Tenofovir Diphosphate in Dried Blood Spots Is Strongly Associated With Viral Suppression in Individuals With Human Immunodeficiency Virus Infections

Increased tenofovir monoester concentrations in patients receiving tenofovir disoproxil fumarate with ledipasvir/sofosbuvir

BACKGROUND

Intracellular tenofovir diphosphate concentrations are markedly increased in HIV/HCV coinfected individuals receiving tenofovir disoproxil fumarate (TDF) with sofosbuvir-containing treatment. Sofosbuvir may inhibit the hydrolysis of TDF to tenofovir, resulting in increased concentrations of the disoproxil or monoester forms, which may augment cell loading. We sought to quantify tenofovir disoproxil and monoester concentrations in individuals receiving TDF with and without ledipasvir/sofosbuvir.

METHODS

HIV/HCV coinfected participants receiving TDF-based therapy were sampled pre-dose and 1 and 4 h post-dose prior to and 4 weeks after initiating ledipasvir/sofosbuvir. Tenofovir disoproxil was not detectable. Tenofovir monoester in plasma and tenofovir diphosphate in PBMC and dried blood spots (DBS) were quantified using LC-MS/MS. Geometric mean ratios (week 4 versus baseline) and 95% CIs were generated for the pharmacokinetic parameters. P values reflect paired t-tests.

RESULTS

Ten participants had complete data. At baseline, geometric mean (95% CI) tenofovir monoester plasma concentrations at 1 and 4 h post-dose were 97.4 ng/mL (33.0-287.5) and 0.74 ng/mL (0.27-2.06), respectively. With ledipasvir/sofosbuvir, tenofovir monoester concentrations at 4 h post-dose were 5.02-fold higher (95% CI 1.40-18.05; P = 0.019), but did not significantly differ at 1 h post-dose (1.72-fold higher, 95% CI 0.25-11.78; P = 0.54), possibly due to absorption variability. Tenofovir diphosphate in PBMC and DBS were increased 2.80-fold (95% CI 1.71-4.57; P = 0.001) and 7.31-fold (95% CI 4.47-11.95; P < 0.0001), respectively, after 4 weeks of ledipasvir/sofosbuvir.

CONCLUSIONS

Tenofovir monoester concentrations were increased in individuals receiving TDF with ledipasvir/sofosbuvir, consistent with inhibition of TDF hydrolysis. Additional studies are needed to determine the clinical relevance of this interaction.

Pharmacokinetics of tenofovir monoester and association with intracellular tenofovir diphosphate following single-dose tenofovir disoproxil fumarate

BACKGROUND

Tenofovir monoester is a relatively lipophilic intermediate formed during the hydrolysis of tenofovir disoproxil to tenofovir. Its clinical pharmacokinetic profile and influence on the cellular pharmacology of tenofovir diphosphate have not been reported.

METHODS

Plasma, PBMC and dried blood spots (DBS) were obtained from HIV-uninfected adults participating in a randomized, cross-over bioequivalence study of single-dose tenofovir disoproxil fumarate (TDF)/emtricitabine unencapsulated or encapsulated with a Proteus® ingestible sensor. Plasma pharmacokinetics of tenofovir monoester and tenofovir were characterized using non-compartmental methods. Relationships with tenofovir diphosphate in DBS and PBMC were examined using mixed-effects models.

RESULTS

Samples were available from 24 participants (13 female; 19 white, 3 black, 2 Hispanic). Tenofovir monoester appeared rapidly with a median (range) Tmax of 0.5 h (0.25-2) followed by a rapid monophasic decline with a geometric mean (coefficient of variation) t½ of 26 min (31.0%). Tenofovir monoester Cmax was 131.6 ng/mL (69.8%) and AUC0-4 was 93.3 ng·h/mL (47.9%). The corresponding values for plasma tenofovir were 222.2 ng/mL (37.1%) and 448.1 ng·h/mL (30.0%). Tenofovir monoester AUC0-∞ (but not tenofovir AUC0-∞) was a significant predictor of tenofovir diphosphate in both PBMC (P = 0.015) and DBS (P = 0.005), increasing by 3.8% (95% CI 0.8%-6.8%) and 4.3% (95% CI 1.5%-7.2%), respectively, for every 10 ng·h/mL increase in tenofovir monoester.

