Single-dose pharmacokinetics and pharmacodynamics of oral tenofovir and emtricitabine in blood, saliva and rectal tissue: a sub-study of the ANRS IPERGAY trial

Whole-body distribution of tenofovir, emtricitabine and dolutegravir in non-human primates

BACKGROUND

One major barrier to HIV cure is the persistence of virus, possibly linked to an insufficient antiretroviral drug (ARV) distribution into tissues.

OBJECTIVES

To draw the whole-body distribution of three antiretroviral drugs-tenofovir disoproxil fumarate, emtricitabine and dolutegravir-in non-human primates (NHPs).

METHODS

Eight uninfected NHPs received a single injection of a solution containing the three ARVs. Forty-five different tissues were sampled 24 h after injection.

RESULTS

Median tissue penetration factors (TPFs) were 45.4, 5.8 and 0.5 for tenofovir, emtricitabine and dolutegravir, respectively, and were statistically different between the three ARVs. Tissues were grouped by system, because TPFs were consistent according to these groups, and ranked in order of decreasing TPFs. The digestive system was the system with the highest tissue concentrations. Next came the two main sites of elimination, the liver and the kidney, as well as the tissues of the cardiopulmonary and urinary systems. Then, it was the whole lymphatic system. The next group included the reproductive system, the adipose tissue and the skin. The last two systems were the muscle and the CNS. The intra-tissue variability was rather low with a median coefficient of variation of the concentrations around 15% and no value greater than 80%.

CONCLUSIONS

Overall, this study determines the first whole-body distribution in a validated NHP model. These data have important implications for future preclinical and clinical studies for the development of novel HIV therapies towards an HIV cure.

Sustained HIV remission after allogeneic hematopoietic stem cell transplantation with wild-type CCR5 donor cells

HIV cure has been reported for five individuals who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) with cells from CCR5Δ32 homozygous donors. By contrast, viral rebound has occurred in other people living with HIV who interrupted antiretroviral treatment after undergoing allo-HSCT, with cells mostly from wild-type CCR5 donors. Here we report the case of a male individual who has achieved durable HIV remission following allo-HSCT with cells from an unrelated HLA-matched (9 of 10 matching for HLA-A, HLA-B, HLA-C, HLA-DRB1 and HLA-DQB1 alleles) wild-type CCR5 donor to treat an extramedullary myeloid tumor. To date, plasma viral load has remained undetectable for 32 months after the interruption of antiretroviral treatment. Treatment with ruxolitinib has been maintained during this period to treat chronic graft-versus-host disease. Low levels of proviral DNA were detected sporadically after allo-HSCT, including defective but not intact HIV DNA. No virus could be amplified in cultures of CD4+ T cells obtained after antiretroviral treatment interruption, while CD4+ T cells remained susceptible to HIV-1 infection in vitro. Declines in HIV antibodies and undetectable HIV-specific T cell responses further corroborate the absence of viral rebound after antiretroviral treatment interruption. These results suggest that HIV remission could be achieved in the context of allo-HSCT with wild-type CCR5.

Can we Predict Drug Excretion into Saliva? A Systematic Review and Analysis of Physicochemical Properties

BACKGROUND AND OBJECTIVES

Saliva is a patient-friendly matrix for therapeutic drug monitoring (TDM) but is infrequently used in routine care. This is due to the uncertainty of saliva-based TDM results to inform dosing. This study aimed to retrieve data on saliva-plasma concentration and subsequently determine the physicochemical properties that influence the excretion of drugs into saliva to increase the foundational knowledge underpinning saliva-based TDM.

METHODS

Medline, Web of Science and Embase (1974-2023) were searched for human clinical studies, which determined drug pharmacokinetics in both saliva and plasma. Studies with at least ten subjects and five paired saliva-plasma concentrations per subject were included. For each study, the ratio of the area under the concentration-time curve between saliva and plasma was determined to assess excretion into saliva. Physicochemical properties of each drug (e.g. pKa, lipophilicity, molecular weight, polar surface area, rotatable bonds and fraction of drug unbound to plasma proteins) were obtained from PubChem and Drugbank. Drugs were categorised by their ionisability, after which saliva-to-plasma ratios were predicted with adjustment for protein binding and physiological pH via the Henderson-Hasselbalch equation. Spearman correlation analyses were performed for each drug category to identify factors predicting saliva excretion (α = 5%). Study quality was assessed by the risk of bias in non-randomised studies of interventions tool.

RESULTS

Overall, 42 studies including 40 drugs (anti-psychotics, anti-microbials, immunosuppressants, anti-thrombotic, anti-cancer and cardiac drugs) were included. The median saliva-to-plasma ratios were similar for drugs in the amphoteric (0.59), basic (0.43) and acidic (0.41) groups and lowest for drugs in the neutral group (0.21). Higher excretion of acidic drugs (n = 5) into saliva was associated with lower ionisation and protein binding (correlation between predicted versus observed saliva-to-plasma ratios: R2 = 0.85, p = 0.02). For basic drugs (n = 21), pKa predicted saliva excretion (Spearman correlation coefficient: R = 0.53, p = 0.02). For amphoteric drugs (n = 10), hydrogen bond donor (R = - 0.76, p = 0.01) and polar surface area (R = - 0.69, p = 0.02) were predictors. For neutral drugs (n = 10), protein binding (R = 0.84, p = 0.004), lipophilicity (R = - 0.65, p = 0.04) and hydrogen bond donor count (R = - 0.68, p = 0.03) were predictors. Drugs considered potentially suitable for saliva-based TDM are phenytoin, tacrolimus, voriconazole and lamotrigine. The studies had a low-to-moderate risk of bias.

