Urine assay for tenofovir to monitor adherence in real time to tenofovir disoproxil fumarate/emtricitabine as pre-exposure prophylaxis

Partner-Based HIV Treatment for Seroconcordant Couples Attending Antenatal and Postnatal Care in Rural Mozambique: A Cluster Randomized Controlled Trial

INTRODUCTION

There is evidence that a supportive male partner facilitates maternal HIV testing during pregnancy, increases maternal antiretroviral therapy initiation and adherence, and increases HIV-free infant survival. Most male partner engagement clinical strategies have focused on increasing uptake of couple-based HIV testing and counseling. We delivered a couple-based care and treatment intervention to improve antiretroviral therapy adherence in expectant couples living with HIV.

METHODS

We implemented a cluster randomized controlled trial for seroconcordant couples living with HIV, comparing retention (using a patient's medication possession ratio) in HIV care for a couple-based care and treatment intervention vs. standard of care services in rural Mozambique. The intervention included couple-based treatment, couple-based education and skills building, and couple-peer educator support.

RESULTS

We recruited 1080 couples to participate in the study. Using a linear mixed effect model with a random effect for clinic, the intervention had no impact on the medication possession ratio among women at 12 months. However, the intervention increased men's medication ratio by 8.77%. Our unadjusted logistic regression model found the odds of an infant seroconverting in the intervention group was 30% less than in the control group, but the results were not statistically significant.

DISCUSSION

Our study found no difference in maternal outcomes by study arm, but our intervention resulted in an improved medication possession ratio among male partners. We provide a community/clinic-based treatment framework that can improve outcomes among male partners. Further work needs to be done to improve social support for pregnant women and to facilitate prevention of vertical transmission to infants among couples living with HIV.

Point-of-care urine tenofovir monitoring of adherence to drive interventions for HIV treatment and prevention

INTRODUCTION

Although effective antiretroviral and pre-exposure prophylaxis/PrEP regimens are available globally, adherence challenges persist. Objective measures of adherence can both measure adherence accurately and can be used to drive interventions. The first point-of-care pharmacologic adherence measure, urine tenofovir testing using a lateral flow assay, is now available.

AREAS COVERED

This review examines the ability of pharmacologic metrics of adherence to predict HIV and PrEP clinical outcomes and the past use of pharmacologic metrics of adherence as tools to drive adherence interventions. The success of preliminary studies using point-of-care adherence metrics to guide interventions is then discussed.

EXPERT OPINION

Large randomized clinical trials are now needed to test the impact of point-of-care adherence interventions on HIV and PrEP clinical outcomes, given promising results of the pilot studies summarized here. Hybrid implementation-effectiveness studies will be needed to examine optimal approaches to incorporating point-of-care testing into routine clinical care delivery, including in guiding resistance testing, adherence counseling, and delivery of other evidence-based adherence interventions. Given the ability of point-of-care tenofovir testing to be implemented in settings where viral load testing is not available, and at more frequent intervals due to its low cost, urine-based tenofovir assays have the potential to be highly scalable in diverse clinical settings.

Sample Matrices for Mass Spectrometry-Based Adherence Monitoring: A Systematic Critical Review

BACKGROUND

Analytical monitoring of adherence using mass spectrometry (MS) plays an important role in clinical toxicology. Unambiguous detection of drugs (of abuse) and/or their metabolites in body fluids is needed to monitor intake of medication as prescribed or to monitor abstinence as a follow-up to detoxification procedures. This study focused on the advantages and disadvantages of different sample matrices used for MS-based adherence monitoring.

METHODS

Relevant articles were identified through a literature search in the PubMed database. English articles published between January 01, 2017, and December 31, 2022, were selected using the keywords "adherence assess*" or "adherence monit*" or "compliance assess*" or "compliance monit*" in combination with "mass spectrom*" in the title or abstract.

RESULTS

A total of 51 articles were identified, 37 of which were within the scope of this study. MS-based monitoring was shown to improve patient adherence to prescribed drugs. However, MS analysis may not be able to assess whether treatment was rigorously followed beyond the last few days before the sampling event, except when hair is the sample matrix. For medication adherence monitoring, blood-based analyses may be preferred because reference plasma concentrations are usually available, whereas for abstinence control, urine and hair samples have the advantage of extended detection windows compared with blood. Alternative sample matrices, such as dried blood samples, oral fluid, and exhaled breath, are suitable for at-home sampling; however, little information is available regarding the pharmacokinetics and reference ranges of drug (of abuse) concentrations.

CONCLUSIONS

Each sample matrix has strengths and weaknesses, and no single sample matrix can be considered the gold standard for monitoring adherence. It is important to have sufficient information regarding the pharmacokinetics of target substances to select a sample matrix in accordance with the desired purpose.

Steady-state pharmacokinetics of plasma tenofovir alafenamide (TAF), tenofovir (TFV) and emtricitabine (FTC), and intracellular TFV-diphosphate and FTC-triphosphate in HIV-1 infected old Japanese patients treated with bictegravir/FTC/TAF

Emtricitabine (FTC) plus tenofovir alafenamide (TAF) has demonstrated efficacy and safety for pre-exposure prophylaxis (PrEP) to prevent HIV-1 infection. We measured the plasma PK of FTC, tenofovir (TFV), and TAF in a steady-state pharmacokinetic (PK) study of bictegravir/FTC/TAF in HIV-1-infected patients. Furthermore, validated liquid chromatography-tandem mass spectrometry was used to measure intracellular TFV-diphosphate (DP) and FTC-triphosphate (TP), the active metabolites of TFV and FTC, respectively. Plasma and dried blood spot samples were collected from 10 male patients aged ≥ 50 years at various time intervals: 0 (trough), 1, 2, 3, 4, 6, 8, 12, and 24 h after drug administration. The mean ± standard deviation of plasma PK parameters were as follows: The maximum concentrations of TAF, TFV, and FTC were 104.0 ± 72.5, 27.9 ± 5.2, and 3,976.0 ± 683.6 ng/mL, respectively. Additionally, their terminal elimination half-lives were 0.6 ± 0.5, 31.6 ± 10.4, and 6.9 ± 1.4 h, respectively. These results were consistent with previously reported data. The intracellular levels of TFV-DP and FTC-TP varied widely among individuals; however, they remained stable over 24 h in each individual at approximately 1,000-1,500 and 2,000-3,000 fmol/punch, respectively, indicating that plasma concentrations did not affect the intracellular concentrations of their active metabolites. These results demonstrated that measuring intracellular TFV-DP and FTC-TP could be useful for monitoring adherence to PrEP in clients on this regimen.

Psychometric Evaluation and Predictive Validity of an Adapted Adherence Self-Efficacy Scale for PrEP

Adherence to and sustainment of HIV pre-exposure prophylaxis (PrEP) are critical to its effectiveness. Adherence self-efficacy, i.e., confidence in one's ability to adhere to a particular medication, is a key psychological determinant of health behavior that strongly predicts HIV treatment adherence but has been understudied in PrEP research. This paper describes the psychometric evaluation and validation of the PrEP Adherence Self-Efficacy Scale (PrEP-ASES), adapted from the previously validated HIV Treatment Adherence Self-Efficacy Scale (HIV-ASES). Data are drawn from two studies conducted at a community health center, one focused on gay and bisexual cisgender men and the other on transgender women. Factor analyses support a one-factor score (eigenvalue = 6.78) that explained 75.3% of the variance, with good test-retest reliability (rs > 0.40). In both studies, higher PrEP-ASES scores were associated with PrEP uptake, adherence, and sustainment. Findings support the utility of the PrEP-ASES in research and suggest the importance of addressing self-efficacy in PrEP programs and services.

MPrEP+ study protocol: a prospective cohort study assessing the feasibility and acceptability of an HIV pre-exposure prophylaxis (PrEP) strategy for male clients of female sex workers in Kisumu, Kenya

INTRODUCTION

Male clients (MCs) are integral to sex work-driven HIV transmission dynamics as sexual partners of female sex worker (FSW). MCs contribute disproportionately to incident HIV globally and in sub-Saharan Africa, with 27% of new infections attributed to MCs of FSW and other partners of key populations. Gaps in coverage of HIV testing and prevention services for men, including MCs, are well-documented, yet research and innovative interventions to improve MC uptake of effective prevention services, including pre-exposure prophylaxis (PrEP), are scarce.

