linear regression model was used to analyze the relation between BVL and the peak reduction of plasma RNA viremia. The variables included in a logistic regression model to determine the likelihood of VLs dropping below detection levels were age, gender, risk group for HIV-1 infection, baseline CD4+ lymphocyte count, BVL, clinical status (AIDS versus non-AIDS), HIV-1 phenotype (syncytium-inducing [SI] versus non-syncytium-inducing [NSI]) and type of treatment (monotherapy versus double therapy). The peak reduction of VL was related to baseline level following a linear model in both monotherapy and double-therapy regimens. In the subgroup of patients treated with two NRTIs, the regression line that fitted best with the data was log10 (peak reduction)=1.8-0.36 log10 (BVL) (F=23.5; p < .0001). This indicates that for every increase of 1 log10 of BVL, the peak reduction would be of 0.64 log10 greater. Forty-nine (29%) of the 169 patients dropped to <200 copies/ml. The likelihood of dropping below detection level was significantly greater in those receiving double therapy versus monotherapy (odds ratio [OR]=16.1; 95% confidence interval [CI], 2-128), in those with baseline CD4+ lymphocyte count >350/microl (OR=2.28; 95% CI, 1.1-4.9) and in those with BVL <10,000 HIV-1 RNA copies/ml (OR= 2.25; 95% CI, 1.1-6.1). None of the 13 patients with an SI phenotype at baseline dropped below detection levels. The reduction of VL in response to two NRTIs was greater in those patients with a higher level of BVL. In conclusion, peak reduction below detection in response to NRTI can be predicted and is associated with double therapy, with a baseline CD4+ cell count >350/microl and with a BVL <10,000 RNA copies/ml.
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PMID:Predictive factors influencing peak viral load drop in response to nucleoside reverse transcriptase inhibitors in antiretroviral-naive HIV-1-infected patients. 973 70

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) have, in addition to the nucleoside reverse transcriptase inhibitors (NRTIs) and protease inhibitors (PIs), gained a definitive place in the treatment of HIV-1 infections. Starting from the HEPT and TIBO derivatives, more than 30 structurally different classes of compounds have been identified as NNRTIs, that is compounds that are specifically inhibitory to HIV-1 replication and targeted at the HIV-1 reverse transcriptase (RT). Two NNRTIs (nevirapine and delavirdine) have been formally licensed for clinical use and several others are in preclinical or clinical development [thiocarboxanilide UC-781, HEPT derivative MKC-442, quinoxaline HBY 097 and DMP 266 (efavirenz)]. The NNRTIs interact with a specific 'pocket' site of HIV-1 RT that is closely associated with, but distinct from, the NRTI binding site. NNRTIs are notorious for rapidly eliciting resistance due to mutations of the amino acids surrounding the NNRTI-binding site. However, the emergence of resistant HIV strains can be circumvented if the NNRTIs, alone or in combination, are used from the start at sufficiently high concentrations. In vitro, this procedure has proved to 'knock-out' virus replication and to prevent resistance from arising. In vivo, various triple-drug combinations of NNRTIs (nevirapine, delavirdine or efavirenz) with NRTIs (AZT, 3TC, ddI or d4T) and/or PIs (indinavir or nelfinavir) have been shown to afford a durable anti-HIV activity, as reflected by both a decrease in plasma HIV-1 RNA levels and increased CD4 T-lymphocyte counts.
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PMID:The role of non-nucleoside reverse transcriptase inhibitors (NNRTIs) in the therapy of HIV-1 infection. 975 86

While many point mutations in the HIV-1 reverse transcriptase (RT) confer resistance to antiretroviral drugs, inserts or deletions in this gene have not been previously characterized. In this report, 14 RT inhibitor-treated patients were found to have HIV-1 strains possessing a 6-basepair insert between codons 69 and 70 of the RT gene. Known drug resistance mutations were also observed in these strains, with T215Y appearing in all strains. Genotypic analysis indicated that the inserts had substantial nucleotide variability that resulted in relatively restricted sets of amino acid sequences. Linkage of patients' treatment histories with longitudinal sequencing data showed that insert strains appeared during drug regimens containing ddI or ddC, with prior or concurrent AZT treatment. Drug susceptibility tests of recombinant patient isolates showed reduced susceptibility to nearly all nucleoside RT inhibitors. Site- directed mutagenesis studies confirmed the role of the inserts alone in conferring reduced susceptibility to most RT inhibitors. The addition of AZT-associated drug resistance mutations further increased the range and magnitude of resistance. These results establish that inserts, like point mutations, are selected in vivo during antiretroviral therapy and provide resistance to multiple nucleoside analogs.
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PMID:A 6-basepair insert in the reverse transcriptase gene of human immunodeficiency virus type 1 confers resistance to multiple nucleoside inhibitors. 981 61

