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

Relationship Between Tenofovir Diphosphate Concentrations in Dried Blood Spots and Virological Outcomes After Initiating Tenofovir-Lamivudine-Dolutegravir as First-Line or Second-Line Antiretroviral Therapy

BACKGROUND

Tenofovir diphosphate (TFV-DP) concentration in dried blood spots is a marker of long-term adherence. We investigated the relationship between TFV-DP concentrations and virological outcomes in participants initiating tenofovir-lamivudine-dolutegravir (TLD) as first-line or second-line antiretroviral therapy.

SETTING

Three primary care clinics in Khayelitsha, Cape Town, South Africa.

METHODS

We conducted a post hoc analysis of 2 randomized controlled trials of participants initiating TLD. TFV-DP concentrations and viral loads were measured at 12, 24, and 48 weeks. Multivariable logistic regression was performed to assess the association with virological suppression (<50 copies/mL) per natural logarithm increase in TFV-DP concentration. Generalized estimating equations with logit link were used to assess associations with virological rebound. The Akaike Information Criterion and Quasi-likelihood Information Criteria were used to compare models built on continuous TFV-DP data to 4 previously defined concentration categories.

RESULTS

We included 294 participants in the analysis, 188 (64%) of whom initiated TLD as second-line therapy. Adjusted odds ratios (95% CIs) of virological suppression were 2.12 (1.23, 3.75), 3.11 (1.84, 5.65), and 4.69 (2.81, 8.68) per natural logarithm increase in TFV-DP concentration at weeks 12, 24, and 48, respectively. In participants with virological suppression at week 12, the adjusted odds ratio for remaining virologically suppressed was 3.63 (95% CI: 2.21 to 5.69) per natural logarithm increase in TFV-DP concentration. Models using continuous TFV-DP data had lower Akaike Information Criterion and Quasi-likelihood Information Criteria values than those using categorical data for predicting virological outcomes.

CONCLUSION

TFV-DP concentrations in dried blood spots exhibit a dose-response relationship with viral load. Analyzing TFV-DP concentrations as continuous variables rather than conventional categorization may be appropriate.

Heavy Alcohol Use and HIV Outcomes: The Moderating Role of Pain

Pain and heavy alcohol consumption are prevalent among people living with HIV/AIDS (PLWH), each contributing to impaired functioning and diminished quality of life. Each of these conditions may have negative effects on the HIV care continuum, but less is known about their combined influences. The current study examined how heavy drinking and pain were associated with HIV viral suppression and CD4 cell count among participants receiving antiretroviral therapy (ART). The study sample consisted of 220 PLWH with past 12-month substance dependence or ever injection drug use enrolled in a large HIV cohort study. Logistic regression analyses showed an interaction between pain level (no/mild pain vs moderate/severe) and heavy drinking on viral suppression such that heavy drinking was a significant predictor of poorer viral suppression only for those who experienced moderate/severe pain. We also examined whether ART adherence differentially mediated the association between heavy drinking and HIV viral suppression by level of pain. Although there was a significant indirect effect of heavy drinking on viral suppression among those with moderate/severe pain, moderated mediational analyses did not indicate that the indirect effect of heavy drinking on viral suppression through ART adherence differed significantly by level of pain. Pain level did not significantly moderate the association between heavy drinking and CD4 cell count. We conclude that heavy drinking may be particularly likely to be associated with poorer HIV viral suppression among PLWH with moderate or severe pain. Providers should routinely address comorbid heavy drinking and pain to improve HIV outcomes.

Tenofovir diphosphate in dried blood spots and HIV-1 resistance in South Africa

BACKGROUND

Suboptimal antiretroviral (ART) adherence can lead to virologic failure with consequent HIV-1 resistance. Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is a powerful biomarker of cumulative adherence, predictive of future viremia. It has been associated with resistance in Persons With HIV (PWH) in South Africa and the US. We explored the relationship of TFV-DP concentrations with antiretroviral drug resistance at the time of treatment failure in SA.

