Alain Pruvost

Unexpected CD4 cell count decline in patients receiving didanosine and tenofovir-based regimens despite undetectable viral load.

Background: We recently observed a significant CD4 cell count decline in patients receiving didanosine (ddI) 400 mg, tenofovir (TDF) and nevirapine (NVP), despite virological suppression. Methods: We identified from our computerized patient database subjects who initiated combinations containing ddI and/or TDF for reasons other than virological failure, including simplification or intolerance. Changes in total, CD4+ and CD8+ lymphocyte counts since the initiation of therapy were analysed retrospectively. Plasma concentration of ddI was prospectively determined in eight of these patients receiving ddI 400 mg + TDF + NVP and 3 weeks after a ddI dosage reduction. Results: A total of 302 patients were studied. A significant decrease in CD4 and CD8 and in total lymphocyte counts was only seen in subjects receiving ddI standard dose + TDF-containing regimens, despite the maintenance of viral suppression. More than 50% of these patients showed a decline of more than 100 CD4 cells at 48 weeks. In contrast, subjects not receiving ddI + TDF together experienced the expected progressive increase in CD4 T-cell counts. Plasma levels of ddI were elevated in all patients receiving the standard ddI dose + TDF. DdI plasma levels significantly decreased when patients weighting > 60 kg reduced ddI dose to 250 mg, achieving similar levels to those generated by ddI 400 mg without TDF. Conclusions: Co-administration of ddI at standard doses plus TDF appears to exert a deleterious effect on CD4 and CD8 counts. Although lymphocyte toxicity related to excessive ddI plasma levels could explain our findings, other mechanisms cannot be excluded. Pharmacokinetic data suggest ddI dose reduction when coadministered with TDF.

Measurement of Intracellular Didanosine and Tenofovir Phosphorylated Metabolites and Possible Interaction of the Two Drugs in Human Immunodeficiency Virus-Infected Patients

ABSTRACT Recent work has demonstrated the existence of a systemic interaction between didanosine (ddI) and tenofovir disoproxyl fumarate (TDF) that leads to a significant increase in plasma ddI levels when coadministered with TDF (40 to 50% increase). These two drugs are, respectively, nucleoside and nucleotide analogues of adenosine and efficiently inhibit the human immunodeficiency virus (HIV) reverse transcriptase when transformed to their triphosphate moieties in the intracellular (IC) medium (ddA-TP and TFV-DP, respectively). Since ddI and TDF partly share the same IC metabolic pathway leading to the active triphosphates, we investigated a putative IC interaction. We used high-performance liquid chromatography-tandem mass spectrometry techniques to determine ddA-TP and TFV-DP IC levels in HIV-infected patients cotreated with both drugs, in comparison with patients treated with just one of the two drugs. These measurements revealed no significant differences in IC levels of the corresponding triphosphates when ddI (250 mg, once a day [QD]) was coadministered with TDF (300 mg, QD) compared to ddI 400 mg (QD) administered without TDF, thus supporting the dose adaptation proposed for this combination. However, we observed that both ddA-TP and TFV-DP have very long IC half-lives, resulting in unusual IC pharmacokinetic profiles with no significant changes in triphosphate concentrations between two dosings. In the case of TFV-DP, this t1/2 of elimination was roughly estimated to be 180 h (7.5 days). This characteristic is certainly interesting in terms of efficacy but could have some drawbacks in terms of virus resistance for patients discontinuing these drugs.

Concentrations of Tenofovir and Emtricitabine in Breast Milk of HIV-1-Infected Women in Abidjan, Côte d'Ivoire, in the ANRS 12109 TEmAA Study, Step 2

ABSTRACT The aim was to evaluate emtricitabine (FTC) and tenofovir (TFV) neonatal ingestion through breast milk. Median TFV and FTC breast milk doses represented 0.03% and 2%, respectively, of the proposed oral infant doses. Neonatal simulated plasma concentrations were extremely low for TFV but between the half-maximal inhibitory concentration and the adult minimal expected concentration for FTC. The rare children who will acquire HIV despite TDF-FTC therapy will need to be monitored for viral resistance acquisition.