HIV-1 reverse transcriptase (RT) is a key enzyme involved in the replication of the virus and is a potential target for therapeutic intervention following infection. Several drugs that inhibit the enzyme from acting have been discovered. These include nucleoside-analogue inhibitors such as AZT (zidovudine), ddI and ddC, and non-nucleoside inhibitors such as nevirapine and delavirdine. All of them, however have been found to be of limited clinical utility because the RT becomes rapidly resistant to them on account of point mutations in the enzyme. One way to partly overcome this limitation is to design an inhibitor that has interactions mainly with the backbone and the conserved residues of RT. Using a rational drug-design approach based on the high resolution X-ray crystal structure of the RT-nevirapine complex (1), and the specific design principles of peptides containing dehydro-Alanine (deltaAla) generated by our theoretical calculations, we present here the design of a peptide inhibitor of RT. Energy minimization and molecular modeling of the interaction of the designed pentapeptide with the nevirapine-binding site indicate that the inhibitor has 60% of its interactions with the conserved regions of RT as compared to 30% in the case of nevirapine, thus making it much less sensitive to mutations in the enzyme.
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PMID:A peptide inhibitor of HIV-1 reverse transcriptase using alpha,beta-dehydro residues: a structure-based computer model. 983 73

Biology of HIV-1 associated neoplasias is modulated by viral and host factors. In addition the development of tumors and their response to therapy may be further influenced by long-term treatment of HIV-1 patients with nucleoside analogs such as AZT (3'-azido-3'deoxythymidine), ddI (2',3'-dideoxyinosine), ddC (2',3'-dideoxycytidine), d4T (2',3'-didehydro-2'3'-dideoxythymidine), and 3TC [(-)-beta-L-2',3'-dideoxy-3'-thiacytidine] alone or in combination. As these compounds can trigger mechanisms involved in chemoresistance, we tested whether prolonged in vitro treatment of H9 cells (T-cell lymphoma) with AZT alters sensitivity of lymphoma cells to antitumor agents used for AIDS-associated malignancies. H9 cells grown for more than two years in medium containing 250 microM AZT developed resistance to the toxic effects of AZT while retaining sensitivity for other nucleoside analogs including ddC or cytosine arabinoside (ARA-C). These cells designated H9rAZT250 were 2 to 10-fold less sensitive to the toxic effects of antitumor agents, including cisplatin (CDDP), vincristine (VCR), doxorubicin (DOX) and etoposide (VP-16), when compared with parental H9 cells. The resistance of H9rAZT250 cells to antitumor agents was associated with inhibition of apoptosis as demonstrated by ultrastructural investigations and DNA-fragmentation assay (ELISA). The expression of the antiapoptotic gene bcl-2 was increased in H9rAZT250 cells while expression of other genes involved in the regulation of apoptosis such as c-myc, p53 and Fas was not changed. These results demonstrate that prolonged in vitro treatment of H9 lymphoma cells with AZT results in the development of resistance to antitumor agents in association with inhibition of apoptosis and increased expression of bcl-2. Therefore AZT long-term treatment of some HIV-1 patients with malignancies may have affected behavior of tumor cells including response to therapy.
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PMID:Azidothymidine resistance of H9 human T-cell lymphoma cells is associated with decreased sensitivity to antitumor agents and inhibition of apoptosis. 985 Jul 37

The immunologic and virologic activity of nevirapine in combination with two nucleosides (zidovudine [ZDV] and didanosine [ddI]) was evaluated in antiretroviral-naive patients with a CD4 count <200/mm3 or clinical AIDS. In all, 68 patients were enrolled in a 48-week double-blind, placebo-controlled trial. A group of 32 patients received ZDV + ddI + nevirapine, and 36 patients received ZDV + ddI. Primary efficacy parameters were the activity on HIV-1 RNA and on peripheral blood CD4+ cells, with differences between groups analyzed by the Wilcoxon's nonparametric two-sample test. Baseline RNA was high in both treatment groups (median values, 5.8 and 5.7 log10). RNA and CD4 responses were significantly higher with the triple combination (median RNA reductions, 2.69 versus 1.05 log10 at 24 weeks and 1.97 versus 1.20 log10 at 48 weeks; median CD4 increases, 81 versus 64 cells/mm3 at 24 weeks and 101 versus 27 cells/mm3 at 48 weeks). This study demonstrates that a triple combination of ZDV + ddI + nevirapine used as first-line regimen in antiretroviral-naive patients can induce sustained virologic and immunologic response in patients with low CD4 count or a previous diagnosis of AIDS.
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PMID:A randomized, double-blind trial on the use of a triple combination including nevirapine, a nonnucleoside reverse transcriptase HIV inhibitor, in antiretroviral-naive patients with advanced disease. 992 24

