State of the science of adherence in pre-exposure prophylaxis and microbicide trials

Systematic review of the values and preferences regarding the use of injectable pre-exposure prophylaxis to prevent HIV acquisition

INTRODUCTION

Pre-exposure prophylaxis (PrEP) is an important HIV prevention option. Two randomized trials have provided efficacy evidence for long-acting injectable cabotegravir (CAB-LA) as PrEP. In considering CAB-LA as an additional PrEP modality for people at substantial risk of HIV, it is important to understand community response to injectable PrEP. We conducted a systematic review of values, preferences and perceptions of acceptability for injectable PrEP to inform global guidance.

METHODS

We searched nine databases and conference websites for peer-reviewed and grey literature (January 2010-September 2021). There were no restrictions on location. A two-stage review process assessed references against eligibility criteria. Data from included studies were organized by constructs from the Theoretical Framework of Acceptability.

RESULTS

We included 62 unique references. Most studies were observational, cross-sectional and qualitative. Over half of the studies were conducted in North America. Men who have sex with men were the most researched group. Most studies (57/62) examined injectable PrEP, including hypothetical injectables (55/57) or placebo products (2/57). Six studies examined CAB-LA specifically. There was overall interest in and often a preference for injectable PrEP, though there was variation within and across groups and regions. Many stakeholders indicated that injectable PrEP could help address adherence challenges associated with daily or on-demand dosing for oral PrEP and may be a better lifestyle fit for individuals seeking privacy, discretion and infrequent dosing. End-users reported concerns, including fear of needles, injection site pain and body location, logistical challenges and waning or incomplete protection.

DISCUSSION

Despite an overall preference for injectable PrEP, heterogeneity across groups and regions highlights the importance of enabling end-users to choose a PrEP modality that supports effective use. Like other products, preference for injectable PrEP may change over time and end-users may switch between prevention options. There will be a greater understanding of enacted preference as more end-users are offered anti-retroviral (ARV)-containing injectables. Future research should focus on equitable implementation, including real-time decision-making and how trained healthcare providers can support choice.

CONCLUSIONS

Given overall acceptability, injectable PrEP should be included as part of a menu of prevention options, allowing end-users to select the modality that suits their preferences, needs and lifestyle.

Fundamental aspects of long-acting tenofovir alafenamide delivery from subdermal implants for HIV prophylaxis

Global efforts aimed at preventing human immunodeficiency virus type one (HIV-1) infection in vulnerable populations appear to be stalling, limiting our ability to control the epidemic. Long-acting, controlled drug administration from subdermal implants holds significant potential by reducing the compliance burden associated with frequent dosing. We, and others, are exploring the development of complementary subdermal implant technologies delivering the potent prodrug, tenofovir alafenamide (TAF). The current report addresses knowledge gaps in the preclinical pharmacology of long-acting, subdermal TAF delivery using several mouse models. Systemic drug disposition during TAF implant dosing was explained by a multi-compartment pharmacokinetic (PK) model. Imaging mass spectrometry was employed to characterize the spatial distribution of TAF and its principal five metabolites in local tissues surrounding the implant. Humanized mouse studies determined the effective TAF dose for preventing vaginal and rectal HIV-1 acquisition. Our results represent an important step in the development of a safe and effective TAF implant for HIV-1 prevention.

Female and male partner perspectives on placebo Multipurpose Prevention Technologies (MPTs) used by women in the TRIO study in South Africa and Kenya

Background

Male partner awareness and acceptance of microbicide and family planning product use has been shown to increase women’s own acceptance and adherence of a product. However, little is known about preferences regarding potential Multipurpose Prevention Technology (MPT) product delivery forms. As part of the TRIO study, men’s reactions to their female partner’s TRIO product use and comparisons of men’s and women’s views of TRIO product attributes and use acceptability were explored to better understand product preferences.

Methods

Women in TRIO used three placebo products that represented potential MPTs: daily oral tablets, monthly vaginal rings, and monthly dual injections. Male partners (N = 39) and women (N = 88) completed in-depth interviews on their own and their partner’s experiences with these products. Qualitative coding and analyses followed a conceptual model of HIV prevention product acceptability, and here, we explored themes of disclosure, trust and infidelity as they informed barriers and facilitators to product use.

Results

Men expressed a desire to know of their partner’s product use decisions and be informed and educated on the products to better support their partners, in some cases, expressing a high level of concern regarding maximizing the ease of product adherence for their partner. They also wanted to understand the effects of products on sexual encounters with their partner, but in some cases, wanted more knowledge in order to control their partner’s product use decisions. Similarly to women, men found long-acting, discreet products that have little to no effect on sexual encounters or libido the most acceptable for their female partners’ use. Product use was most acceptable to men if they were informed of use without inadvertent discovery.

Conclusions

Men’s product attribute preferences often aligned with women’s opinions of the same products. To support women’s correct use of MPTs, further research is needed to determine the best strategy for achieving male partner acceptance and support of product use, particularly for less familiar delivery forms, such as the vaginal ring.

Adherence to Pre-Exposure Prophylaxis in Adolescents and Young Adults: A Systematic Review and Meta-Analysis

This meta-analysis synthesized the proportion of adolescents and young adults (AYAs) who are adherent to pre-exposure prophylaxis (PrEP) and factors moderating adherence. A systematic search was conducted of studies published through May 2020 using PubMed, PsycInfo, Cochrane, EMBASE, and CINAHL. Included studies reported the proportion of AYAs (mean age ≤ 29 years) who were PrEP adherent. PrEP adherence was meta-analyzed using random-effects models. Secondary analyses evaluated potential moderating variables. A total of 41 individual samples, from 29 studies, of 8,679 AYA (weighted average age = 23.8 years) were synthesized. The proportion of AYA who met study-defined thresholds for PrEP adherence was .64 (95% confidence interval .57-.71) across studies. Subgroup analyses revealed that adherence was lower in young cisgender women (.46) than young men who have sex with men (.65) and serodiscordant heterosexual couples (.98). Adherence was higher in studies initiated after 2012 (.70) than earlier studies (.47). No differences based on participant age, country, or strategies to promote adherence were found. Across published studies to date, 64% of AYA demonstrate adequate PrEP adherence. Findings can be used to guide PrEP adherence interventions and also provide directions for future research on PrEP among AYA.

The Value of Assessing Self-Reported and Biological Indicators of Outcomes in Evaluating HIV Programs

PURPOSE OF REVIEW

In this manuscript, we present recent findings concerning concordance and discrepancy between biological measures and self-reports of these three outcomes of HIV programs: HIV status, adherence to antiretroviral medications (ARVs) and use of and adherence to pre-exposure prophylaxis medication (PrEP), and condom use/unprotected sex.

RECENT FINDINGS

Recent studies suggest that three successive rapid HIV tests (for those whose first test in positive) might be reasonably inexpensive and valid biological data to collect to combine with self-reports of HIV status, dried blood spots sufficiently affordable to combine with self-reports of adherence to ARVs and use of or adherence to PrEP, and that the discrepancy between self-reports of condom use and biomarkers of unprotected sex may be relatively small in high-income countries. Additional work on assessment of incorrect condom usage and breakage, standardized self-report measures of condom use, and more private data collection methodologies in low-income settings might reduce the recent observed discrepancies even further. Concordance between self-reports of HIV and biomarkers indicating HIV positive status has varied considerably, with much lower rates in low-income countries, where the stigma of HIV is still very high. Recommendation is for combining self-report data with the results of three successive rapid tests for those testing positive. For adherence, again agreement between self-reports and a variety of more objective and/or biological measures is only moderate. Dried blood spots (DBS) may be sufficiently inexpensive in low-resource settings that this may be the best biological method to combine with self-reports. In publications over the last 8 years, the discrepancy between self-reports of condom use and biomarkers for unprotected sex may be even lower than 20% after controlling for other features of the study, particularly in high-income countries. Our results suggest that more careful assessment of incorrect condom use and breakage as reasons other than intentional misreporting should be investigated more carefully and that more private data collection methods such as audio, computer-assisted self-interviewing (ACASI) might be employed more often in low-resource settings to reduce this discrepancy in those settings further. In addition, further analysis of the discrepancy between self-reports of condom use and biomarkers should be conducted of published studies using the correct calculation methods to be more certain of these findings.

