Urine Tenofovir Levels Strongly Correlate With Virologic Suppression in Patients With Human Immunodeficiency Virus on Tenofovir Alafenamide-Based Antiretroviral Therapy.

We found that urine tenofovir (TFV) levels >1500 ng/mL strongly predict virologic suppression among people with human immunodeficiency virus taking tenofovir alafenamide (odds ratio, 5.66; 95% confidence interval, 1.59-20.14; P = .007). This suggests an existing point-of-care assay developed for tenofovir disoproxil fumarate will support adherence monitoring for patients on all TFV-based antiretrovirals.

Self-Reported Use of HIV Preexposure Prophylaxis Is Highly Accurate Among Sexual Health Clinic Patients in New York City.

ABSTRACT: In New York City, 91% of sexually transmitted infection clinic patients reported preexposure prophylaxis (PrEP) use that matched the detection of PrEP in their serum. Self-report had 80% sensitivity and 96% specificity ( κ = 0.79) compared with measured PrEP. Our findings suggest that self-report may be a valid indicator of PrEP uptake.

Comparison of efavirenz levels in blood and hair with pharmacy refills as measures of adherence and predictors of viral suppression among people living with HIV in Nigeria.

BACKGROUND: Strategies to support adherence are constrained by the lack of tools to objectively monitor medication intake in low-resource settings. Pharmacologic measures are objective, but pharmacy refill data is more accessible and cost-efficient. This study compared short-term and long-term efavirenz (EFV) drug levels with pharmacy refill adherence data (PRA) and evaluated their ability to predict viral suppression among people living with HIV in Nigeria. METHODS: Paired hair and dried blood spot (DBS) samples were obtained from 91 adults living with HIV receiving 600 mg EFV-based antiretroviral therapy (ART) and EFV concentrations were measured via validated methods using liquid-chromatography-mass-spectrometry. PRA was estimated from pharmacy records, based on the number of days a patient collected medication before or after the scheduled pick-up date. PRA was categorized into ≤ 74%, 75-94% and ≥ 95%, defined as poor, medium and high adherence, respectively. HIV viral loads closest to the hair sampling time (within 6 months) were also abstracted. Receiver Operating Characteristics (ROC) curve analyses compared the ability of adherence metrics to predict viral suppression. RESULTS: Based on PRA, 81% of participants had high adherence while 11% and 8% had medium and poor adherence, respectively. The median (IQR) EFV concentrations were 6.85 ng/mg (4.56-10.93) for hair and 1495.6 ng/ml (1050.7-2365.8) for DBS. Of the three measures of adherence, hair EFV concentration had the highest Area Under Curve (AUC) to predict viral suppression. Correlations between EFV concentrations in DBS and hair with PRA were positive (r = 0.12, P = 0.27 and r = 0.21, P = 0.05, respectively) but not strong. CONCLUSIONS: EFV concentrations in hair were the strongest predictor of viral suppression and only weakly correlated with pharmacy refill adherence data in Nigeria. This study suggests that resource-limited settings may benefit from objective adherence metrics to monitor and support adherence.

Extent of In Utero Transfer of Tenofovir From Mother to Fetus: A Paired Analysis of Hair Specimens Collected at Birth From a Cohort in the United States.

Understanding in utero transfer of antiretrovirals is critical for interpreting safety. Hair levels measure cumulative exposure. We measured tenofovir (TFV) concentrations in hair at delivery among women living with human immunodeficiency virus receiving TFV disoproxil fumarate-based treatment and their infants, using liquid chromatography-tandem mass spectrometry. Among 103 mother-infant pairs, the mean log10 ratio of infant-to-maternal TFV levels was 1.08 (95% confidence interval, .97-1.20). TFV transfer was 60% lower from mothers who had preterm compared with term deliveries and 42% lower from mothers who had cesarean compared with vaginal deliveries. Like prior studies assessing transfer via short-term measures (plasma, cord blood, amniotic fluid), we found high cumulative transfer using hair.

Use of Drug-level Testing and Single-genome Sequencing to Unravel a Case of Human Immunodeficiency Virus Seroconversion on Pre-exposure Prophylaxis.

Cases of seroconversion on pre-exposure prophylaxis (PrEP) should be carefully investigated, given their public health implications and rarity. We report a case of transmitted drug resistance causing seroconversion on PrEP in spite of high adherence, confirmed with dried blood spot and segmental hair drug-level testing and single-genome sequencing.

