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

Pharmacokinetics of Tenofovir Diphosphate, Lamivudine Triphosphate and Emtricitabine Triphosphate in Adolescents With HIV Infection With and Without Tuberculosis Coinfection

BACKGROUND

There is limited data on the cellular pharmacokinetics (PK) of the nucleos(t)ide reverse transcriptase inhibitors (NRTIs) in adolescents with HIV (AWH). We examined the steady-state concentrations of the NRTIs anabolites in dried blood spots (DBS) and peripheral blood mononuclear cells (PBMCs) in AWH and those with tuberculosis (TB) confection on rifampin-containing TB treatment.

METHODS

AWH and TB/HIV coinfection on TB treatment receiving tenofovir (TFV) disoproxil fumarate (TDF) 300 mg/lamivudine (3TC) 300 mg or emtricitabine (FTC) 200 mg daily for at least 8 weeks were enrolled. DBS were collected at the study entry. Following 2 weeks of telephone adherence reminders, DBS sampling was repeated, and 4 PBMC samples were collected between 10 and 20 hours postdose. Concentrations of TFV diphosphate (TFV-DP), 3TC triphosphate and FTC triphosphate in DBS and PBMCs were measured. Adherence based on TFV-DP concentrations in DBS and the anabolites concentrations in DBS and PBMCs were compared by TB coinfection status, and ≤14 versus >14 years old.

RESULTS

Of 52 participants (46.2% with TB), the median (interquartile range) age 15.0 (14.5-17.0) years, 25 (48.1%) were male. Adherence based on TFV-DP in DBS was not significantly different by TB coinfection status or age group. The concentrations of the anabolites in DBS and PBMCs were similar in AWH and TB/HIV coinfection and ≤14 versus >14 years of age; and median concentrations at the population level were similar to historical values in adults.

CONCLUSIONS

The concentrations of the recommended NRTIs and pharmacokinetics-determined adherence were not significantly different in adolescents with TB or younger age.

Measurements of tenofovir-diphosphate and emtricitabine-triphosphate concentrations in dried blood spots of people receiving pre-exposure prophylaxis for HIV with co-formulated tenofovir disoproxil fumarate and emtricitabine

BACKGROUND/PURPOSE(S)

Data regarding the concentrations of tenofovir-diphosphate (TFV-DP) and emtricitabine-triphosphate (FTC-TP) in the Asian population receiving pre-exposure prophylaxis (PrEP) for HIV with tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) (TDF/FTC) are limited, and the associations between the frequency of TDF/FTC administration and drug concentration among people receiving on-demand PrEP remain unclear.

METHODS

Fifty-seven participants receiving daily TDF/FTC and 113 participants receiving on-demand TDF/FTC were enrolled in this study. The concentrations of TFV-DP and FTC-TP were measured in dried blood spots using liquid chromatography‒mass spectrometry.

RESULTS

Thirty-six (62.2 %) daily PrEP users and 38 (33.6 %) on-demand PrEP users achieved TFV-DP concentrations ≥700 fmol/punch. Higher proportions of undetectable FTC-TP were observed in participants whose TFV-DP concentrations were ≤350 fmol/punch, regardless of the frequency of TDF/FTC administration. In participants who used on-demand PrEP, the TFV-DP and FTC-TP concentrations were moderately correlated with the TDF/FTC tablets taken when sampling was performed within 12-24 h after the last dose of TDF/FTC (R = 0.63, p = 0.006 and R = 0.75, p = 0.0005). In addition, on-demand PrEP users who had received 8 tablets within the last 28 days had a median TFV-DP concentration similar to that of those participants who had received 16 tablets (544.6 vs. 556.9 fmol/punch, p > 0.99).

CONCLUSIONS

These results underscore the importance of well-controlled sampling times for obtaining reliable TFV-DP and FTC-TP concentrations to estimate the adherence and effectiveness of on-demand PrEP.

Cellular pharmacology of tenofovir alafenamide and emtricitabine in neutrophils and platelets in people with and without HIV

BACKGROUND

Previous studies have primarily focused on nucleos(t)ide reverse transcriptase inhibitor pharmacology in peripheral blood mononuclear cells (PBMCs) and erythrocytes via dried blood spots (DBS), but not other major blood cells.

OBJECTIVES

Our objectives were to describe and compare the concentrations of tenofovir-diphosphate (TFV-DP) and emtricitabine-triphosphate (FTC-TP) in DBS, PBMCs, neutrophils, and platelets in people with HIV (PWH) and people without HIV (PWOH).

METHODS

DBS, PBMCs, neutrophils, and platelets were isolated from whole blood drawn from PWH and PWOH receiving tenofovir alafenamide and emtricitabine. TFV-DP and FTC-TP concentrations were quantified using LC-MS/MS in each cell type. Linear regression models controlled for time on drug, adherence, and time since last dose, where applicable, to determine geometric mean percent differences (95% confidence interval) by HIV status and estimated half-lives.

RESULTS

Data were available in 13 PWH (96% male) and 30 PWOH (53% male). Compared with PWOH, TFV-DP in DBS was 48.9% (15.6%, 91.9%) higher and FTC-TP in platelets was 36.3% (4.5%, 77.7%) higher; TFV-DP in platelets also trended higher [43.5% (-3.24%, 113%)]. No other cell types significantly differed by HIV status. TFV-DP and FTC-TP demonstrated the longest half-lives in neutrophils, followed by PBMCs and then platelets. After normalizing to cell volume, both drugs accumulated from greatest to least in PBMCs, neutrophils, platelets, and erythrocytes across both PWH and PWOH.

CONCLUSIONS

Our findings highlight differential drug disposition across cell types that also vary by serostatus in DBS and platelets. The mechanisms and implications of these findings require additional research.

Antiretroviral therapy adherence among peripartum women with HIV in Kenya: an explanatory mixed methods study using dry blood spot measures and narrative interviews

ABSTRACTAdherence to antiretroviral therapy (ART) remains sub-optimal among pregnant and postpartum women with HIV (PPWH) in high HIV prevalence low resource settings with few effective behavioral interventions. A large body of qualitative literature has established general barriers and facilitators to ART adherence in PPWH at various levels (individual, interpersonal, structural). However, research exploring the underlying behavioral mechanisms of ART adherence in PPWH with objectively verified adherence biomarkers is extremely limited. We conducted 24 in-depth interviews with postpartum women in western Kenya who had linked ART drug concentrations obtained from three dried blood spot samples across the peripartum period. Among PPWH with a low drug concentration (n = 13) compared to those with continuously high drug concentrations (n = 11), distinct themes emerged related to HIV status disclosure, social support, interactions with the health system, and health beliefs. By combining ART biomarkers with patient reported challenges, there is the potential for real-time interventions to support sustained ART adherence among PPWH and improve maternal and infant health outcomes.

