Dose response for starting and stopping HIV preexposure prophylaxis for men who have sex with men

Adherence and HIV Protection Thresholds for Emtricitabine and Tenofovir Disoproxil Fumarate Preexposure Prophylaxis among Cisgender Women: A Systematic Review

PURPOSE OF REVIEW

Adherence-concentration-efficacy benchmarks have not been fully characterized for cisgender women using emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) oral daily pre-exposure prophylaxis (PrEP) for HIV prevention.

RECENT FINDINGS

We conducted a systematic review to investigate current evidence on the adherence-concentration-efficacy relationship of tenofovir-diphosphate (TFV-DP) derived from FTC/TDF PrEP in dried blood spots (DBS) and peripheral mononuclear cells (PBMC) in cisgender women without HIV, including during pregnancy. We searched for completed and ongoing studies published before May 2024 in PubMed, Embase, Cochrane Library, CINAHL, and clinicaltrial.gov.  Overall, 11 studies assessing adherence benchmarks focusing on (n = 5) or involving (n = 6) cisgender women were included. Women-specific median steady-state TFV-DP concentration for daily dosing ranged from 17 to 51 fmol/106 in PBMC and 1389 to 1685 fmol/punch in DBS in non-pregnant women; 50 to 71 fmol/106 in PBMC and 583 to 965 fmol/punch in DBS in pregnant women; and 618 to 1406 fmol/punch in DBS in postpartum women. DBS TFV-DP levels were 14-43% lower in pregnancy versus postpartum or non-pregnant periods, but PBMC TFV-DP levels appear to be comparable. Clinical and modeling studies demonstrate effective HIV protection for women taking at least four doses/week of oral TDF-based PrEP, and emerging evidence suggests that systemic drug levels are more likely to be predictive of efficacy than local tissue levels at the site of exposure. The preponderance of emerging evidence points to comparable efficacy and similar adherence requirement for women as men among those with detectable drug levels, although there was an indication that the highest achievable efficacy may be reached at a lower adherence level in men than women. In this review, we found evidence that women-specific TFV-DP adherence benchmarks in DBS and PBMC are within range of US-based historical thresholds derived from healthy men and women. Emerging evidence suggests that imperfect but adequate adherence to oral FTC/TDF PrEP with at least four doses/week provides sufficient HIV protection in cisgender women as it does in MSM, but more data are still needed to refine intrinsic achievable efficacy estimates for cisgender women.

Gastroenterology healthcare in LGBTQ+ individuals

Lesbian, gay, bisexual, transgender, queer, or questioning individuals, as well as those with another diverse identity (LGBTQ+), present specific nuances in healthcare that physicians must consider in clinical practice. Particularly, gastroenterologists are nowadays facing different issues in several fields regarding LGBTQ+ healthcare, such as endoscopy, inflammatory bowel disease, hepatology, and proctology. In this study, the authors provide a practice-oriented and up-to-date review reinforcing the importance of some of the most prevalent pathologies associated with sexuality that gastroenterologists may encounter in their clinical practice. In terms of endoscopy, authors describe the endoscopic findings related to human papillomavirus (HPV) infection: the esophageal squamous papilloma and cell carcinoma; also highlight the importance of retroflexion maneuver during a routine colonoscopy that allows detection of anal intraepithelial neoplasia lesions that can be anal cancer precursors. Regarding inflammatory bowel disease, some considerations are made about the differential diagnosis with infectious proctitis, and the topic of the risk of anal cancer due to HPV infection, in this specific population, is also addressed. Considering hepatology, the authors review the most important issues related to hepatotropic sexually transmitted infections. The authors also make some comments regarding the possibility of drug-induced liver injury in gender-affirming hormone therapy and pre-exposure prophylaxis for HIV prevention. Finally, considering the proctology field, an up-to-date review is performed regarding anal cancer screening, HPV infection and related diseases, and infectious proctitis management.

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.

Lower PrEP Retention among Young and Black Clients Accessing PrEP at a Cluster of Safety Net Clinics for Gay and Bisexual Men

Young men of color who have sex with men are vulnerable to HIV and experience poor PrEP uptake and retention. We conducted a secondary data analysis and calculated adjusted Prevalence Odds Ratios (aPORs) for PrEP retention along with 95% CIs at 90, 180, and 360 days at an organization running safety net clinics in Texas for gay and bisexual men. We found statistically significant association with age, race, in-clinic versus telehealth appointments, and having healthcare insurance. White clients had an aPOR of 1.29 [1.00, 1.67] as compared to Black clients at 90 days. Age group of 18-24 had a lower aPOR than all other age groups except 55 or older at all three time periods. Clients who met providers in person had an aPOR of 2.6 [2.14, 3.19] at 90, 2.6 [2.2, 3.30] at 180 days and 2.84 [2.27, 3.54] at 360 days. Our findings highlight the need for population-specific targeted interventions.

Viral dissemination and immune activation modulate antiretroviral drug levels in lymph nodes of SIV-infected rhesus macaques

Introduction and methods

To understand the relationship between immunovirological factors and antiretroviral (ARV) drug levels in lymph nodes (LN) in HIV therapy, we analyzed drug levels in twenty-one SIV-infected rhesus macaques subcutaneously treated with daily tenofovir (TFV) and emtricitabine (FTC) for three months.

Results

The intracellular active drug-metabolite (IADM) levels (TFV-dp and FTC-tp) in lymph node mononuclear cells (LNMC) were significantly lower than in peripheral blood mononuclear cells (PBMC) (P≤0.005). Between Month 1 and Month 3, IADM levels increased in both LNMC (P≤0.001) and PBMC (P≤0.01), with a steeper increase in LNMC (P≤0.01). The viral dissemination in plasma, LN, and rectal tissue at ART initiation correlated negatively with IADM levels at Month 1. Physiologically-based pharmacokinetic model simulations suggest that, following subcutaneous ARV administration, ART-induced reduction of immune activation improves the formation of active drug-metabolites through modulation of kinase activity and/or through improved parent drug accessibility to LN cellular compartments.