Pharmacokinetics of a weekly transdermal delivery system of tenofovir alafenamide in hairless rats

Tenofovir alafenamide (TAF) is a potent prodrug of tenofovir (TFV) for HIV prophylaxis, and HIV and HBV treatment. Compared to oral daily doses, transdermal administration of TAF may be more advantageous for long-term adherence by offering sustained drug delivery and reduced dosing frequency. Here, we described the plasma pharmacokinetics (PK) of an optimized once-weekly suspension transdermal delivery system (TDS) for TAF (96 mg/25 cm² of TDS) in female hairless rats. Over the study period, the TAF TDS delivered an overall low level of TAF (median: 1.43 [0.02-3.28] ng/mL) and a sustained level of the stable metabolite and parent drug, TFV. Relative to the projected exposure corresponding to six-day oral daily doses, a comparable TAF exposure but a substantially lower TFV exposure was resulted from the TAF TDS, suggesting a lower risk of TFV-associated adverse effects. TAF, TFV, and phosphorylated TFVs (TFV-monophosphate and diphosphate) were found distributed in vaginal tissue, the portal of entry for HIV during male-to-female sexual transmission. Skin adhesion and tolerance were acceptable given the animal model used. PK evaluation of the TAF TDS in hairless rats demonstrates the proof of concept that transdermal delivery can be an alternative route for a sustained, once-weekly systemic delivery of TAF.

Comparing Self-Report Pre-Exposure Prophylaxis Adherence Questions to Pharmacologic Measures of Recent and Cumulative Pre-Exposure Prophylaxis Exposure

As pre-exposure prophylaxis (PrEP) effectiveness is strongly linked to adherence, we sought to determine if certain self-report measures could be used to inform objective PrEP adherence. We studied participants from the TAPIR study (a multicenter randomized study of daily text messages to support adherence to PrEP In At-Risk), a 48-week randomized controlled trial of HIV-uninfected men who have sex with men (MSM) randomized to receive text message to support adherence versus standard of care. Self-reported medication adherence was assessed using several validated measures modified for PrEP. Objective PrEP adherence was determined through dried blood spot (DBS) measurement of intracellular tenofovir diphosphate (TFV-DP) and emtricitabine triphosphate (FTC-TP). A summary of adherence was estimated using responses to the seven adherence items at weeks 12 and 48 using confirmatory factor analysis. Correlations between self-report questions and drug concentrations were estimated with Pearson's correlations for continuous outcomes and point-biserial correlations for dichotomous outcomes. Receiver operating characteristic (ROC) analyses were conducted to assess the performance of self-report measures in predicting protective or perfect TFV-DP concentrations. Of the 369 participants who completed week 12 or 48 visits, the mean age was 35 (standard deviation 9 years), with 79% White, 12% Black, and 29% Hispanic. Correlations between self-report measures of adherence (both individual items and the adherence factor) and quantifiable FTC-TP and continuous TFV-DP concentrations showed that all self-report measures were significantly associated with these objective measures. Compared to a summary measure of self-reported adherence, the 4-week percent taken question medication recall was the only self-report item similarly or more strongly associated with recent adherence and long-term protective and perfect adherence at weeks 12 and 48. ROC analysis also showed that 4-week percent taken question had a reasonable AUC (0.798 at week 12 and 0.758 at week 48) in predicting protective TFV-DP concentrations. All single-item self-report questions assessing PrEP adherence were significantly associated with biomarker quantification, with the 4-week percent taken question performing best. Therefore, in the absence of drug concentration measurements, a 4-week self-report percent taken question may be a good single-item measure of PrEP adherence.

Associations between perceived barriers and benefits of using HIV pre-exposure prophylaxis and medication adherence among men who have sex with men in Western China

BACKGROUND

To investigate the associations between the perceived barriers and benefits of using HIV pre-exposure prophylaxis medication, including worries about the side effects, disliking taking drugs, perceived burden of taking medication, positive expectations as to the efficacy of the drugs, favourable doctor-patient relationships, and medication adherence among men who have sex with men (MSM) to provide a target for improving medication adherence and reducing HIV infection among MSM.

METHODS

MSM were recruited in western China from April 2013 to October 2014, administered oral tenofovir (TDF) daily and followed up every 12 weeks for 2 years. At each follow-up, the medication rate was calculated based on the self-reported number of missed doses over 2 weeks, and then, the medication adherence was evaluated. The barriers and benefits perceived during medication were obtained by a self-administered questionnaire, and their effects on medication adherence were analysed by linear mixed models.

RESULTS

A total of 411 participants were enrolled in this study, and 1561 follow-up observation points were obtained. The average medication rate was 0.62 ± 0.37, and the medication rate increased with longer follow-up (P < 0.05). The medication rate was higher among MSM who were divorced (compared to those who were unmarried, P < 0.0001). MSM with more positive expectations as to the efficacy of the drugs showed higher rates of medication (P < 0.0001), while those who were more worried about side effects had a lower medication rate (P = 0.0208). In contrast, the dislike of taking the drugs and the burden perceived during medication had no effects on the actual medication rate of taking TDF (P > 0.05).

CONCLUSION

How to obtain and maintain high medication adherence among MSM is the key to the PrEP intervention strategy for effective reduction of HIV infection. For MSM in China, we should deepen their understanding of the effectiveness and safety of PrEP and increase their confidence in PrEP, thereby improving their medication adherence.

TRIAL REGISTRATION

ChiCTR-TRC-13003849 . Registered on 24/06/2013.

Adherence to pre-exposure prophylaxis among men who have sex with men: A prospective cohort study

OBJECTIVE

To evaluate adherence to pre-exposure prophylaxis (PrEP) in a clinical trial of a population of men who have sex with men (MSM), to explore the influence of social psychology and objective factors (e.g., forgetting, too busy) on adherence, and to provide evidence for subsequent PrEP research.

METHODS

This study analyzed the data from the daily medication group within a PrEP study (a randomized placebo-controlled trial of oral tenofovir among MSM in Western China from April 2013 to March 2015). A total of 331 participants were analyzed. PrEP adherence was self-reported by the subjects at every 3-month follow-up visit for 24 months. AIDS-related information including HIV prevention, transmission, and treatment knowledge, as well as PrEP-related motivation (including personal and social motivation) and behavior skills, i.e., self-efficacy, were collected using questionnaires. The objective reasons for non-adherence were collected during face-to-face follow-up visits every 3 months. A theoretical model of information motivation behavior skills (IMB) was constructed. Then confirmatory factor analysis was performed to test the fit of each IMB construct. Finally, the structure equation model was used to evaluate the IMB model.

RESULTS

The median adherence rate was 64.29%. During the follow-up period, the percentage of high adherence (adherence ≥80%) was 32.33%, intermediate adherence (adherence 40-80%) was 38.97%, and low adherence (adherence ≤40%) was 28.70%. The final IMB model showed that there was no significant correlation between adherence to PrEP and the psychological constructs: information, motivation, and behavior skills. The main objective reasons for non-adherence were 'forgetting to take medicine' (70.21%), 'too busy' (29.08%), 'worrying about side effects' (28.01%), and 'too much trouble' (18.44%).