CONCLUSIONS

Many commonly used drugs are excreted into saliva, which can be partly predicted by a drug's ionisation state, protein binding, lipophilicity, hydrogen bond donor count and polar surface area. The contribution of drug transporters and physiological factors to the excretion needs to be evaluated. Continued research on drugs potentially suitable for saliva-based TDM will aid in adopting this person-centred TDM approach to improve patient outcomes.

Ex-vivo rectal tissue infection with HIV-1 to assess time to protection following oral preexposure prophylaxis with tenofovir disoproxil/emtricitabine

OBJECTIVES

We wished to assess time to protection from HIV-1 infection following oral tenofovir disoproxil and emtricitabine (TDF/FTC) as preexposure prophylaxis (PrEP), using ex-vivo rectal tissue infections and drug concentration measures in blood and rectal tissue.

DESIGN/METHODS

Participants from the ANRS PREVENIR study (NCT03113123) were offered this sub-study after a 14-day wash-out. We used an ex-vivo model to evaluate rectal tissue HIV-1 susceptibility before and after PrEP, 2 h after two pills or 7 days of a daily pill of TDF/FTC. PrEP efficacy was expressed by the difference (after-before) of 14-day cumulative p24 antigen levels. TFV-DP and FTC-TP levels were measured in rectal tissue and PBMCs and correlated with HIV-1 infection.

RESULTS

Twelve and 11 men were analyzed in the 2 h-double dose and 7 days-single dose groups, respectively. Cumulative p24 differences after-before PrEP were -144 pg/ml/mg (IQR[-259;-108]) for the 2 h-double dose group ( P  = 0.0005) and -179 pg/ml/mg (IQR [-253;-86]) for the 7 days-single dose group ( P  = 0.001), with no differences between groups ( P  = 0.93). Rectal TFV-DP was below quantification after a double dose, but FTC-TP levels were similar to levels at 7 days. There was a significant correlation between rectal FTC-TP levels and p24 changes after a double dose ( R  = -0.84; P  = 0.0001).

CONCLUSION

Oral TDF/FTC provided similar protection against HIV-1 infection of rectal tissue 2 h after a double dose or 7 days of a daily dose. At 2 h, this protection seems driven by high FTC-TP concentrations in rectal tissue. This confirms the importance of combining TDF and FTC to achieve early protection.

Cytosolic 5'-Nucleotidase III and Nucleoside Triphosphate Diphosphohydrolase 1 Dephosphorylate the Pharmacologically Active Metabolites of Gemcitabine and Emtricitabine

Gemcitabine (dFdC) and emtricitabine (FTC) are first-line drugs that are used for the treatment of pancreatic cancer and human immunodeficiency virus, respectively. The above drugs must undergo sequential phosphorylation to become pharmacologically active. Interindividual variability associated with the responses of the above drugs has been reported. The molecular mechanisms underlying the observed variability are yet to be elucidated. Although this could be multifactorial, nucleotidases may be involved in the dephosphorylation of drug metabolites due to their structural similarity to endogenous nucleosides. With these in mind, we performed in vitro assays using recombinant nucleotidases to assess their enzymatic activities toward the metabolites of dFdC and FTC. From the above in vitro experiments, we noticed the dephosphorylation of dFdC-monophosphate in the presence of two 5'-nucleotidases (5'-NTs), cytosolic 5'-nucleotidase IA (NT5C1A) and cytosolic 5'-nucleotidase III (NT5C3), individually. Interestingly, FTC monophosphate was dephosphorylated only in the presence of NT5C3 enzyme. Additionally, nucleoside triphosphate diphosphohydrolase 1 (NTPDase 1) exhibited enzymatic activity toward both triphosphate metabolites of dFdC and FTC. Enzyme kinetic analysis further revealed Michaelis-Menten kinetics for both NT5C3-mediated dephosphorylation of monophosphate metabolites, as well as NTPDase 1-mediated dephosphorylation of triphosphate metabolites. Immunoblotting results confirmed the presence of NT5C3 and NTPDase 1 in both pancreatic and colorectal tissue that are target sites for dFdC and FTC treatment, respectively. Furthermore, sex-specific expression patterns of NT5C3 and NTPDase 1 were determined using mass spectrometry-based proteomics approach. Based on the above results, NT5C3 and NTPDase 1 may function in the control of the levels of dFdC and FTC metabolites. SIGNIFICANCE STATEMENT: Emtricitabine and gemcitabine are commonly used drugs for the treatment of human immunodeficiency virus and pancreatic cancer. To become pharmacologically active, both the above drugs must be phosphorylated. The variability in the responses of the above drugs can lead to poor clinical outcomes. Although the sources of drug metabolite concentration variability are multifactorial, it is vital to understand the role of nucleotidases in the tissue disposition of the above drug metabolites due to their structural similarities to endogenous nucleosides.

Salivary Therapeutic Drug Monitoring of Antimicrobial Therapy: Feasible or Futile?

Personalised drug dosing through therapeutic drug monitoring (TDM) is important to maximise efficacy and to minimise toxicity. Hurdles preventing broad implementation of TDM in routine care include the need of sophisticated equipment and highly trained staff, high costs and lack of timely results. Salivary TDM is a non-invasive, patient-friendly alternative to blood sampling, which has the potential to overcome barriers with traditional TDM. A mobile UV spectrophotometer may provide a simple solution for analysing drug concentrations in saliva samples. Salivary TDM utilising point-of-care tests can support personalised dosing in various settings including low-resource as well as remote settings. In this opinion paper, we describe how hurdles of implementing traditional TDM may be mitigated by salivary TDM with new strategies for patient-friendly point-of-care testing.

Detection of unreported usage of the antiretroviral drug lamivudine in two blood donors

BACKGROUND

Unreported HIV antiretroviral (ARV) drug usage by blood donors compromises the ability to detect evidence of HIV infection in blood screening tests and represents a risk for blood transfusion safety. Our objective was to determine the frequency of undeclared ARV drug use by blood donors with altered HIV markers.

