Tenofovir Diphosphate In Dried Blood Spots Research Articles

Drug concentrations in hair and dried blood spots as PrEP adherence metrics during pregnancy and postpartum.

We evaluated hair tenofovir (TFV) concentrations as an adherence metric for HIV pre-exposure prophylaxis (PrEP) during pregnancy and postpartum and compared hair levels with tenofovir-diphosphate (TFV-DP) levels in dried blood spots (DBS). Overall, 152 hair samples from 102 women and 36 hair-DBS paired samples from 29 women were collected from a subset of women in a cluster randomized trial. Having a partner known to be living with HIV was associated with higher hair TFV levels (p<0.001). Hair TFV concentrations were strongly correlated with DBS TFV-DP levels (r=0.76, p<0.001), indicating hair as promising cumulative adherence metric for perinatal PrEP assessment.

High study participation but diverging adherence levels: qualitatively unpacking PrEP use among adolescent girls and young women over two years in Eastern Cape, South Africa

In Southern and Eastern Africa, initiation of daily oral pre-exposure prophylaxis (PrEP) for HIV prevention has been high among adolescent girls and young women (AGYW) offered PrEP. However, persistence and prevention-effective use of PrEP among this critical group continues to be a challenge. We conducted a qualitative sub-study of AGYW from the Community PrEP Study in Eastern Cape Province, South Africa who had high rates of pick up for monthly PrEP refills over two years, but differing levels of PrEP adherence based on tenofovir-diphosphate (TFV-DP) measurements in dried blood spots (DBS). Contrasting 22 AGYW with low versus high levels of TFV-DP in DBS, we qualitatively explored factors which influenced PrEP persistence vs. non-persistence, unique patterns of PrEP use (e.g., discarding or stockpiling), and participant recommendations for improving AGYW prevention-effective use of PrEP in the future. Results showed that PrEP misconceptions and mistrust among participants’ social networks negatively influenced adherence. In comparison, supportive families and/or partners and personal trust that PrEP works positively influenced adherence. Those with low adherence described being motivated to come to the site for other study benefits (e.g., reimbursement money, snacks, sanitary pads) and discarding PrEP to avoid stigma associated with being seen with pills. Future PrEP implementation strategies should focus on involving families and partners in PrEP support for AGYW and minimizing PrEP stigma at a community level.Trial registration NCT03977181. Retrospectively registered on June 6, 2019.

Urine point-of-care tenofovir test demonstrates strong predictive clinical and research utility.

Preexposure prophylaxis (PrEP) significantly reduces HIV infection risk but is dependent on adherence. Available approaches to measuring adherence have limitations related to accuracy, cost, practicality, and timeliness. This study compared the performance of two methods implementable in clinics and research studies [interview and urine point of care (POC) assay] to the gold-standard for measuring recent and longer term adherence in dried blood spots (DBS). Participants were recruited from RADAR, a cohort study of young MSM, or via online advertisements. At 3 monthly visits, an interviewer administered 7-day timeline follow-back (TLFB) questionnaire, DBS samples were tested for tenofovir-diphosphate (TFV-DP) to estimate average dosing over the prior month and emtricitabine-triphosphate (FTC-TP) to assess recent dosing (past 2-3 days), and a urine POC TFV test to qualitatively assess recent adherence (past 4 days). Eighty-three PrEP users contributed 163 observations. At visit 1, self-reported adherence was 86% (4+ doses in last 7 days), versus urine TFV (74%), DBS FTC-TP (76%), and DBS TFV-DP (69%). The objective measures of short-term adherence performed similarly well in predicting longer term adherence. In multivariable logistic regression analyses, the urine assay was a significant predictor of DBS TFV-DP (adjusted OR = 19.4, P < 0.0001); self-report did not add significantly. The urine POC TFV assay had excellent predictive values for adherence and self-report did not add significantly to prediction. The POC assay provides results in several minutes to enable same-visit counseling, requires no specialized training, and is projected to be low-cost.

Food Insecurity Is Associated With Low Tenofovir Diphosphate in Dried Blood Spots in South African Persons With HIV.