Conclusion

These observations have broad implications for drugs that need to phosphorylate to exert their pharmacological activity, especially in the settings of the pre-/post-exposure prophylaxis and efficacy of antiviral therapies targeting pathogenic viruses such as HIV or SARS-CoV-2 replicating in highly inflammatory anatomic compartments.

Human Immunodeficiency Virus Seroconversion Among Men Who Have Sex With Men Who Use Event-Driven or Daily Oral Pre-Exposure Prophylaxis (CohMSM-PrEP): A Multi-Country Demonstration Study From West Africa

BACKGROUND

Data on human immunodeficiency virus (HIV) seroconversion among men who have sex with men (MSM) using pre-exposure prophylaxis (PrEP) in West Africa are needed. This study aimed to document HIV seroconversion and associated determinants, PrEP adherence, plasma drug concentrations, and HIV drug resistance in MSM using event-driven or daily PrEP in Burkina Faso, Côte d'Ivoire, Mali, and Togo.

METHODS

A prospective cohort study was conducted in 2017-2021 among HIV-seronegative MSM aged 18 or over who were at high risk of HIV infection. Participants could choose between event-driven and daily PrEP, switch regimens, and discontinue or restart PrEP. The determinants of HIV incidence were investigated using a multivariate mixed-effects Poisson regression analysis.

RESULTS

A total of 647 participants were followed for a total time of 1229.3 person-years. Of 5371 visits, event-driven PrEP was chosen in 3873 (72.1%), and daily PrEP in 1400 (26.1%). HIV incidence was 2.4 per 100 person-years (95% confidence interval [CI] 1.5-3.6) for event-driven PrEP, and 0.6 per 100 person-years (95% CI .1-2.3) for daily PrEP (adjusted incidence rate ratio 4.40, 95% CI 1.00-19.36, P = .050). Adequate adherence was lower with event-driven than daily PrEP (44.3% vs 74.9%, P < .001). Plasma drug concentrations were undetectable in 92 (97.9%) of the 94 measures taken for 23 participants who seroconverted. Only 1 participant had resistance to PrEP drugs.

CONCLUSIONS

HIV seroconversions mainly occurred in participants who chose event-driven PrEP. The study's data highlighted major difficulties with adherence to this regimen. Improving adherence to event-driven PrEP constitutes a major research and public health priority in this context.

Advances in the treatment and prevention of HIV: what you need to know

The global epidemic of HIV/AIDs has seen many advances in the development of effective treatments, including antiretroviral therapy that provides increasing sustained viral suppression, robust immune reconstitution and fewer side effects than before. Early HIV treatment regimens were notoriously complex, comprising up to 22 pills that needed to be taken at different times of the day. However, the advent of a single fixed dose combination drug formation simplified the treatment regimen so this could be taken once daily. Novel drugs are constantly being developed to provide better tolerated medications with robust, sustained viral suppression and immune reconstitution; these include long-acting injectables and implants, and preventative treatments for pre-exposure prophylaxis. This article provides an overview of emerging therapeutics for the treatment and prevention of HIV infection.

Oral pre-exposure prophylaxis uptake, adherence, and adverse events among South African men who have sex with men and transgender women

Background

HIV prevention programmes that include pre-exposure prophylaxis (PrEP) for men who have sex with men (MSM) and transgender women (TGW) in South Africa have not been widely implemented.

Objectives

The authors examined oral PrEP uptake, adherence, and adverse events among HIV-uninfected MSM and TGW to inform intervention acceptability and feasibility.

Method

In 2015, MSM and TGW in two South African cities were offered a comprehensive package of HIV prevention services, including daily oral PrEP, and were followed for one year. Different models of PrEP delivery were used at each site. Adherence was measured using self-report and pill-count data and tenofovir-diphosphate (TFV-DP) concentrations.

Results

Among 135 participants who were eligible for PrEP, 82 (61%) initiated PrEP, of whom 67 (82%) were on PrEP at study end. Participants were on PrEP for a median of 294 out of 314.5 possible days (93% protected days). The median time from PrEP initiation to discontinuation or study end was 305 days (interquartile range: 232-325 days). Across the follow-up time points, 57% - 72% of participants self-reported taking protective levels of PrEP and 59% - 74% were adherent to PrEP as indicated by pill counts. Fewer (≤ 18%) achieved protective TFV-DP concentrations of ≥ 700 fmol/punch in dried blood spots. Side effects, while typically mild, were the most commonly cited reason by participants for early PrEP discontinuation.

Conclusion

Many MSM and TGW initiated and maintained PrEP, demonstrating that PrEP can be successfully delivered to South African MSM and TGW in diverse programmatic contexts. Biologic adherence measures suggest MSM and TGW may experience challenges taking PrEP regularly. Counselling for coping with side effects and motivating daily pill taking is recommended to support South African MSM and TGW in achieving protection with PrEP.

HIV pre-exposure prophylaxis and sexually transmitted infections: intersection and opportunity

Pre-exposure prophylaxis (PrEP) has revolutionized HIV prevention, but PrEP does not protect against other sexually transmitted infections (STIs). Rates of STIs are rising worldwide, with notably high incidences among PrEP-using men who have sex with men in high-income countries; in low-income and middle-income countries, data are sparse, but results from a limited number of studies among African women initiating and taking PrEP have shown high STI prevalence and incidence. Efforts aimed at markedly reducing HIV in populations worldwide include a major focus on increasing PrEP use, along with improving HIV testing and treatment in order to eliminate HIV transmission. Together, these efforts could augment continued expansion of the global STI epidemic, but they could alternatively create an opportunity to improve STI control, including the development of comprehensive sexual health programmes and research to develop new STI prevention strategies. The introduction of PrEP globally has been characterized by challenges and many successes, and its role as part of a range of robust strategies to reduce HIV infections is clear. Looking ahead, understanding rising rates of curable STIs and their relationship to HIV prevention, and considering the future directions for synergies in PrEP and STI prevention will be integral to improving sexual health.

