Associations Between Tenofovir Diphosphate in Dried Blood Spots, Impaired Physical Function, and Fracture Risk

BACKGROUND

In this study, we evaluate associations between cumulative antiretroviral adherence/exposure, quantified using tenofovir diphosphate (TFV-DP) in dried blood spots (DBS), and human immunodeficiency virus (HIV)-related aging factors.

METHODS

This is a cross-sectional analysis of younger (ages 18-35) and older (ages ≥60) persons with HIV (PWH) taking TFV disoproxil fumarate. Tenofovir diphosphate concentrations were quantified in DBS. Linear and logistic regression models were used to evaluate associations between TFV-DP and bone mineral density (BMD), physical function, frailty, and falls.

RESULTS

Forty-five PWH were enrolled (23 younger, 22 older). Every 500 fmol/punch (equivalent to an increase in ~2 doses/week) increase in TFV-DP was associated with decreased hip BMD (-0.021 g/cm2; 95% confidence interval [CI], -0.040 to -0.002; P = .03). Adjusting for total fat mass, every 500 fmol/punch increase in TFV-DP was associated with higher odds of Short Physical Performance Battery impairment (score ≤10; adjusted odds ratio [OR], 1.6; 95% CI, 1.0-2.5; P = .04). Every 500 fmol/punch increase in TFV-DP was associated with slower 400-meter walk time (14.8 seconds; 95% CI, 3.8-25.8; P = .01) and remained significant after adjusting for age, lean body mass, body mass index (BMI), and fat mass (all P ≤ .01). Every 500 fmol/punch increase in TFV-DP was associated with higher odds of reporting a fall in the prior 6 months (OR, 1.8; 95% CI, 1.1-2.8; P = .02); this remained significant after adjusting for age, lean body mass, BMI, and total fat mass (all P < .05).

CONCLUSIONS

Higher TFV-DP levels were associated with lower hip BMD, poorer physical function, and greater risk for falls, a concerning combination for increased fracture risk.

Effects of sofosbuvir-based hepatitis C treatment on the pharmacokinetics of tenofovir in HIV/HCV-coinfected individuals receiving tenofovir disoproxil fumarate

Background

The nucleotide analogues tenofovir and sofosbuvir are considered to have low potential for drug interactions.

Objectives

To determine the effect of sofosbuvir-based HCV treatment on plasma concentrations of tenofovir and cellular concentrations of tenofovir diphosphate.

Methods

HIV-infected participants with acute HCV were treated for 12 weeks with sofosbuvir + ribavirin in Cohort 1 or 8 weeks with ledipasvir/sofosbuvir in Cohort 2 of AIDS Clinical Trials Group study 5327. Only participants taking tenofovir disoproxil fumarate were included in this analysis. Tenofovir in plasma, tenofovir diphosphate in dried blood spots and tenofovir diphosphate in PBMCs were measured pre-HCV therapy and longitudinally during the study using validated LC/MS-MS.

Results

Fifteen and 22 men completed Cohorts 1 and 2, respectively. In Cohort 1, tenofovir diphosphate was 4.3-fold higher (95% CI geometric mean ratio 2.46-7.67; P = 0.0001) in dried blood spots and 2.3-fold higher (95% CI 1.09-4.92; P = 0.03) in PBMCs following 12 weeks of sofosbuvir + ribavirin versus study entry. Tenofovir in the plasma was unchanged. In Cohort 2, tenofovir diphosphate was 17.8-fold higher (95% CI 12.77-24.86; P < 0.0001) in dried blood spots after 8 weeks of ledipasvir/sofosbuvir versus study entry. Tenofovir plasma concentrations were 2.1-fold higher (95% CI 1.44-2.91; P = 0.0005). Despite the increase in cellular tenofovir diphosphate concentrations, only a small decline in CLCR (6%-7%) was observed in both cohorts between study entry and end of treatment.

Conclusions

These data indicate an unexpected drug interaction with tenofovir disoproxil fumarate and sofosbuvir at the cellular level. Additional studies are needed to determine the mechanism and clinical significance.