Pilot Pharmacokinetic Study of Human Immunodeficiency Virus-Infected Patients Receiving Tenofovir Disoproxil Fumarate (TDF): Investigation of Systemic and Intracellular Interactions between TDF and Abacavir, Lamivudine, or Lopinavir-Ritonavir

ABSTRACT Previous work has demonstrated the existence of systemic interaction between tenofovir (TFV) disoproxil fumarate (TDF) and didanosine as well as between TDF and lopinavir-ritonavir (LPV/r). Here we investigated TDF interactions with the nucleoside reverse transcriptase inhibitors (NRTIs) lamivudine (3TC) and abacavir (ABC), comparing both the concentrations of nucleoside/nucleotide reverse transcriptase inhibitors in plasma and the intracellular concentrations of their triphosphate metabolites (NRTI-TP) for human immunodeficiency virus-infected patients receiving these NRTIs with TDF and after 4 weeks of TDF interruption. We also looked at interactions between TDF-ABC and LPV/r, comparing patients receiving or not receiving LPV/r. Blood samples were taken at baseline and at 1, 2, and 4 h after dosing. Liquid chromatography-tandem mass spectrometry was used to measure NRTIs and NRTI-TPs. Statistical analyses were performed on pharmacokinetic parameters: the area under the concentration-time curve from 0 to 4 h (AUC0-4), the maximum concentration of the drug (Cmax), and the residual concentration of the drug at the end of the dosing interval (Ctrough) for plasma and the AUC0-4 and Ctrough for intracellular data. Among the groups of patient discontinuing TDF, the very long intracellular half-life of elimination (150 h) of TFV-DP (the diphosphorylated metabolite of TFV, corresponding to a triphosphorylated species) was confirmed. Comparison between groups as well as the longitudinal study showed no significant systemic or intracellular interaction between TDF and ABC or 3TC. Significant differences were observed between patients receiving LVP/r and those receiving nevirapine. For ABC, plasma exposure was decreased (40%) under LVP/r, while, in contrast, plasma exposure to TFV was increased by 50% and the intracellular TFV-DP AUC0-4 was increased by 59%. A trend for a gender effect was observed for TFV-DP at the intracellular level, with higher and Ctrough values for women.

Liquid chromatography–tandem mass spectrometry assays for intracellular deoxyribonucleotide triphosphate competitors of nucleoside antiretrovirals

This study was aimed to apply an LC-MS-MS method previously developed for intracellular nucleoside reverse transcriptase inhibitors-triphosphate (NRTI-TPs) to the determination of natural deoxyribonucleotides (dNTPs) in human peripheral blood mononuclear cells. The LC-MS-MS method was directly used in assay of dATP and dTTP. Interferences by ribonucleotides (rNTPs) prevented direct application to the two other analytes: dGTP and dCTP. A periodate oxidation procedure was therefore optimized to remove rNTPs from the cell medium in order to quantitate dCTP and dGTP. The determination of the intracellular ratio of NRTI-TP/dNTP in HIV-infected patients now involves use of the same chromatographic system for simultaneous assay of several analytes.

Combination of Tenofovir and Emtricitabine plus Efavirenz: In Vitro Modulation of ABC Transporter and Intracellular Drug Accumulation

ABSTRACT Efflux proteins have been shown to greatly affect the uptake of antiretroviral drugs by cells and to hamper their access to the human immunodeficiency virus type 1 replication site. This study evaluated the factors that may lead to drug-drug interactions between emtricitabine (FTC), tenofovir (TFV), and efavirenz (EFV), including the modulation of efflux transporter expression and function. Peripheral blood mononuclear cells from healthy volunteers were used to determine whether or not an interaction between antiretroviral drugs and target cells occurred in any combination of FTC, TFV, EFV, FTC-TFV, TFV-EFV, or FTC-TFV-EFV. Following 20 h of treatment, intracellular drug concentrations were measured by liquid chromatography-tandem mass spectrometry. Efflux transporter functionality and inhibitor drug properties were assessed by measuring fluorescent dye efflux. ABCB1 (P-glycoprotein), ABCC 1 to 6 (multidrug resistance-associated protein), and OAT (organic anion transporter) expression in response to the treatments was quantified by semiquantitative real-time PCR. Cells treated with a double combination (FTC-TFV or TFV-EFV) or the triple combination (FTC-TFV-EFV) produced higher FTC and TFV intracellular concentrations than cells treated with FTC or TFV alone. However, no change in the EFV intracellular concentration was observed. FTC tended to induce abcc5 mRNA expression and EFV tended to induce abcc1 and abcc6 mRNA expression, whereas TFV tended to reduce mdr1, abcc1, abcc5, and abcc6 mRNA expression. Under these conditions, a decrease in the functionality of ABCC was observed, and this decrease was associated with the direct inhibitory actions of these drugs. This in vitro study reveals a benefit of the combination FTC-TFV-EFV in terms of the intracellular FTC and TFV concentrations and highlights the pharmacological mechanisms that lead to this effect.