Insurance- and medical provider-related barriers and facilitators to staying on PrEP: results from a qualitative study

Pre-exposure prophylaxis (PrEP) is a highly effective biobehavioral strategy for preventing HIV acquisition. Although PrEP uptake has increased steadily, discontinuation rates are high among members of key populations like gay and bisexual men (GBM). Understanding the challenges that arise for PrEP users is key to better PrEP implementation and sustained use over time. We report on barriers that arose for PrEP-using GBM, as well as facilitating factors that aided PrEP persistence, with the goal of informing PrEP implementation efforts. In 2015-2016, 103 PrEP-using GBM in NYC completed qualitative interviews about their engagement with PrEP, including their experiences navigating PrEP-related medical care. Interviews were transcribed verbatim, coded, and analyzed thematically. Over half of participants (53%) received their PrEP-related care from their primary care provider (PCP), one-third (33%) from a community-based health clinic, and 13% from multiple medical providers. Emergent themes regarding the barriers and facilitators to PrEP persistence fell into two categories: insurance- and medical appointment-related barriers and facilitators to continued PrEP use. The experiences of PrEP-using GBM can provide useful insights for providers, program developers, and policymakers aiming to improve the implementation of PrEP. To support PrEP persistence, reliable insurance coverage, cost-assistance, and easy appointment scheduling are key to maintenance. Removing insurance- and appointment-related barriers to persistence may prove essential for sustaining use among GBM.

Plasma and intracellular pharmacokinetics of tenofovir disoproxil fumarate and emtricitabine in transgender women receiving feminizing hormone therapy

BACKGROUND

Transwomen have an increased risk of HIV acquisition compared with other adults. Drug-drug interactions between pre-exposure prophylaxis (PrEP) and gender-affirming therapy are cited as a reason for poor PrEP uptake among transwomen. We evaluated plasma tenofovir and emtricitabine pharmacokinetics and their active intracellular anabolites, tenofovir-diphosphate and emtricitabine-triphosphate, in transwomen receiving feminizing hormones.

METHODS

We enrolled HIV-negative transwomen (≥19 years) not receiving PrEP. Participants took oral tenofovir disoproxil fumarate/emtricitabine 300/200 mg daily for 14 days. Plasma was collected at 0 h (pre-dose), 0.5, 1, 2, 3, 4, 6, 8 and 12 h on day 14 post-tenofovir disoproxil fumarate/emtricitabine dose. The plasma AUC0-24 was calculated using the trapezoidal rule and compared with historical HIV-negative cisgender adults as geometric mean ratios (GMRs, 90% CI). Secondarily, tenofovir-diphosphate and emtricitabine-triphosphate from PBMCs collected at 0 h and 12 h were reported descriptively as geometric means (90% CI). Clinical trials registration: NCT03270969.

RESULTS

Among 15 transwomen (mean age 32 years), geometric mean tenofovir and emtricitabine plasma AUC0-24 were lower compared with controls: tenofovir, 2.10 versus 2.76 mg·h/L, GMR 0.76 (0.65-0.90), P = 0.01; emtricitabine, 9.15 versus 10.64 mg·h/L, GMR 0.86 (0.75-0.98), P = 0.07. Tenofovir-diphosphate and emtricitabine-triphosphate concentrations were higher than previously reported in the literature: 167.1 (146.6-190.5) fmol/106 cells and 15.4 (13.8-17.3) pmol/106 cells, respectively.

CONCLUSIONS

We observed lower plasma tenofovir and emtricitabine concentrations in transwomen compared with historical cisgender adults, yet intracellular tenofovir-diphosphate and emtricitabine-triphosphate concentrations were higher than previously reported in PBMCs. Understanding the differences of PrEP pharmacokinetics in plasma and tissue compartments and the resultant impact on efficacy remains important for transwomen.

Statistical approaches to accelerate the development of long-acting antiretrovirals for HIV pre-exposure prophylaxis

PURPOSE OF REVIEW

This review considers statistical issues in the design and analysis of the studies used to develop long-acting formulations of antiretrovirals for pre-exposure prophylaxis (PrEP).

RECENT FINDING

An abundant pipeline of products is maturing. Accelerating their evaluation as clinical products requires abandonment of noninferiority standards. Randomized trials should be based on the comparison of principled but innovative estimates of background HIV risk and enrich enrollment for those who do not desire current PrEP products. At every stage of testing, innovative analyses can be applied to help inform and accelerate later studies.

SUMMARY

The development of new long-acting PrEP regimens can be accelerated by innovations in design, ingenuity in synthesizing data sources, and application of causal inference methods.

Perceived Interruptions to HIV Prevention and Treatment Services Associated With COVID-19 for Gay, Bisexual, and Other Men Who Have Sex With Men in 20 Countries

BACKGROUND

The coronavirus pandemic has necessitated a range of population-based measures to stem the spread of infection. These measures may be associated with disruptions to other health services including for gay, bisexual, and other men who have sex with men (MSM) at risk for or living with HIV. Here, we assess the relationship between stringency of COVID-19 control measures and interruptions to HIV prevention and treatment services for MSM.

SETTING

Data for this study were collected between April 16, 2020, and May 24, 2020, as part of a COVID-19 Disparities Survey implemented by the gay social networking app, Hornet. Pandemic control measures were quantified using the Oxford Government Response Tracker Stringency Index: each country received a score (0-100) based on the number and strictness of 9 indicators related to restrictions, closures, and travel bans.

METHODS

We used a multilevel mixed-effects generalized linear model with Poisson distribution to assess the association between stringency of pandemic control measures and access to HIV services.