CONCLUSIONS

This study found no association between PrEP adherence and social psychological factors, and the main objective factor in non-adherence was forgetting to take the medicine. In the future, the MSM population could be reminded to take their medicine regularly using electronic devices, which may improve PrEP adherence to some extent and may further reduce the incidence of HIV. The strategy to improve PrEP adherence requires further study.

Rapid measures of user's adherence to vaginal drug products using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and multivariate discriminant techniques

Background

The topical HIV prevention (microbicides) field is in acute need of a method to rapidly and objectively measure adherence to product use in clinical trials. Infrared (IR) spectroscopy has been used in many pharmaceutical and forensic applications but has yet to be applied to adherence monitoring. In this study, we report on efforts to test the feasibility of using IR spectroscopy as a means to measure residual active or placebo vaginal product, semen exposure and vaginal insertion from a single swab.

Methods

A portable IR spectrometer equipped with diamond attenuated total reflectance (ATR) was used to capture spectra of unused vs. vaginally-used swabs, vaginal swabs containing semen, and vaginal swabs to which either tenofovir-containing or matching placebo products (vaginal gel or insert) were added. Spectral data obtained from swabs placed directly on the spectrometer were divided into calibration and testing sets for developing and validating discriminant models set up to provide yes/no predictions of: vaginal vs. non-vaginal use, presence vs. no presence of each test product, and presence vs. no presence of semen. Further validation of models was performed using vaginal swabs collected from a clinical study evaluating vaginally administered placebo insert formulations.

Results

For each discriminant model developed to predict vaginal vs. non-vaginal use, presence vs. no presence of each test product, and presence vs. no presence of semen, classified validation samples not included in the model development were correctly identified into their respective classes with minimal prediction error. Clinically obtained vaginal swabs collected 15–60 minutes after placebo insert use were also correctly identified, further validating the models.

Conclusion

Our findings demonstrate the proof of concept that IR spectroscopy can be a method for rapid detection and characterization of microbicide products and biological fluids present in vaginal swabs. This novel method has potential to support real-time, on-site adherence monitoring in clinical or field settings.

Nanotechnologies for early diagnosis, in situ disease monitoring, and prevention

Nanotechnology is an enabling technology with great potential for applications in stem cell research and regenerative medicine. Fluorescent nanodiamond (FND), an inherently biocompatible and nontoxic nanoparticle, is well suited for such applications. We had developed a prospective isolation method using CD157, CD45, and CD54 to obtain lung stem cells. Labeling of CD45⁻CD54⁺CD157⁺ cells with FNDs did not eliminate their abilities for self-renewal and differentiation. The FND labeling in combination with cell sorting, fluorescence lifetime imaging microscopy, and immunostaining identified transplanted stem cells allowed tracking of their engraftment and regenerative capabilities with single-cell resolution. Time-gated fluorescence (TGF) imaging in mouse tissue sections indicated that they reside preferentially at the bronchoalveolar junctions of lungs, especially in naphthalene-injured mice. Our results presented in Subchapter 1.1 demonstrate not only the remarkable homing capacity and regenerative potential of the isolated stem cells, but also the ability of finding rare lung stem cells in vivo using FNDs.

The topical use of antiretroviral-based microbicides, namely of a dapivirine ring, has been recently shown to partially prevent transmission of HIV through the vaginal route. Among different formulation approaches, nanotechnology tools and principles have been used for the development of tentative vaginal and rectal microbicide products. Subchapter 1.2 provides an overview of antiretroviral drug nanocarriers as novel microbicide candidates and discusses recent and relevant research on the topic. Furthermore, advances in developing vaginal delivery platforms for the administration of promising antiretroviral drug nanocarriers are reviewed. Although mostly dedicated to the discussion of nanosystems for vaginal use, the development of rectal nanomicrobicides is also addressed.

Infectious diseases are currently responsible for over 8 million deaths per year. Efficient treatments require accurate recognition of pathogens at low concentrations, which in the case of blood infection (septicemia) can go as low as 1 mL^–1. Detecting and quantifying bacteria at such low concentrations is challenging and typically demands cultures of large samples of blood (∼1 mL) extending over 24–72 h. This delay seriously compromises the health of patients and is largely responsible for the death toll of bacterial infections. Recent advances in nanoscience, spectroscopy, plasmonics, and microfluidics allow for the development of optical devices capable of monitoring minute amounts of analytes in liquid samples. In Subchapter 1.3 we critically discuss these recent developments that will, in the future, enable the multiplex identification and quantification of microorganisms directly on their biological matrix with unprecedented speed, low cost, and sensitivity.

Radiolabeled nanoparticles (NPs) are finding an increasing interest in a broad range of biomedical applications. They may be used to detect and characterize diseases, to deliver relevant therapeutics, and to study the pharmacokinetic/pharmacodynamic parameters of nanomaterials. The use of radiotracer techniques in the research of novel NPs offers many advantages, but there are still some limitations. The binding of radionuclides to NPs has to be irreversible to prevent their escape to other tissues or organs. Due to the short half-lives of radionuclides, the manufacturing process is time limited and difficult, and there is also a risk of contamination. Subchapter 1.4 presents the main selection criteria for radionuclides and applicable radiolabeling procedures used for the radiolabeling of various NPs. Also, an overview of different types of NPs that have so far been labeled with radionuclides is presented.

First-in-Human Trial of MIV-150 and Zinc Acetate Coformulated in a Carrageenan Gel: Safety, Pharmacokinetics, Acceptability, Adherence, and Pharmacodynamics

OBJECTIVE

To evaluate the safety and pharmacokinetics of MIV-150 and zinc acetate in a carrageenan gel (PC-1005). Acceptability, adherence, and pharmacodynamics were also explored.

DESIGN

A 3-day open-label safety run-in (n = 5) preceded a placebo-controlled, double-blind trial in healthy, HIV-negative, abstinent women randomized (4:1) to vaginally apply 4 mL of PC-1005 or placebo once daily for 14 days.

METHODS

Assessments included physical examinations, safety labs, colposcopy, biopsies, cervicovaginal lavages (CVLs), and behavioral questionnaires. MIV-150 (plasma, CVL, tissue), zinc (plasma, CVL), and carrageenan (CVL) concentrations were determined with LC-MS/MS, ICP-MS, and ELISA, respectively. CVL antiviral activity was measured using cell-based assays. Safety, acceptability, and adherence were analyzed descriptively. Pharmacokinetic parameters were calculated using noncompartmental techniques and actual sampling times. CVL antiviral EC50 values were calculated using a dose-response inhibition analysis.

RESULTS

Participants (n = 20) ranged from 19-44 years old; 52% were black or African American. Among those completing the trial (13/17, PC-1005; 3/3, placebo), 11/17 reported liking the gel overall; 7 recommended reducing the volume. Adverse events, which were primarily mild and/or unrelated, were comparable between groups. Low systemic MIV-150 levels were observed, without accumulation. Plasma zinc levels were unchanged from baseline. Seven of seven CVLs collected 4-hour postdose demonstrated antiviral (HIV, human papillomavirus) activity. High baseline CVL anti-herpes-simplex virus type-2 (HSV-2) activity precluded assessment of postdose activity.

CONCLUSIONS

PC-1005 used vaginally for 14 days was well tolerated. Low systemic levels of MIV-150 were observed. Plasma zinc levels were unchanged. Postdose CVLs had anti-HIV and anti-human papillomavirus activity. These data warrant further development of PC-1005 for HIV and sexually transmitted infection prevention.