STUDY DESIGN AND METHODS

This was a retrospective cross-sectional analysis of donations that were tested for HIV antibody (ab), antigen (ag), and RNA by chemiluminescent immunoassay and nucleic acid screening tests. Positive samples were retested and were subjected to ARV drug testing by high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

Of 345,252 blood donations, 361 (0.1%) were positive on initial testing. Samples from 296 (81.9%) of these donations were available for further analysis. The presence of HIV ab/ag and/or RNA was confirmed in 83 (28.0%) of these samples. All 296 bloods were subjected to ARV testing. The ARV drug lamivudine, at 11.3 and 6.7 ng/mL, was detected in 2 of 83 (2.4%) donations that were HIV positive. Other drugs were not detected.

CONCLUSION

Unreported ARV usage was identified in two candidates for blood donation. More intensive efforts to educate donors about disclosure and to investigate the extent of this phenomenon in Brazil are needed.

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

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

Dose finding study for on-demand HIV pre-exposure prophylaxis for insertive sex in sub-Saharan Africa: results from the CHAPS open label randomised controlled trial

BACKGROUND

The efficacy of on-demand HIV pre-exposure prophylaxis (PrEP) for men in sub-Saharan Africa has not been evaluated, and the on-demand PrEP dosing requirement for insertive sex remains unknown.

METHODS

HIV-negative males 13-24 years, requesting voluntary medical male circumcision (VMMC), were enrolled into an open-label randomised controlled trial (NCT03986970), and randomised 1:1:1:1:1:1:1:1:1 to control arm or one of eight arms receiving emtricitabine-tenofovir disoproxil fumarate (F/TDF) or emtricitabine-tenofovir alafenamide (F/TAF) over one or two days, and circumcised 5 or 21 h thereafter. The primary outcome was foreskin p24 concentrations following ex vivo HIV-1BaL challenge. Secondary outcomes included peripheral blood mononuclear cell (PBMC) p24 concentration, and drug concentrations in foreskin tissue, PBMCs, plasma and foreskin CD4+/CD4-cells. In the control arm, post-exposure prophylaxis (PEP) activity of non-formulated tenofovir-emtricitabine (TFV-FTC) or TAF-FTC was assessed with ex vivo dosing 1, 24, 48 or 72 h post-HIV-1 challenge.

FINDINGS

144 participants were analysed. PrEP with F/TDF or F/TAF prevented ex vivo infection of foreskins and PBMCs both 5 and 21 h after PrEP dosing. There was no difference between F/TDF and F/TAF (p24day15 geometric mean ratio 1.06, 95% confidence interval: 0.65-1.74). Additional ex vivo dosing did not further increase inhibition. In the control arm, PEP ex vivo dosing was effective up to 48 post-exposure diminishing thereafter, with TAF-FTC showing prolonged protection compared to TFV-FTC. Participants receiving F/TAF had higher TFV-DP concentrations in foreskin tissue and PBMCs compared with F/TDF, irrespective of dose and sampling interval; but F/TAF did not confer preferential TFV-DP distribution into foreskin HIV target cells. FTC-TP concentrations with both drug regimens were equivalent and ∼1 log higher than TFV-DP in foreskin.

INTERPRETATION

A double dose of either F/TDF or F/TAF given once either 5 or 21 h before ex vivo HIV-challenge provided protection across foreskin tissue. Further clinical evaluation of pre-coital PrEP for insertive sex is warranted.

FUNDING

EDCTP2, Gilead Sciences, Vetenskapsrådet.

Development and In-House Validation of an Enzyme-Linked Immunosorbent Assay and a Lateral Flow Immunoassay for the Dosage of Tenofovir in Human Saliva

Highly active antiretroviral therapy (HAART) includes very potent drugs that are often characterized by high toxicity. Tenofovir (TFV) is a widely used drug prescribed mainly for pre-exposure prophylaxis (PreP) and the treatment of human immunodeficiency virus (HIV). The therapeutic range of TFV is narrow, and adverse effects occur with both underdose and overdose. The main factor contributing to therapeutic failure is the improper management of TFV, which may be caused by low compliance or patient variability. An important tool to prevent inappropriate administration is therapeutic drug monitoring (TDM) of compliance-relevant concentrations (ARCs) of TFV. TDM is performed routinely using time-consuming and expensive chromatographic methods coupled with mass spectrometry. Immunoassays, such as enzyme-linked immunosorbent assays (ELISAs) and lateral flow immunoassays (LFIAs), are based on antibody-antigen specific recognition and represent key tools for real-time quantitative and qualitative screening for point-of-care testing (POCT). Since saliva is a non-invasive and non-infectious biological sample, it is well-suited for TDM. However, saliva is expected to have a very low ARC for TFV, so tests with high sensitivity are required. Here, we have developed and validated a highly sensitive ELISA (IC50 1.2 ng/mL, dynamic range 0.4-10 ng/mL) that allows the quantification of TFV in saliva at ARCs and an extremely sensitive LFIA (visual LOD 0.5 ng/mL) that is able to distinguish between optimal and suboptimal ARCs of TFV in untreated saliva.

Between- and Within-Individual Sociodemographic and Psychological Determinants of PrEP Adherence Among Men Who have Sex with Men Prescribed a Daily PrEP Regimen in Wales

We investigated the determinants of daily PrEP use and coverage of condomless anal sex (CAS) by PrEP among men who have sex with men in Wales, UK. We measured PrEP use by electronic monitors and CAS by secure online surveys. We defined PrEP use based on daily medication cap openings and coverage as CAS episodes preceded by ≥ 3 days of PrEP use and followed by ≥ 2 days of PrEP use. We included 57 participants (5463 observations). An STI diagnosis was associated with lower PrEP use but also lower PrEP coverage. Older adults had higher PrEP use. A belief that other PrEP users took PrEP as prescribed was associated with lower PrEP coverage. An STI diagnosis is an important cue for an intervention, reflecting episodes of high-risk sexual behaviour and low PrEP coverage. Other results provide a basis for the development of an evidence-informed intervention for promoting coverage of PrEP.