RESULTS

A total of 10,654 MSM across 20 countries were included. Thirty-eight percent (3992/10,396) reported perceived interruptions to in-person testing, 55% (5178/9335) interruptions to HIV self-testing, 56% (5171/9173) interruptions to pre-exposure prophylaxis, and 10% (990/9542) interruptions to condom access. For every 10-point increase in stringency, there was a 3% reduction in the prevalence of perceived access to in-person testing (aPR: 0·97, 95% CI: [0·96 to 0·98]), a 6% reduction in access to self-testing (aPR: 0·94, 95% CI: [0·93 to 0·95]), and a 5% reduction in access to pre-exposure prophylaxis (aPR: 0·95, 95% CI: [0·95 to 0·97]). Among those living with HIV, 20% (218/1105) were unable to access their provider; 65% (820/1254) reported being unable to refill their treatment prescription remotely.

CONCLUSIONS

More stringent responses were associated with decreased perceived access to services. These results support the need for increasing emphasis on innovative strategies in HIV-related diagnostic, prevention, and treatment services to minimize service interruptions during this and potential future waves of COVID-19 for gay men and other MSM at risk for HIV acquisition and transmission.

Persistence With Human Immunodeficiency Virus Pre-exposure Prophylaxis in the United States, 2012-2017

BACKGROUND

Daily oral pre-exposure prophylaxis (PrEP) is highly effective in preventing human immunodeficiency virus (HIV) infection if used adherently throughout periods of HIV risk. We estimated PrEP persistence among cohorts of persons with commercial or Medicaid insurance.

METHODS

We analyzed data from the IBM MarketScan Research Database to identify persons aged 18-64 years who initiated PrEP between 2012 and 2017. We assessed PrEP persistence by calculating the time period that each person continued filling PrEP prescriptions until there was a gap in prescription fills > 30 days. We used Kaplan-Meier time-to-event methods to estimate the proportion of PrEP users who persisted with PrEP at 3, 6, and 12 months after initiation, and constructed Cox proportional hazards models to determine patient characteristics associated with nonpersistence.

RESULTS

We studied 11 807 commercially insured and 647 Medicaid insured persons with PrEP prescriptions. Commercially insured patients persisted for a median time of 13.7 months (95% confidence interval [CI], 13.3-14.1), compared to 6.8 months (95% CI, 6.1-7.6) among Medicaid patients. Additionally, female sex, younger age, residence in rural location, and black race were associated with shorter persistence. After adjusting for covariates, we found that female sex (hazard ratio [HR], 1.81 [95% CI, 1.56-2.11]) and younger age (18-24 years: HR, 2.38 [95% CI, 2.11-2.69]) predicted nonpersistence.

CONCLUSIONS

More than half of commercially insured persons who initiated PrEP persisted with it for 12 months, compared to a third of those with Medicaid. A better understanding of reasons for nonpersistence is important to support persistent PrEP use and to develop interventions designed for the diverse needs of at-risk populations.

Pre-exposure Prophylaxis Uptake and Discontinuation Among Young Black Men Who Have Sex With Men in Atlanta, Georgia: A Prospective Cohort Study

BACKGROUND

Human immunodeficiency virus (HIV) preexposure prophylaxis (PrEP) has great potential to reduce HIV incidence among young black men who have sex with men (YBMSM); however, initiation and persistence for this group remain low. We sought to understand the patterns and predictors of PrEP uptake and discontinuation among YBMSM in Atlanta, Georgia.

METHODS

PrEP was offered to all participants in a prospective cohort of YBMSM aged 18-29 years not living with HIV. Time to PrEP uptake, first discontinuation, and final discontinuation were assessed using the Kaplan-Meier method. Cox proportional hazard models were used to identify predictors of uptake and discontinuation.

RESULTS

After 440 person-years of follow-up, 44% of YBMSM initiated PrEP through the study after a median of 122 days. Of PrEP initiators, 69% had a first discontinuation and 40% had a final discontinuation during the study period. The median time to first PrEP discontinuation was 159 days. Factors associated with PrEP uptake included higher self-efficacy, sexually transmitted infection (STI), and condomless anal intercourse. Factors associated with discontinuation included younger age, cannabis use, STI, and fewer sex partners. HIV incidence was 5.23/100 person-years (95% confidence interval [CI], 3.40-7.23), with a lower rate among those who started PrEP (incidence rate ratio, 0.39; 95% CI, .16-.92).

CONCLUSIONS

Persistent PrEP coverage in this cohort of YBMSM was suboptimal, and discontinuations were common despite additional support services available through the study. Interventions to support PrEP uptake and persistence, especially for younger and substance-using YBMSM, are necessary to achieve full PrEP effectiveness.

CLINICAL TRIALS REGISTRATION

NCT02503618.

Lamivudine/Tenofovir Disoproxil Fumarate is an Appropriate PrEP Regimen

Oral pre-exposure prophylaxis (PrEP) containing tenofovir disoproxil fumarate (TDF) co-formulated with emtricitabine (FTC) or lamivudine (3TC) is recommended as an additional prevention option for persons at substantial risk of HIV infection by both the World Health Organization (WHO) and the US President's Emergency Plan for AIDS Relief (PEPFAR). The WHO and PEPFAR consider 3TC clinically interchangeable with FTC for PrEP given comparable pharmacologic equivalence, resistance and toxicity patterns, and indirect clinical trial evidence from TDF-containing studies. Globally, FTC/TDF has been widely used in clinical trials, open-label extension studies and demonstration projects. Thus, most PrEP efficacy and safety data are based on FTC/TDF use in heterosexual women and men, men who have sex with men, and people who inject drugs. However, generic 3TC/TDF is less expensive than FTC/TDF, is already available in supply chains for HIV drugs, and has 60-70% of the global adult market share, making it particularly appealing in settings with limited availability or affordability of FTC/TDF. Compelling indirect evidence suggests that scaling up use of 3TC/TDF is potentially cost saving for HIV programs in settings where restricting drug choice to FTC/TDF would delay PrEP implementation. Guideline committees and public health decision-makers in countries should encourage flexibility in PrEP drug selection, support off-label use of 3TC/TDF, and approve use of generic formulations to decrease the cost of PrEP medications and accelerate PrEP delivery through the public and private sectors.

