Antiviral and Cellular Metabolism Interactions between Dexelvucitabine and Lamivudine

Hernandez-Santiago, Brenda I.; Mathew, Judy; Rapp, Kimberly L.; Grier, Jason; Schinazi, Raymond F.

doi:10.1128/aac.01543-06

Cited by 12 publications

(9 citation statements)

References 17 publications

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“…3). d4T diphosphate (DP) is more readily phosphorylated to the triphosphate form by nucleoside diphosphate kinase, the final kinase in the activation pathway for d4T and AZT, as well as other analogs and deoxynucleoside diphosphates (dNDPs) (39,(55)(56)(57)(58), than is AZT-DP, addressing why the potency of AZT is affected more than that of d4T with SAMHD1 depletion and increased dNTP concentrations.…”

Section: H Uman Immunodeficiency Virus Type 1 (Hiv-1) Replicates Primmentioning

confidence: 99%

SAMHD1 Has Differential Impact on the Efficacies of HIV Nucleoside Reverse Transcriptase Inhibitors

Huber

Michailidis

Schultz

et al. 2014

Antimicrob Agents Chemother

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e Sterile alpha motif-and histidine/aspartic acid domain-containing protein 1 (SAMHD1) limits HIV-1 replication by hydrolyzing deoxynucleoside triphosphates (dNTPs) necessary for reverse transcription. Nucleoside reverse transcriptase inhibitors (NRTIs) are components of anti-HIV therapies. We report here that SAMHD1 cleaves NRTI triphosphates (TPs) at significantly lower rates than dNTPs and that SAMHD1 depletion from monocytic cells affects the susceptibility of HIV-1 infections to NRTIs in complex ways that depend not only on the relative changes in dNTP and NRTI-TP concentrations but also on the NRTI activation pathways. Human immunodeficiency virus type 1 (HIV-1) replicates primarily in activated CD4 ϩ T cells, while showing poor reproductive capacity in monocytes, macrophages, dendritic cells, and resting CD4 ϩ T cells (1-10). Sterile alpha motif-and histidine/ aspartic acid domain-containing protein 1 (SAMHD1) is responsible for blocking HIV-1 replication in such cells (5,(11)(12)(13), reportedly by acting as a dGTP-stimulated deoxynucleotide triphosphohydrolase that hydrolyzes deoxynucleoside triphosphates (dNTPs), thus decreasing the amounts of dNTPs available for reverse transcription (3,4,(14)(15)(16)(17)(18)(19).Nucleoside reverse transcriptase inhibitors (NRTIs) are nucleoside analogs and key components of antiretroviral therapies (20-26). They generally lack a 3=-OH group and thus act as chain terminators upon incorporation into viral DNA by reverse transcriptase (RT) (26-29). However, 4=-ethynyl-2-fluoro-2=-deoxyadenosine (EFdA) retains a 3=-OH group, acts primarily by blocking RT translocation following incorporation of EFdA monophosphate (MP) into the template-primer, and has picomolar antiviral potency (30-37). NRTIs are administered as nucleosides and are phosphorylated to their active forms by cellular kinases (38). Hence, they compete with dNTPs for activation by cellular kinases, and their incorporation by RT is influenced by the cellular concentrations of dNTPs, which compete with NRTI triphosphates (TPs) at the RT active site (39,40). Amie et al. (19) recently reported that SAMHD1 does not significantly hydrolyze dideoxynucleoside triphosphates (ddNTPs) or zidovudine (AZT)-TP and that depletion of SAMHD1 in monocytic THP-1 cells decreased the potency of these NRTIs in a pseudotype-based assay. Strong evidence that the decreased potency of these NRTIs was due to increased amounts of competing dNTPs was presented. Our parallel independent study confirmed their data, extended the number of NRTIs studied, validated the results with fully infectious HIV-1, and found an unexpected disparity in the effects of SAMHD1 on the deoxyribosylthymine (dT) analogs AZT and stavudine (d4T). We demonstrate that this is due to differences in the activation of AZT and d4T, highlighting the importance of distinct metabolic pathways in NRTI activation, in addition to competition with dNTPs.We tested purified Escherichia coli-produced recombinant SAMHD1 for dGTP-regulated NRTI-TP hydrolysis (using dNTPs as a re...