METHODS

Adult PWH from health clinics in Cape Town, South Africa on efavirenz-based first-line ART containing tenofovir disoproxil fumarate (TDF) with an undetectable (< 50 copies/mL) HIV-1 viral load (VL) were prospectively enrolled in an observational cohort for 12 months. Monthly study visits included blood collection for HIV-1 VL and DBS for TFV-DP. The first confirmed viral breakthrough (VB) > 400 copies/mL triggered HIV-1 genotyping at the subsequent visit. An electronic adherence (EA) device monitored ART adherence in real-time, estimated as a percent for the 30-days prior to VB. Wilcoxon rank sum test was used to compare median [IQR] TFV-DP by genotype outcome.

RESULTS

Of 250 individuals, (n = 195, 78% women), 21 experienced VB, with a median of 5 [4;7] months on study, and a median EA of 33.3 [13.3;53.3]%. Demographic characteristics between those with and without VB were similar. Median VL at VB was 4.0 [3.2;4.5] log copies/mL. TFV-DP concentrations trended down towards the VB visit. Median TFV-DP concentrations were significantly higher in those HIV-1 genotype did not amplify due to being virally suppressed at the subsequent visit (n = 10; 380 [227-661] fmol/punch, p = 0.035; EA 45 [24.9; 59.2]%); than in those who were successfully genotyped with evidence of drug resistance (n = 5, 241 [150-247] fmol/punch, EA 20 [6.7;36.7]%) and in individuals who did not have resistance (n = 3, 39.9 [16.6; 93.9] fmol/punch; EA 33.3 [16-38]%). Three genotype collections were not done. Only non-nucleoside reverse transcriptase inhibitor-associated mutations were identified on resistance testing. (K103N, E138K, Y118H).

CONCLUSION

TFV-DP in DBS showed a step-wise inverse relationship with VB and drug resistance, with evidence of low cumulative ART adherence in PWH who developed antiretroviral resistance. Monitoring TFV-DP concentrations could be a valuable tool for predicting future VB and future resistance.

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

BACKGROUND

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.

SETTING

Four primary health clinics in Cape Town, South Africa.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Prevalence and predictors of viral load suppression in adults living with HIV in the western region of Ghana: A cross-sectional study

Background

Although antiretroviral therapy is beneficial and available free of cost to patients, several roadblocks still prevent patients from reaching viral suppression. This research aimed to determine the prevalence rate of viral suppression among people living with HIV in the western region of Ghana and identify the factors contributing to viral non-suppression.

Methods

A cross-sectional study was conducted on 7199 HIV-positive adults. All data from the Sekondi Public Health Laboratory database was exported to Microsoft Excel and then verified and filtered before being exported to STATA 16.1. Viral non-suppression was modeled statistically using logistic regression.

Results

Viral load suppression was achieved in 5465 (75.91%) study participants who received antiretroviral treatment. However, 1734 participants (24.0%) did not achieve viral suppression. Patients with poor adherence to ARV (AOR 0.30; 95% CI 0.16, 0.58) and fair adherence to ARV (AOR 0.23; 95% CI 0.12, 0.45) were associated with a lower odd of viral non-suppression. Patients with six (6) months to two (2) years of treatment before viral load testing (AOR 0.67; 95% CI 0.46, 0.98) were also associated with a lower likelihood of viral non-suppression.

Conclusions

The rate of non-suppression was high, and the suppression rate fell short of the UNAIDS target. Poor ARV adherence, fair ARV adherence, and a treatment duration of six (6) months to two (2) years before viral load testing appear to be obstacles to viral load suppression. The research findings seem to suggest that viral load testing supports viral non-suppression. Therefore, using viral load tests to monitor medication's effects on health can motivate patients to adhere to their prescribed medication regimen. More research is needed to determine whether viral load testing can improve adherence. Given the high rate of virologic failure, the study highlights the importance of identifying antiretroviral resistance patterns.