Initiation, discontinuation, and restarting HIV pre-exposure prophylaxis: ongoing implementation strategies

When used appropriately, pre-exposure prophylaxis (PrEP) substantially reduces the risk of HIV acquisition. Early implementation outcomes often suggest poor PrEP adherence and persistence; however, this intervention is time-limited and the need for PrEP fluctuates as risk behaviours change. In this Viewpoint we examine the current guidelines and early programmatic outcomes after starting, stopping, and restarting PrEP, and we review the implications of PrEP in relation to HIV testing algorithms. Guidelines suggest to discontinue PrEP when a person is no longer at risk for HIV, but effectively implementing this strategy requires support tools to make the decision of stopping and restarting PrEP that considers the complex relationship between risk perceptions and risk behaviours. Safely discontinuing PrEP also requires greater understanding of the daily dosing duration that is needed to protect the person after their last HIV exposure. Additionally, clear strategies are needed to re-engage a person as their HIV exposure risk changes over time.

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.

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.

Performance of HIV pre-exposure prophylaxis indirect adherence measures among men who have sex with men and transgender women: Results from the PrEP Brasil Study

Introduction

Efficacy of daily emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) for PrEP is strongly dependent on the adherence. We examined the concordance between indirect adherence measures and protective drug levels among participants retained through 48 weeks in the PrEP Brasil Study.

Methods

PrEP Brasil was a prospective, multicenter, open-label demonstration project evaluating PrEP provision for men who have sex with men (MSM) and transgender women (TGW) at higher risk for HIV infection within the setting of Brazilian Public Health System. Three indirect adherence measures were obtained at week 48: medication possession ratio (MPR), pill count and self-report (30-days recall). Tenofovir diphosphate (TFV-DP) concentration in Dried Blood Spot (DBS) was measured at week 48. Areas under (AUC) the receiver operating characteristics (ROC) curve were used to evaluate the concordance between achieving protective drug levels (TFV-DP≥700fmol/punch) and the indirect adherence measures. Youden’s index and distance to corner were used to determine the optimal cutoff points for each indirect adherence measure. We calculated sensitivity, specificity, negative (NPV) and positive (PPV) predictive values for the found cutoff points. Finally, Delong test was used to compare AUCs.

Results and discussion

From April, 2014 to July, 2016, 450 participants initiated PrEP, 375(83.3%) were retained through 48 weeks. Of these, 74% (277/375) had TFV-DP ≥700fmol/punch. All adherence measures discriminated between participants with and without protective drug levels (AUC>0.5). High indirect adherence measure was predictive of protective drug levels (PPV>0.8) while low indirect adherence measure was not predictive of lack of protective drug levels (NPV<0.5). No significant differences were found between the adherence methods (p = 0.44).

Conclusions

Low-burden measurements such as MPR and self-report can be used to predict PrEP adherence in a public health context in Brazil for MSM and TGW retained through 48 weeks.

Clinical Trial Number: NCT01989611.

Current and Future PrEP Medications and Modalities: On-demand, Injectables, and Topicals

PURPOSE OF REVIEW

Pre-exposure prophylaxis (PrEP) is a potent HIV prevention strategy, but uptake of daily oral PrEP remains low. This review covers PrEP agents currently available and agents and modalities under investigation.

RECENT FINDINGS

Injectable ARV preparations have high acceptability among users but are likely to require adherence to 8-week interval injections. Topical microbicide gels and vaginal rings have underperformed by intention-to-treat analyses in efficacy studies, at least in large part due to challenges with adherence and/or sustained use. However, daily oral TDF-FTC also underperformed in randomized, placebo-controlled trials compared to expectations and subsequent real-world pragmatic use. On-demand (2-1-1 dosing strategy for MSM) and injectable PrEP appear to be acceptable among participants in clinical trials. These modalities are particularly compelling alternatives for individuals who either do not want to take a daily medication (both on-demand and injectable) and/or want to take PrEP without a long commitment (on-demand). Emerging modalities such as vaginal films, microneedles, and subdermal implants have numerous advantages but are still in early stages of development.

"You can smell the freedom": a qualitative study on perceptions and experiences of sex among Swedish men who have sex with men in Berlin

PURPOSE

The purpose of this study was to explore the perceptions and experiences of sex among Swedish Men who have Sex with Men (MSM) in Berlin.

BACKGROUND

MSM are disproportionally affected by HIV.Berlin is also a key destination when looking into where Swedish MSM sero-convert, while travelling.

METHOD

A qualitative study with semi-structured interviews using open-ended questions with participants recruited through network sampling. Data were analysed with content analysis.

PARTICIPANTS

15 Swedish cis-men (as in non-transgender) who have sex with men aged 25-44 years, who travelled to or were living in Berlin. To be included in the study, the participants had to be cis-MSM, Swedish citizens, spending time in Berlin and having sex in both settings.

RESULTS

For a majority of the participants, sex was the main reason for going to Berlin but cultural aspects like art and the techno scene were also important. Berlin was perceived as a sex-oriented city providing venues where respondents did not have to care about reputation and status and where social and sexual spaces co-existed side by side. This in sharp contrast to Sweden, which represented a limiting environment both in culture and what was available culturally and sexually.

CONCLUSION

The men interviewed experienced multiple partners and had a broad sexual repertoire both abroad and at home. However, the behaviour was amplified in Berlin. The men did not alter their safer sex practice depending on if they had sex in Sweden or Berlin. The high mobility and vulnerability for HIV/sexually transmitted infection (STI) among these men highlights the need of increased access to antiretroviral treatment, pre-exposure prophylaxis for HIV and low-threshold HIV/STI testing services in Europe.

Transcutaneously refillable nanofluidic implant achieves sustained level of tenofovir diphosphate for HIV pre-exposure prophylaxis

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.