Inflammation and pharmacokinetics: potential implications for HIV-infection

INTRODUCTION

The physiological changes accompanying inflammation may alter the pharmacokinetics (PK) of certain medications. Individuals infected with HIV have chronically elevated inflammatory markers despite viral suppression following effective antiretroviral therapy (ART), as well as age-related inflammation. Understanding the potential clinical implications of inflammation on the PK of medications is important for understanding dose-response relationships and necessitates future research. Areas covered: An extensive literature search was carried out using PubMed and associated bibliographies to summarize the current state of knowledge regarding altered PK in response to inflammation and its application to the field of HIV. Expert opinion: Preclinical and clinical studies show that inflammation leads to a downregulation of certain drug metabolizing enzymes and both up and down regulation of transporters depending on the transporter and cell type. Decreased gastric acidity, fluid shifts, and plasma protein alterations also occur with inflammation, leading to potential absorption, distribution, and clearance changes. More research is needed including controlled PK studies to address the clinical relevance of these observations, especially in the aging HIV-infected population. Results from future studies will enable us to better predict drug concentrations in individuals with inflammation, in line with efforts to provide personalized pharmacotherapy in our healthcare system.

Decline in Bone Mass With Tenofovir Disoproxil Fumarate/Emtricitabine Is Associated With Hormonal Changes in the Absence of Renal Impairment When Used by HIV-Uninfected Adolescent Boys and Young Men for HIV Preexposure Prophylaxis

BACKGROUND

We aimed to define the relative importance of renal and endocrine changes in tenofovir disoproxil fumarate (TDF)-related bone toxicity.

METHODS

In a study of daily TDF/emtricitabine (FTC) preexposure prophylaxis (PrEP) in human immunodeficiency virus (HIV)-uninfected young men who have sex with men, we measured changes from baseline in blood and urine markers of the parathyroid hormone (PTH)-vitamin D-fibroblast growth factor 23 (FGF23) axis, creatinine, and renal tubular reabsorption of phosphate (TRP). We explored the relationship of those variables to changes in bone mineral density (BMD). Tenofovir-diphosphate (TFV-DP) in red blood cells was used to categorize participants into high and low drug exposure groups.

RESULTS

There were 101 participants, median age 20 years (range 15 to 22). Compared with low drug exposure, high-exposure participants showed increase from baseline in PTH and decline in FGF23 by study week 4, with no differences in creatinine, phosphate, or TRP. At 48 weeks, the median (interquartile range) percent decline in total hip BMD was greater in those with high- compared to low- exposure (-1.59 [2.77] vs +1.54 [3.34] %, respectively; P = .001); in high-exposure participants, this correlated with week 4 TFV-DP (inversely; r = -0.60, P = .002) and FGF23 (directly; r = 0.42; P = .039) but not other variables.

CONCLUSIONS

These findings support the short-term renal safety of TDF/FTC PrEP in HIV-seronegative young men and suggest that endocrine disruption (PTH-FGF23) is a primary contributor to TDF-associated BMD decline in this age group.

CLINICAL TRIALS REGISTRATION

NCT01769469.

Model Linking Plasma and Intracellular Tenofovir/Emtricitabine with Deoxynucleoside Triphosphates

The coformulation of the nucleos(t)ide analogs (NA) tenofovir (TFV) disoproxil fumarate (TDF) and emtricitabine (FTC) is approved for HIV-infection treatment and prevention. Plasma TFV and FTC undergo complicated hybrid processes to form, accumulate, and retain as their active intracellular anabolites: TFV-diphosphate (TFV-DP) and FTC-triphosphate (FTC-TP). Such complexities manifest in nonlinear intracellular pharmacokinetics (PK). In target cells, TFV-DP/FTC-TP compete with endogenous deoxynucleoside triphosphates (dNTP) at the active site of HIV reverse transcriptase, underscoring the importance of analog:dNTP ratios for antiviral efficacy. However, NA such as TFV and FTC have the potential to disturb the dNTP pool, which could augment or reduce their efficacies. We conducted a pharmacokinetics-pharmacodynamics (PKPD) study among forty subjects receiving daily TDF/FTC (300 mg/200 mg) from the first-dose to pharmacological intracellular steady-state (30 days). TFV/FTC in plasma, TFV-DP/FTC-TP and dNTPs in peripheral blood mononuclear cells (PBMC) were quantified using validated LC/MS/MS methodologies. Concentration-time data were analyzed using nonlinear mixed effects modeling (NONMEM). Formations and the accumulation of intracellular TFV-DP/FTC-TP was driven by plasma TFV/FTC, which was described by a hybrid of first-order formation and saturation. An indirect response link model described the interplay between TFV-DP/FTC-TP and the dNTP pool change. The EC₅₀ (interindividual variability, (%CV)) of TFV-DP and FTC-TP on the inhibition of deoxyadenosine triphosphate (dATP) and deoxycytidine triphosphate (dCTP) production were 1020 fmol/10⁶ cells (130%) and 44.4 pmol/10⁶ cells (82.5%), resulting in (90% prediction interval) 11% (0.45%, 53%) and 14% (2.6%, 35%) reductions. Model simulations of analog:dNTP molar ratios using IPERGAY dosing suggested that FTC significantly contributes to the protective effect of preexposure prophylaxis (PrEP). Simulation-based intracellular operational multiple dosing half-lives of TFV-DP and FTC-TP were 6.7 days and 33 hours. This model described the formation of intracellular TFV-DP/FTC-TP and the interaction with dNTPs, and can be used to simulate analog:dNTP time course for various dosing strategies.