Tenofovir-Diphosphate and Emtricitabine-Triphosphate Adherence Benchmarks in Dried Blood Spots for Persons With HIV Receiving Tenofovir Alafenamide and Emtricitabine-Based Antiretroviral Therapy (QUANTI-TAF)

BACKGROUND

QUANTI-TAF aimed to establish tenofovir-diphosphate (TFV-DP)/emtricitabine-triphosphate (FTC-TP) adherence benchmarks in dried blood spots (DBS) for persons with human immunodeficiency virus (PWH) receiving tenofovir alafenamide/emtricitabine (TAF/FTC)-based antiretroviral therapy (ART).

METHODS

For 16 weeks, PWH received TAF/FTC-based ART co-encapsulated with an ingestible sensor to directly measure cumulative (enrollment to final visit) and 10-day adherence. At monthly visits, intraerythrocytic concentrations of TFV-DP and FTC-TP in DBS were quantified and summarized at steady-state (week 12 or 16) as median (interquartile range). Linear mixed-effects models evaluated factors associated with TFV-DP/FTC-TP.

RESULTS

Eighty-four participants (11% female, 4% transgender) predominantly receiving bictegravir/TAF/FTC (73%) were enrolled. Ninety-two percent completed week 12 or 16 (94% unboosted ART). TFV-DP for <85% (7/72), 85%-<95% (9/72), and ≥95% (56/72) cumulative adherence was 2696 (2039-4108), 3117 (2332-3339), and 3344 (2605-4293) fmol/punches. Adjusting for cumulative adherence, TFV-DP was higher with boosted ART, lower body mass index, and in non-Black participants. FTC-TP for <85% (14/77), 85%-<95% (6/77), and ≥95% (57/77) 10-day adherence was 3.52 (2.64-4.48), 4.58 (4.39-5.06), and 4.96 (4.21-6.26) pmol/punches. All participants with ≥85% cumulative and 10-day adherence had TFV-DP ≥1800 fmol/punches and FTC-TP ≥2.5 pmol/punches, respectively. Low-level viremia (HIV-1 RNA 20-199 copies/mL) occurred at 18% of visits in 39% of participants with similar TFV-DP (3177 [2494-4149] fmol/punches) compared with suppressed visits (3279 [2580-4407] fmol/punches).

CONCLUSIONS

TFV-DP ≥1800 fmol/punches and FTC-TP ≥2.5 pmol/punches represent DBS benchmarks for ≥85% adherence to unboosted TAF/FTC-based ART. Among PWH with high adherence, low-level viremia was common.

CLINICAL TRIALS REGISTRATION

NCT04065347.

The impact of diabetes mellitus on HIV virologic control: results of the MACS/WIHS combined cohort study

OBJECTIVE

Diabetes mellitus (DM) is associated with lower antiretroviral (ART) drug exposure among persons with HIV (PWH) compared to PWH without DM. The association between DM and virologic control in PWH, however, remains unknown.

METHODS

We included participants in the Multicenter AIDS Cohort Study/Women's Interagency HIV Study Combined Cohort Study (MWCCS) who had initiated ART between 1999 and 2020 and had a suppressed HIV viral load (≤200 copies/ml) within 1 year of ART initiation. We compared the frequency of incident HIV viremia (HIV-1 RNA >200 copies/ml) between adult PWH with and without DM. Poisson regression was used to examine the rate of incident viremia based on the diagnosis of DM among PWH. DM was defined as two consecutive fasting glucose measurements ≥126 mg/dl, use of antidiabetic medications, preexisting DM diagnosis, or a confirmed HbA1c >6.5%.

RESULTS

1061 women (112 with DM, 949 without DM) and 633 men (41 with DM, and 592 without DM) were included in the analysis. The relative rate (RR) of incident HIV viremia for women with HIV and DM was lower when compared to women without DM (0.85 [95% CI: 0.72-0.99]; P  = 0.04). The RR of incident viremia for women with uncontrolled DM (HbA1c > 7.5%) was higher when compared to women with controlled DM (HbA1c < 7.5%) (1.46 [95% CI: 1.03-2.07]; P  = 0.03). In contrast, the RR of incident viremia for men with HIV and DM was not statistically different compared to men without DM (1.2 [95% CI: 0.96-1.50]; P  = 0.12). The results were stratified by adherence levels (100%, 95-99%, and <95% based on self-report).

CONCLUSIONS

Women with DM who are highly adherent to ART (100% self-reported adherence) have a lower risk of viremia compared to women with HIV without DM. However, women with poorly controlled DM were at higher risk of HIV viremia than women with controlled DM. Further research is necessary to understand the impact of sex, DM, and ART adherence on HIV viremia.

Pharmacogenetic determinants of tenofovir diphosphate and lamivudine triphosphate concentrations in people with HIV/HBV coinfection

The nucleos(t)ide analogs require phosphorylation to the pharmacologically active anabolites in cells. We investigated the hypothesis that single-nucleotide polymorphisms (SNPs) in genes that encode transporters and phosphodiesterase (PDE) enzymes involved in tenofovir (TFV), disoproxil fumarate (TDF), and lamivudine (3TC) disposition will be associated with concentrations of their phosphate anabolites and virologic response. Individuals with human immunodeficiency virus (HIV) and hepatitis B virus (HBV) coinfection receiving TDF/3TC-containing antiretroviral therapy were enrolled. Steady-state TFV diphosphate (TFV-DP) and 3TC triphosphate (3TC-TP) concentrations in peripheral blood mononuclear cells (PBMCs) and dried blood spot samples were quantified. The relationship between genetic variants and TFV-DP and 3TC-TP concentrations as well as with virologic response were examined using multivariable linear regression. Of the 136 participants (median age 43 years; 63% females), 6.6% had HBV non-suppression, and 7.4% had HIV non-suppression. The multidrug resistance protein 2 (encoded by ABCC2 rs2273697) SNP was associated with 3TC-TP concentrations in PBMCs. The human organic anion transporter-1 (encoded by SLC28A2) rs11854484 SNP was associated with HIV non-suppression, and when evaluated together with SNPs with marginal associations (ABCC2 rs717620 and PDE1C rs30561), participants with two or three variants compared to those with none of these variants had an adjusted odds ratio of 48.3 (confidence interval, 4.3-547.8) for HIV non-suppression. None of the SNPs were associated with HBV non-suppression. Our study identified ABCC2 SNP to be associated with 3TC-TP concentrations in PBMCs. Also, a combination of genetic variants of drug transporters and PDE was associated with HIV non-suppression.