Measurement of Vaginal Microbicide Adherence Using Visual Inspection as Compared to Ultra Violet Light Assessment of Returned Empty Gel Applicators

Accurate and objective measurement of adherence is critical in microbicide trials. We compared two applicator tests: visual inspection of returned empty tenofovir gel applicators (VIREA) and ultraviolet light (UVL) assessment in terms of sensitivity and specificity, and for concordance. Sensitivity and specificity analysis of 24 control applicators (12 known-inserted and 12 sham-inserted) at 4-months after receipt was 75.0 and 66.7 % for VIREA and 83.3 and 91.7 % for UVL, respectively. After an additional 3 months of storage sensitivity and specificity was 100 and 58.3 % for VIREA and 100 and 66.7 % for UVL, respectively. In January 2015, 1316 empty applicators were returned as used by 115 participants enrolled at one site in a randomized controlled trial. Assessment outcomes showed 78.8 % agreement between the techniques. Methods concurred that 22.0 % of the returned empty applicators appeared unused. By UVL assessment, 40.0 % of returned empty applicators had no evidence of vaginal insertion, translating to a potential 28.0 % less product used as compared to that returned as used by women. UVL assessment may be considered a more accurate and less subjective measure of adherence as compared to VIREA.

Breaking Down the Siloes: Developing Effective Multidisciplinary HIV Research Teams

As the HIV epidemic passes its 35 years mark, the role of multidisciplinary approaches to HIV research has become increasingly important. Development of diverse, cross-cutting research teams has been found to be key to engaging and retaining participants in population-based studies; it is also a crucial component of designing studies capable of examining the sensitive and nuanced issues that surround HIV related risk and adherence behavior. Expanding our understanding of these issues is central to being able to overcome them and ultimately to the development of best practices for translation of research discovery into improvements in prevention and care. The objectives of this paper are to characterize the importance of multidisciplinary teams in HIV research where they are critical to gaining information that can have a positive impact on the epidemic and to propose specific methods for creating teams to conduct research with optimal public health impact.

Will dapivirine redeem the promises of anti-HIV microbicides? Overview of product design and clinical testing

Microbicides are being developed in order to prevent sexual transmission of HIV. Dapivirine, a non-nucleoside reverse transcriptase inhibitor, is one of the leading drug candidates in the field, currently being tested in various dosage forms, namely vaginal rings, gels, and films. In particular, a ring allowing sustained drug release for 1month is in an advanced stage of clinical testing. Two parallel phase III clinical trials are underway in sub-Saharan Africa and results are expected to be released in early 2016. This article overviews the development of dapivirine and its multiple products as potential microbicides, with particular emphasis being placed on clinical evaluation. Also, critical aspects regarding regulatory approval, manufacturing, distribution, and access are discussed.

Divergent adherence estimates with pharmacokinetic and behavioural measures in the MTN-003 (VOICE) study

INTRODUCTION

In the Microbicide Trial Network MTN-003 (VOICE) study, a Phase IIB pre-exposure prophylaxis trial of daily oral or vaginal tenofovir (TFV), product adherence was poor based on pharmacokinetic (PK) drug detection in a random subsample. Here, we sought to compare behavioural and PK measures of adherence and examined correlates of adherence misreporting.

METHODS

We included participants with PK and behavioural data from VOICE random subsample. Behavioural assessments included face-to-face interviews (FTFI), audio computer-assisted self-interviewing (ACASI) and pharmacy-returned product counts (PC). TFV concentrations < 0.31 ng/mL in plasma (oral group) and < 8.5 ng/swab in vaginal group were defined as "PK non-adherent." Logistic regression models were fit to calculate the combined predictive ability of the behavioural measures as summarized by area under the curve (AUC). Baseline characteristics associated with over-reporting daily product use relative to PK measures was assessed using a Generalized Linear Mixed Model.

RESULTS

In this random adherence cohort of VOICE participants assigned to active products, (N = 472), PK non-adherence was 69% in the oral group (N = 314) and 65% in the vaginal group (N = 158). Behaviourally, ≤ 10% of the cohort reported low/none use with any behavioural measure and accuracy was low (≤ 43%). None of the regression models had an AUC > 0.65 for any single or combined behavioural measures. Significant (p < 0.05) correlates of over-reporting included being very worried about getting HIV and being unmarried for the oral group; whereas for the vaginal group, being somewhat worried about HIV was associated with lower risk of over-reporting.

CONCLUSIONS

PK measures indicated similarly low adherence for the oral and vaginal groups. No behavioural measure accurately predicted PK non-adherence. Accurate real-time measures to monitor product adherence are urgently needed.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00705679.

Optimizing HIV prevention for women: a review of evidence from microbicide studies and considerations for gender-sensitive microbicide introduction

Introduction

Microbicides were conceptualized as a product that could give women increased agency over HIV prevention. However, gender-related norms and inequalities that place women and girls at risk of acquiring HIV are also likely to affect their ability to use microbicides. Understanding how gendered norms and inequalities may pose obstacles to women's microbicide use is important to inform product design, microbicide trial implementation and eventually microbicide and other antiretroviral-based prevention programmes. We reviewed published vaginal microbicide studies to identify gender-related factors that are likely to affect microbicide acceptability, access and adherence. We make recommendations on product design, trial implementation, positioning, marketing and delivery of microbicides in a way that takes into account the gender-related norms and inequalities identified in the review.

Methods

We conducted PubMed searches for microbicide studies published in journals between 2000 and 2013. Search terms included trial names (e.g. “MDP301”), microbicide product names (e.g. “BufferGel”), researchers’ names (e.g. “van der Straten”) and other relevant terms (e.g. “microbicide”). We included microbicide clinical trials; surrogate studies in which a vaginal gel, ring or diaphragm was used without an active ingredient; and hypothetical studies in which no product was used. Social and behavioural studies implemented in conjunction with clinical trials and surrogate studies were also included. Although we recognize the importance of rectal microbicides to women, we did not include studies of rectal microbicides, as most of them focused on men who have sex with men. Using a standardized review template, three reviewers read the articles and looked for gender-related findings in key domains (e.g. product acceptability, sexual pleasure, partner communication, microbicide access and adherence).

Results and discussion

The gendered norms, roles and relations that will likely affect women's ability to access and use microbicides are related to two broad categories: norms regulating women's and men's sexuality and power dynamics within intimate relationships. Though norms about women's and men's sexuality vary among cultural contexts, women's sexual behaviour and pleasure are typically less socially acceptable and more restricted than men's. These norms drive the need for woman-initiated HIV prevention, but also have implications for microbicide acceptability and how they are likely to be used by women of different ages and relationship types. Women's limited power to negotiate the circumstances of their intimate relationships and sex lives will impact their ability to access and use microbicides. Men's role in women's effective microbicide use can range from opposition to non-interference to active support.

Conclusions

Identifying an effective microbicide that women can use consistently is vital to the future of HIV prevention for women. Once such a microbicide is identified and licensed, positioning, marketing and delivering microbicides in a way that takes into account the gendered norms and inequalities we have identified would help maximize access and adherence. It also has the potential to improve communication about sexuality, strengthen relationships between women and men and increase women's agency over their bodies and their health.

Acceptability and preferences for vaginal dosage forms intended for prevention of HIV or HIV and pregnancy

This paper reviews key issues found to affect acceptability and preferences for vaginal products to prevent HIV infection or HIV and pregnancy. We focus on the interplay between the biological and physico-chemical aspects of formulation and the social and behavioral issues that may affect use. The need for an HIV prevention product that women can use is driven by women's increased biological and social vulnerability to HIV infection, and thus social and behavioral research on microbicide acceptability has been conducted alongside, as well as separate from, the earliest product development efforts. Some acceptability and preference issues are specific to a product's dosage form, use-requirements, and/or use indications, while others pertain to any vaginal product used for prevention of HIV or pregnancy. Although most of the work cited here was published since 2010, it draws on a much longer trajectory of research.