CONCLUSIONS

Tenofovir monoester Cmax and AUC0-4 were 59.2% and 20.6% of corresponding plasma tenofovir concentrations. Tenofovir monoester was significantly associated with intracellular tenofovir diphosphate concentrations in PBMC and DBS, whereas tenofovir concentrations were not. Tenofovir monoester likely facilitates cell loading, thereby increasing tenofovir diphosphate exposures in vivo.

Emtricitabine triphosphate in dried blood spots is a predictor of viral suppression in HIV infection and reflects short-term adherence to antiretroviral therapy

BACKGROUND

Emtricitabine triphosphate (FTC-TP), the phosphorylated anabolite of emtricitabine, can be quantified in dried blood spots (DBS). We evaluated FTC-TP in DBS as a predictor of viral suppression and evaluated self-reported adherence as a predictor of FTC-TP.

METHODS

Persons living with HIV (PLWH) on an FTC-containing regimen were prospectively recruited. A DBS and HIV viral load were obtained during routine clinical visits. Self-reported adherence for 3 days, 30 days and 3 months was captured. Generalized estimating equations were used to estimate the adjusted odds ratio (aOR) of viral suppression for quantifiable FTC-TP versus below the limit of quantification (BLQ). The utility of self-reported adherence to predict quantifiable FTC-TP was assessed by calculating the area under receiver operating characteristic (ROC) curve.

RESULTS

One thousand one hundred and fifty-four person-visits from 514 participants who had DBS assayed for FTC-TP were included in the analysis. After adjusting for age, gender, race, BMI, ART class, ART duration, estimated glomerular filtration rate and CD4+ T cell count, the aOR (95% CI) for viral suppression for quantifiable FTC-TP versus BLQ was 7.2 (4.3-12.0; P < 0.0001). After further adjusting for tenofovir diphosphate, the aOR was 2.1 (1.2-4.0; P < 0.015). The area under the ROC curve for 3 day self-reported adherence was 0.82 (95% CI 0.75-0.88) compared with 0.70 (95% CI 0.62-0.77, P = 0.004) and 0.79 (95% CI 0.71-0.86, P = 0.32) for 3 month and 30 day self-reported adherence, respectively.

CONCLUSIONS

In PLWH, FTC-TP from DBS is a strong predictor of viral suppression, even after adjusting for tenofovir diphosphate, and was best predicted by 3 day self-reported adherence.

Intracellular Tenofovir-Diphosphate and Emtricitabine-Triphosphate in Dried Blood Spots Following Tenofovir Alafenamide: The TAF-DBS Study

BACKGROUND

Tenofovir alafenamide (TAF), in combination with FTC, was recently approved for PrEP in the United States. The objective of this study was to assess the relationship between tenofovir-diphosphate (TFV-DP) and emtricitabine-triphosphate (FTC-TP) in dried blood spots (DBS) with adherence to TAF/FTC.

METHODS

TAF-DBS was a randomized, crossover clinical study of TFV-DP in DBS, following directly observed dosing of 33%, 67%, or 100% of daily TAF (25 mg)/FTC (200 mg). Healthy volunteers were randomized to 2 different, 12-week dosing regimens, separated by a 12-week washout. DBS were collected weekly. TFV-DP and FTC-TP were extracted from two 7-mm punches and assayed with LC-MS/MS.