HIV incidence after pre-exposure prophylaxis initiation among women and men at elevated HIV risk: A population-based study in rural Kenya and Uganda.

BACKGROUND: Oral pre-exposure prophylaxis (PrEP) is highly effective for HIV prevention, but data are limited on HIV incidence among PrEP users in generalized epidemic settings, particularly outside of selected risk groups. We performed a population-based PrEP study in rural Kenya and Uganda and sought to evaluate both changes in HIV incidence and clinical and virologic outcomes following seroconversion on PrEP. METHODS AND FINDINGS: During population-level HIV testing of individuals ≥15 years in 16 communities in the Sustainable East Africa Research in Community Health (SEARCH) study (NCT01864603), we offered universal access to PrEP with enhanced counseling for persons at elevated HIV risk (based on serodifferent partnership, machine learning-based risk score, or self-identified HIV risk). We offered rapid or same-day PrEP initiation and flexible service delivery with follow-up visits at facilities or community-based sites at 4, 12, and every 12 weeks up to week 144. Among participants with incident HIV infection after PrEP initiation, we offered same-day antiretroviral therapy (ART) initiation and analyzed HIV RNA, tenofovir hair concentrations, drug resistance, and viral suppression (<1,000 c/ml based on available assays) after ART start. Using Poisson regression with cluster-robust standard errors, we compared HIV incidence among PrEP initiators to incidence among propensity score-matched recent historical controls (from the year before PrEP availability) in 8 of the 16 communities, adjusted for risk group. Among 74,541 individuals who tested negative for HIV, 15,632/74,541 (21%) were assessed to be at elevated HIV risk; 5,447/15,632 (35%) initiated PrEP (49% female; 29% 15-24 years; 19% in serodifferent partnerships), of whom 79% engaged in ≥1 follow-up visit and 61% self-reported PrEP adherence at ≥1 visit. Over 7,150 person-years of follow-up, HIV incidence was 0.35 per 100 person-years (95% confidence interval [CI] 0.22-0.49) among PrEP initiators. Among matched controls, HIV incidence was 0.92 per 100 person-years (95% CI 0.49-1.41), corresponding to 74% lower incidence among PrEP initiators compared to matched controls (adjusted incidence rate ratio [aIRR] 0.26, 95% CI 0.09-0.75; p = 0.013). Among women, HIV incidence was 76% lower among PrEP initiators versus matched controls (aIRR 0.24, 95% CI 0.07-0.79; p = 0.019); among men, HIV incidence was 40% lower, but not significantly so (aIRR 0.60, 95% CI 0.12-3.05; p = 0.54). Of 25 participants with incident HIV infection (68% women), 7/25 (28%) reported taking PrEP ≤30 days before HIV diagnosis, and 24/25 (96%) started ART. Of those with repeat HIV RNA after ART start, 18/19 (95%) had <1,000 c/ml. One participant with viral non-suppression was found to have transmitted viral resistance, as well as emtricitabine resistance possibly related to PrEP use. Limitations include the lack of contemporaneous controls to assess HIV incidence without PrEP and that plasma samples were not archived to assess for baseline acute infection. CONCLUSIONS: Population-level offer of PrEP with rapid start and flexible service delivery was associated with 74% lower HIV incidence among PrEP initiators compared to matched recent controls prior to PrEP availability. HIV infections were significantly lower among women who started PrEP. Universal HIV testing with linkage to treatment and prevention, including PrEP, is a promising approach to accelerate reductions in new infections in generalized epidemic settings. TRIAL REGISTRATION: ClinicalTrials.gov NCT01864603.

TransPrEP: Results from the Pilot Study of a Social Network-Based Intervention to Support PrEP Adherence Among Transgender Women in Lima, Peru.