Mucosal Responses to Zika Virus Infection in Cynomolgus Macaques

Zika virus (ZIKV) cases continue to be reported, and no vaccine or specific antiviral agent has been approved for the prevention or treatment of infection. Though ZIKV is primarily transmitted by mosquitos, cases of sexual transmission and prolonged viral RNA presence in semen have been reported. In this observational study, we report the mucosal responses to sub-cutaneous and mucosal ZIKV exposure in cynomolgus macaques during acute and late chronic infection. Subcutaneous challenge induced a decrease in the growth factor VEGF in colorectal and cervicovaginal tissues 100 days post-challenge, in contrast to the observed increase in these tissues following vaginal infection. This different pattern was not observed in the uterus, where VEGF was upregulated independently of the challenge route. Vaginal challenge induced a pro-inflammatory profile in all mucosal tissues during late chronic infection. Similar responses were already observed during acute infection in a vaginal tissue explant model of ex vivo challenge. Non-productive and productive infection 100 days post-in vivo vaginal challenge induced distinct proteomic profiles which were characterized by further VEGF increase and IL-10 decrease in non-infected animals. Ex vivo challenge of mucosal explants revealed tissue-specific modulation of cytokine levels during the acute phase of infection. Mucosal cytokine profiles could represent biosignatures of persistent ZIKV infection.

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

Background

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

Methods

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

Results

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

Conclusions

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

Pre-Clinical Evaluation of Tenofovir and Tenofovir Alafenamide for HIV-1 Pre-Exposure Prophylaxis in Foreskin Tissue

Background: HIV-1 pre-exposure prophylaxis (PrEP) has focused predominantly on protective efficacy in receptive sex, with limited research on the dosing requirements for insertive sex. We pre-clinically assessed the ex vivo pharmacokinetic–pharmacodynamic (PK–PD) profile of tenofovir (TFV) and tenofovir alafenamide (TAF) in foreskin tissue. Methods: Inner and outer foreskin explants were exposed to serial dilutions of TFV or TAF prior to addition of HIV-1_BaL at a high (HVT) or a low viral titer (LVT). Infection was assessed by measurement of p24 in foreskin culture supernatants. TFV, TAF and TFV–diphosphate (TFV–DP) concentrations were measured in tissues, culture supernatants and dosing and washing solutions. Results: Dose–response curves were obtained for both drugs, with greater potency observed against LVT. Inhibitory equivalency mimicking oral dosing was defined between 1 mg/mL of TFV and 15 µg/mL of TAF against HVT challenge. Concentrations of TFV–DP in foreskin explants were approximately six-fold higher after ex vivo dosing with TAF than with TFV. Statistically significant negative linear correlations were observed between explant levels of TFV or TFV–DP and p24 concentrations following HVT. Conclusions: Pre-clinical evaluation of TAF in foreskin explants revealed greater potency than TFV against penile HIV transmission. Clinical evaluation is underway to support this finding.

PrEP Use, Sexual Behaviour, and PrEP Adherence Among Men who have Sex with Men Living in Wales Prior to and During the COVID-19 Pandemic

We examined PrEP use, condomless anal sex (CAS), and PrEP adherence among men who have sex with men (MSM) attending sexual health clinics in Wales, UK. In addition, we explored the association between the introduction of measures to control transmission of SARS-CoV-2 on these outcomes. We conducted an ecological momentary assessment study of individuals in receipt of PrEP in Wales. Participants used an electronic medication cap to record PrEP use and completed weekly sexual behaviour surveys. We defined adherence to daily PrEP as the percentage of CAS episodes covered by daily PrEP (preceded by ≥ 3 days of PrEP and followed by ≥ 2 days). Sixty participants were recruited between September 2019 and January 2020. PrEP use data prior to the introduction of control measures were available over 5785 person-days (88%) and following their introduction 7537 person-days (80%). Data on CAS episodes were available for 5559 (85%) and 7354 (78%) person-days prior to and following control measures respectively. Prior to the introduction of control measures, PrEP was taken on 3791/5785 (66%) days, there were CAS episodes on 506/5559 (9%) days, and 207/406 (51%) of CAS episodes were covered by an adequate amount of daily PrEP. The introduction of pandemic-related control measures was associated with a reduction in PrEP use (OR 0.44, 95%CI 0.20–0.95), CAS (OR 0.35, 95%CI 0.17–0.69), and PrEP adherence (RR = 0.55, 95%CI 0.34–0.89) and this may have implications for the health and wellbeing of PrEP users and, in addition to disruption across sexual health services, may contribute to wider threats across the HIV prevention cascade.

Estimated pill intake with on-demand PrEP with oral TDF/FTC using TFV-DP concentration in dried blood spots in the ANRS IPERGAY trial

BACKGROUND

Tenofovir diphosphate (TFV-DP) concentration in dried blood spots (DBSs) is a reliable pharmacokinetics biomarker of adherence to tenofovir disoproxil fumarate (TDF). We aimed to use DBSs to estimate pill intake among participants using on-demand pre-exposure prophylaxis (PrEP) and to identify predictive factors associated with higher TFV-DP concentrations.