RESULTS

Thirty-seven participants (17 female, 7 African American, and 6 Hispanic) were included. TFV-DP exhibited a mean half-life of 20.8 days (95% confidence interval: 19.3 to 21.3). The slope for TFV-DP versus dosing arm was 1.14 (90% confidence interval: 1.07 to 1.21). The mean (SD) TFV-DP after 12 weeks was 657 (186), 1451 (501), and 2381 (601) fmol/2 7-mm punches for the 33%, 67%, and 100% arms. The following adherence interpretations are proposed: <450 fmol/punches, <2 doses/wk; 450-949 fmol/punches, 2-3 doses/wk; 950-1799 fmol/punches, 4-6 doses/wk; and ≥1800 fmol/punches, 7 doses/wk. FTC-TP was quantifiable for 1 week after drug cessation in 50%, 92%, and 100% of participants in the 33%, 67%, and 100% arms, respectively.

CONCLUSION

TFV-DP in DBS after TAF/FTC exhibited a long half-life and was linearly associated with dosing, similar to its predecessor tenofovir disoproxil fumarate. FTC-TP was quantifiable for up to 1 week after drug cessation. Together, these moieties provide complementary measures of cumulative adherence and recent dosing for TAF/FTC.

The crosstalk between antiretrovirals pharmacology and HIV drug resistance

INTRODUCTION

The clinical development of antiretroviral drugs has been followed by a rapid and concomitant development of HIV drug resistance. The development and spread of HIV drug resistance is due on the one hand to the within-host intrinsic HIV evolutionary rate and on the other to the wide use of low genetic barrier antiretrovirals.

AREAS COVERED

We searched PubMed and Embase on 31 January 2020, for studies reporting antiretroviral resistance and pharmacology. In this review, we assessed the molecular target and mechanism of drug resistance development of the different antiretroviral classes focusing on the currently approved antiretroviral drugs. Then, we assessed the main pharmacokinetic/pharmacodynamic of the antiretrovirals. Finally, we retraced the history of antiretroviral treatment and its interconnection with antiretroviral worldwide resistance development both in , and middle-income countries in the perspective of 90-90-90 World Health Organization target.

EXPERT OPINION

Drug resistance development is an invariably evolutionary driven phenomenon, which challenge the 90-90-90 target. In high-income countries, the antiretroviral drug resistance seems to be stable since the last decade. On the contrary, multi-intervention strategies comprehensive of broad availability of high genetic barrier regimens should be implemented in resource-limited setting to curb the rise of drug resistance.

Brief Report: Relationship Between ABCC4 SNPs and Hepatitis B Virus Suppression During Tenofovir-Containing Antiretroviral Therapy in Patients With HIV/HBV Coinfection

BACKGROUND

Incomplete hepatitis B virus (HBV) suppression during antiretroviral therapy (ART) in HIV and HBV coinfected patients is common, but underlying factors are not fully elucidated. We hypothesize that genetic factors that influence nucleoside analog pharmacokinetics will affect HBV treatment response.

METHODS

HIV/HBV coinfected patients on tenofovir disoproxil fumarate/lamivudine (TDF/3TC)-containing ART were enrolled. Selected ABCC4 single nucleotide polymorphisms (SNPs) with known effects on nucleoside pharmacokinetics were genotyped using TaqMan assays. Relationship between ABCC4 SNPs and unsuppressed HBV DNA (HBV DNA ≥20 IU/mL) were examined.

RESULTS

Of the 50 participants on TDF/3TC-containing ART for a median (range) of 1.5 (1-7.4) years, 20 (40%) had unsuppressed HBV DNA. Participants with unsuppressed compared with those with suppressed HBV DNA were more likely to have negative HBe antibody, lower body mass index, and lower CD4 count at enrollment. Carriers of ABCC4 rs11568695 (G3724A) variant allele were more likely than noncarriers to have unsuppressed HBV (61.1% vs. 29.0%, P = 0.038). Among 36 patients with suppressed HIV RNA (presumed good ART adherence), ABCC4 rs11568695 variant carriers were more likely than noncarriers to have unsuppressed HBV (58.8% vs. 20.0% P = 0.021). Logistic regression analysis that included genetic and nongenetic factors identified ABCC4 rs11568695 variant allele, body mass index, and male sex as predictors of unsuppressed HBV DNA.