We conducted a pilot randomized controlled trial of a social network-based intervention to promote PrEP adherence among transgender women (TW) in Lima, Peru. We enrolled 89 TW from six social networks and cluster-randomized them 1:1 to standard of care (n = 44) or the TransPrEP intervention (n = 45). Core workshops discussed strategies to support PrEP adherence and defined group adherence objectives. Maintenance workshops discussed participants' experiences taking PrEP and collective adherence goals. At 3-month follow-up, we evaluated 40 participants and obtained 29 hair samples for tenofovir level measurements. Though no significant differences were observed, 36.4% (4/11) of participants of TransPrEP participants and 10.0% (1/10) of control participants had tenofovir levels > 0.023 ng/mg, consistent with ≥ 4 doses per week. 81.8% (9/11) of intervention and 40.0% (4/10) of control participants had any detectable tenofovir in their hair. Pilot assessment of our network-based intervention suggested a trend towards improved PrEP adherence, measured objectively, for TW in Peru.

RESUMEN: Realizamos un estudio piloto controlado y aleatorizado de una intervención basada en redes sociales para promover la adherencia al PrEP en mujeres transgénero (MT) de Lima, Perú. Enrolamos a 89 MT de 6 redes sociales y las aleatorizamos por grupos a razón 1:1 al estándar de atención como control (n = 44) o a la intervención TransPrEP (n = 45). En los talleres centrales se discutieron estrategias para respaldar la adherencia al PrEP y se definieron los objetivos de adherencia del grupo. En los talleres de mantenimiento se discutieron las experiencias de los participantes al tomar PrEP y los objetivos de adherencia colectiva. A los 3 meses de seguimiento, evaluamos a 40 participantes y obtuvimos 29 muestras de cabello para medir el nivel de tenofovir. Aunque no se observaron diferencias significativas, el 36.4% (4/11) de los participantes de TransPrEP y el 10.0% (1/10) de los participantes del grupo control tenían niveles de tenofovir> 0.023 ng/mg, congruente con 4 o más dosis por semana. El 81.8% (9/11) del grupo de intervención y el 40.0% (4/10) de los participantes de control tenían tenofovir detectable en el cabello. La evaluación piloto de nuestra intervención basada en redes sugiere una tendencia hacia una mejor adherencia al PrEP, medida objetivamente, para las MT en Perú.

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

Social Support Mitigates Negative Impact of Food Insecurity on Antiretroviral Adherence Among Postpartum Women in Western Kenya.

Food insecurity (FI), low social support, and low health-related quality of life (HRQoL) are associated with self-reported nonadherence to antiretroviral therapy (ART) among postpartum women, but these relationships have not been evaluated using objective adherence indicators. Hair samples were therefore analyzed among 83 postpartum Kenyan women living with HIV on efavirenz and nevirapine ART drug regimens in an observational cohort (NCT02974972). FI (0-27), social support (0-40), and HRQoL (8-40) in the prior month were also assessed. In multivariable models, each point increase in FI and decrease in HRQoL were associated with a 45.1% (95% CI: -64.3%, -15.6%) and 10.5% decrease (95% CI: 1.0%, 22.1%) in hair ART drug concentrations respectively, when social support was held constant. A significant interaction between social support and FI (ß = 0.02, p = 0.017) indicated that greater social support was predicted to mitigate the negative impacts of FI on ART adherence. Addressing these modifiable barriers could improve ART adherence during this critical period.

Antiretroviral Concentrations in Hair Strongly Predict Virologic Response in a Large Human Immunodeficiency Virus Treatment-naive Clinical Trial.

Concentrations of antiretrovirals in hair are associated with virologic outcomes in cohorts of human immunodeficiency virus (HIV)-positive individuals but have never been examined in a clinical trial. We show for the first time the predictive utility of hair antiretroviral concentrations in a large HIV treatment-naive trial (AIDS Clinical Trials Group protocol A5257).

The Presence of a Transporter-Induced Protein Binding Shift: A New Explanation for Protein-Facilitated Uptake and Improvement for In Vitro-In Vivo Extrapolation.

Accurately predicting hepatic clearance is an integral part of the drug-development process, and yet current in vitro to in vivo (IVIVE) extrapolation methods yield poor predictions, particularly for highly protein-bound transporter substrates. Explanations for error include inaccuracies in protein-binding measurements and the lack of recognition of protein-facilitated uptake, where both unbound and bound drug may be cleared, violating the principles of the widely accepted free drug theory. A new explanation for protein-facilitated uptake is proposed here, called a transporter-induced protein binding shift High-affinity binding to cell-membrane proteins may change the equilibrium of the nonspecific binding between drugs and plasma proteins, leading to greater cellular uptake and clearance than currently predicted. The uptake of two lower protein-binding organic anion transporting polypeptide substrates (pravastatin and rosuvastatin) and two higher binding substrates (atorvastatin and pitavastatin) were measured in rat hepatocytes in incubations with protein-free buffer versus 100% plasma. Decreased unbound K m values and increased intrinsic clearance values were seen in the plasma incubations for the highly bound compounds, supporting the new hypothesis and mitigating the IVIVE underprediction previously seen for highly bound transporter substrates.