Urine tenofovir and dried blood spot tenofovir diphosphate concentrations and viraemia in people taking efavirenz and dolutegravir-based antiretroviral therapy

OBJECTIVE

We aimed to determine whether urine tenofovir (TFV) and dried blood spot (DBS) tenofovir diphosphate (TFV-DP) concentrations are associated with concurrent HIV viraemia.

DESIGN

Cross-sectional study among people with HIV (PWH) receiving tenofovir disoproxil fumarate (TDF)-based antiretroviral therapy (ART).

METHODS

We used dual tandem liquid chromatography and mass spectrometry to measure urine TFV and DBS TFV-DP concentrations, and evaluated their associations with concurrent viraemia at least 1000 copies/ml using logistic regression models. In exploratory analyses, we used receiver operating curves (ROCs) to estimate optimal urine TFV and DBS TFV-DP thresholds to predict concurrent viraemia.

RESULTS

Among 124 participants, 68 (54.8%) were women, median age was 39 years [interquartile range (IQR) 34-45] and 74 (59.7%) were receiving efavirenz versus 50 (40.3%) receiving dolutegravir. Higher concentrations of urine TFV [1000 ng/ml increase, odds ratio (OR) 0.97 95% CI 0.94-0.99, P  = 0.005] and DBS TFV-DP (100 fmol/punch increase, OR 0.76, 95% CI 0.67-0.86, P  < 0.001) were associated with lower odds of viraemia. There was evidence that these associations were stronger among people receiving dolutegravir than among people receiving efavirenz (urine TFV, P  = 0.072; DBS TFV-DP, P  = 0.003). Nagelkerke pseudo- R2 for the DBS TFV-DP models was higher for the urine TFV models, demonstrating a stronger relationship between DBS TFV-DP and viraemia. Among people receiving dolutegravir, a DBS TFV-DP concentration of 483 fmol/punch had 88% sensitivity and 85% specificity to predict concurrent viraemia ≥1000 copies/ml.

CONCLUSION

Among PWH receiving TDF-based ART, urine TFV concentrations, and in particular DBS TFV-DP concentrations, were strongly associated with concurrent viraemia, especially among people receiving dolutegravir.

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.

Association of tenofovir diphosphate and lamivudine triphosphate concentrations with HIV and hepatitis B virus viral suppression

OBJECTIVE

Concentrations of tenofovir diphosphate (TFV-DP) and lamivudine triphosphate (3TC-TP) in cells are correlates of medication adherence and antiviral activity. However, studies have yet to characterize the simultaneous relationship between TFV-DP and 3TC-TP concentrations with HIV and hepatitis B virus (HBV) suppression.

METHODS

Individuals with HIV/HBV coinfection on tenofovir disoproxil fumarate (TDF)-containing antiretroviral therapy (ART) were enrolled. Peripheral blood mononuclear cells (PBMCs) and dried blood spots (DBS) samples were collected and steady-state TFV-DP and 3TC-TP concentrations quantified using validated methods. The relationship between patient factors, TFV-DP, and 3TC-TP concentrations in PBMCs and DBS with HBV and HIV viral suppression were examined.

RESULTS

Of 138 participants on TDF-containing ART for a median duration (range) of 6 (0.75-15) years, the median age was 43 years and 64% were women. Overall, 128 (92.8%) and 129 (93.5%) had suppressed HIV and HBV viral loads, respectively. Of the 128 participants with suppressed HIV, 122 (95.3%) had suppressed HBV. Self-reported ART adherence, recent change to dolutegravir-based ART, TFV-DP, and 3TC-TP concentrations in PBMCs and DBS were associated with HIV RNA suppression, while HBe antigen positivity, HIV suppression, and TFV-DP concentrations in DBS were associated with HBV DNA suppression (including six persons with HBV nonsuppression and HIV suppression).

CONCLUSION

Long-term TDF/3TC-conatining ART was highly efficacious in individuals with HIV/HBV coinfection. Higher TFV-DP concentrations were predictive of suppression for both viruses. Persistent HBV viremia on TDF/3TC-containg ART requires additional research, but may represent poor adherence and the need for adherence interventions or novel antivirals.

Standards for clinical trials for treating TB

BACKGROUND: The value, speed of completion and robustness of the evidence generated by TB treatment trials could be improved by implementing standards for best practice.METHODS: A global panel of experts participated in a Delphi process, using a 7-point Likert scale to score and revise draft standards until consensus was reached.RESULTS: Eleven standards were defined: Standard 1, high quality data on TB regimens are essential to inform clinical and programmatic management; Standard 2, the research questions addressed by TB trials should be relevant to affected communities, who should be included in all trial stages; Standard 3, trials should make every effort to be as inclusive as possible; Standard 4, the most efficient trial designs should be considered to improve the evidence base as quickly and cost effectively as possible, without compromising quality; Standard 5, trial governance should be in line with accepted good clinical practice; Standard 6, trials should investigate and report strategies that promote optimal engagement in care; Standard 7, where possible, TB trials should include pharmacokinetic and pharmacodynamic components; Standard 8, outcomes should include frequency of disease recurrence and post-treatment sequelae; Standard 9, TB trials should aim to harmonise key outcomes and data structures across studies; Standard 10, TB trials should include biobanking; Standard 11, treatment trials should invest in capacity strengthening of local trial and TB programme staff.CONCLUSION: These standards should improve the efficiency and effectiveness of evidence generation, as well as the translation of research into policy and practice.

Measuring ART Adherence Among Young Adults with Perinatally Acquired HIV: Comparison Between Self-report, Telephone-Based Pill Count, and Objective Pharmacologic Measures

Tenofovir diphosphate (TVF-DP) can be quantified in red blood cells (RBCs) and dried blood spots (DBS) and can objectively measure ART adherence and predict viral suppression. Data on the association of TFV-DP with viral load are very limited in adolescents and young adults (AYA) living with perinatally-acquired HIV (PHIV), as are data comparing TFV-DP to other measures of ART adherence, such as self-report and unannounced telephone pill count. Viral load and ART adherence (self-report, TFV-DP and unannounced telephone pill count) were assessed and compared among 61 AYAPHIV recruited from an ongoing longitudinal study (CASAH) in New York City.

