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

Adherence determination using urine-tenofovir point-of-care testing and pharmacy refill records: A cross-sectional study

Pharmacy refill records (PRR), are an accessible strategy for estimating adherence in low- and middle-income countries (LMICs). However, the low-cost urine-tenofovir point-of-care test opens up the possibility of an objective metric of adherence that is scalable to LMICs. This study compared adherence to tenofovir-based regimens using urine-tenofovir point-of-care (POC) test with pharmacy refill records in a Nigerian population of HIV-positive persons. This was a cross-sectional study among 94 HIV-positive adults, which was conducted from June to August 2021, in a large outpatient clinic in Lagos, Nigeria. Adherence to pharmacy appointments was automatically calculated using a computerized pharmacy appointment system (FileMaker Pro™). Urine drops on the urine-tenofovir POC test strip developed 2 lines for a negative test (tenofovir absent) and one line for a positive test. Fisher's exact test was used to examine the association between pharmacy refill record and urine-tenofovir point-of-care test. Logistic regression was performed to predict viral suppression (<1000 copies/mL, based on WHO recommendations) using both methods of adherence determination. A Receiver Operating Characteristic (ROC) curve of the association between specificity and sensitivity was generated to evaluate the predictive value of adherence determined using pharmacy-refill record and urine-tenofovir point-of-care test in forecasting viral suppression. The statistical significance level was set at 0.05. Fisher's exact test showed no statistically significant difference in adherence using urine-tenofovir point-of-care test or pharmacy refill record. The logistic regression model showed that an increase in pharmacy-refill record of ≥ 95% was associated with viral suppression (P = .019). From the ROC curve, the sensitivity was same at 95.5% for both methods, but the specificity of the urine-tenofovir point-of-care test was greater (96.6% vs 95.5%) than pharmacy refill record (P = .837). Urine-tenofovir point-of-care test provided equivalent adherence data to pharmacy refill data.

A mAb for the detection of the antiretroviral drug emtricitabine

Antibody-based testing for emtricitabine (FTC), a critical component of pre-exposure prophylaxis and antiretroviral therapy, would provide low-cost detection for clinical monitoring to improve adherence. We developed a mAb (5D2) to FTC and demonstrated its high specificity and physiologically relevant linear range of detection in a competitive enzyme immunoassay. Thus, this mAb is a key reagent that will enable simple and low-cost lateral flow assays and enzyme immunoassays for adherence monitoring.

Plasma and breast milk pharmacokinetics of tenofovir alafenamide in mothers with chronic hepatitis B infection

BACKGROUND

Antenatal antiviral therapy (AVT) is effective in preventing mother-to-child transmission (MTCT) in chronic hepatitis B (CHB); tenofovir disoproxil fumarate (TDF) is the preferred agent. Tenofovir alafenamide (TAF) is a prodrug of tenofovir (TFV) similar to TDF, with improved bone and renal safety. There are no data on TAF breast milk pharmacokinetics and exposure to breastfeeding infants in CHB.

AIM

To assess the pharmacokinetics of TAF/TFV in breastfeeding women with CHB on TAF monotherapy.

METHODS

Pregnant women with CHB requiring AVT commenced TAF 25 mg daily at third trimester or postpartum. Sample collection occurred while breastfeeding and taking TAF for minimum 4 weeks. Maternal blood, breast milk and infant urine samples were collected. Drug concentrations were measured by LCMS/MS analyses using validated methods. Non-compartmental analyses were performed to quantify the pharmacokinetic parameters.

RESULTS

Eight women provided samples. In breast milk and plasma, median TAF half-life was 0.81 and 0.94 h, respectively, and C_max 1.69 and 120.5 ng/ml, respectively. Median maternal breast milk to plasma (M/P) ratio of TAF was 0.029; for and TFV it was 2.809. The relative infant dose of TAF was 0.005% of maternal dose, well below safety threshold of 5-10%. TFV was detectable in three out of seven infant urine samples with median steady-state concentration of 5 ng/ml being 300-2500 times less than reported adult steady-state urine concentrations in those taking TAF and TDF, respectively.

CONCLUSIONS

In this first pharmacokinetic study of TAF monotherapy in breastfeeding women with CHB, concentrations of TAF and TFV were low in breast milk with negligible infant exposure, supporting the use of TAF to prevent MTCT.

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.

Brief Report: No Difference in Urine Tenofovir Levels in Patients Living With HIV on Unboosted Versus Dose-Adjusted Boosted Tenofovir Alafenamide

BACKGROUND

Tenofovir alafenamide (TAF) is increasingly used in HIV treatment, with or without agents that require pharmacologic boosters such as ritonavir/cobicistat. Boosters increase TAF levels, so the TAF dose is lowered in single-pill combinations. We hypothesized that individuals on dose-adjusted boosted TAF would have similar urine tenofovir (TFV) concentrations to those on unboosted TAF.

SETTING/METHODS

We collected urine samples from patients with HIV on TAF, with evidence of virologic suppression and high self-reported adherence at 2 San Francisco clinics from June 2019 to January 2020. We measured urine TFV levels by liquid chromatography/tandem mass spectrometry and used linear regression to compare natural log-transformed urine TFV levels for patients on boosted versus unboosted TAF.