Food insecurity has been linked to suboptimal antiretroviral therapy (ART) adherence in persons with HIV (PWH). This association has not been evaluated using tenofovir diphosphate (TFV-DP) in dried blood spots (DBSs), a biomarker of cumulative ART adherence and exposure. Within a prospective South African cohort of treatment-naive PWH initiating ART, a subset of participants with measured TFV-DP in DBS values was assessed for food insecurity status. Bivariate and multivariate median-based regression analysis compared the association between food insecurity and TFV-DP concentrations in DBSs adjusting for age, sex, ethnicity, medication possession ratio (MPR), and estimated glomerular filtration rate. Drug concentrations were available for 285 study participants. Overall, 62 (22%) PWH reported worrying about food insecurity and 44 (15%) reported not having enough food to eat in the last month. The crude median concentrations of TFV-DP in DBSs differed significantly between those who expressed food insecurity worry versus those who did not (599 [interquartile range {IQR}, 417-783] fmol/punch vs 716 [IQR, 453-957] fmol/punch; P = .032). In adjusted median-based regression, those with food insecurity worry had concentrations of TFV-DP that were 155 (95% confidence interval, -275 to -35; P = .012) fmol/punch lower than those who did not report food insecurity worry. Age and MPR remained significantly associated with TFV-DP. In this study, food insecurity worry is associated with lower TFV-DP concentrations in South African PWH. This highlights the role of food insecurity as a social determinant of HIV outcomes including ART failure and resistance.

Acceptability and Feasibility of Providing Adherence Feedback Based on Tenofovir Diphosphate in Dried Blood Spots: Results from a Pilot Study Among Patients and Providers in Cape Town, South Africa.

Tenofovir diphosphate (TFV-DP) concentrations in dried blood spots (DBS) predict viral breakthrough, but their use remains understudied in real-world clinic settings. This pilot study examined acceptability, feasibility, and initial adherence outcomes of providing adherence feedback using TFV-DP concentrations on patient- and provider-levels in Cape Town, South Africa. We enrolled 60 persons with HIV (PWH) receiving tenofovir-containing ART attending a primary health clinic. They were randomized 1:1 to an intervention receiving TFV-DP concentration feedback by research staff vs. no feedback at monthly visits for 4 months. Acceptability among medical providers and level of clinical follow-up of TFV-DP results was examined. Patient acceptability was assessed descriptively. Mean electronic adherence (EA), as measured by WisePill device, and TFV-DP in DBS were compared between the two arms. All participants in the intervention group (100%) reported finding TFV-DP feedback helpful and 86% reported changing adherence behaviors. Medical providers indicated high acceptability of incorporating TFV-DP concentration feedback into the clinic, yet among 29 results < 1000 fmol/punch, only 2 were reviewed with no follow-up actions performed. In the intervention arm, mean TFV-DP concentrations were significantly higher (t = 2.5, p < .01) during follow-up and EA in upper quartile (96-100%) was greater compared to controls (x2 = 7.8, p ≤ .05). This study found high acceptability among patients for receiving adherence feedback based on TFV-DP concentrations. TFV-DP and EA data demonstrated greater adherence in the intervention group. Providers indicated high acceptability of incorporating TFV-DP feedback into the clinic, but few providers reviewed results, which could impact clinic-level feasibility.

Comparing Predictive Ability of Two Objective Adherence Measures in a Community-Based Cohort on Antiretroviral Therapy in South Africa: Tenofovir Diphosphate Concentrations and Electronic Adherence Monitors.