Didanosine (Videx, ddI) has been shown to be an effective agent in the treatment of HIV disease. However, patients have had difficulties adhering to didanosine preparations due to taste aversion and/or associated nausea. The efficacy of didanosine may, therefore, be compromised. This is of concern to clinicians who seek to promote patient adherence to medication regimes and to foster the quality of patient well-being. In this study, focus groups were used to gather exploratory data about patient (n = 15) response to the new mandarin orange didanosine preparation. Data were audiotaped, transcribed verbatim, and systematically analyzed by the investigators using inductive techniques. Findings provide information regarding client evaluation of the new didanosine preparation and patterns of usage. Although clients generally find the mandarin orange preparation more tolerable, they describe engaging in numerous strategies aimed at attenuating what they experience as the inconvenience of taking the medication. Mental tricks, systematic restructuring of daily routines and environment, and dietary schemes were among the strategies devised by patients through trial and error to self-promote their adherence.
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PMID:Patient appraisal of mandarin orange didanosine: implications for adherence and well-being. 1039 67

The synthesis, hydrolysis, and antiviral evaluation of novel, lipophilic cycloSal-ddAMP (9a-d) and cycloSal-d4AMP (10a-d) derivatives of the antiviral purine dideoxynucleoside analogues 2', 3'-dideoxyadenosine (ddA) (2) and 2',3'-dideoxy-2', 3'-didehydroadenosine (d4A) (3) are reported. These potential pronucleotides release ddAMP (7) or d4AMP (8) selectively by a controlled, chemically induced tandem reaction. All new compounds 9 and 10a-d were synthesized in good yields using our previously reported phosphorus(III) method starting from substituted salicyl alcohols 14a-h. The phosphotriesters 9 and 10 were obtained with a stereochemical preference of 2:1 with respect to the configuration at the phosphorus center. In an 1-octanol/water mixture phosphotriesters 9 and 10 exhibited 7-43-fold higher lipophilicity than the parent nucleosides ddA (2) and d4A (3) as judged by their log P values. In hydrolysis studies, 9 and 10 decomposed under mild aqueous basic conditions releasing solely ddAMP (7) and d4AMP (8), as well as the diols 14. Further hydrolysis studies under acidic conditions showed a marked increase in stability with respect to the acid-catalyzed cleavage of the glycosyl bond. Phosphotriesters 9 and 10 exhibited antiviral potencies against wild-type HIV-1 and HIV-2 strains in human T-lymphocyte (CEM/O) cells that were, respectively, 100- and 600-fold higher than those of ddA (2) and d4A (3). Furthermore, all triesters 9 and 10 were markedly more active than the corresponding ddI compounds 11 and 12, which supports the concept of the delivery of the adenine nucleotides. Studies with adenosine deaminase (ADA) and adenosine monophosphate deaminase (AMPDA) showed that the triesters were not substrates for enzymatic deamination. The studies reported herein demonstrate conclusively that the cycloSal triesters deliver exclusively the nucleotides ddAMP and d4AMP, not only under chemical-simulated hydrolysis but also under intracellular conditions fulfilling the adenosine deaminase bypass premise.
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PMID:cycloSal-Pronucleotides of 2',3'-dideoxyadenosine and 2', 3'-dideoxy-2',3'-didehydroadenosine: synthesis and antiviral evaluation of a highly efficient nucleotide delivery system. 1022 29

To define factors predictive of failure to respond to nucleoside reverse-transcriptase inhibitors in human immunodeficiency virus type-1 (HIV-1)-infected subjects pretreated with zidovudine (ZDV), three groups of subjects shifted to double therapy with ZDV plus didanosine (ddI, n = 13), zalcitabine (ddC, n = 14), or lamivudine (3TC, n = 12) were retrospectively evaluated, with respect to addition of the second NRTI, at week 0 and week 24. Factors considered included duration of ZDV pretreatment, CD4+ cell counts, plasma HIV-1 RNA load, peripheral blood mononuclear cell HIV-1 DNA load, and HIV-1 DNA genotypic resistance to nucleoside reverse-transcriptase inhibitors. The three groups were well matched for baseline characteristics and did not differ significantly in virological and immunological response to the different combination treatments. Drug-specific resistance mutations were selected in more than half the cases by 3TC, but not by ddI and ddC. Low-level and substantial genotypic resistance to ZDV was detected 13 (33.3%) and in 19 (48.7%) patients at baseline, respectively, and evolved through week 24 in several patients. When subjects were divided into responders and nonresponders to the second nucleoside reverse-transcriptase inhibitor on the basis of a decrease of more than 0.5 log10 (n = 15) or less than 0.5 log10 (n = 21) in HIV-1 RNA, respectively, baseline genotypic ZDV resistance was the only independent predictor of failure in a logistic regression model (P = 0.003 or P = 0.024, depending on whether low-level resistance was considered or not, respectively). Thus, selection of ZDV resistance mutations may impair subsequent use of different nucleoside reverse-transcriptase inhibitor compounds.
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PMID:Genotypic resistance to zidovudine as a predictor of failure of subsequent therapy with human immunodeficiency virus type-1 nucleoside reverse-transcriptase inhibitors. 1038 16

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