CONCLUSIONS

We identified a novel association between ABCC4 rs11568695 SNP and poor HBV treatment response. If confirmed in further studies, ABCC4 genotyping could be used to identify individuals who may need intensified HBV therapy.

Enzymatic Assay for Rapid Measurement of Antiretroviral Drug Levels

Poor adherence to pre-exposure prophylaxis (PrEP) and antiretroviral therapy (ART) can lead to human immunodeficiency virus (HIV) acquisition and emergence of drug-resistant infections, respectively. Measurement of antiviral drug levels provides objective adherence information that may help prevent adverse health outcomes. Gold-standard drug-level measurement by liquid chromatography/mass spectrometry is centralized, heavily instrumented, and expensive and is thus unsuitable and unavailable for routine use in clinical settings. We developed the REverSe TRanscrIptase Chain Termination (RESTRICT) assay as a rapid and accessible measurement of drug levels indicative of long-term adherence to PrEP and ART. The assay uses designer single-stranded DNA templates and intercalating fluorescent dyes to measure complementary DNA (cDNA) formation by reverse transcriptase in the presence of nucleotide reverse transcriptase inhibitor drugs. We optimized the RESTRICT assay using aqueous solutions of tenofovir diphosphate (TFV-DP), a metabolite that indicates long-term adherence to ART and PrEP, at concentrations over 2 orders of magnitude above and below the clinically relevant range. We used dilution in water as a simple sample preparation strategy to detect TFV-DP spiked into whole blood and accurately distinguished TFV-DP drug levels corresponding to low and high PrEP adherences. The RESTRICT assay is a fast and accessible test that could be useful for patients and clinicians to measure and improve ART and PrEP adherence.

Tenofovir alafenamide use in pregnant and lactating women living with HIV

Introduction: Tenofovir alafenamide (TAF)-containing fixed-dose drug combinations (FDCs) are increasingly being used in managing pregnant women living with HIV. However, TAF is not currently recommended during pregnancy due to limited pharmacokinetic and safety data. TAF, a newer nucleotide phosphonamidate prodrug of tenofovir (TFV), achieves high levels of tenofovir-diphosphate in lymphoid cells and hepatocytes, and 90% lower systemic concentrations of TFV compared to tenofovir disoproxil fumarate (TDF), thereby maximizing TAF's antiviral efficacy, potency and clinical safety.Areas covered: This review discusses the currently available information on the pharmacology of TAF in pregnant women living with HIV. Pharmacokinetic studies with TAF during pregnancy have yielded varying results compared to postpartum, but TAF exposures during pregnancy have been within the range of those typically observed in non-pregnant adults. The efficacy and safety of TAF in treatment-naïve pregnant women living with HIV is currently being evaluated in the VESTED study, a phase-III NIH randomized clinical trial.Expert opinion: Initial pregnancy data suggest that TAF-based FDCs have high efficacy and low risk of adverse effects during pregnancy. TAF is likely to become part of first-line regimens for use in pregnant women living with HIV once additional pregnancy data from phase III trials are available.

Short Communication: Cascade of Antiretroviral Therapy Adherence in Virologically Suppressed Persons Living with HIV

Variable adherence to antiretroviral therapy (ART) can maintain HIV viral suppression, but our understanding of the ART adherence continuum remains limited. In a clinical cohort of adult persons living with HIV treated with a tenofovir (TFV) disoproxil fumarate/emtricitabine (TDF/FTC)-based regimen, data on 3-month self-reported adherence and dried blood spots (DBS) for TFV diphosphate (TFV-DP) and FTC triphosphate (FTC-TP) were collected. Among 521 participants in whom DBS were available upon enrollment, 333 were virologically suppressed (<20 copies/mL). Only 145 (44%) of them reported 100% 3-month adherence, and 69 (21%) had drug concentrations in the highest adherence categories (TFV-DP ≥1,850 fmol/punch and quantifiable FTC-TP). These findings demonstrate a wide range of ART adherence and drug exposure associated with viral suppression, indicating that modern regimens are pharmacologically forgiving. Additional research is needed to understand the biologic effects of variable adherence and drug exposure beyond plasma virologic suppression.