Pharmacokinetics of long-acting tenofovir alafenamide (GS-7340) subdermal implant for HIV prophylaxis

Oral or topical daily administration of antiretroviral (ARV) drugs to HIV-1-negative individuals in vulnerable populations is a promising strategy for HIV-1 prevention. Adherence to the dosing regimen has emerged as a critical factor determining efficacy outcomes of clinical trials. Because adherence to therapy is inversely related to the dosing period, sustained release or long-acting ARV formulations hold significant promise for increasing the effectiveness of HIV-1 preexposure prophylaxis (PrEP) by reducing dosing frequency. A novel, subdermal implant delivering the potent prodrug tenofovir alafenamide (TAF) with controlled, sustained, zero-order (linear) release characteristics is described. A candidate device delivering TAF at 0.92 mg day(-1) in vitro was evaluated in beagle dogs over 40 days for pharmacokinetics and preliminary safety. No adverse events related to treatment with the test article were noted during the course of the study, and no significant, unusual abnormalities were observed. The implant maintained a low systemic exposure to TAF (median, 0.85 ng ml(-1); interquartile range [IQR], 0.60 to 1.50 ng ml(-1)) and tenofovir (TFV; median, 15.0 ng ml(-1); IQR, 8.8 to 23.3 ng ml(-1)), the product of in vivo TAF hydrolysis. High concentrations (median, 512 fmol/10(6) cells over the first 35 days) of the pharmacologically active metabolite, TFV diphosphate, were observed in peripheral blood mononuclear cells at levels over 30 times higher than those associated with HIV-1 PrEP efficacy in humans. Our report on the first sustained-release nucleoside reverse transcriptase inhibitor (NRTI) for systemic delivery demonstrates a successful proof of principle and holds significant promise as a candidate for HIV-1 prophylaxis in vulnerable populations.

Lay Social Resources for Support of Adherence to Antiretroviral Prophylaxis for HIV Prevention Among Serodiscordant Couples in sub-Saharan Africa: A Qualitative Study

Effectiveness of antiretroviral pre-exposure prophylaxis (PrEP) for HIV prevention will require high adherence. Using qualitative data, this paper identifies potential lay social resources for support of PrEP adherence by HIV serodiscordant couples in Uganda, laying the groundwork for incorporation of these resources into adherence support initiatives as part of implementation. The qualitative analysis characterizes support for PrEP adherence provided by HIV-infected spouses, children, extended family members, and the larger community. Results suggest social resources for support of PrEP adherence in Africa are plentiful outside formal health care settings and health systems and that couples will readily use them. The same shortage of health professionals that impeded scale-up of antiretroviral treatment for HIV/AIDS in Africa promises to challenge delivery of PrEP. Building on the treatment scale-up experience, implementers can address this challenge by examining the value of lay social resources for adherence support in developing strategies for delivery of PrEP.

Factors Associated with Adherence and Concordance Between Measurement Strategies in an HIV Daily Oral Tenofovir/Emtricitibine as Pre-exposure Prophylaxis (Prep) Clinical Trial, Botswana, 2007-2010

This study examined study product adherence and its determinants in the Botswana oral pre-exposure prophylaxis efficacy trial. Among the 1,219 participants, the mean adherence by pill count and 3-day self-report was 94 % for each. In multivariable models, pill count adherence was significantly associated with adverse events (nausea, dizziness, vomiting) (RR 0.98 95 % CI 0.98-1.00; p = 0.03) and side effect concerns (RR 0.98 95 % CI 0.96-0.99; p = 0.01). Self-reported adherence was significantly associated with having an HIV-positive partner (RR 1.02 95 % CI 1.00-1.04; p = 0.02) and Francistown residence (RR 0.98 95 % CI 0.96, 0.99; p = 0.0001). Detectable drug concentrations showed modest associations with self-report and pill count adherence, and drug levels were higher among those self-reporting 100 % adherence than those reporting <100 %. Most common adherence barriers involved refill delays and other logistic challenges; cellphone alarm reminder use was the most common facilitator.

Estimating the range of potential epidemiological impact of pre-exposure prophylaxis: run-away success or run-away failure?

OBJECTIVE

To investigate the influence of potential interactions between key aspects of a pre-exposure prophylaxis (PrEP) intervention on projections of epidemiological impact and cost-effectiveness.

METHODS

A mathematical model representing the HIV epidemic and intervention context in Nyanza province in Kenya was developed. We consider a scenario whereby a fixed annual budget is allocated to a PrEP intervention. A standard projection of impact is generated, assuming that the unit cost of PrEP, adherence to PrEP and the ability of the programme to direct PrEP to those at high risk, all stay constant. The influence of dynamic assumptions and possible interactions between PrEP intervention assumptions is then assessed in comparison.

RESULTS

The cumulative impact of a PrEP intervention could be increased approximately two-fold, relative to the standard projection, if positive interactions (between coverage and cost, coverage and adherence, prioritization and time) are assumed, whereas negative interactions between these factors could almost entirely negate the preventive benefit of the PrEP intervention. The corresponding estimates of cost per infection averted span a wide range from $2060 to $36360.

CONCLUSIONS

Multiple potentially interacting factors will determine the impact of PrEP. Model forecasts should reflect that uncertainty and programmes should focus on these factors and measure them, to maximize the impact of programmes.

Patterns and correlates of PrEP drug detection among MSM and transgender women in the Global iPrEx Study

BACKGROUND

Adherence to pre-exposure prophylaxis (PrEP) is critical for efficacy. Antiretroviral concentrations are an objective measure of PrEP use and correlate with efficacy. Understanding patterns and correlates of drug detection can identify populations at risk for nonadherence and inform design of PrEP adherence interventions.

METHODS

Blood antiretroviral concentrations were assessed among active arm participants in iPrEx, a randomized placebo-controlled trial of emtricitabine/tenofovir in men who have sex with men and transgender women in 6 countries. We evaluated rates and correlates of drug detection among a random sample of 470 participants at week 8 and a longitudinal cohort of 303 participants through 72 weeks of follow-up.

RESULTS

Overall, 55% of participants (95% confidence interval: 49 to 60) tested at week 8 had drug detected. Drug detection was associated with older age and varied by study site. In longitudinal analysis, 31% never had drug detected, 30% always had drug detected, and 39% had an inconsistent pattern. Overall detection rates declined over time. Drug detection at some or all visits was associated with older age, indices of sexual risk, including condomless receptive anal sex, and responding "don't know" to a question about belief of PrEP efficacy (0-10 scale).

CONCLUSIONS

Distinct patterns of study product use were identified, with a significant proportion demonstrating no drug detection at any visit. Research literacy may explain greater drug detection among populations having greater research experience, such as older men who have sex with men in the United States. Greater drug detection among those reporting highest risk sexual practices is expected to increase the impact and cost-effectiveness of PrEP.

Medication adherence among men who have sex with men at risk for HIV infection in the United States: implications for pre-exposure prophylaxis implementation

Pre-exposure prophylaxis (PrEP) is a promising HIV prevention approach for men who have sex with men (MSM), however non-adherence could limit its effectiveness. Understanding the experiences of HIV-uninfected MSM taking routine medications can provide valuable insights into open label PrEP adherence in real world settings and guide development of PrEP adherence interventions. In this study, we examined self-reported medication-taking experiences and facilitators and barriers of medication adherence among a geographically-diverse online sample of HIV-uninfected US MSM. Among 1480 participants, 806 (54%) reported taking medications regularly, of whom 80% reported taking medications for treatment and 55% for prevention purposes. Facilitators of medication adherence included establishing a routine, keeping medication visible, and using a pill-box; barriers included forgetting, changes in routine, and being busy or away from home. Only 45% rated their medication-taking ability as excellent, and 36% reported not missing any doses in the past 30 days. In multivariable analyses, older men and those not reporting any adherence barriers were more likely to report excellent adherence, and men willing to use PrEP were more likely to report perfect 30-day adherence. Counseling strategies to build pill-taking routines and support younger MSM are suggested to maximize the public health impact of PrEP.