Use of Tenofovir Diphosphate Levels to Predict Viremia During the Postpartum Period in Women Living With Human Immunodeficiency Virus (HIV): A Nested Case-Control Study

BACKGROUND

There are few data on the utility of tenofovir diphosphate (TFV-DP) in dried blood spots (DBSs) to predict future viral load (VL) in postpartum women with HIV on antiretroviral therapy (ART).

METHODS

We conducted a nested case-control study within a trial of postpartum ART delivery strategies. Participants started ART containing tenofovir disoproxil fumarate (TDF) in pregnancy, were <10 weeks postpartum, and had a VL <400 copies/mL. VL and TFV-DP samples were taken every 3-6 months over 24 months. Cases had ≥1 VL ≥20 copies/mL; controls were randomly sampled from women with persistent viral suppression (VS; VL <20 copies/mL). Generalized estimating equations were used to calculate likelihood odds ratios (LORs) for future VL ≥20 copies/mL by TFV-DP concentration at the preceding visit.

RESULTS

61 cases and 20 controls contributed 365 DBS-VL pairs (median ART duration, 16 months). Sensitivity and specificity of TFV-DP <700 fmol/punch to detect future viremia were 62.9% (95% CI, 54.7-70.6%) and 89.7% (84.9-93.4%), respectively. Adjusting for age, ART duration, previous VL, and duration between the TFV-DP and VL measures, LORs of viremia for TFV-DP concentrations 350-699 and <350 fmol/punch versus TFV-DP ≥1850 fmol/punch were 3.5 (95% CI, 1.1-10.8; P = .033) and 12.9 (3.6-46.6; P < .0001), respectively. Including only samples taken during VS, the LOR of future viremia for TFV-DP concentration <350 fmol/punch versus TFV-DP ≥1850 fmol/punch was 9.5 (1.9-47.0).

CONCLUSIONS

TFV-DP concentrations in DBSs were strongly associated with future viremia and appear useful to identify nonadherence and predict future elevated VL.

Cumulative tenofovir diphosphate exposure in persons with HIV taking single- vs. multiple-tablet regimens

BACKGROUND

We assessed cumulative antiretroviral exposure-using tenofovir diphosphate (TFV-DP) in dried blood spots (DBS)-in persons with HIV (PWH) receiving tenofovir disoproxil fumarate (TDF)-based antiretroviral therapy (ART) as single-tablet regimens (STR) or multiple-tablet regimens (MTR).

METHODS

Blood for DBS was prospectively collected in PWH on TDF during 1144 person visits (n = 523). Linear mixed-effects models, adjusted for baseline characteristics, were used to compare TFV-DP in STR versus MTR. Models adjusted for ART regimen using either anchor drug class, pharmacokinetic booster status (unboosted [u/] or boosted [b/]), or a combined STR/MTR and booster categorical variable.

RESULTS

In the anchor class-adjusted model, STR had 19% (95% confidence interval [CI]: 3%-37%; p = 0.02) higher TFV-DP concentrations than MTR. However, in the booster-adjusted model, STR was not significantly higher than MTR (estimate 5%, 95% CI: -9% to 21%; p = 0.48), although PWH on b/ART had 35% (95% CI: 16%-58%; p = 0.0001) higher TFV-DP than u/ART. In the STR/MTR-boosted variable model, when compared to u/MTR, b/STR, b/MTR, and u/STR had 25% (95% CI: 7%-47%; p = 0.005), 37% (95% CI: 17%-59%; p < 0.0001), and 7% (95% CI: -7% to 24%; p = 0.34) higher TFV-DP, respectively. Compared with b/MTR, b/STR had 9% (95% CI: -31% to 10%; p = 0.37) lower TFV-DP. In a sensitivity analysis of PWH with HIV viral load <20 copies/ml at all visits, b/STR and b/MTR had 34% (95% CI: 16%-55%; p < 0.0001) and 12% (95% CI: -2% to 27%; p = 0.09) higher TFV-DP, respectively, compared with u/MTR, while u/STR had 4% (95% CI: -15% to 8%; p = 0.50) lower TFV-DP. Compared with b/MTR, b/STR had 17% (95% CI: 2%-30%; p = 0.03) higher TFV-DP.

