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HPTN 083 demonstrated that injectable cabotegravir (CAB) was superior to oral tenofovir disoproxil fumarate-emtricitabine (TDF-FTC) for HIV prevention in cisgender men and transgender women who have sex with men. We previously analyzed 58 infections in the blinded phase of HPTN 083 (16 in the CAB arm and 42 in the TDF-FTC arm).

OBJECTIVE Tenofovir alafenamide (TAF) preferentially loads peripheral blood mononuclear cells (PBMC), resulting in higher PBMC tenofovir-diphosphate (TFV-DP) vs. tenofovir disoproxil fumarate (TDF). No studies have yet compared TFV-DP in PBMC from lower than daily dosing between prodrugs, which has potential implications for event-driven pre-exposure prophylaxis and pharmacologic forgiveness. DESIGN Two separate randomized, directly observed therapy (DOT) crossover studies (DOT-DBS and TAF-DBS) were conducted to mimic low, medium, and high adherence. METHODS HIV-negative adults were randomized to two 12-week DOT regimens of 33%, 67%, or 100% of daily dosing with emtricitabine (F)/TAF 200 mg/25 mg (TAF-DBS) or F/TDF 200 mg/300 mg (DOT-DBS), separated by a 12-week washout. PBMC steady-state concentrations (Css) of TFV-DP and FTC-TP were estimated using nonlinear mixed models and compared between F/TAF and F/TDF. RESULTS Thirty-five participants contributed to 33% (n = 23), 67% (n = 23), and 100% (n = 23) of daily F/TAF regimens. Forty-four contributed to 33% (n = 15), 67% (n = 16), and 100% (n = 32) of daily F/TDF regimens. PBMC TFV-DP Css were 7.3- (95% CI: 6.4-8.2), 7.1- (5.9-8.2), and 6.7- (4.4-8.9) fold higher (p

Tenofovir diphosphate (TFV-DP) concentrations measured with dried blood spots (DBS) can be used to classify adherence to emtricitabine/tenofovir disoproxil fumarate (F/TDF) for HIV pre-exposure prophylaxis (PrEP). A TFV-DP of 700 fmol/punch was previously associated with high PrEP efficacy, and was estimated to represent ≥4 doses/week on average. However, interindividual variability in TFV-DP concentrations may lead to adherence misclassification and decrease the precision of adherence–efficacy relationships. The purpose of this analysis was to evaluate sources of TFV-DP variability to improve the precision of TFV-DP for adherence assessments by incorporating individual characteristics. Data and samples from a 36-week study of TFV-DP in DBS, collected biweekly, among 48 HIV-negative volunteers (25 Females/26 Caucasian/10 African American/14 Hispanic) receiving F/TDF at 33%, 67%, and 100% of daily dosing under directly observed therapy were used for analysis. The simplest pharmacokinetic model to describe TFV-DP accumulation with acceptable performance was a one-compartment constant input model. Covariates, including laboratory values and demographics were ranked in importance of their association with post hoc pharmacokinetic (PK) parameters using random forest analyses. Weight and platelet count were included in the final model and simulations were conducted to generate benchmarks for 110 kg) doses/week, amounting to a much lower rate of misspecification (17% vs. 30%) with this individualized model versus previous interpretations. Incorporating body weight and platelet count improved the precision of TFV-DP concentrations for adherence assessments. Previous benchmarks were conservative, indicating that the pharmacological forgiveness of F/TDF may be higher than currently recognized and supports continued investigation of intermittent PrEP dosing regimens. Clinical Trial Registration number, NCT02022657.

STUDY OBJECTIVE To assess the association between tenofovir diphosphate (TFV-DP) in dried blood spots (DBS), a measure of cumulative tenofovir-based antiretroviral (ART) adherence, with medication regimen complexity in persons with human immunodeficiency virus (PWH). DESIGN Prospective clinical cohort (up to three visits over 48 weeks). SETTING Academic-based HIV clinic. PATIENTS PWH receiving tenofovir disoproxil fumarate (TDF)-based ART. MEASUREMENTS DBS for TFV-DP were collected at every study visit. Baseline patient-level medication regimen complexity index (pMRCI) scores were calculated and categorized into three sub-scores (disease-specific [ART], non-ART, and over-the-counter [OTC]). The pMRCI scores were evaluated to assess the association with TFV-DP in DBS

Background Adherence is critical to achieve the benefits of antiretroviral therapy. A smart-pill bottle service that transmits real-time adherence data via cellular networks to a central service and prompts nonadherent patients with phone or text messages may improve adherence. Methods Adults with HIV taking a tenofovir-containing regimen with suboptimal adherence were randomized to adherence counseling ± a smart-pill bottle service for 12 weeks. Tenofovir diphosphate (TFV-DP) levels by dried blood spot, HIV RNA levels, CD4 cell counts, and self-reported adherence were collected. Results Sixty-three participants (22% women; 48% black, 25% Latino) were randomized: 30 to the smart-pill bottle (2 of whom were lost to follow-up before the baseline visit), and 33 to control arms. At baseline, 49% of participants had HIV RNA ≤20 copies/mL and 61% reported 100% adherence with ART over 4 days. From baseline to week 12, median TFV-DP levels were +252 and -41 fmol/punch in the bottle and control arms, respectively (P = 0.10). Exploratory exclusion of 3 participants with known or suspected drug-drug interactions found median TFV-DP levels of +278 and -38 fmol/punch, respectively (P = 0.04). There were no differences in study discontinuations, HIV RNA suppression, CD4 cell counts, or self-reported adherence at week 12. Conclusions In a diverse group of participants with suboptimal adherence to ART, the smart-pill bottle service was associated with higher TFV-DP levels.

OBJECTIVE People living with HIV (PLWH) are living longer and developing more non-AIDS comorbidities, which negatively impact antiretroviral therapy (ART) adherence. Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is a novel pharmacologic measure of cumulative ART adherence that is predictive of viral suppression and future viremia. However, the relationship between non-AIDS comorbidities and this adherence measure is unknown. We aimed to evaluate the association between 3 non-AIDS comorbidities (diabetes mellitus (DM), hypertension, and hyperlipidemia) and TFV-DP in DBS in PLWH. METHODS Blood for TFV-DP in DBS and HIV viral load was prospectively collected from PLWH on tenofovir disoproxil fumarate for up to 3 times over 48 weeks. Non-AIDS comorbidities were recorded. Mixed effect multivariable linear regression models were used to estimate the changes in TFV-DP concentrations in DBS according to the presence of comorbidities and to estimate the percent differences in TFV-DP concentrations between these groups. RESULTS A total of 1144 person-visits derived from 523 participants with available concentrations of TFV-DP in DBS were included in this analysis. In univariate analysis, no significant association between non-AIDS comorbidities (categorized as having 0, 1, 2, or 3 comorbidities) and the concentrations of TFV-DP in DBS was observed (P = 0.40). Participants who had DM had 25% lower (95% confidence interval: -36% to -12%; P < 0.001) TFV-DP in DBS than participants without DM after adjusting for age, gender, race, body mass index, estimated glomerular filtration rate, CD4 T-cell count, hematocrit, ART class, patient-level medication regimen complexity index, and 3-month self-reported adherence. CONCLUSIONS Diabetic PLWH have lower concentrations of TFV-DP in DBS compared with those without DM. Further research is required to identify the clinical implications and biological mechanisms underlying these findings.