METHODS AND ANALYSIS

MPrEP+ is a cohort study designed to assess the feasibility and acceptability of a PrEP-focused HIV prevention strategy providing daily oral tenofovir/emtricitabine (TDF/FTC) in combination with three adherence self-management interventions: (1) use of a validated point-of-care urine drug-level assay with real-time feedback and tailored self-management counselling; (2) frequent HIV self-testing; and (3) weekly one-way text messaging. This package of interventions is being delivered to 120 MCs enrolled in the study in Kisumu, Kenya over a 6-month period. The primary outcome is PrEP adherence at 6 months as measured by PrEP drug levels. Bivariate and multivariable regression models will be used to identify predictors of PrEP adherence. We will also explore associations of sociodemographic characteristics and PrEP beliefs with PrEP adherence.

ETHICS AND DISSEMINATION

The study was approved by the Columbia University Irving Medical Center Institutional Review Board and the Maseno University Ethical Review Committee. Study enrolment was initiated in November 2021 with participant follow-up planned through August 2022. Study results will be submitted for publication in peer-reviewed journals. Summaries and infographics of study findings will be developed and distributed to MC, FSW and stakeholders working in HIV prevention and support for people who sell and buy sex, including Kenya's Ministry of Health.

TRIAL REGISTRATION NUMBER

NCT04898699; Registered on 24 May 2021.

Tenofovir-Diphosphate in Dried Blood Spots versus 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.

Determining the acceptability of point-of-care urine tenofovir testing and its performance in predicting HIV RNA suppression

BACKGROUND

The detection of tenofovir (TFV) metabolites by point-of-care (POC) urine lateral flow immunoassays (LFIA) indicates adherence to tenofovir-containing HIV pre-exposure prophylaxis. However, the association between urine TFV metabolites as detected by LFIA and HIV viral load suppression in people receiving TFV-based antiretroviral therapy (ART) is unknown as is patient and clinician acceptability of POC urine LFIA testing in clinical practice in low- and middle-income country settings.

METHODS

We enrolled 409 people living with HIV from two HIV clinics in Lesotho and investigated the performance of POC urine LFIA TFV testing in predicting viral suppression. We interviewed 12 study participants and conducted a focus-group discussion with 5 clinicians to gather opinions on POC urine TFV testing.

RESULTS

Using a viral load threshold of 1000 copies/mL, 398 (98%) participants were virologically suppressed, and 8 were viremic. Tenofovir was detected in the urine of 405 (99%) participants. The sensitivity of the POC urine LFIA test in detecting TFV in participants with viral suppression was 99.3% (95% CI: 97.8-99.8); the specificity was 12.5% (95% CI: 0.3-52.6). The positive and negative predictive values were 98.3% and 25%, respectively. Point-of-care urine TFV testing was viewed favorably by both participants and clinicians. However, clinicians stated that the 2-3-days detection window of the assay studied limits adherence categorization.

CONCLUSIONS

In our study cohort, urine POC TFV testing demonstrated high sensitivity in predicting viral suppression, but low specificity and negative predictive value. Urine POC TFV testing was highly acceptable to participants and clinicians; however, clinicians expressed concern about its clinical utility because of its limitations. While further research is needed to assess performance in less adherent populations, this test may support adherence counseling in some clinical settings.

Brief Report: Transgender Women and Preexposure Prophylaxis Care: High Preexposure Prophylaxis Adherence in a Real-World Health Care Setting in New York City

BACKGROUND

Transgender women and trans feminine individuals (TGW/TFI) are a high priority population for the provision of HIV preexposure prophylaxis (PrEP) care within the United States, but there is limited research that focuses specifically on PrEP adherence within this population.

SETTING

Observational study of patients prescribed PrEP at a community-based health center.

METHODS

We enrolled 100 TGW/TFI PrEP patients at a community health center during clinic visits. Adherence data were collected at 3 time points, using self-report surveys, patient interviews, and urine assays measuring tenofovir. Data were summarized descriptively.

RESULTS

The sample was diverse in age, race/ethnicity, and socioeconomic characteristics. Participants demonstrated strong PrEP adherence; at least 80% of the sample reported 90% or greater adherence at each time point. Concordance between self-report and urine assay was high. Among patients who reported taking PrEP within the past 48 hours, 82%-92% had detectable urine tenofovir. However, many patients reported PrEP stop periods of 4 or more days (28%-39% per time point).

CONCLUSIONS

Our data highlight TGW/TFI's capacity to adhere to daily PrEP and sustain PrEP use over time. The concordance between patient self-report and urine TFV levels suggest that providers can trust patient reports of PrEP adherence behavior and support the use of adherence conversations in clinical settings, without the need for point of care biological monitoring. Findings also underscore the importance of continued attention to drivers of PrEP stops at the patient, clinic, and systems levels and the development of strategies that support sustained PrEP use.

Brief Report: Transgender Women and Preexposure Prophylaxis Care: High Preexposure Prophylaxis Adherence in a Real-World Health Care Setting in New York City

BACKGROUND

Transgender women and trans feminine individuals (TGW/TFI) are a high priority population for the provision of HIV preexposure prophylaxis (PrEP) care within the United States, but there is limited research that focuses specifically on PrEP adherence within this population.

SETTING

Observational study of patients prescribed PrEP at a community-based health center.

METHODS

We enrolled 100 TGW/TFI PrEP patients at a community health center during clinic visits. Adherence data were collected at 3 time points, using self-report surveys, patient interviews, and urine assays measuring tenofovir. Data were summarized descriptively.

RESULTS

The sample was diverse in age, race/ethnicity, and socioeconomic characteristics. Participants demonstrated strong PrEP adherence; at least 80% of the sample reported 90% or greater adherence at each time point. Concordance between self-report and urine assay was high. Among patients who reported taking PrEP within the past 48 hours, 82%-92% had detectable urine tenofovir. However, many patients reported PrEP stop periods of 4 or more days (28%-39% per time point).

CONCLUSIONS

Our data highlight TGW/TFI's capacity to adhere to daily PrEP and sustain PrEP use over time. The concordance between patient self-report and urine TFV levels suggest that providers can trust patient reports of PrEP adherence behavior and support the use of adherence conversations in clinical settings, without the need for point of care biological monitoring. Findings also underscore the importance of continued attention to drivers of PrEP stops at the patient, clinic, and systems levels and the development of strategies that support sustained PrEP use.

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.

Adherence to Daily Oral TDF/FTC for PrEP in Community Health Center Populations: The Sustainable Health Center Implementation PrEP Pilot (SHIPP) Study

The prevention effectiveness of oral preexposure prophylaxis (PrEP) is highly dependent on medication adherence but no validated longer term PrEP adherence measures are readily available for use by primary care clinicians caring for diverse populations. We compared two self-report measures (number of doses missed in past 7 days and day-by-day past week pill taking) to results of tenofovir concentrations in dried blood spot (DBS) samples at quarterly visits over the first 12 months of PrEP use. 1420 men and women in five US community health centers enrolled in a medication adherence substudy. For 3, 6, 9 and 12 months, the respective percentages of persons with self-report vs DBS levels consistent having taken all 7 doses in the week prior were 71% (51%), 70% (47%), 71% (46%) and 69% (44%). Conversely, the percentage of participants reporting taking 0-1 doses in the week prior by self-report vs DBS drug levels at 3, 6, 9 and 12 months consistent with this level of nonadherence of 6% (9%), 5% (10%), 8% (9%), and 9% (15%). The estimated risk of low adherence (estimated 0-1 doses in the week prior) was higher for participants of Black (RR 1.60, CI 1.09-2.34) or "Other" race (RR 1.62, CI 0.99-2.65) compared with participants of White race; being a transgender female (RR 2.31, CI 1.33-4.02) compared to men who have sex with men; or enrollment at a study site with less experience in the provision of PrEP. The estimated risk of low adherence by DBS was lower for participants with a higher number of sex partners in the past 3 months and those having a bachelor's degree or higher. More work is needed to provide clinicians with measures to assess medication adherence in diverse US populations being prescribed PrEP to support its effective use in reducing HIV acquisition in individuals and at the community level.