Electronic adherence (EA) and tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) are objective measures of antiretroviral therapy (ART) adherence. We characterized the association between these measures in a prospective cohort of persons with HIV (PWH) on ART. Four primary health clinics in Cape Town, South Africa. We enrolled 250 virally suppressed PWH receiving tenofovir-based ART. We collected EA data, monthly viral load, and TFV-DP in DBS for 12 months. We used logistic regression to estimate the adjusted odds ratio (aOR) and 95% confidence intervals (CIs) for future viral breakthrough (VB) (>400 copies/mL) for each adherence measure. Receiver operating characteristics (ROCs) provided the predictive power of these measures. Participants had a median (IQR) age of 34 (27-42); 78% were women. Twenty-one (8%) developed VB. Logistic regression showed that when percent EA and TFV-DP concentrations increased, the odds of VB decreased. This relationship was consistent at the time of VB (aOR of 0.41 [95% CI: 0.25 to 0.66] for TFV-DP and aOR of 0.64 [95% CI: 0.54 to 0.76] for EA) and for up to 2 months before VB. Both adherence measures predicted future VB at both 1 month and 2 months before viral load measurement. We established that 2 objective adherence measures, EA and TFV-DP in DBS, have a positive association with, and are both strongly predictive of, VB in a community-based South African cohort on ART. Future research is needed to determine the feasibility of implementing these adherence measures in resource-limited settings to facilitate adherence interventions.

Demographic and Clinical Characteristics of Persons with HIV with Viral Load:Adherence Mismatch Who Are at Risk of Future Viremia.

The potency of modern antiretroviral therapy (ART) allows for greater forgiveness to missed doses while still achieving, and maintaining, viral suppression. However, imperfect ART adherence, even if sufficient to maintain viral suppression, has been associated with adverse clinical outcomes. ART adherence can be objectively quantified using tenofovir diphosphate (TFV-DP) in dried blood spots (DBS), a biomarker of cumulative adherence that is predictive of future viremia-even among persons with HIV (PWH) with an undetectable HIV viral load (VL). Within a prospective cohort of PWH on tenofovir disoproxil fumarate-including ART, mismatch between drug concentration and HIV VL (i.e., low concentrations of TFV-DP in DBS in the setting of viral suppression with subsequent viremia at the following visit) was observed more frequently in PWH who were Black (36% vs. 15%; p = .04), had body mass index >30 kg/m2 (40% vs. 13%; p = .01), and reported <100% 3 months (68% vs. 50%; p = .005) and 30 days (56% vs. 31%; p = .001) adherence, compared with PWH without mismatch. Identifying PWH at risk for future viremia could help clinicians implement targeted timely interventions before episodes of breakthrough viremia.

Tenofovir Diphosphate in Dried Blood Spots in Pregnant and Postpartum Women With HIV in Kenya: A Novel Approach to Measuring Peripartum Adherence.

Adherence to antiretroviral therapy (ART) among pregnant and postpartum women with HIV (PWLWH) is critical to promote maternal health and prevent HIV transmission. Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is an objective assessment of cumulative ART adherence that has not been fully assessed in PWLWH. Southwestern Kenya. PWLWH receiving tenofovir disoproxil fumarate-based ART from 24 health facilities provided DBS samples at 3 time points [pregnancy/early postpartum (PP), 6 months PP, and 9-12 months PP]. Thresholds for daily adherence were defined as TFV-DP in DBS ≥650 fmol/punch in pregnancy and ≥950 PP. Descriptive analysis is presented. Cluster adjusted χ2 and t-tests were used to test for association with clinical and demographic factors. A total of 419 DBS samples were collected from 150 PWLWH. Median TFV-DP in DBS was lowest, 552 fmol/punch [interquartile range (IQR), 395-759] in pregnancy and declined over time [914 (IQR, 644-1176) fmol/punch; early PP; 838 (IQR, 613-1063) fmol/punch 6 months PP; and 785 (IQR, 510-1009) fmol/punch 9-12 months; P < 0.001]. Only 42% of samples in pregnancy and 38.5% of samples in PP met thresholds for daily adherence. Clinical or demographic factors were not associated with suboptimal adherence levels. Cumulative ART exposure in PWLWH, quantified by TFV-DP in DBS, demonstrated a stepwise decrease (ie, adherence) PP. Most women demonstrated less than daily adherence throughout the peripartum period. Use of TFV-DP in DBS as a measure of cumulative ART adherence could help optimize health outcomes in PWLWH and their infants.

Tenofovir diphosphate in dried blood spots predicts future viremia in persons with HIV taking antiretroviral therapy in South Africa.

Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is used as a biomarker of antiretroviral therapy (ART) adherence. Recent treatment studies have shown that TFV-DP predicts future viremia in persons with HIV (PWH) but there are few data from high-burden settings. We investigated whether TFV-DP in DBS predicts future viral breakthrough in South African PWH. Prospective observational cohort. We enrolled 250 adults receiving tenofovir-containing regimens, currently virally suppressed (<50 copies/ml) but at risk of future viral breakthrough, from four primary health clinics in Cape Town. Paired viral load and DBS for TFV-DP were collected monthly for 12 months. Viral breakthrough was the first confirmed viral load greater than 400 copies/ml. Logistic regression estimated the odds ratio (OR) and 95% confidence intervals for future viral breakthrough at the next visit. Participants provided 2944 paired DBS and viral load samples. Median (IQR) age was 34 (27-42) years; median duration on ART at study entry was 11 (4-12) months;78% were women. Twenty-one (8%) participants developed viral breakthrough. Participants with TFV-DP 400 fmol/punch or less had an adjusted OR of 16.1 (95% CI: 3.9-67.4; P < 0.001) for developing viral breakthrough 1 month later compared with participants with TFV-DP greater 800 fmol/punch. TFV-DP in DBS strongly predicted future viral breakthrough in a clinical cohort of South African PWH. A biomarker able to identify PWH at risk for future viral breakthrough has the potential to improve health outcomes through timely intervention. Future studies exploring the clinical use of TFV-DP in DBS in conjunction with viral load in ART monitoring are warranted.

Estimated pill intake with on-demand PrEP with oral TDF/FTC using TFV-DP concentration in dried blood spots in the ANRS IPERGAY trial.

Tenofovir diphosphate (TFV-DP) concentration in dried blood spots (DBSs) is a reliable pharmacokinetics biomarker of adherence to tenofovir disoproxil fumarate (TDF). We aimed to use DBSs to estimate pill intake among participants using on-demand pre-exposure prophylaxis (PrEP) and to identify predictive factors associated with higher TFV-DP concentrations. DBSs were collected at the last study visit of the open-label phase of the ANRS IPERGAY study, assessing on-demand oral TDF/emtricitabine for PrEP among MSM and transgender female participants. We quantified TFV-DP in DBSs centrally. We assessed correlation between pill count and TFV-DP concentration by Spearman correlation and explored associations between participant demographics, sexual behaviour and PrEP use during sexual intercourse (SI) with TFV-DP concentrations by univariate and multivariate logistic regression models. The median age of the 245 participants included in this study was 40 years, with a median body weight of 73 kg. Median (IQR) TFV-DP concentration reached 517 (128-868) fmol/punch, corresponding to an estimated intake of 8-12 tablets per month (2-3 doses per week). Only 39% of participants had a TFV-DP concentration above 700 fmol/punch. TFV-DP concentrations were moderately correlated with pill count (r: 0.59; P < 0.001). In multivariate analysis, only systematic use of PrEP during SI and more frequent episodes of SI in the past 4 weeks were significantly associated with higher TFV-DP levels [OR (95% CI): 11.30 (3.62-35.33) and 1.46 (1.19-1.79), respectively; P < 0.001]. Among participants using on-demand PrEP, estimated pill intake reached 8-12 tablets per month and was correlated with frequency and systematic use of PrEP for SI.

Lower Cumulative Antiretroviral Exposure in People Living With HIV and Diabetes Mellitus.

People living with HIV (PLWH) are living longer and developing more non-AIDS comorbidities, which negatively impact antiretroviral therapy (ART) adherence. Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is a novel pharmacologic measure of cumulative ART adherence that is predictive of viral suppression and future viremia. However, the relationship between non-AIDS comorbidities and this adherence measure is unknown. We aimed to evaluate the association between 3 non-AIDS comorbidities (diabetes mellitus (DM), hypertension, and hyperlipidemia) and TFV-DP in DBS in PLWH. Blood for TFV-DP in DBS and HIV viral load was prospectively collected from PLWH on tenofovir disoproxil fumarate for up to 3 times over 48 weeks. Non-AIDS comorbidities were recorded. Mixed effect multivariable linear regression models were used to estimate the changes in TFV-DP concentrations in DBS according to the presence of comorbidities and to estimate the percent differences in TFV-DP concentrations between these groups. A total of 1144 person-visits derived from 523 participants with available concentrations of TFV-DP in DBS were included in this analysis. In univariate analysis, no significant association between non-AIDS comorbidities (categorized as having 0, 1, 2, or 3 comorbidities) and the concentrations of TFV-DP in DBS was observed (P = 0.40). Participants who had DM had 25% lower (95% confidence interval: -36% to -12%; P < 0.001) TFV-DP in DBS than participants without DM after adjusting for age, gender, race, body mass index, estimated glomerular filtration rate, CD4 T-cell count, hematocrit, ART class, patient-level medication regimen complexity index, and 3-month self-reported adherence. Diabetic PLWH have lower concentrations of TFV-DP in DBS compared with those without DM. Further research is required to identify the clinical implications and biological mechanisms underlying these findings.