METHODS

DBSs were collected at the last study visit of the open-label phase of the ANRS IPERGAY study, assessing on-demand oral TDF/emtricitabine for PrEP among MSM and transgender female participants. We quantified TFV-DP in DBSs centrally. We assessed correlation between pill count and TFV-DP concentration by Spearman correlation and explored associations between participant demographics, sexual behaviour and PrEP use during sexual intercourse (SI) with TFV-DP concentrations by univariate and multivariate logistic regression models.

RESULTS

The median age of the 245 participants included in this study was 40 years, with a median body weight of 73 kg. Median (IQR) TFV-DP concentration reached 517 (128-868) fmol/punch, corresponding to an estimated intake of 8-12 tablets per month (2-3 doses per week). Only 39% of participants had a TFV-DP concentration above 700 fmol/punch. TFV-DP concentrations were moderately correlated with pill count (r: 0.59; P < 0.001). In multivariate analysis, only systematic use of PrEP during SI and more frequent episodes of SI in the past 4 weeks were significantly associated with higher TFV-DP levels [OR (95% CI): 11.30 (3.62-35.33) and 1.46 (1.19-1.79), respectively; P < 0.001].

CONCLUSIONS

Among participants using on-demand PrEP, estimated pill intake reached 8-12 tablets per month and was correlated with frequency and systematic use of PrEP for SI.

Two-dose emtricitabine/tenofovir alafenamide plus bictegravir prophylaxis protects macaques against SHIV infection

OBJECTIVES

Current prophylaxis options for people at risk for HIV infection include two US FDA-approved daily pre-exposure prophylaxis (PrEP) regimens and guidelines for a 2-1-1 event-driven course specifically for men who have sex with men. Despite this, PrEP use rates remain suboptimal, and additional PrEP options may help to improve uptake among diverse populations. Here, we evaluated protective efficacy of two-dose PrEP and two-dose postexposure prophylaxis (PEP) schedules with emtricitabine (FTC)/tenofovir alafenamide (TAF) with or without bictegravir (BIC) in an SHIV macaque model.

METHODS

Macaques received one oral dose of 200 mg emtricitabine, 25 mg tenofovir alafenamide and 25-100 mg of bictegravir to establish pharmacokinetic profiles of each drug either in the plasma or the peripheral blood mononuclear cells. Protective efficacy of multiple two-dose PrEP and PEP schedules with FTC/TAF with or without bictegravir was then assessed in two repeat low-dose rectal SHIV challenge studies.

RESULTS

The data revealed over 95% per-exposure risk reduction with FTC/TAF PrEP initiated 2 h before the exposure, but a loss of significant protection with treatment initiation postexposure. In contrast, FTC/TAF plus BIC offered complete protection as PrEP and greater than 80% per-exposure risk reduction with treatment initiation up to 24 h postexposure.

CONCLUSIONS

Together, these results demonstrate that two-dose schedules can protect macaques against SHIV acquisition and highlight the protective advantage of adding the integrase inhibitor bictegravir to the reverse transcriptase inhibitors emtricitabine and tenofovir alafenamide as part of event-driven prophylaxis.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Inflammatory cytologic alterations in the oral epithelium associated with HIV pre-exposure prophylaxis: a preliminary study

OBJECTIVE

The objective of this study was to assess inflammatory cytologic alterations in the oral epithelium of patients on human immunodeficiency virus pre-exposure prophylaxis (PrEP).

MATERIAL AND METHODS

Epithelial cells from the buccal mucosa of 30 patients were collected by exfoliative cytology and were evaluated according to inflammatory cellular alterations: karyomegaly, bi- or multinucleation, karyopyknosis, karyorrhexis, perinuclear halo formation, metachromasia, cytoplasmic vacuolization, indistinct cytoplasmic border, keratinization, and atrophy. Epithelial cells were collected initially before PrEP onset (T1) and then after 30 days of PrEP use (T2). Two experienced cytopathologists independently analyzed the slides.

RESULTS

The nonparametric Wilcoxon test showed that there was a statistically significant increase in the number of cells with karyomegaly at T2 compared to T1 (P = .033). The other cellular alterations did not present with statistically significant differences between the 2 moments of evaluation (P > .05).

CONCLUSION

The increased number of oral epithelial cells with karyomegaly after 30 days of using PrEP suggests the presence of inflammatory alterations at this site.

Southern African guidelines on the safe, easy and effective use of pre-exposure prophylaxis: 2020

No abstract  available.

Coverage of Sex Acts by Event-Driven Pre-exposure Prophylaxis: A Sub-Study of the ANRS IPERGAY Trial

We assessed the coverage of sex acts by event-driven pre-exposure prophylaxis (ED-PrEP) over a 2-month period in 54 participants in the open label phase of the ANRS Ipergay trial. Participants received an electronic monitoring system device to record bottle openings. Self-questionnaires collected daily information on PrEP intake and sexual behavior. Intake was also estimated through returned pill counts. Full coverage of sex acts was defined as at least one pill taken both within 24 h before and within 48 h following sex. There was a strong correlation (r =  - 0.92) between the number of bottle openings and returned pill counts. During the study, 42 participants (78%) practiced ED-PrEP and 12 (22%) daily PrEP with bottle openings at least 5 days/week whatever their sexual activity. Out of the 154 reported receptive anal sex acts, 81% were condomless: among them, PrEP coverage was hight: 97% among those practicing daily PrEP and 82% among those using ED-PrEP.