Development and validation of an assay to analyze atazanavir in human hair via liquid chromatography/tandem mass spectrometry.

RATIONALE: Assays to quantify antiretrovirals in hair samples are increasingly used to monitor adherence and exposure in both HIV prevention and treatment studies. Atazanavir (ATV) is a protease inhibitor used in combination antiretroviral therapy (ART). We developed and validated a liquid chromatography/tandem mass spectrometry (LC/MS/MS)-based method to quantify ATV in human hair, per the NIH Division of AIDS Clinical Pharmacology Quality Assurance (CPQA) program and the FDA bioanalytical method validation guidelines. METHODS: ATV was extracted from hair using optimized methods and the extracts were injected onto a BDS C-18 column (5 µm, 4.6 × 100 mm), followed by isocratic elution via a mobile phase composed of 55% acetonitrile, 45% water, 0.15% acetic acid, and 4 mM ammonium acetate, at a flow rate of 0.8 mL/min prior to analysis by MS/MS. Levels were quantified using positive electrospray ionization by multiple reaction monitoring (MRM) for the transitions MH+ m/z 705.3 to m/z 168.0 and MH+ m/z 710.2 to m/z 168.0 for ATV and ATV-d5 (internal standard), respectively. RESULTS: Our assay demonstrated a linear standard curve (r = 0.99) over the concentration range of 0.0500 ng ATV/mg hair to 20.0 ng/mg hair. The inter- and intraday accuracy of ATV quality control (QC) samples was -1.33 to 4.00% and precision (% coefficient of variation (%CV)) was 1.75 to 6.31%. The %CV for ATV levels in hair samples from highly adherent patients (incurred samples) was less than 10%. No significant endogenous peaks or crosstalk were observed in the specificity test with other HIV drugs. The overall extraction efficiency of ATV from incurred hair samples was greater than 95%. CONCLUSIONS: This highly sensitive, highly specific and validated assay can be considered for therapeutic drug monitoring for HIV-infected patients on ATV-based ART.

pH Dependent but not P-gp Dependent Bidirectional Transport Study of S-propranolol: The Importance of Passive Diffusion.

PURPOSE: Recent controversial publications, citing studies purporting to show that P-gp mediates the transport of propranolol, proposed that passive biological membrane transport is negligible. Based on the BDDCS, the extensively metabolized-highly permeable-highly soluble BDDCS class 1 drug, propranolol, shows a high passive permeability at concentrations unrestricted by solubility that can overwhelm any potential transporter effects. Here we reinvestigate the effects of passive diffusion and carrier-mediated transport on S-propranolol. METHODS: Bidirectional permeability and inhibition of efflux transport studies were carried out in MDCK, MDCK-MDR1 and Caco-2 cell lines at different concentrations. Transcellular permeability studies were conducted at different apical pHs in the rat jejunum Ussing chamber model and PAMPA system. RESULTS: S-propranolol exhibited efflux ratios lower than 1 in MDCK, MDCK-MDR1 and Caco-2 cells. No significant differences of Papp, B->A in the presence and absence of the efflux inhibitor GG918 were observed. However, an efflux ratio of 3.63 was found at apical pH 6.5 with significant decrease in Papp, A->B and increase in Papp, B->A compared to apical pH 7.4 in Caco-2 cell lines. The pH dependent permeability was confirmed in the Ussing chamber model. S-propranolol flux was unchanged during inhibition by verapamil and rifampin. Furthermore, pH dependent permeability was also observed in the PAMPA system. CONCLUSIONS: S-propranolol does not exhibit active transport as proposed previously. The "false" positive efflux ratio can be explained by the pH partition theory. As expected, passive diffusion, but not active transport, plays the primary role in the permeability of the BDDCS class 1 drug propranolol.

Dynamic choice HIV prevention intervention at outpatient departments in rural Kenya and Uganda.