RESULTS

Our analysis included 30 patients on unboosted TAF (25 mg daily TAF) and 15 on boosted TAF (12 on 10 mg daily TAF and 3 on 25 mg daily TAF). Patients on unboosted vs. boosted TAF had similar baseline age, weight, sex, and creatinine. In unadjusted univariate linear regression, there were no significant differences in urine TFV levels based on presence/absence of boosting after TAF dose reduction to 10 mg (geometric mean ratio 1.07; 95% confidence interval: 0.53 to 2.16). This finding was unchanged in adjusted analysis.

CONCLUSIONS

No significant differences in urine TFV levels were seen for patients on unboosted vs. boosted dose-reduced TAF. These results have important implications for our forthcoming point-of-care urine immunoassay for TAF, implying that separate adherence cutoffs will not be necessary for patients on boosters and dose-reduced TAF. A single POC TAF immunoassay will, thus, support monitoring on most TAF-based antiretroviral therapy.

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.

Antiretroviral drug exposure in urethral and glans surface sampling of the penis

BACKGROUND

HIV exposure to penile tissues provides a risk of acquisition among men, yet studies evaluating penile antiretroviral (ARV) drug distribution have been lacking. We measured ARVs on urethral and glans surface swabs collected following a dose of tenofovir alafenamide, emtricitabine, elvitegravir, darunavir and cobicistat.

METHODS

Thirty-five HIV-negative male participants provided urethral swabs, glans swabs, rectal swabs, blood and urine up to 96 h following a single dose of tenofovir alafenamide/emtricitabine/elvitegravir/cobicistat and darunavir. ARVs were measured by liquid chromatography-mass spectrometry with a lower limit of detection (LOD) of 1 ng/swab for swabs and 10 ng/mL for plasma and urine. Concentrations are reported as median and range.

RESULTS

Urethral swab emtricitabine and darunavir concentrations peaked at 4 h for emtricitabine (36 ng/swab; 3-307 ng/swab) and 8 h for darunavir (25 ng/swab; 2-52 ng/swab). Glans swab emtricitabine and darunavir concentrations peaked 24 h after dosing (emtricitabine 14 ng/swab, <LOD-328 ng/swab; darunavir 6 ng/swab, <LOD-149 ng/swab). Estimated peak urethral secretion emtricitabine and darunavir concentrations are between 10 and 20 μg/mL, similar to rectal secretions, 4-fold greater than in plasma, but 2-fold lower than in urine. Tenofovir and elvitegravir were detected on less than 20% of urethral or glans swabs collected within 24 h of dosing.

CONCLUSIONS

We document ARV dosing in the urethra and on the glans surface with high drug concentrations noted for emtricitabine and darunavir and lower tenofovir and elvitegravir concentrations. Data suggest a potential protective role of urethral emtricitabine or darunavir against penile HIV acquisition.

Lower Urine Tenofovir Concentrations Among Individuals Taking Tenofovir Alafenamide Versus Tenofovir Disoproxil Fumarate: Implications for Point-of-Care Testing

From directly observed therapy studies, urine tenofovir (TFV) levels were 74% lower when taking tenofovir alafenamide (TAF) vs tenofovir disoproxil fumarate. Urine TFV remains quantifiable across a range of TAF adherence patterns, but a separate point-of-care lateral flow immunoassay with a lower TFV threshold will be needed to support TAF adherence monitoring.

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.

Brief Report: High Accuracy of a Real-Time Urine Antibody-Based Tenofovir Point-of-Care Test Compared With Laboratory-Based ELISA in Diverse Populations

BACKGROUND

Therapeutic drug monitoring measures antiretroviral adherence more accurately than self-report but has not been available at the point-of-care (POC) until now. We compare a novel POC test for urine tenofovir to laboratory-based enzyme-linked immunosorbent assay (ELISA) testing in diverse patient populations urine pre-exposure prophylaxis (PrEP).

SETTING

Urine samples were analyzed using ELISA and the POC lateral flow immunoassay (LFA) test from 2 cohorts of PrEP users taking tenofovir disoproxil fumarate/emtricitabine: the Partners PrEP Study, which recruited Kenyan and Ugandan heterosexual men and women, and the IBrEATHe Study, which recruited US transgender women and men using gender-affirming hormone therapy.

METHODS

We calculated the sensitivity, specificity, and accuracy of the POC test compared with ELISA at a cutoff of 1500 ng/mL.

RESULTS

Overall, 684 urine samples were tested from 324 participants in the 2 cohorts. In Partners PrEP, 454 samples from 278 participants (41% women) were tested with a median age of 33 years. In IBrEATHe, 231 samples from 46 individuals (50% transwomen) were tested with a median age of 31 years. Comparison of the LFA read-out to ELISA yielded 100% sensitivity [97.5% one-sided confidence interval (CI) = 99.3%], 98.3% specificity (95% CI = 95.2% to 99.7%), and 99.6% accuracy (95% CI = 98.7% to 99.9%).

CONCLUSION

The sensitivity, specificity, and accuracy of a novel POC test for urine tenofovir all exceeded 98% when compared with a laboratory-based ELISA method when tested in diverse patient populations. Given the LFA's high accuracy and expected low cost, this POC test is a promising tool to support antiretroviral adherence that could be widely scalable to real-world clinical settings.