Tenofovir diphosphate and emtricitabine triphosphate concentrations in blood cells compared with isolated peripheral blood mononuclear cells: a new measure of antiretroviral adherence?

Abstract

Background: The active metabolites of tenofovir (TFV) and emtricitabine (FTC) in peripheral blood mononuclear cells (PBMCs) have been used as markers of long-term antiretroviral (ARV) adherence. However, the process of isolating PBMCs is expensive, complex, and not feasible in many settings. We compared concentrations of TFV-diphosphate (TFV-DP) and FTC-triphosphate (FTC-TP) in the upper layer packed cells (ULPCs) obtained after whole blood centrifugation to isolated PBMCs as a possible alternative marker of adherence.

Methods: Ten HIV+ adults with HIV RNA <50 copies/mL on a TDF/FTC-containing regimen provided 5 paired PBMC and ULPC samples over 6 hours. TFV-DP and FTC-TP concentrations were analyzed by liquid chromatography/mass spectrometry. Partial areas under the curve were calculated using noncompartmental methods and Spearman Rank Correlations (rho) between PBMC and ULPC were determined.

Results: The median (25th-75th percentile) concentration of TFV-DP in PBMCs was 143 (103-248) fmol/10(6) cells and in ULPC was 227 (160-394) fmol/10(6) cells (rho = 0.65; P < 0.0001). The concentration of FTC-TP in PBMCs was 6660 (5650-10,000) fmol/10(6) cells and in ULPC was 19.0 (12.0-27.8) fmol/10(6) cells (rho = 0.55; P < 0.0001). Compared to PBMCs, ULPC TFV-DP was 64% higher and FTC-TP was 99.7% lower. ULPC concentrations of TFV-DP and FTC-TP in one additional subject receiving a single dose of TDF/FTC were only 0.05% and 25%, of the other 10 subjects, respectively.

Conclusions: ULPC concentrations significantly correlated with PBMC concentrations. Preliminary single-dose data suggest some discrimination between intermittent versus consistent dosing. ULPC concentrations of TFV-DP and FTC-TP should be further investigated as a simply collected surrogate measure of ARV adherence.

Figures

Figure 1

Individual concentration/time points plotted for TFV-DP (figure 1a) and FTC-TP (figure 1b) concentrations in ULPC and PBMCs. A significant (p

Figure 1

Individual concentration/time points plotted for TFV-DP (figure 1a) and FTC-TP (figure 1b) concentrations in ULPC and PBMCs. A significant (p

Figure 1

Individual concentration/time points plotted for TFV-DP (figure 1a) and FTC-TP (figure 1b) concentrations in ULPC and PBMCs. A significant (p

Figure 2

Individual subject concentration/time profiles for TFV-DP (figure 2a) and FTC-TP (figure 2b) in both PBMCs and ULPC. The subjects that sampled 0-6 hours following a dose are separated by time from the subjects that sampled 12-18 hours following a dose. *For this subject, PBMC samples obtained at 12h, 13h, and 14h post-dose were compromised, and consequently not use in the analysis. a. Individual Subject Pharmacokinetics of TFV-DP in ULPC and PBMCs b. Individual Subject Pharmacokinetics of FTC-TP in ULPC and PBMCs

Figure 2

Individual subject concentration/time profiles for TFV-DP (figure 2a) and FTC-TP (figure 2b) in both PBMCs and ULPC. The subjects that sampled 0-6 hours following a dose are separated by time from the subjects that sampled 12-18 hours following a dose. *For this subject, PBMC samples obtained at 12h, 13h, and 14h post-dose were compromised, and consequently not use in the analysis. a. Individual Subject Pharmacokinetics of TFV-DP in ULPC and PBMCs b. Individual Subject Pharmacokinetics of FTC-TP in ULPC and PBMCs

Figure 3

The median (range) concentration/time profiles of TFV-DP and FTC-TP in ULPC with comparison to the concentration/time profiles of the additional non-adherent subject. The open shapes represent the median (range) concentrations for each time point for the 10 adherent subjects included in the analysis and the solid shapes represent the concentrations for each time point for the additional non-adherent subject. The circle data points connected by a solid line represent TFV-DP concentrations and the square data points connected by a dashed line represent FTC-TP concentrations. Data from the additional subject are consistent with single versus multiple dosing. Subjects that sampled from 0-6 hours following a dose are seperated by time from the subjects that sampled 12-18 hours following a dose. Median (range) ULPC Concentrations of TFV-DP and FTC-TP with Additional Subject

Figure 4

ULPC Concentrations of TFV-DP or FTC-TP in ULPC at a single time point per subject immediately frozen at −80°C compared to that same time point kept refrigerated at 4°C for 14 hours prior to freezing. The dashed lines represent changes to individual subject samples and the solid black line represents the median change of all subject samples. ULPC Concentrations (fmol/106 cells) in TFV-DP and FTC-TP after Immediate Freezing and 14 hour Refrigeration Prior to Freezing