Adherence to Pre-Exposure Prophylaxis in Adolescents and Young Adults: A Systematic Review and Meta-Analysis

This meta-analysis synthesized the proportion of adolescents and young adults (AYAs) who are adherent to pre-exposure prophylaxis (PrEP) and factors moderating adherence. A systematic search was conducted of studies published through May 2020 using PubMed, PsycInfo, Cochrane, EMBASE, and CINAHL. Included studies reported the proportion of AYAs (mean age ≤ 29 years) who were PrEP adherent. PrEP adherence was meta-analyzed using random-effects models. Secondary analyses evaluated potential moderating variables. A total of 41 individual samples, from 29 studies, of 8,679 AYA (weighted average age = 23.8 years) were synthesized. The proportion of AYA who met study-defined thresholds for PrEP adherence was .64 (95% confidence interval .57-.71) across studies. Subgroup analyses revealed that adherence was lower in young cisgender women (.46) than young men who have sex with men (.65) and serodiscordant heterosexual couples (.98). Adherence was higher in studies initiated after 2012 (.70) than earlier studies (.47). No differences based on participant age, country, or strategies to promote adherence were found. Across published studies to date, 64% of AYA demonstrate adequate PrEP adherence. Findings can be used to guide PrEP adherence interventions and also provide directions for future research on PrEP among AYA.

Point-of-Care Test for Assessing Tenofovir Adherence: Feasibility and Recommendations from Women in an Oral PrEP Program in Kenya and Their Healthcare Providers

Oral pre-exposure prophylaxis (PrEP) is a highly effective HIV prevention modality when taken as recommended. Women in sub-Saharan Africa may have adherence challenges that remain undisclosed to providers. Real-time measures that identify non-adherence can allow for immediate exploration of adherence challenges, counseling and interventions. We conducted a formative qualitative study in Kenya to explore oral PrEP experiences and reactions to a point-of-care urine test (UT) identifying recent (past 4 days) non-adherence to tenofovir-based PrEP among female PrEP users (25 in-depth interviews; 4 focus groups) and health care provider (10 key informant interviews). Findings indicate that use of the UT would be highly feasible in the context of regular PrEP care, largely acceptable to clients and providers, and could improve adherence. Clients emphasized the need for transparent client-centered strategies in delivering results. This formative study informs the development of tools to implement this point-of-care UT in future interventional studies and clinical settings.

Short Communication: Evaluation of Antiretroviral Drug Concentrations in Minimally Invasive Specimens for Potential Development of Point-of-Care Drug Assays

Point-of-care (POC) tests for antiretroviral drugs (ARVs) could help improve individual adherence. This study sought to define the utility of urine, blood, and buccal swabs as minimally invasive specimens amenable to development of POC tests for ARVs. Urine, dried blood spots (DBS) and buccal swabs were collected from 35 HIV-negative men between 2 and 96 h after a single dose of tenofovir (TFV) alafenamide/emtricitabine (FTC)/elvitegravir (EVG)/cobicistat and darunavir (DRV). ARV concentrations were measured by high-performance liquid chromatography-mass spectrometry. High concentrations of FTC, DRV, and TFV were detectable in urine at least 24 h after dosing. FTC, DRV, and EVG remained detectable in DBS at least 24 h postdose. FTC and DRV were detectable on buccal swabs up to 2 and 24 h postdose, respectively. TFV was not detectable in DBS or buccal swabs collected between 2 and 96 h after dosing. Variable distribution of ARVs in minimally invasive specimens highlights the challenge of developing POC assays for recent ARV exposure.

Point-of-Care Detection of Nonadherence to Antiretroviral Treatment for HIV-1 in Resource-Limited Settings Using Drug Level Testing for Efavirenz, Lopinavir, and Dolutegravir: A Validation and Pharmacokinetic Simulation Study

BACKGROUND

Virological failure during antiretroviral treatment (ART) may indicate the presence of drug resistance, but may also originate from nonadherence. Qualitative detection of ART components using drug level testing may be used to differentiate between these scenarios. We aimed to validate and implement qualitative point-of-care drug level tests for efavirenz (EFV), lopinavir (LPV), and dolutegravir (DTG) in rural South Africa.

METHODS

Qualitative performance of immunoassays for EFV, LPV, and DTG was assessed by calculating limit of detection (LoD), region of uncertainty, and qualitative agreement with a reference test. Minimum duration of nonadherence resulting in a negative drug level test was assessed by simulation of treatment cessation using validated population pharmacokinetic models.

RESULTS

LoD was 0.05 mg/L for EFV, 0.06 mg/L for LPV, and 0.02 mg/L for DTG. Region of uncertainty was 0.01-0.06 mg/L for EFV, 0.01-0.07 mg/L for LPV, and 0.01-0.02 mg/L for DTG. Qualitative agreement with reference testing at the LoD in patient samples was 95.2% (79/83) for EFV, 99.3% (140/141) for LPV, and 100% (118/118) for DTG. After simulated treatment cessation, median time to undetectability below LoD was 7 days [interquartile range (IQR) 4-13] for EFV, 30 hours (IQR 24-36) for LPV, and 6 days (IQR 4-7) for DTG.

CONCLUSIONS

We demonstrate that qualitative ART drug level testing using immunoassays is feasible in a rural resource-limited setting. Implementation of this technology enables reliable detection of recent nonadherence and may allow for rapid and cost-effective differentiation between patients in need for adherence counseling and patients who require drug resistance testing or alternative treatment.

Tenofovir and emtricitabine concentrations in hair are comparable between individuals on tenofovir disoproxil fumarate versus tenofovir alafenamide-based ART

Tenofovir disoproxil fumarate (TDF) in combination with emtricitabine (FTC) is the backbone for both human immunodeficiency virus (HIV) treatment and pre-exposure prophylaxis (PrEP) worldwide. Tenofovir alafenamide (TAF) with FTC is increasingly used in HIV treatment and was recently approved for PrEP among men-who-have-sex-with-men. TDF and TAF are both metabolized into tenofovir (TFV). Antiretrovirals in plasma are taken up into hair over time, with hair levels providing a long-term measure of adherence. Here, we report a simple, robust, highly sensitive, and validated high-performance liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS)-based analytical method for analyzing TFV and FTC from individuals on either TDF/FTC or TAF/FTC in small hair samples. TFV/FTC are extracted from ~5 mg hair and separated on a column using a gradient elution. The lower quantification limits are 0.00200 (TFV) and 0.0200 (FTC) ng/mg hair; the assay is linear up to 0.400 (TFV) and 4.00 (FTC) ng/mg hair. The intra-day and inter-day coefficients of variance (CVs) are 5.39-12.6% and 6.40-13.5% for TFV and 0.571-2.45% and 2.45-5.16% for FTC. TFV concentrations from participants on TDF/FTC-based regimens with undetectable plasma HIV RNA were 0.0525 ± 0.0295 ng/mg, whereas those from individuals on TAF/FTC-based regimens were 0.0426 ± 0.0246 ng/mg. Despite the dose of TFV in TDF being 10 times that of TAF, hair concentrations of TFV were not significantly different for those on TDF versus TAF regimens. Pharmacological enhancers (ritonavir and cobicistat) did not boost TFV concentrations in hair. In summary, we developed and validated a sensitive analytical method to analyze TFV and FTC in hair and found that hair concentrations of TFV were essentially equivalent among those on TDF and TAF.

Pilot evaluation of an enzymatic assay for rapid measurement of antiretroviral drug concentrations

Objective

Maintaining adequate drug adherence is crucial to ensure the HIV prevention benefits of pre-exposure prophylaxis (PrEP). We developed an enzymatic assay for rapidly measuring tenofovir-diphosphate (TFV-DP) concentrations—a metabolite that indicates long-term PrEP adherence.

Setting

The study was conducted at the Madison HIV Clinic at Harborview Medical Center in Seattle.

Methods

We enrolled adults receiving standard oral PrEP, and individuals not receiving any antiretrovirals. We measured TFV-DP concentrations in diluted whole blood using our novel REverSe TRanscrIptase Chain Termination (RESTRICT) assay, based on inhibition of HIV reverse transcriptase (RT) enzyme. Blood samples were diluted in water, DNA templates, nucleotides, RT, and intercalating dye added, and results measured with a fluorescence reader—stronger fluorescence indicated higher RT activity. We compared RESTRICT assay results to TFV-DP concentrations from matched dried blood spot samples measured by liquid chromatography tandem mass spectrometry (LC–MS/MS) using ≥ 700 fmol/punch TFV-DP as a threshold for adequate adherence (≥ 4 doses/week).

Results

Among 18 adults enrolled, 4 of 7 participants receiving PrEP had TFV-DP levels ≥ 700 fmol/punch by LC–MS/MS. RESTRICT fluorescence correlated with LC–MS/MS measurements (r = − 0.845, p < 0.0001). Median fluorescence was 93.3 (95% confidence interval [CI] 90.9 to 114) for samples < 700 fmol/punch and 54.4 (CI 38.0 to 72.0) for samples ≥ 700 fmol/punch. When calibrated to an a priori defined threshold of 82.7, RESTRICT distinguished both groups with 100% sensitivity and 92.9% specificity.