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.

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

Background

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.

Methods

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.

Results

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.

Conclusions

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.

Application of novel plasma separation filter cards for quantification of nucleoside/nucleotide reverse transcriptase inhibitor di/triphosphates in dried blood spots using LC-MS

Background: A rapid and sensitive LC-MS method has been developed and validated for the quantification of nucleoside di/triphosphates using a novel plasma separation card (HemaSep). Materials & methods: Cards were spotted with whole blood and stored at -80°C. Metabolites were extracted using 70:30 MeOH:20% formic acid, followed by weak anion exchange SPE and eluted using a Biobasic-AX column. Quantification was performed using a triple quadrupole mass spectrometer with a calibration range of 1.25-250 pmol/sample. Results: The recovery of metabolites was high (>93%). Precision and accuracy were acceptable and metabolites remained stable on the card after 29 days (stored at ambient temperature). Conclusion: HemaSep dried blood spots are a useful microsampling tool and offer an alternative to liquid plasma as they maintain stability over time.

REverSe TRanscrIptase chain termination (RESTRICT) for selective measurement of nucleotide analogs used in HIV care and prevention

Sufficient drug concentrations are required for efficacy of antiretroviral drugs used in HIV care and prevention. Measurement of nucleotide analogs, included in most HIV medication regimens, enables monitoring of short- and long-term adherence and the risk of treatment failure. The REverSe TRanscrIptase Chain Termination (RESTRICT) assay rapidly infers the concentration of intracellular nucleotide analogs based on the inhibition of DNA synthesis by HIV reverse transcriptase enzyme. Here, we introduce a probabilistic model for RESTRICT and demonstrate selective measurement of multiple nucleotide analogs using DNA templates designed according to the chemical structure of each drug. We measure clinically relevant concentrations of tenofovir diphosphate, emtricitabine triphosphate, lamivudine triphosphate, and azidothymidine triphosphate with agreement between experiment and theory. RESTRICT represents a new class of activity-based assays for therapeutic drug monitoring in HIV care and could be extended to other diseases treated with nucleotide analogs.

Adherence challenges with daily oral pre-exposure prophylaxis during pregnancy and the postpartum period in South African women: a cohort study

INTRODUCTION

Daily oral pre-exposure prophylaxis (PrEP) can reduce HIV acquisition. However, prevention effectiveness requires daily adherence prior to and during periods of sexual activity. Little is known about pharmacologic measures of PrEP adherence during pregnancy and postpartum and the factors related to optimal adherence during periods of sexual activity in this population.

METHODS

Between August 2019 and October 2021, we enrolled pregnant women without HIV at their first antenatal care visit followed-up through 12 months postpartum. Eligible women ≥16 years old received HIV prevention counselling and were offered oral PrEP (TDF-FTC). We quantified tenofovir-diphosphate (TFV-DP) in dried blood spots in women who reported taking PrEP in the past 30 days (at quarterly follow-up visits). We used regression models with generalized estimating equations to evaluate correlates of TFV-DP (any vs. none, and ≥2 vs. <2 doses/week), adjusting for maternal age and pregnancy status.

RESULTS AND DISCUSSION

In 382 women who started PrEP in pregnancy, returned for follow-up and reported PrEP use in the past 30 days, the median age was 27 years (interquartile range [IQR] = 23-32), and the median time on PrEP was 168 days (IQR = 84-252 days). Half of the samples had quantifiable TFV-DP at any time point (52%), declining from 67% of pregnant women 3 months post-initiation to 31% of postpartum women by 12 months. Overall, 72% had concentrations corresponding to <2 doses/week; 25% ≥2 doses/week; 3% 7 doses/week. Concentrations were lower in postpartum versus pregnancy (age-adjusted odds ratio [aOR] = 0.44; 95% confidence interval [CI] = 0.35-0.54). The correlation of self-reported adherence and TFV-DP ranged from -0.07 in pregnancy to 0.25 in postpartum women. Variables associated with having quantifiable TFV-DP included partner living with HIV/unknown serostatus (aOR = 1.50; 95% CI = 1.01-2.22), and reported frequency of sexual activity in the past month (aOR sex >5/month vs. no sex or <5 times/month = 2.11; 95% CI = 1.58-2.82) adjusting for age and pregnancy versus postpartum status. TFV-DP concentrations declined over follow-up time (aOR for 6 vs. 3 months = 0.49; 95% CI = 0.36-0.67).

CONCLUSIONS

Objectively measured adherence to PrEP was low overall and did not correlate with self-reported use. There is an urgent need for objective adherence measures to support clinical decision-making as well as adherence support interventions as part of PrEP services for pregnant and postpartum women at risk of HIV.

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.

Tenofovir-Diphosphate in Dried Blood Spots vs Tenofovir in Urine/Plasma for Oral Preexposure Prophylaxis Adherence Monitoring

Background

Tenofovir-diphosphate (TFV-DP) measured in dried blood spots (DBS) and tenofovir (TFV) measured in urine/plasma have been used to measure TFV-based oral pre-exposure prophylaxis (PrEP) adherence. However, there are limited data comparing these 3 metrics and their appropriate use for PrEP adherence monitoring.

Methods

We collected DBS, urine, and plasma samples from HIV-negative adults randomized to a low (2 doses/week), moderate (4 doses/week), or perfect (7 doses/week) adherence group (via directly observed therapy) of tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) for 6 weeks, followed by a 4-week washout phase. Drug concentrations were measured using liquid chromatography tandem mass spectrometry. Linear mixed-effects modeling was used to examine associations between drug concentrations and dosing time.

Results

Among 28 participants, the median age was 33 years, and 12 (43%) were female. At steady state, 25th percentile TFV-DP concentrations were 466, 779, and 1375 fmol/3 mm punch in the low, moderate, and perfect adherence group, respectively. Correlation was stronger between quantifiable TFV-DP and plasma TFV (r = 0.65; P < .01) than between TFV-DP and urine TFV (r = 0.50; P < .01). Among all participants, each additional week of cumulative dosing on average led to a mean increase of 158 fmol/3 mm punch (P < .001) in TFV-DP during the dosing phase. Each additional day after the last dose was associated with 43 fmol/3 mm punch lower TFV-DP (P = .07).