CONCLUSIONS

Persons with HIV on b/TDF-based ART had higher TFV-DP than u/ART, regardless of STR or MTR use. No significant differences in TFV-DP between regimens of the same boosting status (i.e., b/STR vs. b/MTR; u/STR vs. u/MTR) were observed in the full cohort. Future research should examine the clinical utility of these findings in patient-tailored ART selection.

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

OBJECTIVES

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.

DESIGN

Prospective observational cohort.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Drug Resistance, Rather than Low Tenofovir Levels in Blood or Urine, Is Associated with Tenofovir, Emtricitabine, and Efavirenz Failure in Resource-Limited Settings

The high cost of viral load (VL) testing limits its use for antiretroviral therapy (ART) adherence support. A low-cost lateral flow urine tenofovir (TFV) rapid assay predicts pre-exposure prophylaxis breakthroughs, but has not yet been investigated in HIV treatment. We therefore evaluated its utility in a pilot cross-sectional study of TFV-containing ART recipients at an increased risk of virologic failure (VF). Participants who had a treatment interruption ≥30 days or had ≥1 episode of viremia (VL ≥400 copies/mL) in the previous year were recruited from a public health setting in Cape Town, South Africa. Self-reported adherence data were collected, the urine TFV assay performed, and concurrent TFV-diphosphate analyzed in dried blood spots. VL testing was done concurrently and, if viremic, genotypic HIV drug resistance testing was performed. Of 48 participants, 18 (37.5%) had VL (>400 copies/mL) at the time of the study, including 16 of 39 receiving efavirenz (EFV), 2 of 6 receiving protease inhibitors, and 0 of 3 receiving dolutegravir. Resistance testing succeeded in 17/18, of which 14 had significant mutations compromising ≥2 agents of the current EFV-based regimen. Of these 14, all had detected urine TFV. Urine TFV was undetectable in two out of three without regimen-relevant resistance; p = .02. In participants on EFV-based regimens returning to care, VF was largely due to viral resistance, where detectable urine TFV had 100% sensitivity (14/14 participants) in predicting resistance. Conversely, when undetectable, the urine-based assay could be used to preclude participants with poor adherence from undergoing costly HIV drug resistance testing.

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

BACKGROUND

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.

SETTING

Southwestern Kenya.

METHODS

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.

RESULTS

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.

CONCLUSION

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 levels in dried blood spots are associated with virologic failure and resistance to first-line therapy in South Africa: a case-control cohort study

INTRODUCTION

Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS), a measure of cumulative antiretroviral therapy (ART) adherence, is associated with viral suppression and predicts future viremia in persons with HIV (PWH). However, its utility to identify those at risk for virologic failure (VF) and drug resistance is unknown. To address this, we aimed to establish the association between this adherence biomarker and VF with drug resistance in a cohort of PWH initiating first-line ART in KwaZulu-Natal, South Africa.

METHODS

PWH initiating TFV disoproxil fumarate (TDF)-based ART within a parent prospective cohort were evaluated. Using a nested design, DBS for TFV-DP were collected from cases who developed VF (HIV-1 RNA ≥1000 copies/ml) after ≥5 months on ART versus controls, matched 1:2 by site, age, gender, race and ART duration. Cases were categorized as having VF with or without resistance using genotyping. One-way analysis of variance (ANOVA) was used to compare TFV-DP for controls, cases with VF and resistance, and cases with VF without resistance. Data are presented as mean (standard deviation, SD) or geometric mean [95% confidence interval, 95% CI].

RESULTS AND DISCUSSION

One thousand participants were enrolled in the parent study between 2014 and 2016, of which 288 (29%) had DBS available. Of these, 94 (33%) were cases and 194 (67%) were controls; 59% were women. Mean age of our population was 33 (SD 8) years. Genotyping was available in 50 (53%) of the 94 cases. Geometric mean TFV-DP in DBS from controls was 708 [95% CI; 647-773] fmol/punch, which was higher compared to participants having VF with resistance (n = 36), 386 [95% CI; 241-617] fmol/punch and VF without resistance (n = 14), 61 [95% CI; 22-164] fmol/punch; p<0.001. Genotype could not be obtained in 44 (47%) cases.