Conclusions

This novel enzymatic assay for measuring HIV reverse transcriptase activity may be suitable for distinguishing TFV-DP concentrations in blood that correspond to protective PrEP adherence.

Drug level testing as a strategy to determine eligibility for drug resistance testing after failure of ART: a retrospective analysis of South African adult patients on second-line ART

Introduction

When protease inhibitor (PI)‐based second‐line ART fails, guidelines recommend drug resistance testing and individualized third‐line treatment. However, PI‐resistant viral strains are rare and drug resistance testing is costly. We investigated whether less costly PI‐exposure testing can be used to select those patients who would benefit most from drug resistance testing.

Methods

We performed a retrospective analysis of South African adults living with HIV experiencing failure of ritonavir‐boosted‐lopinavir (LPV/r)‐based second‐line ART for whom drug resistance testing results were available. We included patients who received plasma‐based drug resistance testing at a central South African reference laboratory in 2017 and patients who received dried blood spots (DBS)‐based drug resistance testing at a rural South African clinic between 2009 and 2017. PI‐exposure testing was performed on remnant plasma or DBS using liquid chromatography mass spectrometry (LCMS). Additionally, a low‐cost immunoassay was used on plasma. Population genotypic drug resistance testing of the pol region was performed on plasma and DBS using standard clinical protocols.

Results

Samples from 544 patients (494 plasma samples and 50 DBS) were included. Median age was 41.0 years (IQR: 33.3 to 48.5) and 58.6% were women. Median HIV‐RNA load was 4.9 log10 copies/mL (4.3 to 5.4). Prevalence of resistance to the NRTI‐backbone was 70.6% (349/494) in plasma samples and 56.0% (28/50) in DBS. Major PI‐resistance mutations conferring high‐level resistance to LPV/r were observed in 26.7% (132/494) of plasma samples and 12% (6/50) of DBS. PI‐exposure testing revealed undetectable LPV levels in 47.0% (232/494) of plasma samples and in 60.0% (30/50) of DBS. In pooled analysis of plasma and DBS samples, detectable LPV levels had a sensitivity of 90% (84% to 94%) and a negative predictive failure of 95% (91% to 97%) for the presence of major LPV/r resistance.

Conclusions

PI‐exposure testing revealed non‐adherence in half of patients experiencing failure on second‐line ART and accurately predicted the presence or absence of clinically relevant PI resistance. PI‐exposure testing constitutes a novel screening strategy in patients with virological failure of ART that can differentiate between different underlying causes of therapy failure and may allow for more effective use of limited resources available for drug resistance testing.

Brief Report: Discrepancies Between Self-Reported Adherence and a Biomarker of Adherence in Real-World Settings

BACKGROUND

Pre-exposure prophylaxis (PrEP) is only effective in preventing new HIV infections when taken consistently. In clinical practice, asking a patient about their adherence (self-report) is the predominant method of assessing adherence to PrEP. Although inexpensive and noninvasive, self-report is subject to social desirability and recall biases. Several clinical trials demonstrate a discrepancy between self-reported adherence and biomarker-based recent adherence. Less is known about the accuracy of self-report in real-world clinical settings. This brief report addresses this knowledge gap and describes the concordance between self-reported adherence and biomarker-based adherence in real-world clinical settings.

METHODS

A liquid chromatography-mass spectrometry urine test for tenofovir was developed and used clinically to detect recent nonadherence (no dose in at least 48 hours) for each individual. Two clinics' standard operating procedures recommend utilization of the urine-based adherence test for patients who self-report that they are not struggling with adherence. Those who self-report struggling with adherence receive enhanced adherence support without the need for additional testing. The number of results indicating recent nonadherence from these 2 clinics were analyzed to assess the concordance between self-reported adherence and biomarker-based adherence.

RESULTS

Across 2 clinics, 3987 tests were conducted from patients self-reporting as "adherent," and 564 [14.1%; 95% confidence interval (CI): 13.1% to 15.2%] demonstrated recent nonadherence with the liquid chromatography-mass spectrometry test. At clinic #1 in Florida, 3200 tests were conducted, and 465 (14.5%; 95% CI: 13.3% to 15.8%) demonstrated recent nonadherence. At clinic #2 in Texas, 787 tests were conducted, and 99 (12.6%; 95% CI: 10.4% to 14.9%) demonstrated recent nonadherence.

CONCLUSIONS

Utilization of biomarker-based adherence monitoring at these 2 clinics resulted in 564 additional patients receiving enhanced adherence support who otherwise would not have been identified as nonadherent to their prescribed PrEP regimen. These findings suggest that objective adherence monitoring can be used clinically to enable providers to identify nonadherent patients and allocate support services accordingly.

Integrating HIV Preexposure Prophylaxis With Community-Based Syringe Services for Women Who Inject Drugs: Results From the Project SHE Demonstration Study

INTRODUCTION

To guide future preexposure prophylaxis (PrEP) implementation for women who inject drugs (WWID), a population increasingly represented in new HIV cases in the United States, we present results from a demonstration project integrated within a syringe services program (SSP) in Philadelphia, PA.

METHODS

WWID ≥18 years were educated about and offered 24 weeks of daily PrEP. Participants completed surveys and clinical assessments at baseline and at weeks 1, 3, 12, and 24. We used descriptive statistics to estimate feasibility/acceptability, engagement in the care cascade, HIV/sexually transmitted diseases (STI) and pregnancy, issues of safety/tolerability, and preferences/satisfaction with PrEP services. Multivariable logistic regression with generalized estimating equations was used to identify factors associated with PrEP uptake and retention.

RESULTS

We recruited 136 WWID. Of those, 95 were included in the final sample, and 63 accepted a PrEP prescription at week 1. Uptake was associated with greater baseline frequency of SSP access [adjusted odds ratio (aOR) = 1.85; 95% confidence interval (CI): 1.24 to 2.77], inconsistent condom use (aOR = 3.38; 95% CI: 1.07 to 10.7), and experiencing sexual assault (aOR = 5.89; 95% CI: 1.02, 33.9). Of these 95, 42 (44.2%) were retained at week 24. Retention was higher among women who reported more frequent baseline SSP access (aOR = 1.46; 95% CI: 1.04 to 2.24). Self-reported adherence was high but discordant with urine-based quantification of tenofovir. Baseline STI prevalence was 17.9%; there were 2 HIV seroconversions and 1 pregnancy. Safety/tolerability issues were uncommon, and acceptability/satisfaction was high.

CONCLUSIONS

Integrating PrEP with SSP services is feasible and acceptable for WWID. This suggests that daily PrEP is a viable prevention tool for this vulnerable population.

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.

Urine Tenofovir Levels Measured Using a Novel Immunoassay Predict Human Immunodeficiency Virus Protection

New tools are needed to support pre-exposure prophylaxis (PrEP) adherence for human immunodeficiency virus (HIV) prevention, including those that enable real-time feedback. In a large, completed PrEP trial, adequate urine tenofovir levels measured using a novel immunoassay predicted HIV protection and showed good sensitivity and specificity for detectable plasma tenofovir.

The case for prescribing PrEP in community mental health settings

Pre-exposure prophylaxis (PrEP) is a biomedical HIV prevention modality that is up to 99% effective in preventing HIV acquisition through sex if taken as directed. People with serious mental illness (eg, schizophrenia and bipolar disorder) are at high risk of acquiring HIV due to sexual behaviours, injection drug use, social factors, and structural discrimination that limits access to all types of preventive health services. We seek to show the importance of prioritising access to PrEP for people living with serious mental illness treated in community mental health settings. We describe barriers to prescribing PrEP, including provider attitudes and provider knowledge gaps, patient attitudes and knowledge, and systems issues. We also address the concerns that community mental health clinic administrators might have about taking on the responsibility of offering PrEP. In summary, despite the barriers to prescribing PrEP in these settings, we believe that there is a unique opportunity for community mental health settings to help address the HIV epidemic by facilitating the prescribing of PrEP to the at-risk populations they currently serve.