Pre-exposure prophylaxis for human immunodeficiency virus: the past, present, and future

This article presents an overview of pre-exposure prophylaxis (PrEP) for human immunodeficiency virus (HIV) prevention. The authors describe the past animal and human research that has been conducted that informs our current understanding of PrEP; summarize ongoing research in the area, including describing new regimens and delivery mechanisms being studied for PrEP; and highlight key issues that must be addressed in order to implement and optimize the use of this HIV prevention tool.

An interdisciplinary framework for measuring and supporting adherence in HIV prevention trials of ARV-based vaginal rings

INTRODUCTION

Product adherence and its measurement have emerged as a critical challenge in the evaluation of new HIV prevention technologies. Long-acting ARV-based vaginal rings may simplify use instructions and require less user behaviour, thereby facilitating adherence. One ARV-based ring is in efficacy trials and others, including multipurpose rings, are in the pipeline. Participant motivations, counselling support and measurement challenges during ring trials must still be addressed. In previous HIV prevention trials, this has been done largely using descriptive and post-hoc methods that are highly variable and minimally evaluated. We outline an interdisciplinary framework for systematically investigating promising strategies to support product uptake and adherence, and to measure adherence in the context of randomized, blinded clinical trials.

DISCUSSION

The interdisciplinary framework highlights the dual use of adherence measurement (i.e. to provide feedback during trial implementation and to inform interpretation of trial findings) and underscores the complex pathways that connect measurement, adherence support and enacted adherence behaviour. Three inter-related approaches are highlighted: 1) adherence support - sequential efforts to define motivators of study product adherence and to develop, test, refine and evaluate adherence support messages; 2) self-reported psychometric measures - creation of valid and generalizable measures based in easily administered scales that capture vaginal ring use with improved predictive ability at screening, baseline and follow-up that better engage participants in reporting adherence; and 3) more objective measurement of adherence - real-time adherence monitoring and cumulative measurement to correlate adherence with overall product effectiveness through innovative designs, models and prototypes using electronic and biometric technologies to detect ring insertion and/or removal or expulsion. Coordinating research along these three pathways will result in a comprehensive approach to product adherence within clinical trials.

CONCLUSIONS

Better measurement of adherence will not, by itself, ensure that future effectiveness trials will be able to address the most basic question: if the product is used per instructions, will it prevent HIV transmission? The challenges to adherence measurement must be addressed as one component of a more integrated system that has as its central focus adherence as a behaviour emerging from the social context of the user.

Perspectives on use of oral and vaginal antiretrovirals for HIV prevention: the VOICE-C qualitative study in Johannesburg, South Africa

Introduction

Antiretroviral (ARV)-based pre-exposure prophylaxis (PrEP) is a promising new HIV prevention strategy. However, variable levels of adherence have yielded mixed results across several PrEP trials and populations. It is not clear how taking ARV – traditionally used for HIV treatment – is perceived and how that perception may affect the use of these products as preventives. We explored the views and experiences of VOICE participants, their male partners and community members regarding the use of ARV as PrEP in the VOICE trial and the implications of these shared meanings for adherence.

Methods

VOICE-C was a qualitative ancillary study conducted at the Johannesburg site of VOICE, a multisite, double-blind, placebo-controlled randomised trial testing tenofovir gel, oral tenofovir and oral Truvada^® for HIV PrEP. We interviewed 102 randomly selected female VOICE participants, 22 male partners and 40 community members through in-depth interviews, serial ethnography, or focus group discussions. All interviews were audiotaped, transcribed, translated and coded thematically for analysis.

Results

The concept of ARV for prevention was understood to varying degrees across all study groups. A majority of VOICE participants understood that the products contained ARV, more so for the tablets than for the gel. Although participants knew they were HIV negative, ARV was associated with illness. Male partners and community members echoed these sentiments, highlighting confusion between treatment and prevention. Concerned that they would be mistakenly identified as HIV positive, VOICE participants often concealed use of or hid their study products. This occasionally led to relationship conflicts or early trial termination. HIV stigma and its association with ARV, especially the tablets, was articulated in rumour and gossip in the community, the workplace and the household. Although ARV were recognised as potent and beneficial medications, transforming the AIDS body from sickness to health, they were regarded as potentially harmful for those uninfected.

Conclusions

VOICE participants and others in the trial community struggled to conceptualise the idea of using ARV for prevention. This possibly influenced willingness to adopt ARV-based prevention in the VOICE clinical trial. Greater investments should be made to increase community understanding of ARV for prevention and to mitigate pervasive HIV stigma.

Engaging male partners in women's microbicide use: evidence from clinical trials and implications for future research and microbicide introduction

INTRODUCTION

Constructively engaging male partners in women-centred health programs such as family planning and prevention of mother-to-child HIV transmission has resulted in both improved health outcomes and stronger relationships. Concerted efforts to engage men in microbicide use could make it easier for women to access and use microbicides in the future. This paper synthesizes findings from studies that investigated men's role in their partners' microbicide use during clinical trials to inform recommendations for male engagement in women's microbicide use.

METHODS

We conducted primary and secondary analyses of data from six qualitative studies implemented in conjunction with microbicide clinical trials in South Africa, Kenya, and Tanzania. The analyses included data from 535 interviews and 107 focus groups with trial participants, male partners, and community members to answer research questions on partner communication about microbicides, men's role in women's microbicide use, and potential strategies for engaging men in future microbicide introduction. We synthesized the findings across the studies and developed recommendations.

RESULTS

The majority of women in steady partnerships wanted agreement from their partners to use microbicides. Women used various strategies to obtain their agreement, including using the product for a while before telling their partners, giving men information gradually, and continuing to bring up microbicides until resistant partners acquiesced. Among men who were aware their partners were participating in a trial and using microbicides, involvement ranged from opposition to agreement/non-interference to active support. Both men and women expressed a desire for men to have access to information about microbicides and to be able to talk with a healthcare provider about microbicides.

CONCLUSIONS

We recommend counselling women on whether and how to involve their partners including strategies for gaining partner approval; providing couples' counselling on microbicides so men have the opportunity to talk with providers; and targeting men with community education and mass media to increase their awareness and acceptance of microbicides. These strategies should be tested in microbicide trials, open-label studies, and demonstration projects to identify effective male engagement approaches to include in eventual microbicide introduction. Efforts to engage men must take care not to diminish women's agency to decide whether to use the product and inform their partners.

In vitro and in vivo evaluation of two carrageenan-based formulations to prevent HPV acquisition

Commercial vaccines against human papillomavirus (HPV) have low uptake due to parental autonomy, dosing regimen, cost, and cold chain storage requirements. Carrageenan (CG)-based formulations prevent HPV infection in vitro and in vivo but data are needed on the durability of anti-HPV activity and the effect of seminal plasma (SP). The Population Council's PC-515 gel and the lubricant Divine 9 were tested for their physicochemical properties and anti-HPV activity against HPV16, 18, and 45 pseudoviruses (PsVs). Anti-PsV activity was estimated using the luciferase assay in HeLa cells and the HPV PsV luciferase mouse model. Formulations were applied intravaginally either 2h pre/2h post (-2h/+2h) or 24h pre (-24h) relative to challenge with HPV16 or 45 PsV in PBS or SP/PBS. Both formulations showed broad-spectrum anti-HPV activity in vitro (IC50: 1-20ng/ml), significantly decreasing HPV PsV infection in the mouse model (-2h/+2h, p<0.0001). PC-515 protected better than Divine 9 in the -24h dosing regimen (p<0.0001) and comparable to Divine 9 in the -2h/+2h regimen (p=0.9841). PC-515 retained full activity in the murine model when PsV solutions contained human SP. The durable, potential broad-spectrum anti-HPV activity of CG formulations in the presence of SP supports their further development to prevent HPV acquisition.