How Do Gay and Bisexual Men Make Up for Missed PrEP Doses, and What Impact Does Missing a Dose Have on Their Subsequent Sexual Behavior?

HIV pre-exposure prophylaxis (PrEP) is being adopted by members of key populations, such as gay and bisexual men (GBM). Since adherence to a daily PrEP regimen ensures a maximum protection, it is critical to understand GBM's behavioral responses to having missed PrEP doses. We report on qualitative interviews with GBM taking PrEP. We identified three behavioral responses: (1) 59% continued with their next scheduled dose; (2) 49% described "making up" for a missed dose by taking medication as soon as possible; and (3) 11% reported "doubling" the next PrEP dose. Participants provided potentially contradictory narratives about their sexual behavior after a missed dose: (1) 54% described making no changes; (2) 49% described adjusting their sexual behavior to reduce HIV risk; and (3) 10% said their decision would be contingent upon how many doses were missed. For PrEP prescribers, our data provide a useful lens to understand patients' lived experiences with PrEP.

Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine HIV pre-exposure prophylaxis: clinical guidelines. Update April 2018

Daily use of coformulated tenofovir and emtricitabine for HIV pre-exposure prophylaxis (PrEP) by populations at high risk of HIV infection is now recommended in guidelines from the United States, Europe and Australia and globally through the 2015 WHO guidelines. These 2017 Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine's (ASHM) PrEP Guidelines are an updated adaptation of the 2014 US Centers for Disease Control's PrEP guidelines and are designed to: •Support the prescription of PrEP using forms of coformulated tenofovir and emtricitabine that have been registered in Australia by the Therapeutic Goods Administration and other bioequivalent generic drugs that are available in Australia through self-importation, private prescription or Australian PrEP clinical trials•Assist clinicians in the evaluation of patients who are seeking PrEP•Assist clinicians in commencing and monitoring patients on PrEP including PrEP dosing schedules, management of side-effects and toxicity, use of PrEP in pregnancy and in chronic hepatitis B infection and how to cease PrEP Daily PrEP with co-formulated tenofovir and emtricitabine, used continuously or for shorter periods of time, is recommended in these guidelines as a key HIV-prevention option for men who have sex with men (MSM), transgender men and women, heterosexual men and women, and people who inject drugs (PWID) at substantial risk of HIV acquisition. These guidelines were updated in April 2018 and include changes to the recommendations regarding the choice of daily or on-demand PrEP.

Maximizing the Benefits of HIV Preexposure Prophylaxis

Preexposure prophylaxis (PrEP) with tenofovir/emtricitabine (slash indicates coformulation) is highly effective in preventing new HIV infections. PrEP efficacy is strongly associated with adherence. In clinical trials, PrEP has been more effective in men who have sex with men and HIV-serodiscordant heterosexual couples than in women, likely reflecting pharmacokinetic differences between levels of tenofovir disoproxil fumarate in vaginal and rectal tissues, and poorer adherence in studies in women. Current guidelines recommend daily PrEP for men and women; however, PrEP taken at least 4 days per week for men may be as effective as daily PrEP, and women must take PrEP 6 to 7 days per week to maximize efficacy. Data are accumulating on the effectiveness of pericoital PrEP for men who have sex with men, but it is not yet recommended in the United States. PrEP is underprescribed for younger individuals, black individuals, and Hispanic and Latino individuals. This article summarizes a presentation by Susan P. Buchbinder, MD, at the IAS-USA continuing education program, Improving the Management of HIV Disease, held in Chicago, Illinois, in May 2017.

Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine HIV pre-exposure prophylaxis: clinical guidelines. Update April 2018

Daily use of coformulated tenofovir and emtricitabine for HIV pre-exposure prophylaxis (PrEP) by populations at high risk of HIV infection is now recommended in guidelines from the United States, Europe and Australia and globally through the 2015 WHO guidelines. These 2017 Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine's (ASHM) PrEP Guidelines are an updated adaptation of the 2014 US Centers for Disease Control's PrEP guidelines and are designed to: •Support the prescription of PrEP using forms of coformulated tenofovir and emtricitabine that have been registered in Australia by the Therapeutic Goods Administration and other bioequivalent generic drugs that are available in Australia through self-importation, private prescription or Australian PrEP clinical trials•Assist clinicians in the evaluation of patients who are seeking PrEP•Assist clinicians in commencing and monitoring patients on PrEP including PrEP dosing schedules, management of side-effects and toxicity, use of PrEP in pregnancy and in chronic hepatitis B infection and how to cease PrEP Daily PrEP with co-formulated tenofovir and emtricitabine, used continuously or for shorter periods of time, is recommended in these guidelines as a key HIV-prevention option for men who have sex with men (MSM), transgender men and women, heterosexual men and women, and people who inject drugs (PWID) at substantial risk of HIV acquisition. These guidelines were updated in April 2018 and include changes to the recommendations regarding the choice of daily or on-demand PrEP.

Willingness to use HIV pre-exposure prophylaxis among gay men, other men who have sex with men and transgender women in Myanmar

INTRODUCTION

HIV pre-exposure prophylaxis (PrEP) has emerged as a key component of contemporary HIV combination prevention strategies. To explore the local suitability of PrEP, country-specific acceptability studies are needed to inform potential PrEP implementation. In the context of Myanmar, in addition to resource constraints, HIV service access by gay men, other men who have sex with men, and transgender women (GMT) continues to be constrained by legislative and community stigma and marginalization. We aimed to determine PrEP acceptability among GMT in Myanmar and explore the factors associated with willingness to use PrEP.

METHODS

GMT were recruited in Yangon and Mandalay through local HIV prevention outreach programmes in November and December 2014. Quantitative surveys were administered by trained peer educators and collected data on demographics, sexual risk, testing history and PrEP acceptability. A modified six-item PrEP acceptability scale classified self-reported HIV undiagnosed GMT as willing to use PrEP. Multivariable logistic regression identified factors associated with willingness to use PrEP.