In Vitro Primary Human and Animal Cell-Based Blood−Brain Barrier Models as a Screening Tool in Drug Discovery

Brain penetration is characterized by its extent and rate and is influenced by drug physicochemical properties, plasma exposure, plasma and brain protein binding and BBB permeability. This raises questions related to physiology, interspecies differences and in vitro/in vivo extrapolation. We herein discuss the use of in vitro human and animal BBB model as a tool to improve CNS compound selection. These cell-based BBB models are characterized by low paracellular permeation, well-developed tight junctions and functional efflux transporters. A study of twenty drugs shows similar compound ranking between rat and human models although with a 2-fold higher permeability in rat. cLogP < 5, PSA < 120 Å, MW < 450 were confirmed as essential for CNS drugs. An in vitro/in vivo correlation in rat (R² = 0.67; P = 2 × 10⁻⁴) was highlighted when in vitro permeability and efflux were considered together with plasma exposure and free fraction. The cell-based BBB model is suitable to optimize CNS-drug selection, to study interspecies differences and then to support human brain exposure prediction.

Evidence and possible consequences of the phosphorylation of nucleoside reverse transcriptase inhibitors in human red blood cells

ABSTRACT 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.

Relationship between HIV/Highly Active Antiretroviral Therapy (HAART)—associated Lipodystrophy Syndrome and Stavudine-Triphosphate Intracellular Levels in Patients with Stavudine-Based Antiretroviral Regimens

BACKGROUND The link between human immunodeficiency virus/highly active antiretroviral therapy (HAART)-associated lipodystrophy syndrome (HALS) and the use of thymidine analogues has been well established. However, to our knowledge, no relationship has been proven between intracellular levels of stavudine (d4T) and HALS. METHODS We measured peripheral blood mononuclear cell intracellular levels of d4T-triphosphate (TP) in patients who were receiving d4T as part of their antiretroviral regimens. d4T-TP levels were determined by a validated liquid chromatography-tandem mass spectrometry assay method. The diagnosis of HALS was made in accordance with the criteria of a lipodystrophy severity grading scale. The Student t test, Pearson correlations, 1-way analysis of variance with Bonferroni correction, and stepwise logistic regression were used for statistic analyses. RESULTS This was a cross-sectional study. There were 33 patients: 17 with HALS and 16 without HALS. The median concentration of d4T-TP for patients with HALS was 20.60 femtomoles (fmol)/1 x 10(6) cells (interquartile range [IQR], 14.90-26.92 fmol/1 x 10(6) cells) and for patients without HALS was 13.85 fmol/1 x 10(6) cells (IQR, 8.65-20.15 fmol/1 x 10(6) cells) (P=.013). The median d4T-TP intracellular level in patients who had developed an AIDS-defining condition was 22.50 fmol/1 x 10(6) cells (IQR, 15.80-27.37 fmol/1 x 10(6) cells) and in those who had not was 14.40 fmol/1 x 10(6) cells (IQR, 10.80-20.40 fmol/1 x 10(6) cells) (P=.037). There were no statistically significant differences in d4T-TP intracellular levels with respect to the presence of metabolic syndrome, the clinical form of HALS (pure lipoatrophic vs mixed), the degree of facial lipoatrophy, the presence of hepatitis C virus infection, and the pair of nucleosides in HAART. d4T-TP levels correlated only with cumulative d4T exposure in time and dose. d4T-TP intracellular levels were independently associated with HALS (odds ratio, 1.58; 95% confidence interval, 1.08-2.32; P=.019). CONCLUSIONS Intracellular levels of d4T-TP are strongly associated with the development of HALS.

Plasma and Intracellular Tenofovir Pharmacokinetics in the Neonate (ANRS 12109 Trial, Step 2)

ABSTRACT The objective of this study was to investigate for the first time tenofovir (TFV) pharmacokinetics in plasma and peripheral blood mononuclear cells (PBMCs) of the neonate. HIV-1-infected pregnant women received two tablets of tenofovir disoproxil fumarate (TDF; 300 mg) and emtricitabine (FTC; 200 mg) at onset of labor and then one tablet daily for 7 days postpartum. A single dose of 13 mg/kg of body weight of TDF was administered to 36 neonates within 12 h of life after the HIV-1-infected mothers had been administered two tablets of TDF-emtricitabine at delivery. A total of 626 samples collected within the 2 days after the drug administration were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and analyzed by a population approach. In the neonate, the median TFV plasma area under the curve and minimal and maximal concentrations, respectively, were 3.73 mg/liter · h and 0.076 and 0.29 mg/liter. In PBMCs, TFV concentrations were detectable in all fetuses, whereas tenofovir diphosphate (TFV-DP) was quantifiable in only two fetuses, suggesting a lag in appearance of TFV-DP. The median TFV-DP neonatal concentration was 146 fmol/106 cells (interquartile range [IQR], 53 to 430 fmol/106 cells); two neonates had very high TFV-DP concentrations (1,530 and 2963 fmol/106 cells). The 13-mg/kg TDF dose given to neonates produced plasma TFV and intracellular active TFV-DP concentrations similar to those in adults. This dose should be given immediately after birth to reduce the delay before the active compound TFV-DP appears in cells.