Conclusions

TFV-DP levels in DBS provide valuable insight into both dosing recency and cumulative doses from variable adherence patterns. Our observed benchmark TFV-DP concentrations were slightly higher than prior predicted estimates based on convenience samples.

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.

HIV pre-exposure prophylaxis adherence test using reverse transcription isothermal amplification inhibition assay

Current HIV antiretroviral therapy (ART) or pre-exposure prophylaxis (PrEP) therapy adherence monitoring relies on either patient self-reported adherence or monitored drug dispensing, which are not reliable. We report a proof-of-concept adherence monitoring assay which directly measures nucleotide reverse transcriptase inhibitor (NRTI) concentration using a reverse transcription isothermal amplification inhibition assay. We measure the concentration of Tenofovir diphosphate (TFV-DP) - an NRTI that functions as a deoxyadenosine triphosphate (dATP) analog and long-term adherence marker for PrEP - by measuring the inhibition of the reverse transcription of an RNA template. The completion or inhibition of reverse transcription is evaluated by recombinase polymerase amplification (RPA), an isothermal nucleic acid amplification assay commonly used for point-of-care diagnostics. We present and validate a model that predicts the amplification probability as a function of dATP and TFV-DP concentrations, nucleotide insertion sites on the RNA template, and RNA template concentration. The model can be used to rationally design and optimize the assay to operate at clinically relevant TFV-DP concentrations. We provide statistical analysis that demonstrates how the assay may be used as a qualitative or semi-quantitative tool for measuring adherence to NRTI drugs and used to support patient compliance. Due to its simple instrumentation and short runtime (<1 hour), this assay has the potential for implementation in low-complexity laboratories or point-of-care settings, which may improve access to ART and PrEP adherence monitoring.

Point-of-care semi-quantitative test for adherence to tenofovir alafenamide or tenofovir disoproxil fumarate

OBJECTIVES

Objective measurement of antiretrovirals may aid clinical interventions for improving adherence to HIV prevention or treatment regimens. A point-of-care urine test could provide real-time information about recent adherence to regimens containing tenofovir disoproxil fumarate or tenofovir alafenamide. We developed a lateral flow immunoassay (LFA) and ELISA for urinary tenofovir.

METHODS

The intensity of the LFA test line was quantified using an optical reader and visually scored 0-5 by two independent people, using a reference card. The sensitivity and specificity of both the ELISA and LFA were determined for two different tenofovir concentration cut-offs for tenofovir disoproxil fumarate and tenofovir alafenamide adherence-1500 and 150 ng/mL, respectively. To validate the assays, we measured 586 urine samples from 28 individuals collected as part of a study of tenofovir pharmacokinetics in adults, which were also measured by MS for reference.

RESULTS

Both the LFA signal and ELISA signal were each strongly correlated with drug concentrations (0.91 and 0.92, respectively). The LFA signal and ELISA were highly sensitive and specific at both thresholds (LFA sensitivity/specificity: tenofovir disoproxil fumarate, 89%/96%; and tenofovir alafenamide, 90%/96%) (ELISA sensitivity/specificity: tenofovir disoproxil fumarate, 94%/94%; and tenofovir alafenamide, 92%/84%). Visual scoring of the LFA was also highly sensitive and specific at both the tenofovir disoproxil fumarate threshold and the tenofovir alafenamide threshold (sensitivity/specificity: tenofovir disoproxil fumarate, 91%/94%; and tenofovir alafenamide, 87%/90%).

CONCLUSIONS

Our rapid semi-quantitative test can measure tenofovir concentrations relevant to both tenofovir alafenamide and tenofovir disoproxil fumarate adherence, which may support adherence-promoting interventions across a range of HIV care settings.

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.

Antiretroviral refill histories as a predictor of future HIV viremia

Background

The use of adherence measures as markers for virologic failure (VF) has been studied. Yet, there is currently no single adherence metric recommended for VF. Antiretroviral prescription refill histories, for people living with human immunodeficiency virus (HIV), are readily accessible and can be easily quantified to an estimated adherence level.

Methods

Participants from a Midwestern US HIV clinic were retrospectively evaluated from 2018 to 2020. Refill histories (RH) and last HIV RNA for each participant were abstracted for each study year. RH were quantified as a percentage of days covered (PDC) and VF was defined as HIV RNA >200 copies/mL. PDC values were matched with subsequent year HIV RNA (matched pair). Sample t test were used to compare mean PDC level by viral suppression status and generalized estimating equations models were used to determine the predictability of PDC level for VF. An optimal PDC threshold for VF was determined using receiver operating characteristic curve analysis and Youden index.

Results

A total of 1056 participants contributed to 1923 matched pairs (PDC/HIV RNA); mean age was 48.3 years, 24% women, and 30.6% Black. PDC levels differed significantly based on dichotomized HIV RNA (2018–2019: >200: 40% [95% confidence interval {CI}, 33%–46%] vs ≤200: 85% [95% CI, 84%–87%], P < .0001; 2019–2020: >200: 45% [95% CI, 38%–51%] vs ≤200: 87% [95% CI, 86%–89%], P < .0001). Based on the Youden index value of 0.66 (sensitivity 0.77, specificity 0.89), the optimal PDC threshold predictive of VF was 52%.

Conclusions

Lower antiretroviral therapy (ART) adherence levels were predictive of future VF when PDC ≤52%.

Adherence Predictors in Pregnant Women Living with HIV on Tenofovir Alafenamide and Tenofovir Disoproxil Fumarate

BACKGROUND

Medication adherence to antiretroviral medications is critical during pregnancy in women living with HIV (WLHIV) for multiple reasons. In this study, we report medication adherence to tenofovir alafenamide (TAF) compared to tenofovir disoproxil fumarate (TDF) during pregnancy in WLHIV.

METHODS

This is a retrospective cohort study of pregnant women living with HIV aged 18-48 years who received either tenofovir alafenamide (TAF) or tenofovir disoproxil fumarate (TDF) during pregnancy. Medication adherence was assessed during each visit in all trimesters of pregnancy, and was self-reported. Demographics and outcomes were analyzed using standard statistical tests. Logistic regression analysis models accounting for potential confounders, with adjusted odds-ratios (aORs) and associated 95% confidence intervals were reported.