Intracellular Tenofovir and Emtricitabine Anabolites in Genital, Rectal, and Blood Compartments from First Dose to Steady State

The pharmacokinetics (PK) of tenofovir-diphosphate (TFV-DP) and emtricitabine-triphosphate (FTC-TP), the active anabolites of tenofovir disoproxil fumarate (TDF), and emtricitabine (FTC) in blood, genital, and rectal compartments was determined in HIV-positive and seronegative adults who undertook a 60-day intensive PK study of daily TDF/FTC (plus efavirenz in HIV positives). Lymphocyte cell sorting, genital, and rectal sampling occurred once per subject, at staggered visits. Among 19 HIV-positive (3 female) and 21 seronegative (10 female) adults, TFV-DP in peripheral blood mononuclear cells (PBMC) accumulated 8.6-fold [95% confidence interval (CI): 7.2-10] from first-dose to steady-state concentration (Css) versus 1.7-fold (95% CI: 1.5-1.9) for FTC-TP. Css was reached in ∼11 and 3 days, respectively. Css values were similar between HIV-negative and HIV-positive individuals. Css TFV-DP in rectal mononuclear cells (1,450 fmol/10⁶ cells, 898-2,340) was achieved in 5 days and was >10 times higher than PBMC (95 fmol/10⁶ cells, 85-106), seminal cells (22 fmol/10⁶ cells, 6-79), and cervical cells (111 fmol/10⁶ cells, 64-194). FTC-TP Css was highest in PBMC (5.7 pmol/10⁶ cells, 5.2-6.1) and cervical cells (7 pmol/10⁶ cells, 2-19) versus rectal (0.8 pmol/10⁶ cells, 0.6-1.1) and seminal cells (0.3 pmol/10⁶ cells, 0.2-0.5). Genital drug concentrations on days 1-7 overlapped with estimated Css, but accumulation characteristics were based on limited data. TFV-DP and FTC-TP in cell sorted samples were highest and achieved most rapidly in CD14⁺ compared with CD4⁺, CD8⁺, and CD19⁺ cells. Together, these findings demonstrate cell-type and tissue-dependent cellular pharmacology, preferential accumulation of TFV-DP in rectal mononuclear cells, and rapid distribution into rectal and genital compartments.

Dose response for starting and stopping HIV preexposure prophylaxis for men who have sex with men

BACKGROUND

This study estimated the number of daily tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) doses required to achieve and maintain (after discontinuation) intracellular drug concentrations that protect against human immunodeficiency virus (HIV) infection for men who have sex with men (MSM).

METHODS

Tenofovir diphosphate (TFV-DP) concentrations in peripheral blood mononuclear cells (PBMCs) and rectal mononuclear cells from an intensive pharmacokinetic study ("Cell-PrEP" [preexposure prophylaxis]) of 30 days of daily TDF/FTC followed by 30 days off drug were evaluated. A regression formula for HIV risk reduction derived from PBMCs collected in the preexposure prophylaxis initiative study was used to calculate inferred risk reduction. The time required to reach steady state for TFV-DP in rectal mononuclear cells was also determined.

RESULTS

Twenty-one HIV-uninfected adults participated in Cell-PrEP. The inferred HIV risk reduction, based on PBMC TFV-DP concentration, reached 99% (95% confidence interval [CI], 69%-100%) after 5 daily doses, and remained >90% for 7 days after stopping drug from steady-state conditions. The proportion of participants reaching the 90% effective concentration (EC90) was 77% after 5 doses and 89% after 7 doses. The percentage of steady state for natural log [TFV-DP] in rectal mononuclear cells was 88% (95% CI, 66%-94%) after 5 doses and 94% (95% CI, 78%-98%) after 7 doses.

CONCLUSIONS

High PrEP activity for MSM was achieved by approximately 1 week of daily dosing. Although effective intracellular drug concentrations persist for several days after stopping PrEP, a reasonable recommendation is to continue PrEP dosing for 4 weeks after the last potential HIV exposure, similar to recommendations for postexposure prophylaxis.