A Comparison of Plasma Efavirenz and Tenofovir, Dried Blood Spot Tenofovir-Diphosphate, and Self-Reported Adherence to Predict Virologic Suppression Among South African Women

BACKGROUND

Tenofovir-diphosphate (TFV-DP) in dried blood spots (DBS) is an objective long-term adherence measure, but data are limited on its ability to predict virologic suppression (VS) in people on antiretroviral (ARV) treatment. There are also no data comparing DBS TFV-DP with plasma ARV concentrations as predictors of VS.

METHODS

Women who were on a first-line regimen of tenofovir, emtricitabine, and efavirenz (EFV) were enrolled in a cross-sectional study. Plasma EFV and tenofovir (TFV), DBS TFV-DP assays, and 30-day self-reported adherence were evaluated as predictors of VS (<50 copies/mL) with the area under the curve of receiver operating characteristics and logistic regression.

RESULTS

We enrolled 137 women; mean age of 33 years; median 4 years on antiretroviral therapy; 88 (64%) had VS. In receiver operating characteristics analyses: DBS TFV-DP [0.926 (95% CI: 0.876 to 0.976)] had a higher area under the curve than plasma TFV [0.864 (0.797 to 0.932); P = 0.006], whereas plasma EFV [0.903 (0.839-0.967)] was not significantly different from DBS TFV-DP (P = 0.138) or plasma TFV (P = 0.140); all ARV assays performed better than self-report. The association of TFV-DP in DBS with VS strengthened with increasing concentrations [reference <350 fmol/punch: 350-699 fmol/punch aOR 37 (8-178); 700-1249 fmol/punch aOR 47 (13-175); ≥1250 fmol/punch aOR 175 (20-1539)]. "White coat adherence" (defined as DBS TFV-DP <350 fmol/punch with detectable plasma TFV) was only detected in 4 women.

CONCLUSIONS

Plasma EFV, TFV, and DBS TFV-DP were all strong predictors of VS. EFV or TFV assays have potential for development as point-of-care assays for use as objective adherence measures in resource-limited settings.

Engagement in Mental Health Care is Associated with Higher Cumulative Drug Exposure and Adherence to Antiretroviral Therapy

Mental health (MH) disorders are more prevalent among persons living with HIV compared to the general population, and may contribute to suboptimal adherence to antiretroviral therapy (ART). Tenofovir-diphosphate (TFV-DP), the phosphorylated anabolite of tenofovir (TFV), is a biomarker with a 17-day half-life in red blood cells. TFV-DP can be measured in dried blood spots (DBS) using liquid chromatography/tandem mass spectrometry (LC-MS/MS) to assess adherence and cumulative drug exposure to tenofovir disoproxil fumarate (TDF)-based ART. From a larger clinical cohort (N = 807), TFV-DP concentrations and a paired HIV viral load were available from 521 participants at their enrollment visit. We used multivariable linear regression to evaluate the association between TFV-DP in DBS and engagement in MH care. After adjusting for clinical covariates, participants with MH disorders who were engaged in MH care had 40% higher TFV-DP compared to participants with MH disorders who were not engaged in MH care (p < 0.001), and similar TFV-DP to participants without MH disorders (p = 0.219). Further research is needed to identify the mechanism(s) for these findings, with the goal of optimizing engagement and retention in MH care strategies to improve ART adherence and clinical outcomes in PLWH with MH disorders.

Predictive Value of Tenofovir Diphosphate in Dried Blood Spots for Future Viremia in Persons Living With HIV

BACKGROUND

Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is associated with viral suppression in persons living with HIV (PLWH) taking tenofovir disoproxil fumarate (TDF). However, its value as a predictor of future viremia remained unknown.