RESULTS

One hundred women met inclusion criteria, with thirty-four women on TAF and sixty-six women on TDF. While medication adherence was higher in women using TAF compared to TDF, with 76% adherent to TDF vs 83% adherent to TAF; p=0.282, in the 1^st trimester; 82% adherent to TDF vs 88% adherent to TAF; p=0.924, in the 2^nd trimester, and 88% adherent to TDF vs 91% adherent to TAF; p=0.176, in the 3^rd trimester of pregnancy, these differences in medication adherence were not statistically significant. In the third trimester of pregnancy, multiparous women were more likely to be adherent to TDF/TAF antiretroviral medications compared to nulliparous women - univariable odds ratio, OR 1.31, 95% CI 1.12, 1.57; p<0.05; multivariable (adjusted odds ratio, aOR 1.23, 95% CI 1.08, 1.52; p<0.05).

CONCLUSIONS

Pregnant women living with HIV on TDF and TAF achieved high adherence, but medication adherence was better in the third trimester compared to the first or second trimesters of pregnancy. These findings support the need to continually assess medication adherence during pregnancy.

Hair Zidovudine Concentrations Predict Virologic Outcomes Among People Living with HIV/AIDS in China

BACKGROUND

Hair antiretroviral concentrations are an objective and non-invasive measure of adherence to long-term antiretroviral therapy (ART) and can further predict virologic outcomes among people living with HIV/AIDS (PLWH). Zidovudine, one of the mainstream antiretrovirals in China, has been verified to have high reliability in adherence assessment, especially for its hair concentrations. However, data are limited in its predicting virologic outcomes. Therefore, this study aimed to characterize whether hair zidovudine concentrations can predict virologic suppression among Chinese PLWH compared with hair lamivudine concentrations and two self-reported measures, the overall frequency of adherence behaviors and percentage adherence.

METHODS

This cross-sectional study randomly recruited 564 PLWH currently treated with zidovudine, lamivudine, and other ART agents (efavirenz, nevirapine, or lopinavir/ritonavir) in Guangxi, China. Hair antiretroviral concentrations were determined using the LC-ESI⁺-MS/MS method. Receiver operating characteristic (ROC) curves were used to estimate the optimal classification thresholds of hair concentrations of zidovudine and lamivudine, and the two self-reported measures. Based on those optimal classification thresholds, logistic regression was used to examine whether those four adherence measures can predict virologic suppression (HIV-1 RNA <200 copies/mL).

RESULTS

ROC curves demonstrated good classification performance for association with virologic suppression of zidovudine with the optimal threshold at 58 pg/mg and lamivudine at 255 pg/mg but no self-reported measures. PLWH with hair zidovudine concentrations >58 pg/mg had an adjusted odds ratio (aOR) of 43.191 (95% confidence interval (CI) = 10.171‒183.418, p < 0.001) for virologic suppression. Hair lamivudine concentrations were also associated with virologic suppression (aOR = 10.656, 95% CI = 3.670‒30.943, p < 0.001). However, two self-reported measures did not predict virologic suppression (aORs = 1.157 and 2.488, ps >0.149).

CONCLUSION

Hair zidovudine concentrations can be served as an alternative tool for clinically predicting virologic suppression among PLWH in China.

Religiosidade/Espiritualidade e Adesão à Terapia Antirretroviral em Pessoas Vivendo com HIV

Resumo Dentre os fatores associados à adesão à Terapia Antirretroviral (TARV) em pessoas vivendo com HIV, destaca-se a religiosidade/espiritualidade (R/E). O objetivo deste estudo foi apresentar as evidências disponíveis sobre a relação entre a dimensão da R/E e a adesão aos antirretrovirais. Realizou-se uma revisão integrativa de literatura com buscas nas bases/bibliotecas CINAHL, LILACS, PePSIC, PsycINFO, PubMed, SciELO, Scopus e Web of Science. Foram selecionados artigos empíricos publicados entre janeiro de 2008 e junho de 2019, sendo recuperados 49 estudos após a aplicação dos critérios de inclusão/exclusão. Encontraram-se associações positivas, negativas e neutras entre R/E e adesão à TARV, evidenciando que a R/E é uma dimensão psicossocial que pode ser preditora da adesão aos antirretrovirais. O sentido dessa influência, no entanto, ainda não é um consenso na literatura científica. Recomenda-se que essas influências sejam compreendidas a partir de elementos contextuais dessa população e não apenas de marcadores pessoais.

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.

Emtricitabine triphosphate in dried blood spots predicts future viremia in persons with HIV and identifies mismatch with self-reported adherence

OBJECTIVE

Emtricitabine triphosphate (FTC-TP) in dried blood spots (DBS), a measure of short-term antiretroviral therapy (ART) adherence, is associated with viral suppression in persons with HIV (PWH). However, its ability to predict future viremia remains unknown.

DESIGN

Prospective, observational cohort (up to three visits in 48 weeks).

METHODS

PWH receiving TDF/FTC-based ART had DBS and HIV viral load obtained at routine clinical visits. FTC-TP in DBS was dichotomized into quantifiable vs. below the limit of quantification (BLQ). The adjusted odds ratio (aOR) of future viremia (≥20 copies/ml at next study visit) was estimated according to FTC-TP at the current visit. To assess for possible interactions, additional models adjusted for tenofovir diphosphate (TFV-DP) in DBS and 3-day self-reported adherence.

RESULTS

Data from 433 PWH (677 paired DBS/HIV viral load samples) were analyzed. The aOR [95% confidence interval (CI)] for future viremia for BLQ vs. quantifiable FTC-TP was 3.4 (1.8--6.5; P = 0.0002). This diminished after adjusting for TFV-DP [aOR 1.9 (0.9--4.1); P = 0.090]. Among PWH reporting 100% 3-day adherence, the odds of future viremia were 6.0 times higher [(1.8--20.3); P = 0.001] when FTC-TP was BLQ vs. quantifiable. Among participants (n = 75) reporting less than 100% adherence, BLQ FTC-TP in DBS was not predictive of future viremia [aOR 1.3 (0.4--4.6); P = 0.96].

CONCLUSION

Nonquantifiable FTC-TP in DBS predicts future viremia and is particularly informative in PWH reporting perfect adherence. As point-of-care adherence measures become available, mismatches between objective and subjective measures, such as FTC-TP in DBS and self-report, could help clinicians identify individuals at an increased risk of future viremia.