Immunoassay for HIV Drug Metabolites Tenofovir and Tenofovir Diphosphate

Poor patient adherence to antiretroviral medication represents a major obstacle for managing disease and reducing rates of new HIV infections. The measurement of patient drug levels is the most objective method of determining adherence. Tenofovir and tenofovir diphosphate are metabolites of some of the most common HIV medications for treatment and prevention and can be quantified by mass spectrometry. Here, we report the development of a competitive enzyme linked immunoassay as a simplified approach for detecting tenofovir and tenofovir diphosphate. Monoclonal antibodies were produced by two tenofovir-hapten conjugates and screened for binding to immobilized tenofovir, and then for competition by tenofovir and tenofovir diphosphate. Antibody specificity was evaluated against adenosine phosphates, which are close structural analogs. We performed numerical simulations of reaction equilibrium to guide assay optimization. When used to evaluate spiked tenofovir in plasma and spiked tenofovir diphosphate in red blood cell lysate, the optimized assay had high sensitivity and specificity.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

INTRODUCTION

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

AREA COVERED

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

EXPERT OPINION

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

Changes in kidney function among men having sex with men starting on demand tenofovir disoproxil fumarate - emtricitabine for HIV pre-exposure prophylaxis

INTRODUCTION

Daily pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) is associated with a small but statistically significant decrease in estimated glomerular filtration rate (eGFR). We assessed the renal safety of on-demand PrEP with TDF/FTC in HIV-1 uninfected men.

METHODS

We used data from the randomized double-blind placebo-controlled ANRS-IPERGAY trial and its open-label extension conducted between February 2012 and June 2016 among HIV-uninfected MSM starting on-demand PrEP. Using linear mixed model, we evaluated the mean eGFR decline from baseline over time and determined risks factors associated with eGFR decline during the study.

RESULTS

During the blind phase, with a median follow-up of 9.4 months, the mean decline slope of eGFR from baseline was -0.88 and -1.53 mL/min/1.73 m2 per year in the placebo (n = 201) and the TDF/FTC group (n = 198) respectively, with a slope difference of 0.65 mL/min/1.73 m2 per year (p = 0.27). Including both phases, 389 participants started on-demand TDF/FTC with a median follow-up of 19.2 months and a mean decline of eGFR from baseline of -1.14 mL/min/1.73 m2 per year (p < 0.001). The slope of eGFR reduction was not significantly different in participants with baseline eGFR ≤ 90 mL/min/1.73 m2 (p = 0.44), age >40 years (p = 0.24) or hypertension (p = 0.21). There was a dose-response relationship between recent tenofovir exposure and lower eGFR when considering the number of pills taken in the two months prior the visit (eGFR difference of -0.88 mL/min/1.73 m2 between >15 pills/month vs. ≤15 pills/month, p < 0.01) or plasma tenofovir concentrations at the visit (eGFR difference compared to ≤2 ng/mL: >2 to ≤10ng/mL: -0.98 mL/min/1.73 m2 , >10 to ≤40ng/mL: -1.28 mL/min/1.73 m2 , >40 ng/mL: -1.82 mL/min/1.73 m2 , p < 0.001). Three participants discontinued TDF/FTC for eGFR < 60 mL/min/1.73 m2 during the OLE phase. No case of Fanconi syndrome was reported.

CONCLUSIONS

The renal safety of on-demand PrEP with TDF/FTC was good. The overall reduction and intermittent exposure to TDF/FTC may explain this good renal safety.

Inhibitory Effects of Probenecid on Pharmacokinetics of Tenofovir Disoproxil Fumarate and Emtricitabine for On-Demand HIV Preexposure Prophylaxis

In a randomized, crossover pharmacokinetic study in healthy volunteers (N = 14), a single dose of 2 g probenecid (PRO)-boosted 600 mg tenofovir disoproxil fumarate (TDF)/400 mg emtricitabine (FTC) (test (T) +PRO) was compared with the current on-demand HIV preexposure prophylaxis 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 area under the plasma concentration-time curve extrapolated to infinity (AUC_0-∞,SD ) of tenofovir (TFV) and FTC by 61% and 68%, respectively. The TFV-diphosphate (TFV-DP) concentrations in peripheral blood mononuclear cells were higher (~30%) at 24 hours in T +PRO but then fell significantly lower (~40%) at 72 hours compared with C IPERGAY. The interaction between FTC and PRO was unexpected and novel. Further study is needed to determine if this PRO-boosted TDF/FTC regimen would be clinically effective.

On-demand pre-exposure prophylaxis with tenofovir disoproxil fumarate plus emtricitabine among men who have sex with men with less frequent sexual intercourse: a post-hoc analysis of the ANRS IPERGAY trial

BACKGROUND

ANRS IPERGAY found that on-demand pre-exposure prophylaxis (PrEP) with oral tenofovir disoproxil fumarate plus emtricitabine was associated with an 86% relative reduction of HIV-1 incidence compared with placebo among men who have sex with men at high risk of HIV. We aimed to investigate whether on-demand PrEP was similarly effective among individuals with lower exposure to HIV risk.

METHODS

Participants in the ANRS IPERGAY trial were randomly assigned to receive PrEP (fixed-dose combination of 300 mg tenofovir disoproxil fumarate and 200 mg emtricitabine per pill) or placebo. The primary endpoint was the diagnosis of HIV-1 infection. Pill uptake was assessed by counting returned pills at each follow-up and by estimating tenofovir concentration from frozen plasma samples. Participants were interviewed at each visit to assess the pattern of PrEP use. All participants enrolled in the modified intention-to-treat population of the double-blind phase of the ANRS IPERGAY trial were eligible for this post-hoc analysis. We calculated the total follow-up time for periods of less frequent sexual intercourse with high PrEP adherence (15 pills or fewer per month taken systematically or often during sexual intercourse). To estimate the time of HIV acquisition, fourth-generation HIV-1/2 ELISA assays, plasma HIV-1 RNA assays, and western blot analyses were done with use of frozen samples, and the stage of HIV infection was defined according to Fiebig staging. HIV incidence was compared between the two treatment groups among individuals who had less frequent sexual intercourse with high PrEP adherence. The ANRS IPERGAY trial is registered with ClinicalTrials.gov, NCT01473472.