Conceptualisations of masculinity and self-reported medication adherence among HIV-positive Latino men in Los Angeles, California, USA

HIV-positive Latino men have been found to have poorer medication adherence compared to Whites. This study sought to identify how cultural conceptualisations of masculinity are associated with self-reported medication adherence among Latino men. A total of 208 HIV-positive men reported the number of doses of antiretroviral medication missed in the previous seven days (dichotomised at 100% adherence versus less). Conceptualisations of masculinity consisted of traditional machismo (e.g., power and aggressive attitudes, which are normally associated with negative stereotypes of machismo) and caballerismo (e.g., fairness, respect for elders and the importance of family). Multivariate logistic regression was used to identify factors associated with adherence. The mean adherence was 97% (SD = 6.5%; range = 57-100%). In all, 77% of the participants reported 100% adherence in the previous seven days. Caballerismo was associated with a greater likelihood (OR = 1.77; 95% CI: 1.08-2.92; p = 0.03) and machismo with a lower likelihood (OR = 0.60; 95% CI: 0.38-0.95; p = 0.03) of medication adherence. In addition, higher medication side-effects were found to be associated with a lower likelihood (OR = 0.59; 95% CI: 0.43-0.81; p = 0.001) of medication adherence. These findings reinforce the importance of identifying cultural factors that may affect medication adherence among HIV-positive Latino men resident in the USA.

Optimizing content for pre-exposure prophylaxis (PrEP) counseling for men who have sex with men: Perspectives of PrEP users and high-risk PrEP naïve men

Existing trials of antiretroviral (ARV) medication as chemoprophylaxis against HIV reveal that the degree of protection is primarily dependent on product adherence. However, there is a lack of data on targets for behavioral interventions to improve adherence to ARV as prevention. Information from individuals who have used ARV as pre-exposure prophylaxis (PrEP) can inform behavioral intervention development. Thirty-nine HIV-uninfected MSM at high risk for HIV acquisition participated in one of four semi-structured focus groups. Two of the focus groups consisted of MSM who had been prescribed and used PrEP in the context of a clinical trial; the other two consisted of high-risk MSM who had not previously used PrEP. An in-depth, within-case/across-case content analysis resulted in six descriptive themes potentially salient for a PrEP adherence behavioral intervention: (1) motivations to use PrEP, (2) barriers to PrEP use, (3) facilitators to PrEP use, (4) sexual decision-making in the context of PrEP, (5) prospective PrEP education content, and, (6) perceived effective characteristics of PrEP delivery personnel. Addressing these themes in behavioral interventions in the context of prescribing PrEP may result in the optimal "packaging" public health programs that implement PrEP for high-risk MSM.

Helping our patients take HIV pre-exposure prophylaxis (PrEP): a systematic review of adherence interventions

OBJECTIVES

Adherence is critical for maximizing the effectiveness of pre-exposure prophylaxis (PrEP) in preventing HIV infection. Strategies for promoting adherence to HIV treatment, and their potential application to PrEP adherence, have received considerable attention. However, adherence promotion strategies for prevention medications have not been well characterized and may be more applicable to PrEP. We aimed to identify adherence support interventions that have been effective in other prevention fields and could be applied in the HIV prevention context to support pill taking among PrEP users.

METHODS

To identify adherence support interventions that could be evaluated and applied in the PrEP context, we conducted a systematic review across the following prevention fields: hypertension, latent tuberculosis infection, hyperlipidaemia, oral contraceptives, osteoporosis, malaria prophylaxis, and post-exposure prophylaxis for HIV infection. We included randomized controlled trials that evaluated the efficacy of interventions to improve adherence to daily oral medications prescribed for primary prevention in healthy individuals or for secondary prevention in asymptomatic individuals.

RESULTS

Our searches identified 585 studies, of which 48 studies met the eligibility criteria and were included in the review; nine evaluated multiple strategies, yielding 64 separately tested interventions. Interventions with the strongest evidence for improving adherence included complex, resource-intensive interventions, which combined multiple adherence support approaches, and low-cost, low-intensity interventions that provided education or telephone calls for adherence support.

CONCLUSIONS

Our review identified adherence interventions with strong evidence of efficacy across prevention fields and provides recommendations for evaluating these interventions in upcoming PrEP studies.

Adherence challenges with drugs for pre-exposure prophylaxis to prevent HIV infection

BACKGROUND

There are 34 million people living with human immunodeficiency virus (HIV) worldwide and each year this number increases. Until a vaccine is discovered, the prevention of new HIV infections remains an urgent priority. Several trials studying the use of oral and topical agents for the prevention of HIV infection have already been completed. Adherence has proved to be a major challenge in achieving product efficacy.

AIM OF THE REVIEW

To provide the clinical pharmacist with an understanding of the oral pre-exposure prophylaxis (PrEP) and topical microbicide product pipeline whilst emphasizing the critical importance of adherence to these drugs to avert HIV infection.

METHODS

PubMed/Medline and the web-based clinical trials registry (ClinTrials.gov) were searched using appropriate key words. For the time period 1992-2013--all phase II and phase III safety and effectiveness studies--testing agents for prevention of HIV infection were included in the review. Efficacy estimates, adherence estimates and reported challenges with adherence were extracted.

RESULTS

Twenty-four phase II and III clinical trials were found during review. Of these, 20 trials have been completed, and six trials show effectiveness in preventing HIV infection. The majority of the successful trials were to oral PrEP and to date only one microbicide trial of a vaginal antiretroviral microbicide gel has showed effectiveness. Adherence to study product played a major role in trial outcomes and there are several reasons for non-adherence. These include high on-trial pregnancy rates, low trial retention rates, low participant perception of risk, participant characteristics such as age <25 years, single status, migratory partners and trial fatigue. Study product characteristics such as dosage form, dosing interval, as well as associated adverse events may also influence adherence.

CONCLUSION

Moderate to high adherence is critical to demonstrate efficacy of drugs for HIV prevention. For topical agents, intermittent use associated with coitus is more effective than daily use, particularly if sex is infrequent or partners migrant. For oral agents, daily use is effective but the motivation to use the drug and high risk perception is important. In serodiscordant couples, early initiation of highly active antiretroviral therapy in the infected partner affords almost complete protection to the negative partner. Drugs need to be tailored to the population at risk and availability of multiple drug options are important.

Acceptability of oral and topical HIV chemoprophylaxis in India: implications for at-risk women and men who have sex with men

With reducing HIV prevalence, India has made gains in containing the epidemic. Yet, unprotected sex and commercial sex work, unprotected anal sex between men and needle sharing among intravenous drug users continue to drive the epidemic. Development of effective, safe and acceptable topical (microbicides) and oral (pre-exposure prophylaxis (PrEP)) chemoprophylaxis could augment the already available tools for HIV prevention. This paper reviews the acceptability of topical microbicides and oral PrEP, in the context of the nature of the HIV epidemic, the sociocultural norms and the acceptability data obtained from studies carried out in India. Overall, men and women have a positive attitude towards the concept and use of microbicide products. Self-perceptions of HIV risk, product attributes, ease and convenience of use during sex, gender norms, the sociocultural context and the potential for undisclosed use were important factors influencing acceptability. A multipurpose product that would simultaneously address women's contraceptive and disease prevention needs would be devoid of the stigma attached to an anti-HIV product and may be more acceptable. Limited information on the acceptability of oral PrEP amongst high-risk groups merits further research, including carrying out demonstration projects for program introduction.

Evaluation of 3 approaches for assessing adherence to vaginal gel application in clinical trials

BACKGROUND

Accurate measurement of adherence to product use is an ongoing challenge in microbicide trials.