Low-Level Viremia Is Associated With Cumulative Adherence to Antiretroviral Therapy in Persons With HIV

The drivers of low-level viremia (LLV) between 20 and 200 copies/mL remain unclear. In 1042 person-visits from 497 persons with HIV on tenofovir disoproxil fumarate-containing antiretroviral therapy (ART), the association between LLV and cumulative antiretroviral adherence (quantified using tenofovir diphosphate [TFV-DP] in dried blood spots) was assessed. Lower TFV-DP levels were associated with higher odds of LLV. As TFV-DP (fmol/punch) categories decreased from >1650 to 800-1650; 800-1650 to <800; and >1650 to <800, the adjusted odds ratios for LLV vs HIV VL <20 copies/mL were 2.0 (95% CI, 1.2-3.1), 2.4 (95% CI, 1.1-5.0), and 4.6 (95% CI, 2.2-9.9), respectively. This suggests that adherence could impact LLV.

Short Communication: A Descriptive Analysis of Dried Blood Spot Adherence Testing Among Ugandans with HIV Presenting with Cryptococcal Meningitis

Early antiretroviral therapy (ART) initiation after cryptococcal meningitis increases mortality, and those unmasking cryptococcosis after <2 weeks of ART have higher mortality. However, it is unknown if those presenting as ART experienced are actually adherent to their ART. Unknowingly, restarting ART in persons, who have discontinued ART, may be a fatal iatrogenic error. To evaluate ART adherence in an exploratory analysis, we collected dried blood spots on 44 HIV-infected persons presenting with cryptococcal meningitis. We quantified tenofovir diphosphate (TFV-DP) and lamivudine (3TC) from dried blood spots. We quantified cumulative ART adherence over the preceding 6-8 weeks based on TFV-DP concentrations and adherence over the last few days based on 3TC concentrations. Of 22 ART experienced, 20 (91%) had quantifiable concentrations. Of 18 receiving tenofovir, 15 (83%) had TFV-DP consistent with drug intake of ≥4 doses/week or moderate adherence. With 3TC, 72% (18/22) had detectable levels consistent with adherence over the last 3 days before measurement. Only three ART-experienced subjects were alive and virally suppressed at 4 months (n = 2 on ART for <30 days; n = 1 with undetectable antiretrovirals). Surprisingly, of 22 who reported not receiving ART, 4 (18%) had quantifiable tenofovir. Most ART-experienced subjects were taking their ART with moderate to good adherence with the majority likely having viral resistance given generally at good ART levels, receipt of intensive adherence counseling, and lack of subsequent viral suppression. The World Health Organization (WHO) guidelines recommend adherence counseling with ART continuation and repeat viral loads in 1-3 months before switching to second-line ART. These recommendations are likely inappropriate in those with central nervous system infections given the additional possible harm of central nervous system immune reconstitution syndrome. Further study to evaluate continuation of ART regimens when presenting with cryptococcosis has benefit, with checking blood levels at presentation potentially being a helpful option. ClinicalTrials.gov Identifier: NCT01802385.

Pharmacokinetics and renal safety of tenofovir alafenamide with boosted protease inhibitors and ledipasvir/sofosbuvir

BACKGROUND

Ledipasvir/sofosbuvir increases tenofovir plasma exposures by up to 98% with tenofovir disoproxil fumarate (TDF), and exposures are highest with boosted PIs. There are currently no data on the combined use of the newer tenofovir prodrug, tenofovir alafenamide (TAF), boosted PIs and ledipasvir/sofosbuvir.

OBJECTIVES

To compare the plasma and intracellular pharmacokinetics and renal safety of TAF with ledipasvir/sofosbuvir when co-administered with boosted PIs.

METHODS

Persons with HIV between 18 and 70 years and on a boosted PI with TDF were eligible. The study was comprised of four phases: (1) TDF 300 mg with boosted PI; (2) TAF 25 mg with boosted PI; (3) TAF 25 mg with boosted PI and ledipasvir/sofosbuvir; and (4) TAF 25 mg with boosted PI. Pharmacokinetic sampling, urine biomarker collection [urine protein (UPCR), retinol binding protein (RBP) and β2 microglobulin (β2M) normalized to creatinine] and safety assessments occurred at the end of each phase. Plasma, PBMCs and dried blood spots were collected at each visit.

RESULTS

Ten participants were enrolled. Plasma tenofovir exposures were 76% lower and tenofovir-diphosphate (TFV-DP) concentrations in PBMCs increased 9.9-fold following the switch to TAF. Neither of these measures significantly increased with ledipasvir/sofosbuvir co-administration, nor did TAF plasma concentrations. No significant changes in estimated glomerular filtration rate or UPCR occurred, but RBP:creatinine and β2M:creatinine improved following the switch to TAF.

CONCLUSIONS

Ledipasvir/sofosbuvir did not significantly increase plasma tenofovir or intracellular TFV-DP in PBMCs with TAF. These findings provide reassurance that the combination of TAF, boosted PIs and ledipasvir/sofosbuvir is safe in HIV/HCV-coinfected populations.

Factors associated with tenofovir diphosphate concentrations in dried blood spots in persons living with HIV

OBJECTIVES

To determine factors associated with interindividual variability in tenofovir diphosphate (TFV-DP) concentrations in dried blood spots (DBSs) among persons living with HIV (PLWH).

METHODS

PLWH who were at least 18 years old and taking tenofovir disoproxil fumarate-containing ART were prospectively recruited and enrolled from a clinical cohort and followed longitudinally (up to three visits over 48 weeks). With log-transformed TFV-DP concentrations in DBSs as the outcome, mixed-model regression analyses were used to assess associations between self-reported 3 month ART adherence, race and other clinical covariates (gender, age, BMI, CD4+ T cell count, estimated glomerular filtration rate, haematocrit, duration on current ART and anchor drug class) on TFV-DP in DBSs.

RESULTS

Five hundred and twenty-seven participants (1150 person-visits) were analysed. Adjusting for race and other clinical covariates, every 10% increase in self-reported 3 month ART adherence was associated with an average TFV-DP concentration increase in DBSs of 28% (95% CI: 24%-32%; P < 0.0001). In the same model, female participants had 20% (95% CI: 3%-40%; P = 0.02) higher TFV-DP concentrations in DBSs, compared with male participants, and every 1 kg/m2 increase in BMI was associated with a decrease in TFV-DP concentration in DBSs by 2% (95% CI: -3% to -1%; P < 0.0001).