Background HIV Prevention Trials Network 084 demonstrated that long-acting injectable cabotegravir (CAB) was superior to daily oral tenofovir (TFV) disoproxil fumarate (TDF)/emtricitabine (FTC) for preventing human immunodeficiency virus (HIV) infection in sub-Saharan African women. This report describes HIV infections that occurred in the trial before unblinding. Methods Testing was performed using HIV diagnostic assays, viral load testing, a single-copy RNA assay, and HIV genotyping. Plasma CAB, plasma TFV, and intraerythrocytic TFV-diphosphate concentrations were determined by liquid chromatography–tandem mass spectrometry. Results Forty HIV infections were identified (CAB arm, 1 baseline infection, 3 incident infections; TDF/FTC arm, 36 incident infections). The incident infections in the CAB arm included 2 with no recent drug exposure and no CAB injections and 1 with delayed injections; in 35 of 36 cases in the TDF/FTC arm, drug concentrations indicated low or no adherence. None of the cases had CAB resistance. Nine women in the TDF/FTC arm had nonnucleoside reverse-transcriptase inhibitor resistance; 1 had the nucleoside reverse-transcriptase inhibitor resistance mutation, M184V. Conclusions Almost all incident HIV infections occurred in the setting of unquantifiable or low drug concentrations. CAB resistance was not detected. Transmitted nonnucleoside reverse-transcriptase inhibitor resistance was common; 1 woman may have acquired nucleoside reverse-transcriptase inhibitor resistance from study drug exposure.

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

Inadequate adherence to chronic medications is a far-reaching problem with financial and human health consequences. By a wide margin, non-adherence is the leading cause of therapeutic failures of HIV pre-exposure chemoprophylaxis (PrEP) and antiretroviral therapy (ART). It has been proven that HIV infection can be prevented by daily dosing of emtricitabine and tenofovir disoproxil fumarate. Measurement of intracellular tenofovir diphosphate in red blood cells has been established as an effective way to assess cumulative adherence, however, the LC-MS-based analytical method developed for the purpose is both complicated and expensive. Here, we report a simple method for adherence monitoring based on direct MS quantification of intracellular tenofovir diphosphate in human whole blood. The method requires only microliters of whole blood, employs special membranes to perform plasma separation and concomitant desalting during blood collection, and uses nanoelectrospray on a triple quadrupole instrument. Quantitative performance in this proof-of-concept study includes RSDs of

Introduction Tenofovir diphosphate (TFV‐DP) in dried blood spots (DBS), a measure of cumulative antiretroviral therapy (ART) adherence, is associated with viral suppression and predicts future viremia in persons with HIV (PWH). However, its utility to identify those at risk for virologic failure (VF) and drug resistance is unknown. To address this, we aimed to establish the association between this adherence biomarker and VF with drug resistance in a cohort of PWH initiating first‐line ART in KwaZulu‐Natal, South Africa. Methods PWH initiating TFV disoproxil fumarate (TDF)‐based ART within a parent prospective cohort were evaluated. Using a nested design, DBS for TFV‐DP were collected from cases who developed VF (HIV‐1 RNA ≥1000 copies/ml) after ≥5 months on ART versus controls, matched 1:2 by site, age, gender, race and ART duration. Cases were categorized as having VF with or without resistance using genotyping. One‐way analysis of variance (ANOVA) was used to compare TFV‐DP for controls, cases with VF and resistance, and cases with VF without resistance. Data are presented as mean (standard deviation, SD) or geometric mean [95% confidence interval, 95% CI]. Results and discussion One thousand participants were enrolled in the parent study between 2014 and 2016, of which 288 (29%) had DBS available. Of these, 94 (33%) were cases and 194 (67%) were controls; 59% were women. Mean age of our population was 33 (SD 8) years. Genotyping was available in 50 (53%) of the 94 cases. Geometric mean TFV‐DP in DBS from controls was 708 [95% CI; 647–773] fmol/punch, which was higher compared to participants having VF with resistance (n = 36), 386 [95% CI; 241–617] fmol/punch and VF without resistance (n = 14), 61 [95% CI; 22–164] fmol/punch; p

Background Sofosbuvir is converted to its active form, 007 triphosphate (007-TP), within cells. To date, the association between treatment adherence and 007-TP in dried blood spots (DBS) and factors that influence this relationship remain unknown. Objectives To examine relationships between adherence and 007-TP concentrations in DBS and identify factors that influence 007-TP in DBS. Methods Persons with HCV or HIV/HCV coinfection and self-reported drug and/or alcohol use were randomized to one of two technology-based approaches for monitoring 12 week adherence to once-daily ledipasvir/sofosbuvir. Convenience blood samples were collected every 2 weeks during treatment. 007-TP in DBS was quantified using LC/MS and analysed using mixed-effects models. Results A total of 337 observations were available from 58 participants (78% male; 21% black; 22% Hispanic/Latino; 26% cirrhotic; 78% HIV-coinfected). The mean half-life of 007-TP in DBS was 142 h (95% CI 127–156) and concentrations increased by 7.3% (95% CI 2.2–12.6) for every 10% increase in between-visit adherence. Geometric mean (95% CI) 007-TP concentrations in DBS were 301 (247–368), 544 (462–639) and 647 (571–723) fmol/punch by adherence categories of ≤50%, >50 to ≤80%, and >80%. Adherence, time on therapy, increasing age and decreased estimated glomerular filtration rate were associated with higher 007-TP, whereas increased time since last dose, male sex, black race and higher BMI were associated with lower 007-TP. Conclusions 007-TP has an extended half-life in DBS and concentrations increased with adherence. Further research is needed to examine additional factors that affect 007-TP and the clinical utility of this measure.

The drivers of low-level viremia (LLV) between 20 and 200 copies/mL remain unclear. In 1042 person-visits from 497 persons with HIV on tenofovir disoproxil fumarate–containing antiretroviral therapy (ART), the association between LLV and cumulative antiretroviral adherence (quantified using tenofovir diphosphate [TFV-DP] in dried blood spots) was assessed. Lower TFV-DP levels were associated with higher odds of LLV. As TFV-DP (fmol/punch) categories decreased from >1650 to 800–1650; 800–1650 to 1650 to

OBJECTIVE Emtricitabine triphosphate (FTC-TP) in dried blood spots (DBS), a measure of short-term antiretroviral therapy (ART) adherence, is associated with viral suppression in persons with HIV (PWH). However, its ability to predict future viremia remains unknown. DESIGN Prospective, observational cohort (up to three visits in 48 weeks). METHODS PWH receiving TDF/FTC-based ART had DBS and HIV viral load obtained at routine clinical visits. FTC-TP in DBS was dichotomized into quantifiable vs. below the limit of quantification (BLQ). The adjusted odds ratio (aOR) of future viremia (≥20 copies/ml at next study visit) was estimated according to FTC-TP at the current visit. To assess for possible interactions, additional models adjusted for tenofovir diphosphate (TFV-DP) in DBS and 3-day self-reported adherence. RESULTS Data from 433 PWH (677 paired DBS/HIV viral load samples) were analyzed. The aOR [95% confidence interval (CI)] for future viremia for BLQ vs. quantifiable FTC-TP was 3.4 (1.8--6.5; P = 0.0002). This diminished after adjusting for TFV-DP [aOR 1.9 (0.9--4.1); P = 0.090]. Among PWH reporting 100% 3-day adherence, the odds of future viremia were 6.0 times higher [(1.8--20.3); P = 0.001] when FTC-TP was BLQ vs. quantifiable. Among participants (n = 75) reporting less than 100% adherence, BLQ FTC-TP in DBS was not predictive of future viremia [aOR 1.3 (0.4--4.6); P = 0.96]. CONCLUSION Nonquantifiable FTC-TP in DBS predicts future viremia and is particularly informative in PWH reporting perfect adherence. As point-of-care adherence measures become available, mismatches between objective and subjective measures, such as FTC-TP in DBS and self-report, could help clinicians identify individuals at an increased risk of future viremia.

BackgroundTenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is associated with viral suppression in persons living with HIV (PLWH) taking tenofovir disoproxil fumarate (TDF). However, its value as a predictor of future viremia remained unknown.MethodsBlood for plasma viral load (VL) and TFV-DP in DBS were collected (up to 3 visits within 48 weeks) in PLWH on TDF. TFV-DP cut points were selected using logistic prediction models maximizing the area under the receiver operation characteristic curve, and estimated adjusted odds ratio (aOR) of future viremia (≥20 copies/mL) were compared to the highest TFV-DP category.ResultsAmong all 451 participants in the analysis, aOR of future viremia for participants with TFV-DP ConclusionsTFV-DP in DBS predicts future viremia in PLWH on TDF, even in those who are virologically suppressed. This highlights the utility of this biomarker to inform about adherence beyond VL.Clinical Trials Registration. NCT02012621.

BACKGROUND: Emtricitabine triphosphate (FTC-TP), the phosphorylated anabolite of emtricitabine, can be quantified in dried blood spots (DBS). We evaluated FTC-TP in DBS as a predictor of viral suppression and evaluated self-reported adherence as a predictor of FTC-TP. METHODS: Persons living with HIV (PLWH) on an FTC-containing regimen were prospectively recruited. A DBS and HIV viral load were obtained during routine clinical visits. Self-reported adherence for 3 days, 30 days and 3 months was captured. Generalized estimating equations were used to estimate the adjusted odds ratio (aOR) of viral suppression for quantifiable FTC-TP versus below the limit of quantification (BLQ). The utility of self-reported adherence to predict quantifiable FTC-TP was assessed by calculating the area under receiver operating characteristic (ROC) curve. RESULTS: One thousand one hundred and fifty-four person-visits from 514 participants who had DBS assayed for FTC-TP were included in the analysis. After adjusting for age, gender, race, BMI, ART class, ART duration, estimated glomerular filtration rate and CD4+ T cell count, the aOR (95% CI) for viral suppression for quantifiable FTC-TP versus BLQ was 7.2 (4.3–12.0; P

Pre-exposure prophylaxis (PrEP) using antiretroviral oral drugs is effective at preventing HIV transmission when individuals adhere to the dosing regimen. Tenofovir alafenamide (TAF) is a potent antiretroviral drug, with numerous long-acting (LA) delivery systems under development to improve PrEP adherence. However, none has undergone preventive efficacy assessment. Here we show that LA TAF using a novel subcutaneous nanofluidic implant (nTAF) confers partial protection from HIV transmission. We demonstrate that sustained subcutaneous delivery through nTAF in rhesus macaques maintained tenofovir diphosphate concentration at a median of 390.00 fmol/106 peripheral blood mononuclear cells, 9 times above clinically protective levels. In a non-blinded, placebo-controlled rhesus macaque study with repeated low-dose rectal SHIVSF162P3 challenge, the nTAF cohort had a 62.50% reduction (95% CI: 1.72% to 85.69%; p=0.068) in risk of infection per exposure compared to the control. Our finding mirrors that of tenofovir disoproxil fumarate (TDF) monotherapy, where 60.00% protective efficacy was observed in macaques, and clinically, 67.00% reduction in risk with 86.00% preventive efficacy in individuals with detectable drug in the plasma. Overall, our nanofluidic technology shows potential as a subcutaneous delivery platform for long-term PrEP and provides insights for clinical implementation of LA TAF for HIV prevention.

Background The HIV Prevention Trials Network (HPTN) 083 trial demonstrated that long-acting cabotegravir (CAB-LA) was more effective than tenofovir disoproxil fumarate–emtricitabine (TDF/FTC) in preventing human immunodeficiency virus (HIV) in cisgender men and transgender women who have sex with men. We characterized HIV infections that occurred in the blinded phase of HPTN 083. Methods Retrospective testing included HIV testing, viral load testing, quantification of study drugs, and HIV drug resistance testing. Results Fifty-eight infections were evaluated, including 51 incident infections (12 in CAB arm and 39 in TDF/FTC arm). In many cases (5 in CAB arm and 37 in TDF/FTC arm), infection was associated with low or unquantifiable study drug concentrations. In 4 cases, infection occurred with on-time CAB-LA injections and expected plasma CAB concentrations. CAB exposure was associated with prolonged viral suppression and delayed antibody expression. In some cases, delayed HIV diagnosis resulted in CAB provision to participants with undetected infection, delayed antiretroviral therapy, and emergence of drug resistance; most of these infections would have been detected earlier with viral load testing. Conclusions Early detection of HIV infection and prompt antiretroviral therapy initiation could improve clinical outcomes in persons who become infected despite CAB-LA prophylaxis. Further studies are needed to elucidate the correlates of HIV protection in persons receiving CAB-LA.

BACKGROUND Benin has a long-standing history of HIV prevention programs aimed at female sex workers (FSWs). We used data from a national survey among FSWs (2017) to assess the prevention and care cascades in this population. METHODS Female sex workers were recruited through cluster sampling of sex work sites. A questionnaire was administered, and HIV tested. HIV-positive participants were asked to provide dried blood spots and were tested for antiretroviral and viral load. We assessed 2 prevention cascades (HIV testing and safer sex) and the treatment cascade, using a combination of self-reported and biological variables. RESULTS Mean age of the 1086 FSWs was 30 years. Half of them were Beninese, and two-thirds had a primary school education level or less. Almost all FSWs had ever heard of HIV/AIDS. More than half (79.1%) had ever been tested, and 84.1% of the latter had been tested in the last year. In the previous 6 months, 90.1% were exposed to prevention messages. Women exposed to any HIV prevention message reported a higher level of consistent condom use in the last month (69.0%) than those who were not (48.5%, P < 0.0001). HIV prevalence was 7.7%. Among HIV-positive women, 60.6% knew their status; among those, 90.5% were on antiretroviral and 81.8% of them had a suppressed viral load. CONCLUSIONS Despite long-standing HIV prevention programs for FSWs, the prevention indicators were often low. Linkage to care was good, viral suppression was suboptimal, but knowledge of HIV-positive status was low. Exposing women to prevention messages is necessary, as to increase HIV testing.

Despite being FDA-approved for COVID-19, the clinical efficacy of remdesivir (Veklury®) remains contentious. We previously pointed out pharmacokinetic, pharmacodynamic and toxicology reasons for why its parent nucleoside GS-441524, is better suited for COVID-19 treatment. Here, we assess the oral bioavailability of GS-441524 in beagle dogs and show that plasma concentrations ∼24-fold higher than the EC50 against SARS-CoV-2 are easily and safely sustained. These data support translation of GS-441524 as an oral agent for COVID-19.