OBJECTIVE: HIV prevention service delivery models that offer product choices, and the option to change preferences over time, may increase prevention coverage. Outpatient departments in sub-Saharan Africa diagnose a high proportion of new HIV infections, but are an understudied entry point to biomedical prevention. DESIGN: Individually randomized trial of dynamic choice HIV prevention (DCP) intervention vs. standard-of-care (SOC) among individuals with current/anticipated HIV exposure risk at outpatient departments in rural Kenya and Uganda (SEARCH; NCT04810650). METHODS: Our DCP intervention included 1) product choice (oral preexposure prophylaxis [PrEP] or postexposure prophylaxis [PEP]) with an option to switch over time, 2) HIV provider- or self-testing, 3) service location choice (community vs. clinic-based), and 4) provider training on patient-centered care. Primary outcome was proportion of follow-up covered by PrEP/PEP over 48 weeks assessed via self-report. RESULTS: We enrolled 403 participants (61% women; median 27 years, IQR 22-37). In the DCP arm, 86% ever chose PrEP, 15% ever chose PEP over 48 weeks; selection of HIV self-testing increased from 26 to 51% and of out-of-facility visits from 8 to 52%. Among 376 of 403 (93%) with outcomes ascertained, time covered by PrEP/PEP was higher in DCP (47.5%) vs. SOC (18.3%); difference = 29.2% (95% confidence interval: 22.7-35.7; P  < 0.001). Effects were similar among women and men (28.2 and 31.0% higher coverage in DCP, respectively) and larger during periods of self-reported HIV risk (DCP 64.9% vs. SOC 26.3%; difference = 38.6%; 95% confidence interval: 31.0-46.2; P  < 0.001). CONCLUSION: A dynamic choice HIV prevention intervention resulted in two-fold greater time covered by biomedical prevention products compared to SOC in general outpatient departments in eastern Africa.

Point-of-care urine tenofovir test predicts future HIV pre-exposure prophylaxis discontinuation among young users.

BACKGROUND: Young men who have sex with men and transgender women (YMSM/TGW) have disproportionately high HIV incidence and lower PrEP adherence. Point-of-care (POC) urine tenofovir (TFV) rapid assay (UTRA) testing permits real-time monitoring for nonadherence within clinical settings. We performed UTRA testing among PrEP users to examine the relationship between low PrEP adherence and future PrEP discontinuation, and the accuracy of POC testing compared to gold-standard liquid chromatography tandem mass spectrometry (LC/MS/MS). METHODS: YMSM/TGW participants (n = 100) were recruited during a daily PrEP visit. Logistic regression models analyzed the relationship between the primary predictor of urine POC assay results (cutoff 1,500 ng/mL) and the primary outcome of PrEP discontinuation, defined as no PrEP follow-up or prescription within 120 days. RESULTS: Overall, 19% of participants had low urine TFV and 21% discontinued PrEP, while 11% of participants self-reported low PrEP adherence (< 4 pills per week), which was only 43% sensitive/84% specific in predicting low TFV levels and was not associated with PrEP discontinuation. Low urine TFV level predicted PrEP discontinuation (AOR 6.1; 95% CI: 1.4-11; p = 0.005) and was 71% sensitive/90% specific for discontinuation after 120 days. Compared to LC/MS/MS, UTRA testing had a 98% positive and 100% negative predictive value. CONCLUSIONS: In a sample of YMSM/TGW on daily PrEP, POC UTRA testing predicted PrEP discontinuation more accurately than self-reported adherence, with high predictive values compared to LC/MS/MS. UTRA testing may be a clinical tool for directing preventive interventions towards those likelier to discontinue PrEP despite ongoing HIV vulnerability.

Impact of a point-of-care urine tenofovir assay on adherence to HIV pre-exposure prophylaxis among women in Kenya: a randomised pilot trial.