Real-Time Monitoring and Point-of-Care Testing: A Review of the Current Landscape of PrEP Adherence Monitoring

BACKGROUND

Despite pre-exposure prophylaxis (PrEP) being highly effective at preventing HIV, HIV infections among individuals prescribed PrEP continue to occur. The vast majority of these new infections occur among individuals with sub-optimal adherence. One factor that is likely to decrease HIV incidence among PrEP users is a real-time, objective measurement of adherence. Monitoring adherence to PrEP can identify those at risk of becoming lost to follow-up and therefore at greater risk of HIV infection, those in need of additional layers of support to overcome barriers to PrEP, and individuals who need enhanced adherence support.

OBJECTIVE

This paper reviews subjective and objective methods for monitoring PrEP including self-report, drug level monitoring (including serum, plasma, peripheral blood mononuclear cells [PBMC], red blood cell dried blood spots [DBS], hair, and urine) and by measuring participant interaction with the study drug (pill counts, medication event monitoring systems [MEMS] caps).

CLINICAL USE

A multitude of methods exist for monitoring and supporting adherence. Objective monitoring using DBS and urine will provide a more accurate picture of adherence compared to subjective and non-biomarker objective methods. Preliminary data show that detection of non-adherence using biomarkers, followed by augmented adherence support and counseling, is associated with improved adherence, although more research is needed. PrEP providers will need knowledge of and access to these various strategies, which will require investment and resource allocation from clinics and other PrEP care sites to provide these tools.

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.

Perspectives on the utility and interest in a point-of-care urine tenofovir test for adherence to HIV pre-exposure prophylaxis and antiretroviral therapy: an exploratory qualitative assessment among U.S. clients and providers

Background

Real-time, objective measures of adherence to antiretroviral therapy (ART) and pre-exposure prophylaxis (PrEP) are needed to better assess adherence levels and to expedite clinical response for those with suboptimal adherence. Point-of-care tenofovir (POC-TFV) testing has been proposed as a solution to facilitate real-time antiretroviral adherence monitoring, but little is known about how health care providers, people living with HIV (PLWH) receiving ART, and people receiving PrEP will perceive POC-TFV testing.

Methods

We conducted an exploratory qualitative study to assess perspectives on the utility and interest in POC-TFV testing from potential end users. We conducted three focus group discussions (FGDs) among 17 PLWH receiving ART and four individuals receiving PrEP, as well as eight in-depth interviews (IDIs) with health care providers in the Seattle area and presented participants with a hypothetical urine-based POC-TFV test. FGDs and IDIs were audio recorded, transcribed, coded, and analyzed to describe emerging themes.

Results

Overall, study participants demonstrated divergent opinions about the POC-TFV test. Among study participants, PLWH were most ambivalent about POC-TFV testing, first demonstrating reluctance to TFV-level monitoring and shifting positions during the FGDs. However, all PLWH participants were receptive to POC-TFV testing if requested by their provider. PrEP participants were generally supportive of POC-TFV testing for routine adherence monitoring and emphasized potential value in self-administered testing. Providers’ perceptions were equally divided – half suggested POC-TFV testing would be valuable, particularly for people receiving PrEP, while half indicated the test would have little benefit for most individuals receiving ART or PrEP in the U.S. All providers agreed that POC-TFV test results could be beneficial for assessing discrepancies in viral load results and self-reported adherence among PLWH. The study also revealed that a low-cost, non-urine-based POC-TFV test with a long-term limit of detection would be preferred over the hypothetical urine-based test.

Conclusions

Our findings indicate POC-TFV testing may be beneficial for routine, clinic-based adherence monitoring, particularly for individuals receiving PrEP or for PLWH with persistent viremia or following recent ART initiation. These findings should also be used to formulate a target product profile for a POC-TFV test and to guide further developments in tools for objective antiretroviral adherence monitoring.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Pharmacokinetics of nucleoside/nucleotide reverse transcriptase inhibitors for the treatment and prevention of HIV infection

INTRODUCTION

Despite dramatic increases in new drugs and regimens, a combination of two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) remains the backbone of many regimens to treat HIV.

AREA COVERED

This article summarizes the pharmacokinetic characteristics of approved NRTIs that are currently in the international treatment and prevention guidelines.

EXPERT OPINION

Compared to other NRTIs, tenofovir alafenamide fumarate (TAF) is more advantageous in terms of potency and safety. It is therefore a preferred choice in combination with emtricitabine (FTC) in most HIV treatment guidelines. The efficacy of the two-drug combination of NRTI/Integrase strand-transfer inhibitor, i.e. lamivudine/dolutegravir has been approved as an option for initial therapy. This regimen however has some limitations in patients with HBV coinfection. The two NRTI combinations tenofovir disproxil fumarate (TDF)/FTC and TAF/FTC have also been approved for pre-exposure prophylaxis (PrEP). Interestingly, a promising long-acting nucleoside reverse transcriptase translocation inhibitor, islatravir, formulated for implant was well tolerated and remained effective for up to a year, suggesting its potential as a single agent for PrEP. In the next decade, it remains to be seen whether NRTI-based regimens will remain the backbone of preferred ART regimens, or if the treatment will eventually move toward NRTI-sparing regimens to avoid long-term NRTI-toxicity.

Brief Report: Urine Emtricitabine and Tenofovir Concentrations Provide Markers of Recent Antiretroviral Drug Exposure Among HIV-Negative Men Who Have Sex With Men

BACKGROUND

Urine provides a minimally invasive specimen that may allow for development of rapid tests to detect antiretroviral drugs and provide opportunities to improve individual adherence. This study sought to determine whether urine could provide a biomarker of adherence for currently approved pre-exposure prophylaxis and HIV treatment regimens.

METHODS

Urine and blood were collected from 34 HIV-negative men who have sex with men aged 18-49 years, enrolled in a clinical trial comparing 2 antiretroviral regimens. Specimens were collected 4 and 24 hours after a single oral dose of tenofovir disoproxil fumarate (TDF)/emtricitabine (FTC) (n = 10) or tenofovir alafenamide (TAF)/FTC/cobicistat (COBI)/elvitegravir (EVG) (n = 8), or after 4 and 10 days of daily oral TDF/FTC (n = 9) or TAF/FTC/COBI/EVG (n = 7). Tenofovir (TFV), FTC, and EVG were measured by high-performance liquid chromatography-mass spectrometry.

RESULTS

Median urine FTC concentrations at 4 and 24 hours were similar between men receiving TDF/FTC (4 hours 147 µg/mL; 24 hours 10 µg/mL) and men receiving TAF/FTC/COBI/EVG (4 hours 333 µg/mL, P = 0.173; 24 hours 13 µg/mL, P = 0.681). Median urine TFV concentrations were lower among men receiving TAF/FTC/COBI/EVG (4 hours 1.2 µg/mL; 24 hours 0.8 µg/mL) compared with men receiving TDF/FTC (4 hours 17 µg/mL, P < 0.001; 24 hours 7 µg/mL, P = 0.001). Urine TFV concentrations remained reduced among men receiving TAF/FTC/COBI/EVG compared with men receiving TDF/FTC after daily dosing. EVG was not consistently measurable in urine.

CONCLUSIONS

High urine FTC and TFV concentrations could provide an indication of adherence to daily oral dosing with TDF or TAF-based regimens used for treatment and prevention.

Urine Tenofovir Concentrations Correlate With Plasma and Relate to Tenofovir Disoproxil Fumarate Adherence: A Randomized, Directly Observed Pharmacokinetic Trial (TARGET Study)

BACKGROUND

Direct measurement of tenofovir (TFV) in urine could be an objective measure to monitor adherence to preexposure prophylaxis (PrEP) or TFV-based antiretroviral therapy (ART).

METHODS

We conducted a 3-arm randomized, pharmacokinetic study of tenofovir disoproxil fumarate (TDF) 300 mg/emtricitabine (FTC) 200 mg among adults living with human immunodeficiency virus. Participants were randomized to receive controlled TDF/FTC dosing as (1) "perfect" adherence (daily); (2) "moderate" adherence (4 doses/week); or (3) "low" adherence (2 doses/week). We obtained trough spot urine and plasma samples during a 6-week directly observed therapy period and a 4-week washout period. TFV concentrations were compared between adherence arms using 1-way analysis of variance.