Background Hepatitis C virus treatment in persons who use drugs (PWUD) is often withheld due to adherence and reinfection concerns. In this study, we report treatment outcomes, technology-based adherence data, and adherence predictors in PWUD and/or alcohol. Methods INCLUD was a prospective, open-label study of ledipasvir/sofosbuvir for 12 weeks in PWUD aged 18–70 years. Participants were randomized to wireless (wirelessly observed therapy) or video-based directly observed therapy (vDOT). Drug use was assessed every 2 weeks. Sustained virologic response (SVR) was examined by intention-to-treat and as-treated. Factors associated with missing ≥1 dose(s) between visits were examined using generalized linear models. Results Sixty participants received ≥1 ledipasvir/sofosbuvir dose (47 human immunodeficiency virus [HIV]/hepatitis C virus [HCV], 13 HCV only; 78% male; 22% black; 25% cirrhotic). Substance use occurred at 94% of person-visits: 60% marijuana, 56% alcohol, 37% methamphetamine, 22% opioids, 17% cocaine, and 20% injection drug use. The SVR by intention-to-treat was 86.7% (52 of 60) and as-treated was 94.5% (52 of 55). Confirmed failures included 1 relapse, 1 reinfection, and 1 unknown (suspected reinfection). Median total adherence was 96% (interquartile range [IQR], 85%–100%; range, 30%–101%), and between-visit adherence was 100% (IQR, 86%–100%; range, 0%–107%). The odds of missing ≥1 dose between visits increased with HIV coinfection (2.94; 95% confidence interval [CI], 1.37–6.32; P = .006), black race (4.09; 95% CI, 1.42–11.74; P = .009), methamphetamine use (2.51; 95% CI, 1.44–4.37; P = .0.001), and cocaine use (2.12; 95% CI, 1.08–4.18; P = .03) and decreased with marijuana use (0.34; 95% CI, 0.17–0.70; P = .003) and vDOT (0.43; 95% CI, 0.21–0.87; P = .02). Conclusions Persons who use drugs achieved high SVR rates with high, but variable, ledipasvir/sofosbuvir adherence using technology-based methods. These findings support efforts to expand HCV treatment in PWUD., Persons with HCV and active drug/alcohol use demonstrated high, but variable, adherence to ledipasvir/sofosbuvir using wireless pillboxes and video-based directly observed therapy. High SVR rates were achieved, supporting efforts to expand HCV treatment in this population.

HIV-1 is a chronic disease managed by strictly adhering to daily antiretroviral therapy (ART). However, not all people living with HIV-1 have access to ART, and those with access may not adhere to treatment regimens increasing viral load and disease progression. Here, a subcutaneous nanofluidic implant was used as a long-acting (LA) drug delivery platform to address these issues. The device was loaded with tenofovir alafenamide (TAF) and implanted in treatment-na&iuml, ve simian HIV (SHIV)-positive nonhuman primates (NHP) for a month. We monitored intracellular tenofovir-diphosphate (TFV-DP) concentration in the target cells, peripheral blood mononuclear cells (PBMC). The concentrations of TFV-DP were maintained at a median of 391.0 fmol/106 cells (IQR, 243.0 to 509.0 fmol/106 cells) for the duration of the study. Further, we achieved drug penetration into lymphatic tissues, known for persistent HIV-1 replication. Moreover, we observed a first-phase viral load decay of &minus, 1.14 &plusmn, 0.81 log10 copies/mL (95% CI, &minus, 0.30 to &minus, 2.23 log10 copies/mL), similar to &minus, 1.08 log10 copies/mL decay observed in humans. Thus, LA TAF delivered from our nanofluidic implant had similar effects as oral TAF dosing with a lower dose, with potential as a platform for LA ART.

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.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.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.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.

Background Ledipasvir/sofosbuvir increases tenofovir plasma exposures by up to 98% with tenofovir disoproxil fumarate (TDF), and exposures are highest with boosted PIs. There are currently no data on the combined use of the newer tenofovir prodrug, tenofovir alafenamide (TAF), boosted PIs and ledipasvir/sofosbuvir. Objectives To compare the plasma and intracellular pharmacokinetics and renal safety of TAF with ledipasvir/sofosbuvir when co-administered with boosted PIs. Methods Persons with HIV between 18 and 70 years and on a boosted PI with TDF were eligible. The study was comprised of four phases: (1) TDF 300 mg with boosted PI; (2) TAF 25 mg with boosted PI; (3) TAF 25 mg with boosted PI and ledipasvir/sofosbuvir; and (4) TAF 25 mg with boosted PI. Pharmacokinetic sampling, urine biomarker collection [urine protein (UPCR), retinol binding protein (RBP) and β2 microglobulin (β2M) normalized to creatinine] and safety assessments occurred at the end of each phase. Plasma, PBMCs and dried blood spots were collected at each visit. Results Ten participants were enrolled. Plasma tenofovir exposures were 76% lower and tenofovir-diphosphate (TFV-DP) concentrations in PBMCs increased 9.9-fold following the switch to TAF. Neither of these measures significantly increased with ledipasvir/sofosbuvir co-administration, nor did TAF plasma concentrations. No significant changes in estimated glomerular filtration rate or UPCR occurred, but RBP:creatinine and β2M:creatinine improved following the switch to TAF. Conclusions Ledipasvir/sofosbuvir did not significantly increase plasma tenofovir or intracellular TFV-DP in PBMCs with TAF. These findings provide reassurance that the combination of TAF, boosted PIs and ledipasvir/sofosbuvir is safe in HIV/HCV-coinfected populations.

ObjectivesTo determine factors associated with interindividual variability in tenofovir diphosphate (TFV-DP) concentrations in dried blood spots (DBSs) among persons living with HIV (PLWH).MethodsPLWH who were at least 18 years old and taking tenofovir disoproxil fumarate-containing ART were prospectively recruited and enrolled from a clinical cohort and followed longitudinally (up to three visits over 48 weeks). With log-transformed TFV-DP concentrations in DBSs as the outcome, mixed-model regression analyses were used to assess associations between self-reported 3 month ART adherence, race and other clinical covariates (gender, age, BMI, CD4+ T cell count, estimated glomerular filtration rate, haematocrit, duration on current ART and anchor drug class) on TFV-DP in DBSs.ResultsFive hundred and twenty-seven participants (1150 person-visits) were analysed. Adjusting for race and other clinical covariates, every 10% increase in self-reported 3 month ART adherence was associated with an average TFV-DP concentration increase in DBSs of 28% (95% CI: 24%–32%; P ConclusionsIndividual patient characteristics were predictive of TFV-DP concentration in DBSs in PLWH receiving tenofovir disoproxil fumarate-based ART. Future research to incorporate these predictors into the interpretation of this ART adherence biomarker, and to establish whether these associations extend to PLWH taking tenofovir alafenamide-containing ART, is needed.

Slug flow microextraction (SFME)-nanoESI was originally explored as a single-step sampling ionization method for MS analysis of biofluids. In this work, a comprehensive study and development of the SFME has been carried out. Revers-phase SFME was developed to analyze chemical compounds in oil samples. A three-phase SFME system was introduced as a suitable approach for analyzing polar compounds in biofluids. The impacts by the capillary inner diameter, solvent and sample properties were also investigated, leading the use of fused silica capillaries for performing SFME.