BACKGROUND: Adherence challenges with oral tenofovir-based pre-exposure prophylaxis (PrEP) are common. We developed a point-of-care assay to objectively assess tenofovir in urine and conducted a pilot trial examining the impact of counselling informed by use of this urine assay on long-term PrEP adherence. METHODS: This randomised trial enrolled women not in serodiscordant partnerships 3 months after PrEP initiation at the Kenya Medical Research Institute to compare standard-of-care adherence counselling versus counselling informed by the urine assay (urine-test counselling group) every 3 months for 12 months. In the standard of care group, urine samples were stored and tested at study end without participant feedback. Here we report the adherence primary outcome of hair concentrations of tenofovir at 12 months as a long-term metric (undetectable levels defined long-term non-adherence), as well as urine concentrations of tenofovir at each visit as a short-term adherence metric and acceptability of the assay assessed by quantitative surveys. Data were analysed by randomisation group. This completed trial was registered with ClinicalTrials.gov (NCT03935464). FINDINGS: From March 17, 2021 to Jan 18, 2022 we enrolled 49 women in the urine-test counselling group and 51 in the standard of care group; retention was 86 (86%) of 100. Nine (21%) of 42 in the urine-test counselling group had hair samples at 12 months with tenofovir concentrations below the limit of quantification compared with 15 (37%) of 41 in the standard of care group. The relative odds of long-term non-adherence in the standard of care group compared with urine-test counselling were 3·53 (95% CI 1·03-12·03; p=0·044). Pre-intervention, urine tenofovir was detectable in 65% in the urine-test counselling group and 71% in the standard of care group (p=0·68). At 12 months, 31 (72%) of 43 in the intervention group had detectable urine tenofovir compared with 19 (45%) of 42 in the standard of care group (p=0·0015). 40 (93%) of 43 participants liked the test very much and only one disliked the test. One participant in the standard of care group was withdrawn at the 6-month visit due to HIV seroconversion. INTERPRETATION: A low-cost urine tenofovir assay to inform PrEP counselling resulted in improvement in both short-term and long-term metrics of adherence. This urine tenofovir assay could help to improve long-term PrEP adherence. FUNDING: National Institute of Allergy and Infectious Diseases and National Institutes of Health.

Sotalol permeability in cultured-cell, rat intestine, and PAMPA system.

PURPOSE: To clarify sotalol's classification in the BCS versus BDDCS systems through cellular, rat everted sac and PAMPA permeability studies. METHODS: Studies were carried out in Madin Darby canine kidney (MDCK) and MDR1-transfected MDCK (MDCK-MDR1) cell lines, rat everted gut sacs and the Parallel Artificial Membrane Permeability Assay (PAMPA) system. Three-hour transport studies were conducted in MDCK cell lines (with apical pH changes) and MDCK-MDR1 cells (with and without the P-glycoprotein inhibitor GG918); male Sprague-Dawley rats (300~350 g) were used to prepare everted sacs. In the PAMPA studies, drug solutions at different pH's were dosed in each well and incubated for 5 h. Samples were measured by LC-MS/MS, or liquid scintillation counting and apparent permeability (P(app)) was calculated. RESULTS: Sotalol showed low permeability in all of the cultured-cell lines, everted sacs and PAMPA systems. It might be a border line P-glycoprotein substrate. The PAMPA study showed that sotalol's permeability increased with a higher apical pH, while much less change was found in MDCK cells. CONCLUSION: The low permeability rate for sotalol correlates with its Class 3 BDDCS assignment and lack of in vivo metabolism.

Brief Report: Use of Remnant Specimens to Assess Use of HIV PrEP Among Populations With Risk of HIV Infection: A Novel Approach.

BACKGROUND: HIV-uninfected persons being evaluated for sexually transmitted infections (STIs) may be good HIV pre-exposure prophylaxis (PrEP) candidates. We measured PrEP use in a sentinel STI patient population. DESIGN: Cross-sectional study, New York City Sexual Health Clinics (January 2019-June 2019). METHODS: Remnant serum samples from 644 HIV-uninfected men who have sex with men (MSM) and 97 women diagnosed with chlamydia, gonorrhea, and/or early syphilis were assayed for tenofovir and emtricitabine levels using a validated liquid chromatography-mass spectrometry assay. Using paired test results and medical records, we assessed (1) prevalence and (2) correlates of PrEP use on the day of STI diagnosis (adjusted prevalence ratios [aPRs]). RESULTS: PrEP use among 741 patients was 32.7% [95% confidence interval (CI): 29.3 to 36.0]; 37.3% for MSM and 2.1% for women. PrEP use was high among White MSM (46.8%) and lowest among women. Among MSM with rectal chlamydia/gonorrhea or early syphilis, PrEP use was associated with age [aPR = 1.7 (95% CI: 1.2 to 2.4) for ages 25-34 years and aPR = 2.0 (1.4 to 2.9) for ages 35-44 years, vs. 15 to 24 years]; number of recent sex partners [aPR = 1.4 (1.0 to 2.0) for 3-5 partners, aPR = 2.1 (1.5 to 3.0) for 6-10 partners, aPR = 2.2 (1.6 to 3.1) for >10 partners, vs. ≤2 partners]; having sex/needle-sharing partners with HIV [aPR = 1.4 (1.1-1.7)]; and inconsistent condom use [aPR = 3.3 (1.8-6.1)]. Race/ethnicity, past-year STI diagnosis, and postexposure prophylaxis use were not associated. CONCLUSIONS: One in 3 people with newly diagnosed STIs had detectable serum PrEP, and PrEP use was exceedingly rare among women. Routinely collected remnant samples can be used to measure PrEP use in populations at high risk of HIV acquisition.