METHODS

We compared adherence estimates using 2 applicator tests (a dye stain assay [DSA] and an ultraviolet light assay [UVA]), the Wisebag (an applicator container that electronically tracks container openings), and self-reported adherence (ability, frequency, and percent missed doses). Healthy, HIV-negative, nonpregnant US women aged 23 to 45 years received a Wisebag and 32 applicators filled with placebo gel were instructed to insert 1 applicator daily for 30 days, returned the Wisebag and all applicators, and completed an exit interview. Emptied applicators were tested by UVA and then DSA, and scored by 2 blinded readers. Positive and negative controls were randomly included in applicator batches.

RESULTS

Among 42 women enrolled, 39 completed the study. Both DSA and UVA yielded similar sensitivity (97% and 95%) and specificity (79% and 79%). Two participants had fully inoperable Wisebags, and 9 had partially inoperable Wisebags. The proportion of participants considered to have high adherence (≥80%) varied: 43% (Wisebag), 46% (UVA), 49% (DSA), and 62% to 82% (self-reports). For estimating high adherence, Wisebag had a sensitivity of 76% (95% confidence interval, 50%-93%) and a specificity of 85% (95% confidence interval, 62%-97%) compared with DSA. Although 28% of participants reported forgetting to open the Wisebag daily, 59% said that it helped them remember gel use.

CONCLUSIONS

Dye stain assay and UVA performed similarly. Compared with these tests, self-reports overestimated and Wisebag underestimated adherence. Although Wisebag may encourage gel use, the applicator tests currently seem more useful for measuring use in clinical trials.

Summary measures of adherence using pill counts in two HIV prevention trials: the need for standardisation in reporting

For trials of user-dependent HIV prevention products, accurate adherence measurements are essential to interpret and compare results across trials. We used pill count data from two recent HIV prevention trials of herpes simplex virus type 2 (HSV-2) suppression, to show that estimates of adherence vary substantially depending on assumptions that are made in analysing pill count data. We associate calculated adherence with biological markers of anti-HSV-2 activity. In both trials, calculated adherence varied considerably, depending on the summary measure used, and the handling of intervals with apparent ‘over-adherence’ (fewer pills returned than expected), and unreturned pills. Intervals of apparent over-adherence were associated with reduced antiviral effects on biological markers of herpes reactivation, indicating these are likely to represent periods of non-adherence. Our results demonstrate the clear need for standardisation in reporting of adherence data that are based on pill counts.

Use of a novel technology to track adherence to product use in a microbicide trial of short duration (MTN-007)

Adherence measurement in microbicide trials is challenging. To decrease recall and social desirability bias, we used an interactive voice response system (IVR) in a rectal microbicide trial. Forty-six participants were asked to report product use daily for 1 week. Participants received an incentive per call plus a bonus for calling every day. We examined adherence to calling the IVR and to gel use; we compared the latter to applicator counts. Adherence to calling the IVR daily was high (mean = 89.9 %, SD = 20.7 %). Adherence to gel use per IVR was very good (mean = 90.7 %, SD = 19.1 %), and consistent with applicator counts in 80.4 % of cases. Neither adherence to calling nor gel use were associated with temporal factors like day calls started, number of days since first call, or weekday vs. weekend. Daily reporting allowed identification of irregular product use. IVR appears useful for daily reporting in brief trials.

Participant experiences and facilitators and barriers to pill use among men who have sex with men in the iPrEx pre-exposure prophylaxis trial in San Francisco

In 2010, the iPrEx study demonstrated efficacy of daily emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) pre-exposure prophylaxis (PrEP) in reducing HIV acquisition among men who have sex with men. Adherence to study product was critical for PrEP efficacy, and varied considerably, with FTC/TDF detection rates highest in the United States. We conducted a qualitative study to gain insights into the experiences of iPrEx participants in San Francisco (SF) where there was high confirmed adherence, to understand individual and contextual factors influencing study product use in this community. In 2009 and 2011, we conducted focus groups and in-depth interviews in 36 and 16 SF iPrEx participants, respectively. Qualitative analyses indicate that participants joined the study out of altruism. They had a clear understanding of study product use, and pill taking was facilitated by establishing or building on an existing routine. Participants valued healthcare provided by the study and relationships with staff, whom they perceived as nonjudgmental, and found client-centered counseling to be an important part of the PrEP package. This facilitated pill taking and accurate reporting of missed doses. Adherence barriers included changes in routine, side effects/intercurrent illnesses, and stress. Future PrEP adherence interventions should leverage existing routines and establish client-centered relationships/ environments to support pill taking and promote accurate reporting.

Adherence support approaches in biomedical HIV prevention trials: experiences, insights and future directions from four multisite prevention trials

Adherence is a critical component of the success of antiretroviral-based pre-exposure prophylaxis (PrEP) in averting new HIV-infections. Ensuring drug availability at the time of potential HIV exposure relies on self-directed product use. A deeper understanding of how to best support sustained PrEP adherence remains critical to current and future PrEP efforts. This paper provides a succinct synthesis of the adherence support experiences from four pivotal PrEP trials--Centre for the AIDS Programme of Research in South Africa (CAPRISA) 004, FEM-PrEP, Iniciativa Prophylaxis (iPrEx), and Vaginal and Oral Interventions to Control the Epidemic (VOICE). Notwithstanding variability in the design, population/cohort, formulation, drug, dosing strategy, and operationalization of adherence approaches utilized in each trial, the theoretical basis and experiences in implementation and monitoring of the approaches used by these trials provide key lessons for optimizing adherence in future research and programmatic scale-up of PrEP. Recommendations from across these trials include participant-centered approaches, separating measurement of adherence from adherence counseling, incorporating tailored strategies that go beyond education, fostering motivation, and addressing the specific context in which an individual incorporates and negotiates PrEP use.

Antiretroviral pharmacology in mucosal tissues

Strategies to prevent HIV infection using preexposure prophylaxis are required to curtail the HIV pandemic. The mucosal tissues of the genital and rectal tracts play a critical role in HIV acquisition, but antiretroviral (ARV) disposition and correlates of efficacy within these tissues are not well understood. Preclinical and clinical strategies to describe ARV pharmacokinetic-pharmacodynamic relationships within mucosal tissues are currently being investigated. In this review, we summarize the physicochemical and biologic factors influencing ARV tissue exposure. Furthermore, we discuss the necessary steps to generate relevant pharmacokinetic-pharmacodynamic data and the challenges associated with this process. Finally, we suggest how preclinical and clinical data might be practically translated into optimal preexposure prophylaxis dosing strategies for clinical trials testing using mathematical modeling and simulation.

Microbicide clinical trial adherence: insights for introduction

After two decades of microbicide clinical trials it remains uncertain if vaginally- delivered products will be clearly shown to reduce the risk of HIV infection in women and girls. Furthermore, a microbicide product with demonstrated clinical efficacy must be used correctly and consistently if it is to prevent infection. Information on adherence that can be gleaned from microbicide trials is relevant for future microbicide safety and efficacy trials, pre-licensure implementation trials, Phase IV post-marketing research, and microbicide introduction and delivery. Drawing primarily from data and experience that has emerged from the large-scale microbicide efficacy trials completed to-date, the paper identifies six broad areas of adherence lessons learned: (1) Adherence measurement in clinical trials, (2) Comprehension of use instructions/Instructions for use, (3) Unknown efficacy and its effect on adherence/Messages regarding effectiveness, (4) Partner influence on use, (5) Retention and continuation and (6) Generalizability of trial participants' adherence behavior. Each is discussed, with examples provided from microbicide trials. For each of these adherence topics, recommendations are provided for using trial findings to prepare for future microbicide safety and efficacy trials, Phase IV post-marketing research, and microbicide introduction and delivery programs.