Pre-exposure prophylaxis (PrEP) with antiretroviral (ARV) drugs are effective at preventing human immunodeficiency virus (HIV) transmission. However, implementation of PrEP presents significant challenges due to poor user adherence, low accessibility to ARVs and multiple routes of HIV exposure. To address these challenges, we developed the nanochannel delivery implant (NDI), a subcutaneously implantable device for sustained and constant delivery of tenofovir alafenamide (TAF) and emtricitabine (FTC) for HIV PrEP. Unlike existing drug delivery platforms with finite depots, the NDI incorporates ports allowing for transcutaneous refilling upon drug exhaustion. NDI-mediated drug delivery in rhesus macaques resulted in sustained release of both TAF and FTC for 83 days, as indicated by concentrations of TAF, FTC and their respectively metabolites in plasma, PBMCs, rectal mononuclear cells and tissues associated with HIV transmission. Notably, clinically relevant preventative levels of tenofovir diphosphate were achieved as early as 3 days after NDI implantation. We also demonstrated the feasibility of transcutaneous drug refilling to extend the duration of PrEP drug delivery in NHPs. Overall, the NDI represents an innovative strategy for long-term HIV PrEP administration in both developed and developing countries.

In a randomized, cross-over study in healthy volunteers (N=14), 2 g probenecid (PRO)-boosted pharmacokinetics of single dose 600 mg tenofovir disoproxil fumarate (TDF) / 400 mg emtricitabine (FTC) (Treatment, T +PRO) was compared with the current On-Demand HIV Pre-Exposure Prophylaxis (PrEP) from the IPERGAY study (a 600 mg TDF/400 mg FTC on day 1 and 300 mg TDF/200 mg FTC on days 2 and 3) (Control, C IPERGAY). PRO increased mean single dose plasma AUC(0−∞) of TFV and FTC by 64% and 62%, respectively. The 24-hour TFV-diphosphate (TFV-DP) concentrations in peripheral blood mononuclear cells (PBMC) were significantly higher (~30%) in T +PRO compared to C IPERGAY and remained nearly unchanged (on average over 20 fmol/10(6)cells) for 72 hours, suggesting prolonged exposure by PRO. The interaction between FTC and PRO was unexpected and novel. Although further study is needed, PRO-boosted TDF/FTC may allow simpler dosing and improved adherence to HIV PrEP.

BackgroundAlthough tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is a predictor of adherence and pre-exposure prophylaxis efficacy, its utility in human immunodeficiency virus (HIV) treatment remains unknown.MethodsDBS for TFV-DP were collected up to 3 times over 48 weeks in persons living with HIV (PLWH) who were receiving TFV disoproxil fumarate (TDF)-based therapy. Log-transformed baseline TFV-DP was compared using t-tests or analyses of variance; generalized estimating equations were used to estimate the adjusted odds ratio (aOR) of viral suppression (ResultsWe analyzed 1199 DBS from 532 participants (76 female; 101 Black, 101 Hispanic). Among the virologically-suppressed participants at baseline (n = 347), TFV-DP was lower in Blacks (geometric mean 1453, 95% confidence interval [CI] 1291–1635) vs Whites (1793, 95% CI 1678–1916; P = .002) and Hispanics (1760, 95% CI 1563–1982; P = .025); in non-boosted (1610, 95% CI 1505–1723) vs. boosted (1888, 95% CI 1749–2037; P = .002) regimens; and in non-nucleoside reverse transcription inhibitor–based (1563, 95% CI 1432–1707) vs. boosted protease inhibitor–based (1890, 95% CI 1704–2095; P = .006) and multiclass-based (1927, 95% CI 1650–2252; P = .022) regimens. The aOR of virologic suppression, after adjusting for age, gender, race, body mass index, estimated glomerular filtration rate, CD4+ T-cell count, antiretroviral drug class and duration of therapy, was 73.5 (95% CI 25.7–210.5; P < .0001) for a TFV-DP concentration ≥1850 fmol/punch compared to ConclusionsTFV-DP in DBS is strongly associated with virologic suppression in PLWH on TDF-based therapy and is associated with certain participant characteristics. Further research is required to evaluate this drug adherence and exposure measure in clinical practice.Clinical Trials RegistrationNCT02012621.

Drug-drug interactions have been demonstrated to alter cytochrome 2D6 (CYP2D6) enzyme phenotype due to inhibitor ingestion, although it is unclear how substrate interactions affect phenotype. This was a pragmatic clinical trial examining the kinetics of a CYP2D6 enzyme probe drug with and without CYP2D6-dependent substrates. Patients were enrolled into an inpatient study unit, and orally administered a 2 mg microdose of dextromethorphan (DM) to probe enzyme activity with and without CYP2D6-dependent drug-drug interactions. Thirty-nine subjects were enrolled in this trial. Twelve subjects were on no CYP2D6-dependent drugs and 27 were on one or more CYP2D6-dependent drugs. There were 1 poor metabolizer, 5 intermediate metabolizers, 31 normal metabolizers, and 2 ultra-rapid metabolizers. Those with co-ingestion of another CYP2D6-dependent drug were 9.49 (95% confidence interval (CI): 1.54-186.41; P = 0.01) times more likely to have genotype-phenotype discordance based upon the 3 hours dextrophan/dextromethorphan (DX/DM) ratio. CYP2D6 substrate co-ingestions can cause genotype-phenotype discordance.

Background Dolutegravir, an HIV integrase strand-transfer inhibitor, and simeprevir, an HCV NS3/4A PI, have the potential to interact as dolutegravir is a P-glycoprotein, uridine glucuronosyl transferase 1A1 and cytochrome P4503A substrate and simeprevir has been shown to mildly inhibit these. Objectives To compare dolutegravir and simeprevir pharmacokinetics (PK) when given separately versus in combination. Methods Healthy volunteers received: (i) 150 mg of simeprevir once daily for 7 days; (ii) 50 mg of dolutegravir once daily for 7 days; and (iii) 150 mg of simeprevir once daily plus 50 mg of dolutegravir once daily for 7 days, with randomization to treatment sequence. Twenty-four hour intensive PK sampling was performed on day 7 of each sequence following observed dosing and a standardized meal. PK parameters were determined using non-compartmental methods and compared using paired t-tests. Bioequivalence for area under the curve (AUCtau) and maximum concentration (Cmax) were also assessed. NCT02404805. Results Twenty-four subjects completed all three sequences. Dolutegravir trough was increased 24% (P = 0.0003) with simeprevir. Dolutegravir AUCtau was increased 15% (P = 0.002), but was deemed bioequivalent as the 90% CI for the geometric mean ratio was 107%-123%. Dolutegravir Cmax was bioequivalent. Simeprevir PK was unaffected by dolutegravir. There were no discontinuations due to adverse events and all adverse events were mild to moderate in severity. Conclusions Dolutegravir trough was increased slightly with simeprevir, but AUCtau was bioequivalent. Despite the increase in trough, dolutegravir concentrations were well within the range with established safety data. Suggesting that simeprevir and dolutegravir can be safely co-administered.