FINDINGS

400 participants who were randomly assigned to receive PrEP (n=199) or placebo (n=201) between Feb 22, 2012, and Oct 17, 2014, were included in this analysis. 270 participants had at least one period of less frequent sexual intercourse with high PrEP adherence during the study, representing 134 person-years of follow-up and 31% of the total study follow-up. During these periods, participants in both groups reported a median of 5·0 (IQR 2·0-10·0) episodes of sexual intercourse per month and used a median of 9·5 (6·0-13·0) pills per month. Six HIV-1 infections were diagnosed in the placebo group (HIV incidence of 9·2 per 100 person-years; 95% CI 3·4-20·1) and none were diagnosed in the tenofovir disoproxil fumarate plus emtricitabine arm (HIV incidence of 0 per 100 person-years; 0-5·4; p=0·013), with a relative reduction of HIV incidence of 100% (95% CI 39-100).

INTERPRETATION

A choice between daily or on-demand PrEP regimens could be offered to men who have sex with men who have less frequent sexual intercourse.

FUNDING

ANRS (France Recherche Nord and Sud Sida-HIV Hépatites), the Canadian HIV Trials Network, Fonds Pierre Bergé (Sidaction), Gilead Sciences, and the Bill & Melinda Gates Foundation.

Pre-exposure Prophylaxis for HIV Infection in the Older Patient: What can be Recommended?

Over the past 15 years, a significant increase in new HIV/AIDS diagnoses has been observed in the elderly population. This new epidemiological shift has been attributed to a longer sex life, lifestyle and changes in sexual behavior, poor sexual health education, and misconceptions about the absence of sexually transmitted disease in later life. Although many biomedical and behavioral interventions have proven useful to prevent sexually transmitted infections and HIV, pre-exposure prophylaxis (PrEP) has been shown to be the most successful biomedical intervention to prevent HIV in high-risk individuals. This approach is based on delivering a fixed dose of tenofovir disoproxil fumarate (300 mg), alone or combined with emtricitabine (300/200 mg) daily or on demand, before and after sexual intercourse. Despite the consistent number of clinical trials proving the effectiveness and safety of this strategy, no studies have focused specifically on elderly people. These individuals, who may benefit substantially from (PrEP), are at a higher risk of experiencing side effects secondary to tenofovir exposure. This review critically discusses the efficacy and safety of PrEP in people aged over 50 years and translates the knowledge of tenofovir management in patients with HIV into monitoring and stopping rules to be used in this special population. We provide practical recommendations to properly identify PrEP candidates among older adults. Furthermore, we define correct case management before and during PrEP  delivery, and we suggest stopping rules and alternative sexually transmitted infection prevention strategies.

Semi-solid prodrug nanoparticles for long-acting delivery of water-soluble antiretroviral drugs within combination HIV therapies

The increasing global prevalence of human immunodeficiency virus (HIV) is estimated at 36.7 million people currently infected. Lifelong antiretroviral (ARV) drug combination dosing allows management as a chronic condition by suppressing circulating viral load to allow for a near-normal life; however, the daily burden of oral administration may lead to non-adherence and drug resistance development. Long-acting (LA) depot injections of nanomilled poorly water-soluble ARVs have shown highly promising clinical results with drug exposure largely maintained over months after a single injection. ARV oral combinations rely on water-soluble backbone drugs which are not compatible with nanomilling. Here, we evaluate a unique prodrug/nanoparticle formation strategy to facilitate semi-solid prodrug nanoparticles (SSPNs) of the highly water-soluble nucleoside reverse transcriptase inhibitor (NRTI) emtricitabine (FTC), and injectable aqueous nanodispersions; in vitro to in vivo extrapolation (IVIVE) modelling predicts sustained prodrug release, with activation in relevant biological environments, representing a first step towards complete injectable LA regimens containing NRTIs.

Non-adherence to daily drug regimens is responsible for many negative clinical effects including drug resistance in life-long treatments for HIV. Here, the authors report on a HIV prodrug nanoparticle platform for long-acting sustained release of water-soluble drug compounds following injection.

Drug resistance among patients who acquired HIV infection in a preexposure prophylaxis trial

BACKGROUND

The IPERGAY ANRS trial showed that on-demand preexposure prophylaxis (PrEP) with tenofovir (TDF) and emtricitabine (FTC) was highly effective in preventing HIV infection among highly exposed MSM. Here, we analyzed drug resistance-associated mutations (RAMs) among all participants who acquired HIV infection during this trial.

METHODS

Resistance was analyzed on frozen plasma at the time of HIV diagnosis among participants enrolled in the double-blind and open-label phases of the ANRS IPERGAY trial. Reverse transcriptase sequencing was performed, using population-based and ultradeep sequencing (454 GS Flex). Adherence was measured by pill counting and by plasma tenofovir and FTC assay.

RESULTS

During the trial, 31 participants were diagnosed with HIV-1 infection (subtype B, 64.5%), using antigen/antibody immune assay in 29 cases and plasma HIV RNA assay in two. The median plasma HIV-1 RNA level was 5.52 log10 copies/ml. Drug resistance was tested in 12 participants before starting PrEP, in six assigned to TDF/FTC group and in 13 assigned to placebo group. Primary resistance to nucleoside reverse transcriptase inhibitors (zidovudine) and/or nonnucleoside reverse transcriptase inhibitors was detected in six participants (19%; 95% confidence interval 7-42). No major or minor TDF-resistant or FTC-resistant variants were detected.

CONCLUSION

No TDF or FTC resistance-associated mutations were found among participants who acquired HIV in the ANRS IPERGAY trial.

