Time-dependent changes in HIV nucleoside analogue phosphorylation and the effect of hydroxyurea

Abstract

Hydroxyurea does not affect measurable pools of endogenous nucleosides in vivo. Decreased lamivudine phosphorylation over time may provide a novel pharmacological explanation for the mechanism of resistance to this drug.

High Levels of Zidovudine (AZT) and Its Intracellular Phosphate Metabolites in AZT- and AZT-Lamivudine-Treated Newborns of Human Immunodeficiency Virus-Infected Mothers

“…To circumvent this deficiency, we have simultaneously monitored the endogenous nucleotide dT-TP as a surrogate for nucleotides. The median dT-TP concentration was 1.2 pmol/10 6 cells and was in the range of dT-TP values obtained using different methodologies in previous studies (31,32,46), with all studies exhibiting marked interindividual variability. As additional evidence of stability, we investigated the effect of the sample storage duration on the concentration of both AZT-TP and 3TC-TP (Fig.…”

Effect of Ribavirin on Intracellular and Plasma Pharmacokinetics of Nucleoside Reverse Transcriptase Inhibitors in Patients with Human Immunodeficiency Virus-Hepatitis C Virus Coinfection: Results of a Randomized Clinical Study

“…Large interpatient variation in both intracellular phosphorylation and plasma exposure of NRTIs have been reported previously (4,17,24,28,31,33,34,38). In addition, wide variation also exists in the intracellular concentrations of endogenous nucleoside triphosphates (16,17,24,37).…”

“…The template primer extension assays have been described in detail elsewhere (16,18,22,23,30). Briefly, the three triphosphate anabolites of interest (3TC-TP, ZDV-TP, or d4T-TP) as well as endogenous deoxythymidine-triphosphate (dTTP) and deoxcytidine triphosphate (dCTP) present in PBMCs were extracted with methanol, dried by rotary evaporation, and reextracted with perchloric acid (0.4 N; 200 l; 4°C).…”

“…Prior to this study the intrapatient variability in the ratio of AUC 0-12 h of nucleoside analogue triphosphates to the AUC 0-12 h of endogenous nucleoside triphosphates was unknown; therefore, it was not possible to conduct a formal sample size calculation. However, data from two previous studies (3,16) (with a standard deviation of approximately 50% for intracellular concentrations of ZDVTP), suggested that approximately 20 patients would give a power of 80% to detect a difference of 30% in the intracellular concentrations of drug and endogenous triphosphates. To ensure that we obtained data for each drug in approximately 20 patients, a total enrollment of approximately 60 patients was planned.…”

Evidence and Possible Consequences of the Phosphorylation of Nucleoside Reverse Transcriptase Inhibitors in Human Red Blood Cells

“…These cells are the primary targets of human immunodeficiency virus (HIV) and are readily available from a single blood sample of around 7 ml. Concentrations of NRTI-TP in PBMC (and/or the ratio of the level of NRTI-TP to that of the deoxynucleoside triphosphate [dNTP], the corresponding natural triphosphate) (18) are now regarded as relevant to investigations of new NRTI (24), drug-drug interaction studies (9,15,17,22,27), and prescription strategies (33, 35). On the other hand, few studies (30) have addressed the role of NRTI phosphate concentrations in drug toxicity or in the persistence of virus in protected areas.…”