RESULTS

Among 28 participants, the median age was 33 years and 16 (57%) were male. Correlation between TFV plasma and urine concentrations was strong (ρ = 0.78; P < .0001). Median (interquartile range) steady-state trough TFV concentrations (ng/mL) for perfect, moderate, and low TDF adherence were 41 (26-52), 16 (14-19), and 4 (3-5) in plasma; and 6480 (3940-14 300), 3405 (2210-5020), and 448 (228-675) in urine. Trough TFV concentrations at steady state were significantly different between the 3 adherence arms for plasma (P < .0001) and urine (P = .0002). Following drug cessation, TFV concentrations persisted longer in urine than plasma samples. Washout urine TFV concentrations and time to undetectable concentrations did not differ between the 3 randomized adherence groups.

CONCLUSIONS

Urine TFV concentrations can inform interpretation of novel point-of-care urine-based TFV assays to assess recent TDF adherence.

CLINICAL TRIALS REGISTRATION

NCT03012607

Hyphenated mass spectrometry techniques for assessing medication adherence: advantages, challenges, clinical applications and future perspectives

Nonadherence to prescribed pharmacotherapy is an understated public health problem globally and is costing many patients their chance to return to good health and healthcare systems billions. Clinicians need an accurate assessment of adherence to medications to aid the clinical decision-making process in the event of poor patient progress and to maximise the patient health outcomes from the drug therapies prescribed. An overview of indirect and direct methods used to measure medication adherence is presented, highlighting the potential for accurate measuring of drugs in biological samples using hyphenated mass spectrometry (MS) techniques to provide healthcare professionals with a reliable evidence base for clinical decision making. In this review we summarise published applications of hyphenated MS techniques for a diverse range of clinical areas demonstrating the rise in the use of such direct methods for assessing medication adherence. Although liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods using plasma, serum and urine samples are the most popular, in recent years increased attention has been given to liquid chromatography high-resolution mass spectrometry (LC-HRMS) methods and alternative biosample matrices including hair, saliva and blood microsamples. The advantages and challenges of using hyphenated MS techniques to address this healthcare problem are also discussed alongside future perspectives.

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.

Testing a Real-Time Tenofovir Urine Adherence Assay for Monitoring and Providing Feedback to Preexposure Prophylaxis in Kenya (PUMA): Protocol for a Pilot Randomized Controlled Trial

BACKGROUND

The worldwide expansion of preexposure prophylaxis (PrEP) with oral tenofovir-disoproxil-fumarate/emtricitabine will be critical to ending the HIV epidemic. However, maintaining daily adherence to PrEP can be difficult, and the accuracy of self-reported adherence is often limited by social desirability bias. Pharmacologic adherence monitoring (measuring drug levels in a biomatrix) has been critical to interpreting PrEP trials, but testing usually requires expensive equipment and skilled personnel. We have recently developed a point-of-care (POC) immunoassay to measure tenofovir in urine, allowing real-time adherence monitoring for the first time.

OBJECTIVE

The goal of this study is to examine a point-of-care adherence metric in PrEP to support and increase adherence via a randomized controlled trial.

METHODS

The paper describes the protocol for a pilot randomized controlled trial to test the acceptability, feasibility, and impact on long-term adherence of implementing a POC urine test to provide real-time adherence feedback among women on PrEP. Eligible women (n=100) will be HIV-negative, ≥18 years old, and recruited from a clinic in Kenya that provides PrEP. Participants will be randomized 1:1 to the intervention of providing real-time feedback via the assay versus standard of care adherence counseling. Acceptability by participants will be assessed by a quantitative survey, as well as by qualitative data collected via in-depth interviews (n=20) and focus group discussions (n=4 groups, 5-10 women each). Feasibility will be assessed by the proportion of women retained in the study, the mean number of missed visits, the proportion of planned urine assessments completed, and messages delivered, while in-depth interviews with providers (n=8) will explore the ease of administering the urine test. Tenofovir levels in hair will serve as long-term adherence metrics. A linear mixed-effects model will estimate the effect of the intervention versus standard of care on logarithmically transformed levels of tenofovir in hair.

RESULTS

This study has been funded by the National Institute of Health, approved by the Kenya Medical Research Institute Institutional Review Board, and will commence in June 2020.

CONCLUSIONS

A novel urine assay to measure and deliver information on adherence to PrEP in real-time will be tested for the first time in this trial planned among women on PrEP in Kenya. Study findings will inform a larger-scale trial assessing the impact of real-time adherence monitoring/feedback on HIV prevention. Improving adherence to PrEP will have long-term implications for efforts to end the HIV epidemic worldwide.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03935464; https://clinicaltrials.gov/ct2/show/NCT03935464.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/15029.

Correlation of pre-exposure prophylaxis adherence to a mental health diagnosis or experience of childhood trauma in high-risk youth

Pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate (TDF)/emtricitabine is 99% effective in preventing HIV when taken daily. Young men/transgender women of color who have sex with men are the most at risk to become infected with HIV, with the lowest PrEP adherence. We investigated the association of depression, anxiety, and history of childhood trauma with PrEP adherence. PrEP adherence was measured by urine TDF testing. Patients were evaluated for depression (Patient Health Questionnaire-9 [PHQ-9]), anxiety (Generalized Anxiety Disorder-7 [GAD-7]), and history of childhood trauma (Adverse Childhood Experiences [ACEs]). Urine TDF levels were compared across scores on each screening tool using a Student’s t-test. A p-value of ≤ 0.05 was considered significant. Thirty-one subjects (mean age: 21.7 years, SD: 2.8) were enrolled between 3/2015 and 7/2016. Lower PrEP adherence was associated with a GAD-7 score diagnostic for generalized anxiety (80.7% versus 92.7%, p = 0.04) and a high ACE score (4+) (84.5% versus 95.7%, p = 0.05). A PHQ-9 score diagnostic for major depression was not associated with PrEP adherence. The presence of generalized anxiety and a history of childhood trauma, but not major depression, were associated with decreased PrEP adherence. The benefits of mental health interventions and trauma-informed care in PrEP programs should be considered in larger studies to potentially increase adherence.

Urine Assay to Measure Tenofovir Concentrations in Patients Taking Tenofovir Alafenamide

Background: HIV pre-exposure prophylaxis (PrEP) with tenofovir/emtricitabine is effective when taken daily. Previously, we developed a urine assay capable of detecting the prodrug tenofovir (TFV) in patients taking tenofovir disoproxil fumarate (TDF)-based PrEP. However, tenofovir alafenamide (TAF) has replaced TDF due to its different safety profile for HIV treatment and was recently approved as PrEP. Given the need to ensure the aforementioned assay remains available for the purpose of objective adherence monitoring, it is critical to ensure its accuracy for detecting TFV in patients taking TAF. Methods: Blood and urine samples were collected from 3 cohorts of patients: (1) 10 participants living with HIV (PLWH) with suppressed virus on a TAF-based regimen, (2) 10 HIV-participants administered 1 dose of TAF/FTC followed by urine and plasma sampling for 7 days starting 1-3 h post-dose, and (3) 10 HIV-participants administered 7 doses of TAF/FTC followed by urine and plasma sampling for 10 days starting 1-3 h after the last dose. Samples were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with high sensitivity and specificity for TFV. HIV-samples were compared to a historical cohort administered one dose of TDF/FTC. Results: PLWH were 90% male, 40% African American, and 10% Hispanic (mean age = 57 y; SD 8.88 y). HIV-participants were 55% male and 70% Caucasian (mean age = 31.6 y; SD 7.70 y). Samples from PLWH demonstrated TFV concentrations 2 logs higher in urine than plasma (1,000 ng/mL vs ±10 ng/mL) at the time of collection. Urine samples following a single dose of TAF in HIV-participants yielded TFV concentrations ranging from 100 to 1,000 ng/mL 1-3 h post-dose and remained >100 ng/mL for 6 days in 8 of 10 participants. Urine samples collected after 7 consecutive doses of TAF yielded TFV concentrations >1,000 ng/mL 1-3 h after dosing discontinuation, with TFV concentrations >1,00 ng/mL 7 days post discontinuation in 8 of 10 participants. Urine TFV concentrations following TAF administration were comparable to those from a historical cohort administered TDF/FTC. Plasma TFV concentrations were low(±10 ng/mL) in both HIV-cohorts at all time points. Conclusions: TFV persists in urine at detectable concentrations in participants taking TAF/FTC for at least 7 days despite largely undetectable plasma concentrations, with urine TFV concentrations comparable to patients taking TDF/FTC. This study demonstrates the ability of a urine TFV assay to measure recent TAF adherence.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Brief Report: Validation of a Urine Tenofovir Immunoassay for Adherence Monitoring to PrEP and ART and Establishing the Cutoff for a Point-of-Care Test

BACKGROUND

Current pharmacologic adherence monitoring for antiretrovirals involves expensive, labor-intensive liquid chromatography/tandem mass spectrometry (LC-MS/MS)-based methods. Antibody-based assays can monitor and support adherence in real time. We developed a tenofovir (TFV)-based immunoassay and further validated it in a directly observed therapy (DOT) study.