RESULTS

Among 434 HIV undiagnosed GMT, PrEP awareness was low (5%). PrEP acceptability was high, with 270 (62%) GMT classified as willing to use PrEP. GMT recruited in Mandalay (adjusted odds ratio (aOR) = 1.79; 95%CI = 1.05-3.03), who perceived themselves as likely to become HIV positive (aOR = 1.82; 95%CI = 1.10-3.02), who had more than one recent regular partner (aOR = 2.94; 95%CI = 1.41-6.14), no regular partners (aOR = 2.05; 95%CI = 1.10-3.67), more than five casual partners (aOR = 2.05; 95%CI = 1.06-3.99) or no casual partners (aOR = 2.25; 95%CI = 1.23-4.11) were more likely to be willing to use PrEP. The association between never or only occasionally using condoms with casual partners and willingness to use PrEP was marginally significant (aOR = 2.02; 95%CI = 1.00-4.10). GMT who reported concern about side effects and long-term use of PrEP were less likely (aOR = 0.35; 95%CI = 0.21-0.59) to be willing to use PrEP.

CONCLUSIONS

This is the first study to assess PrEP acceptability in Myanmar. Findings suggest PrEP is an acceptable prevention option among GMT in Myanmar, providing they are not required to pay for it. Implementation/demonstration projects are needed to explore the feasibility and cost-effectiveness of PrEP as a prevention option for GMT in Myanmar.

Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine HIV pre-exposure prophylaxis: clinical guidelines

Daily use of coformulated tenofovir and emtricitabine for HIV pre-exposure prophylaxis (PrEP) by populations at high risk of HIV infection is now recommended in guidelines from the United States, Europe and Australia and globally through the 2015 WHO guidelines. These 2017 Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine's (ASHM) PrEP Guidelines are an updated adaptation of the 2014 US Centers for Disease Control's PrEP guidelines and are designed to: •Support the prescription of PrEP using forms of coformulated tenofovir and emtricitabine that have been registered in Australia by the Therapeutic Goods Administration and other bioequivalent generic drugs that are available in Australia through self-importation, private prescription or Australian PrEP clinical trials•Assist clinicians in the evaluation of patients who are seeking PrEP•Assist clinicians in commencing and monitoring patients on PrEP including PrEP dosing schedules, management of side-effects and toxicity, use of PrEP in pregnancy and in chronic hepatitis B infection and how to cease PrEP Daily PrEP with co-formulated tenofovir and emtricitabine, used continuously or for shorter periods of time, is recommended in these guidelines as a key HIV-prevention option for men who have sex with men (MSM), transgender men and women, heterosexual men and women, and people who inject drugs (PWID) at substantial risk of HIV acquisition.

Inflammation and pharmacokinetics: potential implications for HIV-infection

INTRODUCTION

The physiological changes accompanying inflammation may alter the pharmacokinetics (PK) of certain medications. Individuals infected with HIV have chronically elevated inflammatory markers despite viral suppression following effective antiretroviral therapy (ART), as well as age-related inflammation. Understanding the potential clinical implications of inflammation on the PK of medications is important for understanding dose-response relationships and necessitates future research. Areas covered: An extensive literature search was carried out using PubMed and associated bibliographies to summarize the current state of knowledge regarding altered PK in response to inflammation and its application to the field of HIV. Expert opinion: Preclinical and clinical studies show that inflammation leads to a downregulation of certain drug metabolizing enzymes and both up and down regulation of transporters depending on the transporter and cell type. Decreased gastric acidity, fluid shifts, and plasma protein alterations also occur with inflammation, leading to potential absorption, distribution, and clearance changes. More research is needed including controlled PK studies to address the clinical relevance of these observations, especially in the aging HIV-infected population. Results from future studies will enable us to better predict drug concentrations in individuals with inflammation, in line with efforts to provide personalized pharmacotherapy in our healthcare system.

Emtricitabine-Triphosphate in Dried Blood Spots as a Marker of Recent Dosing

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.).

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

OBJECTIVES

In the ANRS IPERGAY pre-exposure prophylaxis (PrEP) trial, a single dose of tenofovir disoproxil fumarate and emtricitabine was taken orally 2-24 h before sexual intercourse. A sub-study was conducted to assess the pharmacokinetics of tenofovir and emtricitabine in blood, saliva and rectal tissue following this initial oral intake.

METHODS

Plasma, PBMC, saliva and rectal tissue sampling was performed over 24 h in 12 seronegative men before enrolment in the ANRS IPERGAY trial, following a single dose of 600 mg tenofovir disoproxil fumarate/400 mg emtricitabine. Ex vivo HIV infectibility of rectal biopsies was also assessed.

RESULTS

The median plasma T_max of tenofovir (median C_max: 401 μg/L) and emtricitabine (median C_max: 2868 μg/L) was obtained 1 h (range: 0.5-4) and 2 h (range: 1-4) after dosing, respectively. The median C₂₄ of tenofovir and emtricitabine was 40 and 63 μg/L, respectively. The median PBMC tenofovir diphosphate and emtricitabine triphosphate levels were 12.2 and 16.7 fmol/10⁶ cells and 2800 and 2000 fmol/10⁶ cells at 2 and 24 h after dosing, respectively. Saliva/plasma AUC_0-24 ratios were 2% and 17% for tenofovir and emtricitabine, respectively. Emtricitabine was detected in rectal tissue 30 min after dosing, whereas tenofovir was only detectable at 24 h. Ex vivo HIV infectibility assays of rectal biopsies showed partial protection after dosing (P < 0.07).

DISCUSSION

A single high dose of oral tenofovir disoproxil fumarate/emtricitabine provides rapid and high blood levels of tenofovir and emtricitabine, with rapid diffusion of emtricitabine in saliva and rectal tissue.

Intracellular Tenofovir and Emtricitabine Anabolites in Genital, Rectal, and Blood Compartments from First Dose to Steady State

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.