PrEParing for the unexpected: mechanisms and management of HIV pre-exposure prophylaxis failure

Pre-exposure prophylaxis (PrEP) for HIV is a proven and effective tool for preventing HIV. However, there are instances where individuals taking PrEP have contracted HIV infection. Most of these cases are due to nonadherence to the drug, while other cases of apparent PrEP failure are due to unrecognized HIV infection at baseline. Importantly, there are also now at least three well-documented cases of PrEP failing despite adequate adherence; these are cases of PrEP ‘breakthrough’. This article outlines the potential mechanisms of PrEP failure, as well as how to identify and manage these patients. Finally, we provide a perspective on the future of PrEP as a key tool in preventing HIV worldwide.

Daily or on-demand oral tenofovir disoproxil fumarate/emtricitabine for HIV pre-exposure prophylaxis: experience from a hospital-based clinic in France

BACKGROUND

On-demand oral tenofovir disoproxil fumarate and emtricitabine (TDF/FTC) has been approved for pre-exposure prophylaxis (PrEP) in MSM in France following the results of clinical studies, but data are limited on real-world experience.

DESIGN

A single-center, open-label, prospective cohort study that recruited people at high risk of HIV infection in Paris.

METHODS

Participants were enrolled in a single hospital-based outpatient clinic and were proposed to start PrEP with daily or on demand TDF/FTC. At baseline and every 3 months thereafter, patients were tested for HIV and creatinine plasma levels, and data on sexual behavior, other sexually transmitted infections (STIs), and tolerability were collected.

RESULTS

From 10 November 2015 to 30 April 2017, 1069 patients were screened and 1049 (98.1%) started PrEP. Median age was 36 years, 99.4% were MSM with a median number of partners of 10, and 793 (75.6%) opted for on demand PrEP. Over 486 person-years of follow-up, four HIV-infections were diagnosed in poorly or nonadherent patients (incidence 0.82/100 person-years). Rate of condomless sex at last intercourse increased from 53.3% at baseline to 79% at month 12 (P < 10), but increase in bacterial STI rates was modest (14.6% at baseline vs. 19.2% at month 12; P < 10). Most adverse events were gastrointestinal and did not lead to PrEP discontinuation.

CONCLUSIONS

Most PrEP users were high-risk MSM and opted for on-demand PrEP. PrEP use was associated with a low HIV incidence and a high rate of condomless sex with a modest increase in bacterial STIs.

Acceptability of Injectable and On-Demand Pre-Exposure Prophylaxis Among an Online Sample of Young Men Who Have Sex with Men in California

PURPOSE

Pre-exposure prophylaxis (PrEP) is an effective strategy to prevent HIV. However, low uptake of daily oral PrEP since Food and Drug Administration approval and low medication adherence among users have stimulated the investigation of other modalities for delivery, such as injectable PrEP and on-demand PrEP. The objective of this study was to determine the demographic and behavioral predictors of willingness to try alternative PrEP delivery mechanisms among young men who have sex with men (YMSM) who stated that they were unwilling to try daily oral PrEP.

METHODS

YMSM in California were recruited through geosocial networking applications; we analyzed a subsample who stated that they were either ambivalent about trying or unwilling to try daily oral PrEP (n = 265). We used chi-square and Fisher's exact tests to determine characteristics associated with willingness to try injectable PrEP, willingness to try on-demand PrEP, and willingness to try either alternative form.

RESULTS

For individuals who stated that they would not be willing to try daily oral PrEP, ∼85% were willing to try on-demand and/or injectable PrEP. Individuals who reported some college or more reported greater willingness to try injectable PrEP (adjusted odds ratio [aOR]: 2.92; 95% confidence interval [CI]: 1.32-6.46), on-demand PrEP (aOR: 2.28; 95% CI: 1.06-4.90), or either method (aOR: 5.54; 95% CI: 1.78-17.22).

CONCLUSION

Future research should determine how to enhance uptake of emerging forms of PrEP among the individuals most at risk for HIV.

Intracellular Tenofovir-Diphosphate and Emtricitabine-Triphosphate in Dried Blood Spots following Directly Observed Therapy

Studies of daily emtricitabine-tenofovir disoproxil fumarate (FTC-TDF) for HIV preexposure prophylaxis (PrEP) in men who have sex with men (MSM) modeled intracellular tenofovir-diphosphate (TFV-DP) in dried blood spots (DBS) to assess adherence and corresponding PrEP outcomes. We conducted a prospective, randomized, crossover pharmacokinetic study of TFV-DP in DBS during 33%, 67%, or 100% of daily dosing under directly observed therapy (DOT). Participants were assigned to two 12-week dosing regimens, separated by a 12-week washout. Forty-eight adults (25 women) from Denver and San Francisco were included. TFV-DP exhibited a median half-life of 17 days, reaching steady state in 8 weeks. TFV-DP was dose proportional with mean (SD) steady-state concentrations of 530 (159), 997 (267), and 1,605 (405) fmol/punch for the 33%, 67%, and 100% arms, respectively. Prior work in MSM demonstrated clinically meaningful TFV-DP thresholds of 350, 700, and 1,250 fmol/punch, which were estimated 25th percentiles for 2, 4, and 7 doses/week. In the present study, corresponding TFV-DP was within 3% of the prior estimates, and subgroups by site, race, and sex were within 14% of prior estimates, although males had 17.6% (95% confidence intervals [CIs], 6.5, 27.4%) lower TFV-DP than females. The thresholds of 350, 700, and 1,250 fmol/punch were achieved by 75% of men taking ≥1.2, 3.2, and 6 doses/week and 75% of women taking ≥0.6, 2.0, and 5.3 doses/week, indicating that lower dosing reached these thresholds for both sexes. In conclusion, TFV-DP arising from DOT was similar to previous estimates and is useful for interpreting PrEP adherence and study outcomes. (This study has been registered at ClinicalTrials.gov under identifier NCT02022657.).