CONCLUSIONS

Individual patient characteristics were predictive of TFV-DP concentration in DBSs in PLWH receiving tenofovir disoproxil fumarate-based ART. Future research to incorporate these predictors into the interpretation of this ART adherence biomarker, and to establish whether these associations extend to PLWH taking tenofovir alafenamide-containing ART, is needed.

HIV, aging, and adherence: an update and future directions

PURPOSE OF REVIEW

To highlight recent data on antiretroviral adherence in older people living with HIV (PLWH), describe the most relevant pharmacokinetic antiretroviral studies, and identify critical research gaps in this population.

RECENT FINDINGS

Overall, studies have found that older PLWH are more likely to be adherent to antiretroviral therapy (ART). Although multiple methods to measure adherence are available (self-report, pharmacy refills, electronic device monitors, drug concentrations), there is currently no 'gold standard' adherence measure or sufficient evidence to suggest a preferred method in older patients. Recently, studies evaluating antiretroviral concentrations in hair and dried blood spots in older patients identified no major differences when compared with younger individuals. Similarly, although pharmacokinetic studies in older PLWH are scarce, most data reveal no significant pharmacokinetic differences in the aging population. Furthermore, no specific guidelines or treatment recommendations regarding ART dose modification or long-term toxicity in aging PLWH are available, mostly because of the exclusion of this population in clinical trials.

SUMMARY

How aging influences adherence and pharmacokinetics remains poorly understood. As the population of older PLWH increases, research focusing on adherence, toxicity, drug--drug interactions, and the influence of comorbidities 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.

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.

Randomized Pilot Study of an Advanced Smart-Pill Bottle as an Adherence Intervention in Patients With HIV on Antiretroviral Treatment

BACKGROUND

Adherence is critical to achieve the benefits of antiretroviral therapy. A smart-pill bottle service that transmits real-time adherence data via cellular networks to a central service and prompts nonadherent patients with phone or text messages may improve adherence.

METHODS

Adults with HIV taking a tenofovir-containing regimen with suboptimal adherence were randomized to adherence counseling ± a smart-pill bottle service for 12 weeks. Tenofovir diphosphate (TFV-DP) levels by dried blood spot, HIV RNA levels, CD4 cell counts, and self-reported adherence were collected.

RESULTS

Sixty-three participants (22% women; 48% black, 25% Latino) were randomized: 30 to the smart-pill bottle (2 of whom were lost to follow-up before the baseline visit), and 33 to control arms. At baseline, 49% of participants had HIV RNA ≤20 copies/mL and 61% reported 100% adherence with ART over 4 days. From baseline to week 12, median TFV-DP levels were +252 and -41 fmol/punch in the bottle and control arms, respectively (P = 0.10). Exploratory exclusion of 3 participants with known or suspected drug-drug interactions found median TFV-DP levels of +278 and -38 fmol/punch, respectively (P = 0.04). There were no differences in study discontinuations, HIV RNA suppression, CD4 cell counts, or self-reported adherence at week 12.

CONCLUSIONS

In a diverse group of participants with suboptimal adherence to ART, the smart-pill bottle service was associated with higher TFV-DP levels.

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.

Point-of-care and Near Real-time Testing for Antiretroviral Adherence Monitoring to HIV Treatment and Prevention

PURPOSE OF REVIEW

In this report, we review the need for point-of-care (POC) or near real-time testing for antiretrovirals, progress in the field, evidence for guiding implementation of these tests globally, and future directions in objective antiretroviral therapy (ART) or pre-exposure prophylaxis (PrEP) adherence monitoring.

RECENT FINDINGS

Two cornerstones to end the HIV/AIDS pandemic are ART, which provides individual clinical benefits and eliminates forward transmission, and PrEP, which prevents HIV acquisition with high effectiveness. Maximizing the individual and public health benefits of these powerful biomedical tools requires high and sustained antiretroviral adherence. Routine monitoring of medication adherence in individuals receiving ART and PrEP may be an important component in interpreting outcomes and supporting optimal adherence. Existing practices and subjective metrics for adherence monitoring are often inaccurate or unreliable and, therefore, are generally ineffective for improving adherence. Laboratory measures of antiretroviral concentrations using liquid chromatography tandem mass spectrometry have been utilized in research settings to assess medication adherence, although these are too costly and resource-intensive for routine use. Newer, less costly technologies such as antibody-based methods can provide objective drug-level measurement and may allow for POC or near-patient adherence monitoring in clinical settings. When coupled with timely and targeted counseling, POC drug-level measures can support adherence clinic-based interventions to ART or PrEP in near real time.

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

Background

The 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.

Methods

Dried 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.

Results

Data 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.

Conclusions

Higher 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 and Emtricitabine Concentrations in Younger and Older Women with HIV Receiving Tenofovir Disoproxil Fumarate/Emtricitabine

The altered immune states of aging and HIV infection may affect intracellular metabolism of tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC); increased cellular senescence decreases FTC-triphosphate (FTCtp) concentrations. The effects of age and inflammation on the ratio of intracellular metabolites (IMs; tenofovir diphosphate [TFVdp] and FTCtp) to their endogenous nucleotides (ENs; dATP and dCTP), a potential treatment efficacy marker, were assessed among participants of the Women's Interagency HIV Study (WIHS), who ranged from 25 to 75 years. Samples from women receiving TDF-FTC with viral loads of <200 copies/ml were dichotomized by age at collection into two groups (≤45 years and ≥60 years). IM/EN concentrations were measured in peripheral blood mononuclear cell (PBMC) pellets; interleukin-6 (IL-6) and sCD163 were measured in plasma; senescent CD8⁺ T cells were measured in viable PBMCs. The TFVdp:dATP and FTCtp:dCTP ratios had statistically significantly different distributions in older and younger women (log-rank test, P = 0.0023 and P = 0.032, respectively); in general, IM and EN concentrations were higher in the older women. After adjusting for potential confounders, these findings were not significant. In women aged ≤45 years, TFVdp was negatively associated with IL-6 and sCD163, while FTCtp was positively associated with sCD163 and IL-6 in women aged ≥60 years. Body mass index (BMI) was positively associated with IL-6 in both age groups and negatively associated with TFVdp in women aged ≤45 years. After adjustment, age remained significant for sCD163, while black race, BMI, and renal function remained significant for several IMs and ENs, suggesting that factors associated with aging, but not age itself, govern intracellular TDF-FTC pharmacology.