When and why women might suspend PrEP use according to perceived seasons of risk: implications for PrEP-specific risk-reduction counselling

Oral pre-exposure prophylaxis (PrEP) using the antiretroviral drug emtricitabine/tenofovir disoproxil fumarate (Truvada) has been shown to dramatically reduce the risk of HIV acquisition for women at higher risk of infection if taken daily. Understanding when and why women would intentionally stop using an efficacious oral PrEP drug within the context of their 'normal' daily lives is essential for delivering effective PrEP risk-reduction counselling. As part of a larger study, we conducted 60 qualitative interviews with women at higher risk of HIV in Bondo, Kenya, and Pretoria, South Africa. Participants charted their sexual contacts over the previous six months, indicated whether they would have taken PrEP if available and discussed whether and why they would have suspended PrEP use. Nearly all participants said they would have used PrEP in the previous six months; half indicated they would have suspended PrEP use at some point. Participants' reasons for an extended break from PrEP were related to partnership dynamics (e.g., perceived low risk of a stable partner) and phases of life (e.g., trying to conceive). Life events (e.g., holidays and travel) could prompt shorter breaks in PrEP use. These circumstances may or may not correspond to actual contexts of lower risk, highlighting the importance of tailored PrEP risk-reduction counselling.

Analysis of the Endogenous Deoxynucleoside Triphosphate Pool in HIV-Positive and -Negative Individuals Receiving Tenofovir-Emtricitabine

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.).

Seasons of Risk: Anticipated Behavior on Vacation and Interest in Episodic Antiretroviral Pre-exposure Prophylaxis (PrEP) Among a Large National Sample of U.S. Men Who have Sex with Men (MSM)

The current analysis evaluates interest in and acceptability of daily PrEP during short episodes of anticipated increased risk (i.e. Epi-PrEP). In 2013, U.S. members of an internet-based MSM sexual networking site were invited to complete a survey about HIV prevention practices in the context of vacationing. 7305 MSM responded to the survey. Of respondents who had vacationed in the past year, 25.6 % reported condomless anal sex (CAS) with new male sex partners while vacationing. Most (92.6 %) respondents agreed that having to use PrEP every day was a barrier to PrEP use and 74.3 % indicated they would take PrEP if they knew it would be helpful for short periods of anticipated increased risk. MSM who reported increased CAS while on vacation in the past year were more likely to indicate that they would take PrEP if it were helpful when used for short periods than respondents who did not (aOR = 2.02, 95 % CI 1.59-2.56, p < 0.001). Studies designed to evaluate uptake, adherence, and protective benefit of short PrEP courses are warranted.

A Translational Pharmacology Approach to Predicting Outcomes of Preexposure Prophylaxis Against HIV in Men and Women Using Tenofovir Disoproxil Fumarate With or Without Emtricitabine

BACKGROUND

A novel translational pharmacology investigation was conducted by combining an in vitro efficacy target with mucosal tissue pharmacokinetic (PK) data and mathematical modeling to determine the number of doses required for effective human immunodeficiency virus (HIV) preexposure prophylaxis (PrEP).

METHODS

A PK/pharmacodynamic (PD) model was developed by measuring mucosal tissue concentrations of tenofovir, emtricitabine, their active metabolites (tenofovir diphosphate [TFVdp] and emtricitabine triphosphate [FTCtp], respectively), and competing endogenous nucleotides (dATP and dCTP) in 47 healthy women. TZM-bl and CD4(+) T cells were used to identify 90% effective concentration (EC90) ratios of TFVdp to dATP and FTCtp to dCTP (alone and in combination) for protection against HIV. Monte-Carlo simulations were then performed to identify minimally effective dosing strategies to protect lower female genital tract and colorectal tissues.

RESULTS

The colorectal TFVdp concentration was 10 times higher than that in the lower female genital tract, whereas concentrations of endogenous nucleotides were 7-11 times lower. Our model predicted that ≥98% of the population achieved protective mucosal tissue exposure by the third daily dose of tenofovir disoproxil fumarate plus emtricitabine. However, a minimum adherence to 6 of 7 doses/week (85%) was required to protect lower female genital tract tissue from HIV, while adherence to 2 of 7 doses/week (28%) was required to protect colorectal tissue.

CONCLUSIONS

This model is predictive of recent PrEP trial results in which 2-3 doses/week was 75%-90% effective in men but ineffective in women. These data provide a novel approach for future PrEP investigations that can optimize clinical trial dosing strategies.

What people want from sex and preexposure prophylaxis

PURPOSE OF REVIEW

As demand for preexposure prophylaxis (PrEP) increases, we are learning more about what people want from sex and PrEP.

RECENT FINDINGS

PrEP demand has reached a tipping point in the USA and is increasing rapidly. Although the primary benefit of PrEP use is biological, to reduce risk of HIV infection, PrEP users often express an alternative set of social and emotional benefits that are provided by PrEP. These collateral benefits of PrEP have salience, affect, and are experienced in the present, which are compelling drivers of human behavior. PrEP use has been associated with feeling safe during sex, usually in contrast to ruminations related to fear of HIV or intimate partner violence or control. PrEP can create empowerment, or agency, defined as the capacity and autonomy to act on one's own behalf, because it provides control over one's vulnerability to HIV and relief to women and men who may otherwise worry about whether their partners will use a condom, take antiretroviral therapy, or disclose their HIV status accurately. Planning for sexual and social goals in calm moments is also empowering. These highly desired collateral benefits of PrEP could be undermined, or eliminated, if PrEP is implemented in ways that are coercive or that foment fear of sexual risk compensation, drug resistance, toxicity, or moral judgment.

SUMMARY

Current PrEP implementation provides direct and indirect benefits that are highly desired.

Dose Frequency Ranging Pharmacokinetic Study of Tenofovir-Emtricitabine After Directly Observed Dosing in Healthy Volunteers to Establish Adherence Benchmarks (HPTN 066)

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.