PrEP’s potential benefit for men who have sex with men (MSM) who use stimulants may be limited by adherence or prescriber willingness to recommend PrEP due to concerns of non-compliance. Using data from PATH-PrEP, a 48-week study evaluating PrEP for MSM in Los Angeles, we modeled an interaction between stimulant use and condomless sex with multiple partners (CAS-MP) on prevention-effective dried blood spot tenofovir-diphosphate concentrations. At week 4, participants reporting stimulant use and CAS-MP had a decreased odds of prevention-effective adherence compared to non-stimulant use and non-CAS-MP (AOR 0.15, 95% CI 0.04-0.57). From week 4 to 48, participants reporting stimulant use and CAS-MP had increased odds of prevention-effective adherence (AOR 1.06 per week, 95%CI 1.01-1.12). Participants reporting CAS-MP without stimulant use had no significant change in prevention-effective adherence (AOR 0.99 per week, 95%CI 0.96-1.02). Stimulant use moderated the association of CAS-MP on prevention-effective PrEP adherence over time.

Variable adherence to antiretroviral therapy (ART) can maintain HIV viral suppression, but our understanding of the ART adherence continuum remains limited. In a clinical cohort of adult persons living with HIV treated with a tenofovir (TFV) disoproxil fumarate/emtricitabine (TDF/FTC)-based regimen, data on 3-month self-reported adherence and dried blood spots (DBS) for TFV diphosphate (TFV-DP) and FTC triphosphate (FTC-TP) were collected. Among 521 participants in whom DBS were available upon enrollment, 333 were virologically suppressed (

Mental health (MH) disorders are more prevalent among persons living with HIV (PLWH) 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 (RBCs). 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 (VL) 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

New objective measures of antiretroviral adherence are needed. We determined if emtricitabine triphosphate (FTC-TP) in dried blood spots (DBS) can be used as a marker of recent dosing with tenofovir disoproxil fumarate-emtricitabine (TDF-FTC). The half-life of FTC-TP was estimated in DBS samples obtained from an intensive pharmacokinetic (PK) study of coformulated TDF-FTC in HIV-negative and HIV-infected participants. The concordance of quantifiable FTC-TP in DBS with tenofovir (TFV)/FTC in plasma was evaluated by utilizing paired plasma-DBS samples from participants enrolled in 2 large preexposure prophylaxis (PrEP) open-label trials. The time to FTC-TP nondetectability after TDF-FTC dosing was evaluated utilizing DBS from HIV-negative participants enrolled in a directly observed therapy study of variable adherence to TDF-FTC. The mean (95% confidence interval [CI]) terminal half-life of FTC-TP in the PK study was 35 (23 to 47) h. A total of 143/163 (88%) samples obtained 0 to 48 h post-TDF-FTC dose had quantifiable FTC-TP in DBS, compared with 2/93 (2%) and 0/87 (0%) obtained >48 and >96 h postdose. In 746 paired plasma-DBS samples from 445 participants enrolled in PrEP trials, when both TFV/FTC in plasma were below the limit of quantification, FTC-TP was as well in 98.9% of the samples, and when either TFV or FTC in plasma was quantifiable, FTC-TP was as well in 90.5% of the samples. The half-life of FTC-TP in DBS is short relative to that of TFV-diphosphate (TFV-DP), making it a surrogate for TFV-FTC detection in plasma. FTC-TP can be quantified in DBS simultaneously with TFV-DP, which quantifies cumulative adherence to TDF-FTC. (The clinical trials discussed in this article have been registered at ClinicalTrials.gov under identifiers NCT01040091, NCT02022657, NCT00458393, NCT01772823, and NCT02012621.)

The pharmacokinetics (PK) of tenofovir-diphosphate (TFV-DP) and emtricitabine-triphosphate (FTC-TP), the active anabolites of tenofovir disoproxil fumarate (TDF), and emtricitabine (FTC) in blood, genital, and rectal compartments was determined in HIV-positive and seronegative adults who undertook a 60-day intensive PK study of daily TDF/FTC (plus efavirenz in HIV positives). Lymphocyte cell sorting, genital, and rectal sampling occurred once per subject, at staggered visits. Among 19 HIV-positive (3 female) and 21 seronegative (10 female) adults, TFV-DP in peripheral blood mononuclear cells (PBMC) accumulated 8.6-fold [95% confidence interval (CI): 7.2–10] from first-dose to steady-state concentration (Css) versus 1.7-fold (95% CI: 1.5–1.9) for FTC-TP. Css was reached in ∼11 and 3 days, respectively. Css values were similar between HIV-negative and HIV-positive individuals. Css TFV-DP in rectal mononuclear cells (1,450 fmol/106 cells, 898–2,340) was achieved in 5 days and was >10 times higher than PBMC (95 fmol/106 cells, 85–106), seminal cells (22 fmol/106 cells, 6–79), and cervical cells (111 fmol/106 cells, 64–194). FTC-TP Css was highest in PBMC (5.7 pmol/106 cells, 5.2–6.1) and cervical cells (7 pmol/106 cells, 2–19) versus rectal (0.8 pmol/106 cells, 0.6–1.1) and seminal cells (0.3 pmol/106 cells, 0.2–0.5). Genital drug concentrations on days 1–7 overlapped with estimated Css, but accumulation characteristics were based on limited data. TFV-DP and FTC-TP in cell sorted samples were highest and achieved most rapidly in CD14+ compared with CD4+, CD8+, and CD19+ cells. Together, these findings demonstrate cell-type and tissue-dependent cellular pharmacology, preferential accumulation of TFV-DP in rectal mononuclear cells, and rapid distribution into rectal and genital compartments.

Tenofovir (TFV) disoproxil fumarate (TDF) and emtricitabine (FTC), two nucleos(t)ide analogs (NA), are coformulated as an anti-HIV combination tablet for treatment and preexposure prophylaxis (PrEP). TDF/FTC may have effects on the deoxynucleoside triphosphate (dNTP) pool due to their similar structures and similar metabolic pathways. We carried out a comprehensive clinical study to characterize the effects of TDF/FTC on the endogenous dNTP pool, from baseline to 30 days of TDF/FTC therapy, in both treatment-naive HIV-positive and HIV-negative individuals. dATP, dCTP, dGTP, and TTP were quantified in peripheral blood mononuclear cells (PBMC) with a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) methodology. Forty individuals (19 HIV-positive) were enrolled and underwent a baseline visit and then received TDF/FTC for at least 30 days. Longitudinal measurements were analyzed using mixed-model segmented linear regression analysis. The dNTPs were reduced by 14% to 37% relative to the baseline level within 3 days in both HIV-negative and HIV-positive individuals (P≤ 0.003). These reductions persisted to various degrees at day 30. These findings indicate that dNTP pools are influenced by TDF/FTC therapy. This may alter cellular homeostasis and could increase the antiviral effect through a more favorable analog/dNTP ratio. Further work is needed to elucidate mechanisms, to evaluate the clinical significance of these findings, and to further probe differences between HIV-negative and HIV-positive individuals. (This study has been registered at ClinicalTrials.gov under identifier NCT01040091.)