Income Inequality Is Associated With Low Cumulative Antiretroviral Adherence in Persons With Human Immunodeficiency Virus

BackgroundThe adherence biomarker tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is associated with viral suppression and predicts future viremia. However, its association with social determinants of health (SDoH) in people with human immunodeficiency virus (PWH) remains unknown.MethodsDried blood spots for TFV-DP were longitudinally collected from a clinical cohort of PWH receiving tenofovir disoproxil fumarate-based therapy (up to 3 visits over 48 weeks) residing in 5 Colorado counties. To assign SDoH, zip codes at enrollment were matched with SDoH data from AIDSVu (https://aidsvu.org/). The SDoH included household income, percentage living in poverty, education level, and income inequality (quantified using Gini coefficient, where 0 and 1 represent perfect income equality and inequality, respectively). Log-transformed TFV-DP concentrations were analyzed using a mixed-effects model to estimate percentage change (95% confidence interval) in TFV-DP for every significant change in the SDoH and adjusted for relevant covariates including age, gender, race, estimated glomerular filtration rate, body mass index, hematocrit, CD4+ T-cell count, antiretroviral drug class, and 3-month self-reported adherence. ResultsData from 430 PWH totaling 950 person-visits were analyzed. In an adjusted analysis, income inequality was inversely associated with TFV-DP in DBS. For every 0.1 increase in the Gini coefficient, TFV-DP concentrations decreased by 9.2% (−0.5 to −17.1; P = .039). This remained significant after adjusting for human immunodeficiency virus viral suppression, where a 0.1 increase in Gini was associated with a decrease of 8.7% (−0.3 to −17.9; P = .042) in TFV-DP. ConclusionsHigher income inequality was associated with lower cumulative antiretroviral adherence. These findings support the need for further research on how SDoH impact adherence and clinical care.

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

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. 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. 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. 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.

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

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. 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. 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. 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.

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

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. 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. 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. 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.

Tenofovir-Diphosphate as a Marker of HIV Pre-exposure Prophylaxis Use Among East African Men and Women.

Background: Controlled pharmacokinetic (PK) studies in United States populations have defined categories of tenofovir-diphosphate (TFV-DP) in dried blood spots (DBS) for various pre-exposure prophylaxis (PrEP) adherence targets. It is unknown how these categories perform in other populations. Therefore, we evaluated the sensitivity and specificity of these PK-derived categories compared to daily medication electronic adherence monitoring (MEMS) data among East African men and women using daily PrEP.Methods: Participants were enrolled as members of HIV serodiscordant couples as part of an open-label PrEP study in Kenya and Uganda. Blood samples were taken at quarterly visits and stored as DBS, which were analyzed for TFV-DP concentrations.Results: Among 150 samples from 103 participants, MEMs data indicated that 87 (58%) took ≥4 doses and 62 (41%) took ≥6 per week consistently over the 4 weeks prior to sample collection. Sensitivities of DBS TFV-DP levels were 62% for the ≥4 doses/week category (≥700 fmol/punch TFV-DP) and 44% for the ≥6 doses/week category (≥1050 fmol/punch TFV-DP); specificities were 86 and 94%, respectively. There were no statistically significant differences in these sensitivities and specificities by gender.Conclusion: In this sample of East African PrEP users, categories of TFV-DP concentrations developed from directly observed PrEP use among United States populations had high specificity but lower than expected sensitivity. Sensitivity was lowest when MEMS data indicated high adherence (i.e., ≥6 doses/week). PrEP studies and implementation programs should carefully consider the sensitivity and specificity of the TFV-DP levels used for adherence feedback.