Antiretroviral Therapy Adherence During and Postbreastfeeding Cessation Measured by Tenofovir Levels in Hair.

BACKGROUND: We examined change in antiretroviral treatment (ART) adherence after breastfeeding (BF) cessation using hair tenofovir (TFV) concentrations as an objective metric of medication consumption. METHODS: A subset of postpartum women in Zimbabwe randomized in IMPAACT PROMISE to take ART while BF and post-BF cessation had hair TFV measured longitudinally. Using linear mixed-effect models, we estimated differences in hair TFV levels after BF cessation, accounting for trends in levels over time regardless of BF status and change in slope after breastfeeding cessation. We also estimated the relative risk of viremia (>50 copies/mL) per doubling of hair TFV concentration. RESULTS: Among 55 women (median age 26, interquartile range 24-29 years), hair TFV levels (n = 305) were available for a median of 9 visits per woman between 3 and 29 months postpartum. Hair TFV levels ranged from undetected to 0.25 ng/mg (median 0.04 ng/mg). Controlling for trends since delivery [decline of 2.2% per month, 95% confidence interval (CI): -5.3 to 1.0], TFV levels averaged 24.4% higher (95% CI: -5.1 to 63.1) post-BF cessation than during BF, with no change in slope (0.0% per month, 95% CI: -3.8 to 3.9). Postpartum, 42% of women were ever viremic. Higher TFV levels were strongly protective; relative risk of viremia per doubling of TFV was 0.52 (95% CI: 0.43 to 0.63; P < 0.0001). CONCLUSIONS: Leveraging an objective metric of ART use, we observed modestly declining adherence across the postpartum period, but no additional decline associated with breastfeeding cessation. High viremia frequency and varying postpartum TFV levels observed highlight the importance of enhanced adherence support with viral load monitoring among postpartum women.

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

Background: Tenofovir-diphosphate (TFV-DP) measured in dried blood spots (DBS) and tenofovir (TFV) measured in urine/plasma have been used to measure TFV-based oral pre-exposure prophylaxis (PrEP) adherence. However, there are limited data comparing these 3 metrics and their appropriate use for PrEP adherence monitoring. Methods: We collected DBS, urine, and plasma samples from HIV-negative adults randomized to a low (2 doses/week), moderate (4 doses/week), or perfect (7 doses/week) adherence group (via directly observed therapy) of tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) for 6 weeks, followed by a 4-week washout phase. Drug concentrations were measured using liquid chromatography tandem mass spectrometry. Linear mixed-effects modeling was used to examine associations between drug concentrations and dosing time. Results: Among 28 participants, the median age was 33 years, and 12 (43%) were female. At steady state, 25th percentile TFV-DP concentrations were 466, 779, and 1375 fmol/3 mm punch in the low, moderate, and perfect adherence group, respectively. Correlation was stronger between quantifiable TFV-DP and plasma TFV (r = 0.65; P < .01) than between TFV-DP and urine TFV (r = 0.50; P < .01). Among all participants, each additional week of cumulative dosing on average led to a mean increase of 158 fmol/3 mm punch (P < .001) in TFV-DP during the dosing phase. Each additional day after the last dose was associated with 43 fmol/3 mm punch lower TFV-DP (P = .07). Conclusions: TFV-DP levels in DBS provide valuable insight into both dosing recency and cumulative doses from variable adherence patterns. Our observed benchmark TFV-DP concentrations were slightly higher than prior predicted estimates based on convenience samples.