Oral preexposure prophylaxis (PrEP) trials report disparate efficacy attributed to variable adherence. HPTN 066 was conducted to establish objective, quantitative benchmarks for discrete, regular levels of adherence using directly observed dosing of tenofovir (TFV) disoproxil fumarate (TDF)/emtricitabine (FTC). Healthy, HIV-uninfected men and women were randomized to one of four oral regimens of fixed-dose TDF 300 mg/FTC 200 mg tablet for 5 weeks with all doses observed: one tablet weekly (one/week), one tablet twice weekly (two/week), two tablets twice weekly (four/week), or one tablet daily (seven/week). Trough serum TFV and FTC, peripheral blood mononuclear cell (PBMC), and CD4(+) TFV-diphosphate (TFV-DP) and FTC-triphosphate (FTC-TP) concentrations were determined throughout dosing and 2 weeks after the last dose. Rectosigmoidal, semen, and cervicovaginal samples were collected for drug assessment at end of dosing and 2 weeks later in a subset of participants. The 49 enrolled participants tolerated the regimens well. All regimens achieved steady-state concentrations by the second dose for serum TFV/FTC and by 7 days for PBMC TFV-DP/FTC-TP. Steady-state median TFV-DP predose concentrations demonstrated dose proportionality: one/week 1.6 fmol/10(6) PBMCs, two/week 9.1, four/week 18.8, seven/week, 36.3. Further, TFV-DP was consistently quantifiable 2 weeks after the last dose for the ≥4/week regimens. Adherence benchmarks were identified using receiver operating characteristic curves, which had areas under the curve ≥0.93 for all analytes in serum and PBMCs. Intersubject and intrasubject coefficients of variation (%CV) ranged from 33% to 63% and 14% to 34%, respectively, for all analytes in serum and PBMCs. Steady-state PBMC TFV-DP was established earlier and at lower concentrations than predicted and was the only analyte demonstrating predose concentration dose proportionality. Steady-state daily dosing serum TFV and PBMC TFV-DP was consistent with highly effective PrEP clinical trials. HPTN 066 provides adherence benchmarks for oral TFV/FTC regimens to assist interpreting study outcomes.

Sofosbuvir (SOF) is a highly efficacious and well-tolerated uridine nucleotide analog that inhibits the hepatitis C virus (HCV) NS5B polymerase enzyme. SOF is administered as a prodrug, which undergoes intracellular phosphorylation by host enzymes to a monophosphate, diphosphate, and finally a pharmacologically active triphosphate. In order to fully understand the clinical pharmacology of SOF, there is a great need to determine the intracellular phosphate concentrations of the drug. We describe the validation and utilization of a method to characterize SOF's disposition into various in vivo cell types, including hepatocytes, peripheral blood mononuclear cells (PBMC), and red blood cells (RBC). Standard bioanalytical validation criteria were applied to lysed cellular matrices, with a validated linear range of 50 to 50,000 fmol/sample for each phosphate moiety. The assay was utilized to collect the first data demonstrating concentrations of phosphorylated anabolites formed in PBMC, hepatocytes, and RBC in vivo during SOF therapy. Median concentrations in PBMC were 220 (range, 51.5 to 846), 70.2 (range, 25.8 to 275), and 859 (range, 54.5 to 6,756) fmol/10 6 cells in the monophosphate, diphosphate, and triphosphate fractions, respectively. In contrast, RBC triphosphate concentrations were much lower than those of PBMC, as the median concentration was 2.91 (range, 1.14 to 10.4) fmol/10 6 cells. The PBMC triphosphate half-life was estimated at 26 h using noncompartmental approaches, while nonlinear mixed-effect modeling was used to estimate a 69 h half-life for this moiety in RBC. The validated method and the data it generates provide novel insight into the cellular disposition of SOF and its phosphorylated anabolites in vivo .

The recent epidemic of Zika virus (ZIKV) in the Americas and its association with fetal and neurological complications has shown the need to develop a treatment. Repurposing of drugs that are already FDA approved or in clinical development may shorten drug development timelines in case of emerging viral diseases like ZIKV. Initial studies have shown conflicting results when testing sofosbuvir developed for treatment of infections with another Flaviviridae virus, hepatitis C virus. We hypothesized that the conflicting results could be explained by differences in intracellular processing of the compound. We assessed the antiviral activity of sofosbuvir and mericitabine against ZIKV using Vero, A549, and Huh7 cells and measured the level of the active sofosbuvir metabolite by mass spectrometry. Mericitabine did not show activity, while sofosbuvir inhibited ZIKV with an IC50 of ∼4 μM, but only in Huh7 cells. This correlated with differences in intracellular concentration of the active triphosphate metabolite of sofosbuvir, GS-461203 or 007-TP, which was 11–342 times higher in Huh7 cells compared to Vero and A549 cells. These results show that a careful selection of cell system for repurposing trials of prodrugs is needed for evaluation of antiviral activity. Furthermore, the intracellular levels of 007-TP in tissues and cell types that support ZIKV replication in vivo should be determined to further investigate the potential of sofosbuvir as anti-ZIKV compound.

Long-acting (LA) pre-exposure prophylaxis (PrEP) for HIV prevention is poised to address non-adherence and implementation challenges by alleviating the burden of user-dependent dosing. Due to its potency, tenofovir alafenamide (TAF) is a viable candidate for LA PrEP. However, the inherent hydrolytic instability of TAF presents a challenge for application in LA systems. In this work, we examined the mechanism of TAF hydrolysis in a reservoir-based implant system and characterized TAF degradation kinetics as a function of the solution pH. We determined a pH “stability window” between pH 4.8 – 5.8 in which TAF degradation is substantially mitigated, with minimal degradation at pH 5.3. In a pursuit of a TAF formulation suitable for LA PrEP, we studied trans-urocanic acid (UA) as a buffer excipient. Here we show that UA can maintain the pH of TAF free base (TAFfb) solution inside a surrogate implant model at approximately pH 5.4. Through in vitro analysis, we demonstrated preservation of released TAF purity above 90% for over 9 months. Further, we performed an in vivo assessment of TAFfb-UA formulation in a reservoir-based nanofluidic implant inserted subcutaneously in non-human primates. Preventive levels of tenofovir diphosphate above 100 fmol/106 peripheral blood mononuclear cells were achieved in 2 days and sustained over 35 days. Fluid retrieved from implants after 60 days of implantation showed that UA preserved the aqueous phase in the implant at ~ pH 5.5, effectively counteracting the neutralizing action of interstitial fluids. Moreover, residual TAF in the implants maintained > 98% purity. Overall, TAF-UA represents a viable formulation applicable for LA HIV PrEP.

Inadequate adherence to chronic medications is a far-reaching problem with financial and human health consequences. By a wide margin, non-adherence is the leading cause of therapeutic failures of HIV pre-exposure chemoprophylaxis (PrEP) and antiretroviral therapy (ART). It has been proven that HIV infection can be prevented by daily dosing of emtricitabine and tenofovir disoproxil fumarate. Measurement of intracellular tenofovir diphosphate in red blood cells has been established as an effective way to assess cumulative adherence, however, the LC-MS-based analytical method developed for the purpose is both complicated and expensive. Here, we report a simple method for adherence monitoring based on direct MS quantification of intracellular tenofovir diphosphate in human whole blood. The method requires only microliters of whole blood, employs special membranes to perform plasma separation and concomitant desalting during blood collection, and uses nanoelectrospray on a triple quadrupole instrument. Quantitative performance in this proof-of-concept study includes RSDs of < 15% and successful analysis of a small number of patient samples with medium to high adherence levels. The results correlate with those of a validated LC-MS/MS method, and an R(2) value of 0.9962 is achieved. This methodology has promise for extension to point-of-care testing using miniature mass spectrometers.