DESIGN

Pharmacologic DOT study of TFV disoproxil fumarate (TDF)/emtricitabine (FTC) administered to HIV-noninfected volunteers.

METHODS

The TARGET study provided directly observed TDF 300 mg/FTC 200 mg 7 (high adherence), 4 (moderate), and 2 doses/week (low) to 30 volunteers (10/group) in Thailand, collecting a total of 637 urine samples over 6 weeks of administration and during washout. ELISA measured urine TFV levels by the immunoassay and LC-MS/MS-based concentrations served as the gold standard. A mixed-effects regression model evaluated cutoffs for a point-of-care assay. Performance characteristics of the immunoassay were compared with LC-MS/MS at a chosen cutoff.

RESULTS

Median TFV levels were 12,000 ng/mL by the immunoassay 1 day after dosing; 5000 ng/mL 2 days after dosing; 1500 ng/mL 3 days after dosing; and below the lower limit of quantification thereafter (≥4 days). An immunoassay cutoff of 1500 ng/mL accurately classified 98% of patients who took a dose 24 hours ago as adherent. The specificity and sensitivity of the immunoassay compared with LC-MS/MS at the 1500 ng/mL cutoff were 99% and 94%; the correlation between TFV levels by the 2 assays was high (0.92, P < 0.00001).

CONCLUSIONS

We have developed a novel TFV immunoassay that is highly specific, sensitive, and correlates strongly with LC-MS/MS measurements in a large DOT study. Adherence benchmarks from this DOT study will guide the development of a low-cost rapid point-of-care test for pre-exposure prophylaxis and antiretroviral treatment adherence monitoring and interventions.

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

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

Barriers and Facilitators of PrEP Adherence for Young Men and Transgender Women of Color

We aimed to discover barriers and facilitators of HIV pre-exposure prophylaxis (PrEP) adherence in young men and transgender women of color who have sex with men (YMSM/TW). Short-term and sustained adherence were measured by urine tenofovir concentration and pharmacy refills, respectively. Optimal adherence was defined as having both urine tenofovir concentration consistent with dose ingestion within 48 h and pharmacy refills consistent with ≥ 4 doses per week use. Participants completed semi-structured interviews exploring adherence barriers and facilitators. Participants (n = 31) were primarily African-American (68%), mean age 22 years (SD: 1.8), and 48% had optimal adherence. Adherence barriers included stigma, health systems inaccessibility, side effects, competing stressors, and low HIV risk perception. Facilitators included social support, health system accessibility, reminders/routines, high HIV risk perception, and personal agency. Our findings identify targets for intervention to improve PrEP adherence in these populations, including augmenting health activation and improving accuracy of HIV risk perception.

Delivery of TDF/FTC for Pre-exposure Prophylaxis to Prevent HIV-1 Acquisition in Young Adult Men Who Have Sex With Men and Transgender Women of Color Using a Urine Adherence Assay

BACKGROUND

Pre-exposure prophylaxis (PrEP) for HIV prevention with daily tenofovir and emtricitabine is effective when taken consistently. Currently, there is no objective way to monitor PrEP adherence. Urine has been shown to be highly correlated with plasma tenofovir levels, with urine tenofovir levels >1000 ng/mL demonstrating recent (1-2 days) adherence to PrEP.

SETTING

This study was conducted at an urban community health center in Philadelphia, Pennsylvania.

METHODS

PrEP was administered to 50 young men who have sex with men and transgender women of color using weekly, biweekly, and/or monthly dispensation schedules. Primary objectives were retention at 48 weeks (in care at week 48 and completing ≥50% of medication pickups) and adherence assessed by urine tenofovir levels. Risk behaviors and sexually transmitted infection diagnoses were also collected.

RESULTS

Seventy percent of participants were retained in care at 48 weeks. The proportion of subjects with urine tenofovir consistent with recent adherence was 80, 74.4, 82.4, 82.4, and 69.7% at weeks 4, 12, 24, 36, and 48, respectively. Sixty-one sexually transmitted infections were diagnosed over 231 screenings throughout 48 weeks, with no significant change between the first and second 24-week periods (P = 0.43; 0 seroconversions). At week 48, more than half of subjects reported an increase or no change in condom use, an increase in their ability to discuss HIV with partners, and no change in number of sexual partners from baseline.

CONCLUSIONS

These data demonstrate PrEP can be successfully delivered to a high-risk population with high program retention and medication adherence measured by urine tenofovir levels.

Comparing Self-Report Pre-Exposure Prophylaxis Adherence Questions to Pharmacologic Measures of Recent and Cumulative Pre-Exposure Prophylaxis Exposure

As pre-exposure prophylaxis (PrEP) effectiveness is strongly linked to adherence, we sought to determine if certain self-report measures could be used to inform objective PrEP adherence. We studied participants from the TAPIR study (a multicenter randomized study of daily text messages to support adherence to PrEP In At-Risk), a 48-week randomized controlled trial of HIV-uninfected men who have sex with men (MSM) randomized to receive text message to support adherence versus standard of care. Self-reported medication adherence was assessed using several validated measures modified for PrEP. Objective PrEP adherence was determined through dried blood spot (DBS) measurement of intracellular tenofovir diphosphate (TFV-DP) and emtricitabine triphosphate (FTC-TP). A summary of adherence was estimated using responses to the seven adherence items at weeks 12 and 48 using confirmatory factor analysis. Correlations between self-report questions and drug concentrations were estimated with Pearson's correlations for continuous outcomes and point-biserial correlations for dichotomous outcomes. Receiver operating characteristic (ROC) analyses were conducted to assess the performance of self-report measures in predicting protective or perfect TFV-DP concentrations. Of the 369 participants who completed week 12 or 48 visits, the mean age was 35 (standard deviation 9 years), with 79% White, 12% Black, and 29% Hispanic. Correlations between self-report measures of adherence (both individual items and the adherence factor) and quantifiable FTC-TP and continuous TFV-DP concentrations showed that all self-report measures were significantly associated with these objective measures. Compared to a summary measure of self-reported adherence, the 4-week percent taken question medication recall was the only self-report item similarly or more strongly associated with recent adherence and long-term protective and perfect adherence at weeks 12 and 48. ROC analysis also showed that 4-week percent taken question had a reasonable AUC (0.798 at week 12 and 0.758 at week 48) in predicting protective TFV-DP concentrations. All single-item self-report questions assessing PrEP adherence were significantly associated with biomarker quantification, with the 4-week percent taken question performing best. Therefore, in the absence of drug concentration measurements, a 4-week self-report percent taken question may be a good single-item measure of PrEP adherence.

Brief Report: Short-Term Adherence Marker to PrEP Predicts Future Nonretention in a Large PrEP Demo Project: Implications for Point-of-Care Adherence Testing

BACKGROUND

Objective adherence metrics for tenofovir (TFV) disoproxil fumarate/emtricitabine (FTC)-based pre-exposure prophylaxis (PrEP) were critical for interpretation of efficacy in PrEP clinical trials, and there is increasing interest in using drug levels to tailor interventions for reengagement and adherence. Point-of-care immunoassays for TFV, which examine short-term adherence, are in development. However, the ability of poor short-term and long-term adherence to predict future PrEP nonretention is unknown.

SETTING

Secondary data analysis of a large, prospective multi-site U.S. PrEP demonstration project.

METHODS

An adjusted Cox-proportional hazards model examined the relationship of dried blood spot (DBS) levels of FTC-triphosphate (FTC-TP) or TFV-diphosphate (TFV-DP), measures of short-term and long-term PrEP adherence, respectively, with future study nonretention.

RESULTS

Overall, 294 individuals (median age 33 years) contributed drug levels within the U.S. PrEP demonstration project. By the end of study, 27% were lost to follow-up, 25% had at least one undetectable FTC-TP level indicating poor short-term adherence, and 29% had a drug level indicating suboptimal long-term adherence (TFV-DP <700 fmol/punch). The strongest factor associated with future study nonretention using a binary drug-level cut-off was an undetectable DBS FTC-TP level (adjusted hazard ratio 6.3; 95% confidence interval 3.8 to 10.2). The suboptimal long-term adherence based on low DBS TFV-DP levels was also associated with nonretention (adjusted hazard ratio 4.3; 95% confidence interval: 2.4 to 7.6).