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.

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.

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

Although tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is a predictor of adherence and pre-exposure prophylaxis efficacy, its utility in human immunodeficiency virus (HIV) treatment remains unknown. DBS for TFV-DP were collected up to 3 times over 48 weeks in persons living with HIV (PLWH) who were receiving TFV disoproxil fumarate (TDF)-based therapy. Log-transformed baseline TFV-DP was compared using t-tests or analyses of variance; generalized estimating equations were used to estimate the adjusted odds ratio (aOR) of viral suppression (<20 copies/mL) based on the TFV-DP concentration at the study visit. We analyzed 1199 DBS from 532 participants (76 female; 101 Black, 101 Hispanic). Among the virologically-suppressed participants at baseline (n = 347), TFV-DP was lower in Blacks (geometric mean 1453, 95% confidence interval [CI] 1291-1635) vs Whites (1793, 95% CI 1678-1916; P = .002) and Hispanics (1760, 95% CI 1563-1982; P = .025); in non-boosted (1610, 95% CI 1505-1723) vs. boosted (1888, 95% CI 1749-2037; P = .002) regimens; and in non-nucleoside reverse transcription inhibitor-based (1563, 95% CI 1432-1707) vs. boosted protease inhibitor-based (1890, 95% CI 1704-2095; P = .006) and multiclass-based (1927, 95% CI 1650-2252; P = .022) regimens. The aOR of virologic suppression, after adjusting for age, gender, race, body mass index, estimated glomerular filtration rate, CD4+ T-cell count, antiretroviral drug class and duration of therapy, was 73.5 (95% CI 25.7-210.5; P < .0001) for a TFV-DP concentration ≥1850 fmol/punch compared to <350 fmol/punch. TFV-DP in DBS is strongly associated with virologic suppression in PLWH on TDF-based therapy and is associated with certain participant characteristics. Further research is required to evaluate this drug adherence and exposure measure in clinical practice. NCT02012621.

Brief Report: Adherence Biomarker Measurements in Older and Younger HIV-Infected Adults Receiving Tenofovir-Based Therapy.

Concentrations of tenofovir (TFV) in hair and tenofovir diphosphate (TFV-DP) in dried blood spots (DBSs) as measures of cumulative exposure have been primarily studied in younger, HIV-uninfected individuals taking preexposure HIV prophylaxis. Data on these measures among older HIV-infected individuals are limited. We evaluated longitudinal TFV and TFV-DP concentrations in hair and DBS, respectively, from HIV-infected adults. Multivariable model variables included age group (18-35 and 60 years and older), creatinine clearance (CrCl), hematocrit (TFV-DP), and gray hair color (TFV). Baseline hair TFV and DBS TFV-DP were moderately correlated [r = 0.5 (0.2 to 0.7); P = 0.001] across both age groups [younger (N = 23) and older (N = 22)]. In adjusted models, CrCl was associated with increases of 15.9% (7.4% to 25.0%); P = 0.0006, and 5.7% (-0.2% to 11.9%); P = 0.057 for TFV in hair and TFV-DP in DBS, respectively, for every 20-mL/min CrCl decrease. Although older age (versus younger age) was univariately associated with increased TFV hair levels, older age was not significantly associated with higher concentrations in hair [-1.4% (-26.7% to 32.7%); P = 0.93] or DBS [4.0% (-14.1% to 25.9%); P = 0.68] after adjustment. Similarly, gray color was not significantly associated with higher TFV levels in hair [27.6% (-11.1% to 83.0%; P = 0.18)] in adjusted models. In both adjusted and unadjusted models of TFV-DP levels in DBS, a 1% hematocrit increase was associated with a 3.3% (0.2% to 6.5%) TFV-DP increase (P = 0.04). Cumulative drug exposure measures (hair and DBS) were comparable in younger and older HIV-infected individuals on TFV-based therapy after adjustment for renal function.