BackgroundIntracellular tenofovir diphosphate concentrations are markedly increased in HIV/HCV coinfected individuals receiving tenofovir disoproxil fumarate (TDF) with sofosbuvir-containing treatment. Sofosbuvir may inhibit the hydrolysis of TDF to tenofovir, resulting in increased concentrations of the disoproxil or monoester forms, which may augment cell loading. We sought to quantify tenofovir disoproxil and monoester concentrations in individuals receiving TDF with and without ledipasvir/sofosbuvir.MethodsHIV/HCV coinfected participants receiving TDF-based therapy were sampled pre-dose and 1 and 4 h post-dose prior to and 4 weeks after initiating ledipasvir/sofosbuvir. Tenofovir disoproxil was not detectable. Tenofovir monoester in plasma and tenofovir diphosphate in PBMC and dried blood spots (DBS) were quantified using LC-MS/MS. Geometric mean ratios (week 4 versus baseline) and 95% CIs were generated for the pharmacokinetic parameters. P values reflect paired t-tests.ResultsTen participants had complete data. At baseline, geometric mean (95% CI) tenofovir monoester plasma concentrations at 1 and 4 h post-dose were 97.4 ng/mL (33.0–287.5) and 0.74 ng/mL (0.27–2.06), respectively. With ledipasvir/sofosbuvir, tenofovir monoester concentrations at 4 h post-dose were 5.02-fold higher (95% CI 1.40–18.05; P = 0.019), but did not significantly differ at 1 h post-dose (1.72-fold higher, 95% CI 0.25–11.78; P = 0.54), possibly due to absorption variability. Tenofovir diphosphate in PBMC and DBS were increased 2.80-fold (95% CI 1.71–4.57; P = 0.001) and 7.31-fold (95% CI 4.47–11.95; P ConclusionsTenofovir monoester concentrations were increased in individuals receiving TDF with ledipasvir/sofosbuvir, consistent with inhibition of TDF hydrolysis. Additional studies are needed to determine the clinical relevance of this interaction.

Background Tenofovir monoester is a relatively lipophilic intermediate formed during the hydrolysis of tenofovir disoproxil to tenofovir. Its clinical pharmacokinetic profile and influence on the cellular pharmacology of tenofovir diphosphate have not been reported. Methods Plasma, PBMC and dried blood spots (DBS) were obtained from HIV-uninfected adults participating in a randomized, cross-over bioequivalence study of single-dose tenofovir disoproxil fumarate (TDF)/emtricitabine unencapsulated or encapsulated with a Proteus® ingestible sensor. Plasma pharmacokinetics of tenofovir monoester and tenofovir were characterized using non-compartmental methods. Relationships with tenofovir diphosphate in DBS and PBMC were examined using mixed-effects models. Results Samples were available from 24 participants (13 female; 19 white, 3 black, 2 Hispanic). Tenofovir monoester appeared rapidly with a median (range) Tmax of 0.5 h (0.25–2) followed by a rapid monophasic decline with a geometric mean (coefficient of variation) t½ of 26 min (31.0%). Tenofovir monoester Cmax was 131.6 ng/mL (69.8%) and AUC0–4 was 93.3 ng·h/mL (47.9%). The corresponding values for plasma tenofovir were 222.2 ng/mL (37.1%) and 448.1 ng·h/mL (30.0%). Tenofovir monoester AUC0–∞ (but not tenofovir AUC0–∞) was a significant predictor of tenofovir diphosphate in both PBMC (P = 0.015) and DBS (P = 0.005), increasing by 3.8% (95% CI 0.8%–6.8%) and 4.3% (95% CI 1.5%–7.2%), respectively, for every 10 ng·h/mL increase in tenofovir monoester. Conclusions Tenofovir monoester Cmax and AUC0–4 were 59.2% and 20.6% of corresponding plasma tenofovir concentrations. Tenofovir monoester was significantly associated with intracellular tenofovir diphosphate concentrations in PBMC and DBS, whereas tenofovir concentrations were not. Tenofovir monoester likely facilitates cell loading, thereby increasing tenofovir diphosphate exposures in vivo.

BACKGROUND: The nucleotide analogues tenofovir and sofosbuvir are considered to have low potential for drug interactions. OBJECTIVES: To determine the effect of sofosbuvir-based HCV treatment on plasma concentrations of tenofovir and cellular concentrations of tenofovir diphosphate. METHODS: HIV-infected participants with acute HCV were treated for 12 weeks with sofosbuvir + ribavirin in Cohort 1 or 8 weeks with ledipasvir/sofosbuvir in Cohort 2 of AIDS Clinical Trials Group study 5327. Only participants taking tenofovir disoproxil fumarate were included in this analysis. Tenofovir in plasma, tenofovir diphosphate in dried blood spots and tenofovir diphosphate in PBMCs were measured pre-HCV therapy and longitudinally during the study using validated LC/MS-MS. RESULTS: Fifteen and 22 men completed Cohorts 1 and 2, respectively. In Cohort 1, tenofovir diphosphate was 4.3-fold higher (95% CI geometric mean ratio 2.46–7.67; P = 0.0001) in dried blood spots and 2.3-fold higher (95% CI 1.09–4.92; P = 0.03) in PBMCs following 12 weeks of sofosbuvir + ribavirin versus study entry. Tenofovir in the plasma was unchanged. In Cohort 2, tenofovir diphosphate was 17.8-fold higher (95% CI 12.77–24.86; P

Tenofovir disoproxil fumarate/emtricitabine preexposure prophylaxis (PrEP) is effective against HIV acquisition when taken as prescribed. Strategies that identify and intervene with those challenged by adherence to daily medication are needed.PATH-PrEP was an open-label single-arm interventional cohort study conducted at 2 community-based clinical sites in Los Angeles, CA.We enrolled self-identified men who have sex with men and transgender women ≥18 years of age at an elevated risk of HIV acquisition. Participants received a postexposure prophylaxis (PEP)-based or PrEP-based HIV prevention package for at least 48 weeks. Plasma tenofovir levels from each PrEP visit assessed as below the limit of quantitation (10 ng/mL) triggered increased adherence support.Three hundred one participants enrolled. Forty-eight-week retention in the PrEP cohort was 75.1%. Biomarker evidence of PrEP adherence consistent with ≥4 doses per week at weeks 4, 12, 24, 36, and 48 was found in 83.1%, 83.4%, 75.7%, 71.6%, and 65.5% of participants, respectively; younger and African American participants were less likely to have protective drug levels. Most of those with suboptimal adherence had adherence improvement after brief intervention. One seroconversion occurred in a participant who discontinued PrEP. Nearly half (46.4%) of participants were diagnosed with at least 1 incident sexually transmitted infection during 48 weeks of study follow-up.PrEP was acceptable and well tolerated in a diverse population of men who have sex with men in Los Angeles. A brief intervention triggered from biomarkers of poor adherence was associated with improved adherence. Drug level monitoring has the potential to allow targeting of additional adherence support to those struggling with daily tablet adherence.