CONCLUSIONS

Both short- and long-term metrics of PrEP adherence are strongly associated with future loss to follow-up in a U.S. demonstration project study. Short-term metrics of adherence, once available at the point-of-care, could be used to direct real-time tailored retention and adherence interventions.

Antiretroviral agents in pre-exposure prophylaxis: emerging and advanced trends in HIV prevention

OBJECTIVES

Antiretroviral agents (ARVs) have been the most promising line of therapy in the management of human immunodeficiency virus (HIV) infections. Some of these ARVs are used in the pre-exposure prophylaxis (PrEP) to suppress the transmission of HIV. Prophylaxis is primarily used in uninfected people, before exposure, to effectively prevent HIV infection. Several studies have shown that ART PrEP prevents HIV acquisition from sexual, blood and mother-to-child transmissions. However, there are also several challenges and limitations to PrEP. This review focuses on the current antiretroviral therapies used in PrEP.

KEY FINDINGS

Among ARVs, the most common drugs employed from the class of entry inhibitors are maraviroc (MVC), which is a CCR5 receptor antagonist. Other entry inhibitors like emtricitabine (FTC) and tenofovir (TFV) are also used. Rilpivirine (RPV) and dapivirine (DPV) are the most common drugs employed from the Non-nucleoside reverse transcriptase inhibitor (NNRTIs) class, whereas, tenofovir disoproxil fumarate (TDF) is primarily used in the Nucleoside Reverse Transcriptase Inhibitor (NRTIs) class. Cabotegravir (CAB) is an analog of dolutegravir, and it is an integrase inhibitor. Some of these drugs are also used in combination with other drugs from the same class.

SUMMARY

Some of the most common pre-exposure prophylactic strategies employed currently are the use of inhibitors, namely entry inhibitors, non-nucleoside reverse transcriptase inhibitors, nucleoside reverse transcriptase inhibitors, integrase and protease inhibitors. In addition, we have also discussed on the adverse effects caused by ART in PrEP, pharmacoeconomics factors and the use of antiretroviral prophylaxis in serodiscordant couples.

Challenges to PrEP use and perceptions of urine tenofovir adherence monitoring reported by individuals on PrEP

Maximizing the impact of HIV pre-exposure prophylaxis (PrEP) requires optimizing access and adherence for those at risk of contracting HIV. This study examined challenges to the processes of accessing and adhering to PrEP encountered by participants from a large, U.S. urban clinical center and assessed the utility of objectively monitoring PrEP adherence via urine. Most participants (65%) reported starting PrEP within 1-3 months of hearing about it, although 35% of participants encountered a provider unwilling to prescribe PrEP. Self-reported adherence was high among this population, with remembering to take the medication reported as the major barrier to adherence (44%) rather than cost or stigma. Urine tenofovir (TFV) monitoring was highly acceptable to this population, and participants indicated greater willingness to undergo urine monitoring every 3 months compared to finger prick (dried blood spot), phlebotomy, or hair follicle testing. These findings highlight the importance of focusing efforts toward reducing obstacles to PrEP use and support the use of urine TFV adherence monitoring as a marker of PrEP adherence.

Development and clinical assessment of new objective adherence markers for four microbicide delivery systems used in HIV prevention studies

Background

Adherence is critical for successful topical, vaginally delivered anti-retroviral (ARV)-based HIV pre-exposure prophylaxis (PrEP). Quantitating systemic or tissue ARV levels through LC–MS/MS is currently viewed as the most reliable measure of adherence. However, for placebo-controlled trials, this is a high cost analysis that measures adherence only in the drug treatment group. A desirable marker of adherence is one that is measured in both placebo and drug treatment groups using a simple on-site clinical laboratory test, which allows necessary interventions for supporting participant adherence. Our objective was to develop adherence markers for four vaginal placebo products currently used as microbicide delivery systems: gel, film, insert, and intravaginal ring. Excipient and spectroscopy-based approaches were used for preclinical development of the placebo markers and subsequently validated by the CONRAD 135 study. The study collected vaginal swabs collected each day for 1 week post vaginal application of gel, film, or insert in the clinic with or without sex. Intravaginal rings were collected after 1 day, 7, and 30 days of use.

Results

Placebo gel, film, and insert in vaginal swabs were successfully detected by specific excipient colorimetric or probe-based assays for hydroxyethylcellulose, glycerin, and sorbitol respectively, as well as spectroscopy-based prediction models. The range of detection for gel, film, and insert in swabs collected up to 16 h post vaginal application was 70-100% of the total swabs per time point, with some markers showing potential for longer duration. Decreasing residual glycerin levels and increasing bioanalyte penetration of vaginally used intravaginal rings showed significant changes between 1 and 30 days of use.

Conclusions

We demonstrated clinical proof-of-concept that adherence markers for placebo product can be measured using simple, lower cost approaches. Measuring adherence in both placebo and drug arms of a HIV PrEP study would better inform future trial designs.

Electronic supplementary material

The online version of this article (10.1186/s40169-018-0213-6) contains supplementary material, which is available to authorized users.

Efficacy and Safety of Oral TDF-Based Pre-exposure Prophylaxis for Men Who Have Sex With Men: A Systematic Review and Meta-Analysis

Background: Pre-exposure prophylaxis (PrEP) is used as an HIV prevention method by people at substantial risk of HIV infection. This systematic review and meta-analysis evaluates current clinical evidence for use of oral TDF-based PrEP among men who have sex with men.

Methods: A comprehensive literature search in PubMed, web of science, Google Scholar and ClinicalTrials.gov was performed. A random-effects meta-analysis was conducted using the event rate (ER) for estimation of the incidence of HIV and grade 3 or 4 adverse events (AE) among PrEP arm and using risk ratio (RR) for comparison of incidence of HIV and grade 3 or 4 AE between PrEP recipients and PrEP non-users. Blood-based adherence levels were also divided into three categories with reference to previous meta-analysis. Subgroup meta-analysis was also performed to evaluate whether blood-based adherence levels moderated the effect of TDF-based PrEP on HIV incidence. Narrative review was used due to inconsistent measurements of risk behavior and drug resistance. This review is registered on the PROSPERO database (CRD42017077965).

Results: Fourteen studies were included in the review. Oral TDF-based PrEP significantly reduced HIV incidence with minimum drug resistance and tolerable safety risks (HIV incidence, ER = 1.1%, 95% CI 0.6–2.0%, p < 0.001, RR = 0.244, 95% CI 0.111–0.537, p < 0.001 and grade 3 or 4 AEs, ER = 13.0%, 95% CI 9.9–16.9%, p < 0.001, RR = 1.059, 95% CI 0.824–1.362, p = 0.653). Oral TDF-based PrEP was more effective in reducing HIV incidence with high levels of blood-based PrEP adherence (ER, 0.4%) compared to moderate adherence (2.9%; p < 0.001). Most studies found no association between PrEP use and self-reported sexual behavior.

Conclusion: Oral TDF-based PrEP is an effective intervention to prevent against HIV infection among MSM. Well-designed implementation science studies that integrate sociobehavioral and biomedical interventions are needed to identify optimal PrEP delivery models in different populations to translate biomedical efficacy into real-world efficacy.

A competitive lateral flow assay for the detection of tenofovir

Proper management of an HIV infection requires that a patient be at least 80-95% adherent to a prescribed drug regimen to avoid poor health outcomes and the development of drug-resistant HIV strains. Clinicians generally monitor adherence habits indirectly through patient self-reporting, pill counting, and electronic drug monitoring. While direct measurement of patient samples like urine for monitoring drug levels is possible, it requires specialized equipment and training that is not readily available in resource-limited settings where the need is greatest. In this work we report the development of an antibody that binds to tenofovir (TFV), a key small molecule drug for both the treatment and prevention of HIV, and a competitive lateral flow assay that uses that antibody to monitor urine samples for the presence of the drug. TFV was conjugated to an immunogenic protein and injected into rabbits to raise polyclonal antibodies sensitive to the drug. The antibodies were verified for TFV-sensitivity by immunoprecipitation and HPLC. A gold nanoparticle-based competitive assay was developed to detect the presence of TFV in urine samples with a sensitivity of 1 μg mL-1. This TFV assay could be deployed as a point-of-care device for adherence monitoring in resource-limited settings as a low-cost, accurate, and speedy alternative to current methods to better inform changes in treatment.