METHODS

Blood for plasma viral load (VL) and TFV-DP in DBS were collected (up to 3 visits within 48 weeks) in PLWH on TDF. TFV-DP cut points were selected using logistic prediction models maximizing the area under the receiver operation characteristic curve, and estimated adjusted odds ratio (aOR) of future viremia (≥20 copies/mL) were compared to the highest TFV-DP category.

RESULTS

Among all 451 participants in the analysis, aOR of future viremia for participants with TFV-DP <800 and 800 to <1650 fmol/punch were 4.7 (95% CI, 2.6-8.7; P < .0001) and 2.1 (95% CI, 1.3-3.3; P = .002) versus ≥1650 fmol/punch, respectively. These remained significant for participants who were virologically suppressed at the time of the study visit (4.2; 95% CI, 1.5-12.0; P = .007 and 2.2; 95% CI, 1.2-4.0; P = .01).

CONCLUSIONS

TFV-DP in DBS predicts future viremia in PLWH on TDF, even in those who are virologically suppressed. This highlights the utility of this biomarker to inform about adherence beyond VL. Clinical Trials Registration. NCT02012621.

Predictors of Long-Term HIV Pre-exposure Prophylaxis Adherence After Study Participation in Men Who Have Sex With Men

BACKGROUND

Efficacy of HIV pre-exposure prophylaxis (PrEP) among men who have sex with men is well documented in randomized trials. After trial completion, participants are challenged with acquiring PrEP on their own and remaining adherent.

METHODS

This was a follow-up study of the TAPIR randomized controlled multicenter PrEP trial. Participants were contacted after their last TAPIR visit (ie, after study-provided PrEP was discontinued) to attend observational posttrial visits 24 and 48 weeks later. Adherence during TAPIR and posttrial visits was estimated by dried blood spot intracellular tenofovir diphosphate levels (adequate adherence defined as tenofovir diphosphate levels >719 fmol/punch). Binary logistic regression analysis assessed predictors of completing posttrial visits and PrEP adherence among participants completing ≥1 visit.

RESULTS

Of 395 TAPIR participants who were on PrEP as part of the TAPIR trial for a median of 597 days (range 3-757 days), 122 (31%) completed ≥1 posttrial visit (57% of University of California San Diego participants completed posttrial visits, whereas this was 13% or lower for other study sites). Among participants who completed ≥1 posttrial visit, 57% had adequate adherence posttrial. Significant predictors of adequate adherence posttrial were less problematic substance use, higher risk behavior, and adequate adherence in year 1 of TAPIR.

CONCLUSION

More than half of PrEP users followed after trial completion had successfully acquired PrEP and showed adequate adherence. Additional adherence monitoring and intervention measures may be needed for those with low PrEP adherence and problematic substance use during the first year of trial.

Moderately High Tenofovir Diphosphate in Dried Blood Spots Indicates Drug Resistance in Viremic Persons Living with HIV

BACKGROUND

Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is a strong predictor of viral suppression in persons living with HIV (PLWH). Its association with antiretroviral therapy (ART) resistance remains unknown.

METHODS

Blood was collected in PLWH receiving TDF-containing ART enrolled in a 48-week study. Tenofovir diphosphate/emtricitabine triphosphate (FTC-TP) were quantified from the same sample as HIV viral load (VL) in PLWH who developed resistance within ≤12 months.

RESULTS

The study enrolled 807 participants, of whom 10 had new resistance-conferring mutations. Among these, median (interquartile range) TFV-DP and HIV VL were 956 (407-1510) fmol/punch and 9840 (513-68,200) copies/mL, respectively. Five had quantifiable FTC-TP in DBS. Based on previously published data, a TFV-DP concentration of 956 fmol/punch would have an adjusted odds of virologic suppression of 32.8 versus TFV-DP <350 fmol/punch, making viremia of ∼10,000 copies/mL an unexpected outcome.

CONCLUSION

Moderately high TFV-DP in DBS (700-1249 fmol/punch) in PLWH with high viremia suggest that antiretroviral drug resistance might be present.