tenofovir-disoproxil-fumarate and HIV-Infections

CMX157 is a lipid (1-0-hexadecyloxypropyl) conjugate of the acyclic nucleotide analog tenofovir (TFV) with activity against both wild-type and antiretroviral drug-resistant HIV strains, including multidrug nucleoside/nucleotide analog-resistant viruses. CMX157 was consistently >300-fold more active than tenofovir against multiple viruses in several different cell systems. CMX157 was active against all major subtypes of HIV-1 and HIV-2 in fresh human peripheral blood mononuclear cells (PBMCs) and against all HIV-1 strains evaluated in monocyte-derived macrophages, with 50% effective concentrations (EC(50)s) ranging between 0.20 and 7.2 nM. The lower CMX157 EC(50)s can be attributed to better cellular uptake of CMX157, resulting in higher intracellular levels of the active antiviral anabolite, TFV-diphosphate (TFV-PP), inside target cells. CMX157 produced >30-fold higher levels of TFV-PP in human PBMCs exposed to physiologically relevant concentrations of the compounds than did TFV. Unlike conventional prodrugs, including TFV disoproxil fumarate (Viread), CMX157 remains intact in plasma, facilitating uptake by target cells and decreasing relative systemic exposure to TFV. There was no detectable antagonism with CMX157 in combination with any marketed antiretroviral drug, and it possessed an excellent in vitro cytotoxicity profile. CMX157 is a promising clinical candidate to treat wild-type and antiretroviral drug-resistant HIV, including strains that fail to respond to all currently available nucleoside/nucleotide reverse transcriptase inhibitors.

Topics: Adenine; Anti-HIV Agents; Cell Survival; Cells, Cultured; Drug Resistance, Viral; HIV Infections; HIV-1; Humans; Macrophages; Nucleosides; Nucleotides; Organophosphonates; Tenofovir

Although the approved nucleoside reverse transcriptase (RT) inhibitors (NRTI) are integral components of therapy for human immunodeficiency virus type 1 (HIV-1) infection, they can have significant limitations, including the selection of NRTI-resistant HIV-1 and cellular toxicity. Accordingly, there is a critical need to develop new NRTI that have excellent activity and safety profiles and exhibit little or no cross-resistance with existing drugs. In this study, we report that the 3'-azido-2',3'-dideoxypurine nucleosides (ADPNs) 3'-azido-2',3'-dideoxyadenosine (3'-azido-ddA) and 3'-azido-2',3'-dideoxyguanosine (3'-azido-ddG) exert potent antiviral activity in primary human lymphocytes and HeLa and T-cell lines (50% inhibitory concentrations [IC50s] range from 0.19 to 2.1 microM for 3'-azido-ddG and from 0.36 to 10 microM for 3'-azido-ddA) and that their triphosphate forms are incorporated as efficiently as the natural dGTP or dATP substrates by HIV-1 RT. Importantly, both 3'-azido-ddA and 3'-azido-ddG retain activity against viruses containing K65R, L74V, or M184V (IC50 change of <2.0-fold) and against those containing three or more thymidine analog mutations (IC50 change of <3.5-fold). In addition, 3'-azido-ddG does not exhibit cytotoxicity in primary lymphocytes or epithelial or T-cell lines and does not decrease the mitochondrial DNA content of HepG2 cells. Furthermore, 3'-azido-ddG is efficiently phosphorylated to 3'-azido-ddGTP in human lymphocytes, with an intracellular half-life of the nucleoside triphosphate of 9 h. The present data suggest that additional preclinical studies are warranted to assess the potential of ADPNs for treatment of HIV-1 infection.

Topics: Anti-HIV Agents; Cell Line, Tumor; Cell Survival; Cells, Cultured; Dideoxynucleosides; HIV Infections; HIV-1; Humans; Molecular Structure; Reverse Transcriptase Inhibitors

The intracellular metabolism of nucleoside reverse transcriptase inhibitors (NRTI) in mononuclear cells has been thoroughly studied, but that in red blood cells (RBC) has been disregarded. However, the phosphorylation of other analogous nucleosides (in particular, ribavirin) has been described previously. In this study, we investigated for the first time the phosphorylation of NRTI in human RBC. The presence of intracellular zidovudine (AZT) monophosphate, AZT triphosphate, lamivudine (3TC) triphosphate, and tenofovir (TFV) diphosphate, as well as endogenous dATP, dGTP, and dTTP, in RBC collected from human immunodeficiency virus-infected patients was examined. We observed evidence of a selective phosphorylation of 3TC, TFV, and endogenous purine deoxynucleosides to generate their triphosphate moieties. Conversely, no trace of AZT phosphate metabolites was found, and only faint dTTP signals were visible. A comparison of intracellular TFV diphosphate and 3TC triphosphate levels in RBC and peripheral blood mononuclear cells (PBMC) further highlighted the specificity of NRTI metabolism in each cell type. These findings raise the issue of RBC involvement in drug-drug interaction, drug pharmacokinetics, and drug-induced toxicity. Moreover, the typical preparation of PBMC samples by gradient density centrifugation does not prevent their contamination with RBC. We demonstrated that the presence of RBC within PBMC hampers an accurate determination of intracellular TFV diphosphate and dATP levels in clinical PBMC samples. Thus, we recommend removing RBC during PBMC preparation by using an ammonium chloride solution to enhance both the accuracy and the precision of intracellular drug monitoring.

Topics: Adenine; Anti-HIV Agents; Drug Interactions; Drug Therapy, Combination; Erythrocytes; HIV Infections; Humans; Lamivudine; Nucleosides; Organophosphonates; Phosphorylation; Reverse Transcriptase Inhibitors; Tenofovir; Treatment Outcome; Zidovudine