CONCLUSIONS

TFV-DP in DBS showed a stepwise association with VF and drug resistance in South African PWH. Participants having VF with resistance had mid-range concentrations of TFV-DP, which were higher than those for PWH without resistance. Future research on the clinical utility of TFV-DP concentrations in DBS to predict and prevent the development of VF and drug resistance is needed.

Higher medication complexity in persons with HIV is associated with lower tenofovir diphosphate in dried blood spots

STUDY OBJECTIVE

To assess the association between tenofovir diphosphate (TFV-DP) in dried blood spots (DBS), a measure of cumulative tenofovir-based antiretroviral (ART) adherence, with medication regimen complexity in persons with human immunodeficiency virus (PWH).

DESIGN

Prospective clinical cohort (up to three visits over 48 weeks).

SETTING

Academic-based HIV clinic.

PATIENTS

PWH receiving tenofovir disoproxil fumarate (TDF)-based ART.

MEASUREMENTS

DBS for TFV-DP were collected at every study visit. Baseline patient-level medication regimen complexity index (pMRCI) scores were calculated and categorized into three sub-scores (disease-specific [ART], non-ART, and over-the-counter [OTC]). The pMRCI scores were evaluated to assess the association with TFV-DP in DBS <350 fmol/punch after adjusting for clinical covariates. pMRCI scores were also categorized to estimate the adjusted relative risk (aRR) of having a TFV-DP <350 fmol/punch between pMRCI quartiles.

MAIN RESULTS

Data from 525 participants (1,146 person-visits) were analyzed. Baseline median (interquartile range [IQR]) pMRCI scores for participants with TFV-DP in DBS <350 vs. ≥350 fmol/punch were 4 (3, 8) vs. 4 (2, 6) for ART, 27 (12, 31) vs. 12 (5, 22) for non-ART, and 0 (0, 1) vs. 0 (0, 2) for OTC, respectively. For the non-ART scores, the aRR for having a TFV-DP in DBS <350 fmol/punch was 6.4 (95% CI: 2.0, 20.6; P=0.002) when comparing participants in the highest pMRCI quartile with those in the lowest quartile.

CONCLUSIONS

Higher pMRCI for non-ART medications is associated with lower adherence as measured by TFV-DP in DBS. Future research should investigate whether reducing non-ART medication complexity improves ART adherence and exposure in PWH.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Approaches to Objectively Measure Antiretroviral Medication Adherence and Drive Adherence Interventions

PURPOSE OF REVIEW

Traditional methods to assess antiretroviral adherence, such as self-report, pill counts, and pharmacy refill data, may be inaccurate in determining actual pill-taking to both antiretroviral therapy (ART) or pre-exposure prophylaxis (PrEP). HIV viral loads serve as surrogates of adherence on ART, but loss of virologic control may occur well after decreases in adherence and viral loads are not relevant to PrEP.

RECENT FINDINGS

Pharmacologic measures of adherence, electronic adherence monitors, and ingestible electronic pills all serve as more objective metrics of adherence, surpassing self-report in predicting outcomes. Pharmacologic metrics can identify either recent adherence or cumulative adherence. Recent dosing measures include antiretroviral levels in plasma or urine, as well as emtricitabine-triphosphate in dried blood spots (DBS) for those on tenofovir-emtricitabine-based therapy. A urine tenofovir test has recently been developed into a point-of-care test for bedside adherence monitoring. Cumulative adherence metrics assess adherence over weeks to months and include measurement of tenofovir-diphosphate in peripheral blood mononuclear cells or DBS, as well as ART levels in hair. Electronic adherence monitors and ingestible electronic pills can track pill bottle openings or medication ingestion, respectively. New and objective approaches in adherence monitoring can be used to detect nonadherence prior to loss of prevention efficacy or virologic control with PrEP or ART, respectively.

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.