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Section: H Uman Immunodeficiency Virus Type 1 (Hiv-1) Replicates Primmentioning

confidence: 99%

SAMHD1 Has Differential Impact on the Efficacies of HIV Nucleoside Reverse Transcriptase Inhibitors

Huber

Michailidis

Schultz

et al. 2014

Antimicrob Agents Chemother

View full text Add to dashboard Cite

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“…The proportion of activated PBM cells varies between infected individuals and is not usually reported in clinical studies, making it difficult to assess the linearity of d4T-TP versus extracellular d4T using pooled in vivo data from individuals, each with differing activated lymphocyte fractions. Therefore the linearity between d4T and cellular accumulation of d4T-TP was tested in phytohaemagglutinin (PHA) stimulated PBM cells in cell culture, in which the degree of activation is more uniform (Hernandez-Santiago et al, 2005; Hernandez-Santiago et al, 2007a; Hernandez-Santiago et al, 2007b). The concentrations measured in vitro were then compared to average concentrations in humans after normalizing using 8% as an average estimate of dividing lymphocytes measured in infected individuals (Mohri et al, 2001).…”

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confidence: 99%

In silico study supports the efficacy of a reduced dose regimen for stavudine

Hurwitz

Schinazi

2011

Antiviral Research

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Stavudine (d4T) is used extensively as part of HAART in resource poor settings, despite its toxicities. The revised WHO guidelines specify replacement of d4T with less toxic but more expensive drugs when feasible, and that d4T doses be standardized to 30 mg twice daily (bid) (irrespective of body-weight), from the approved 40 mg bid in adults (body-weight ≥ 60 kg). Therefore, an in silico population pharmacokinetic and biochemical model was utilized to compare relative efficacies of the two doses in humans. Assessment of predicted quartile ranges of simulated concentrations of the triphosphate of d4T suggested sufficient trough concentrations to inhibit wild type HIV-1 reverse transcriptase at the reduced dose, lending support to the revised WHO recommendations.

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“…It has also become clear that most reverse transcriptase (RT) inhibitors are much more effective when given in combination than when given alone (Larder et al, 1995; Richman, 1996), although antagonism can be observed in vitro and in humans with nucleosides that use the same initial phosphorylation enzyme (Hernandez et al, 2007). It is widely believed that such synergistic drug interaction arises from the fact that certain combinations of drug resistance mutations are particularly detrimental for the enzyme, which leads to a less fit virus as shown by our group and others for RT variants containing mutations K65R, L74V and M184V (Back et al, 1996; Sharma and Crumpacker, 1997; Sharma and Crumpacker, 1999; White et al, 2002; Sharma et al, 2004; Deval et al, 2004a and 2004b).…”

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confidence: 99%

Comparative analysis of in vitro processivity of HIV-1 reverse transcriptases containing mutations 65R, 74V, 184V and 65R+74V

Sharma¹,

Nettles²,

Feldman³

et al. 2009

Antiviral Research

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While HIV-1 reverse transcriptase (RT) mutations of M to V at position 184 are commonly observed in the clinic, the double mutation of 65R+74V is rarely seen. It has been demonstrated that rapid R→K reversion occurs at RT codon 65 during replication of HIV-1 in human peripheral blood mononuclear cells containing 65R+74V mutations and that processivity of the RT is reduced relative to wild type. However, clinical studies show that M184V can be detected after several months of therapy interruption, suggesting more effective processivity. Herein, the in vitro RT processivity of genetically engineered M184V and double mutant 65R+74V was compared. Virion-associated RTs of WT pNL4-3, K65R, L74V, M184V and 65R+74V were used to perform RT processivity assays in the presence of trap, poly(rC)-oligo(dG). Both RTs with 184V and 65R+74V mutations exhibited similar processivity when compared with each other and a significantly decreased processivity as compared to WT RT. Both mutant RTs synthesized shorter cDNA molecules (37–42 nt) relative to WT RT, which made longer (65–70 nt) cDNA molecules. Since these surprising biochemical results cannot explain the clinical phenotype, a hypothesis is presented to explain the discrepancy and suggest new approaches for future testing.

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Antiviral and Cellular Metabolism Interactions between Dexelvucitabine and Lamivudine

Cited by 12 publications

References 17 publications

SAMHD1 Has Differential Impact on the Efficacies of HIV Nucleoside Reverse Transcriptase Inhibitors

SAMHD1 Has Differential Impact on the Efficacies of HIV Nucleoside Reverse Transcriptase Inhibitors

In silico study supports the efficacy of a reduced dose regimen for stavudine

Comparative analysis of in vitro processivity of HIV-1 reverse transcriptases containing mutations 65R, 74V, 184V and 65R+74V

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