Long acting systemic HIV pre-exposure prophylaxis: an examination of the field

Parenteral platforms for tunable, long-acting administration of a highly hydrophobic antiretroviral drug

GSK2838232 (GSK8232) is a second-generation maturation inhibitor (MI) developed for the treatment of HIV with excellent broad-spectrum virological profiles. The compound has demonstrated promising clinical results as an orally administered agent. Additionally, the compound's physical and pharmacological properties present opportunities for exploitation as long-acting parenteral formulations. Despite unique design constraints including solubility and dose of GSK8232, we report on three effective tunable drug delivery strategies: active pharmaceutical ingredient (API) suspensions, ionic liquids, and subdermal implants. Promising sustained drug release profiles were achieved in rats with each approach. Additionally, we were able to tune drug release rates through a combination of passive and active strategies, broadening applicability of these formulation approaches beyond GSK8232. Taken together, this report is an important first step to advance long-acting formulation development for critical HIV medicines that do not fit the traditional profile of suitable long-acting candidates.

Enzyme-Triggered l-α/d-Peptide Hydrogels as a Long-Acting Injectable Platform for Systemic Delivery of HIV/AIDS Drugs

Eradicating HIV/AIDS by 2030 is a central goal of the World Health Organization. Patient adherence to complicated dosage regimens remains a key barrier. There is a need for convenient long-acting formulations that deliver drugs over sustained periods. This paper presents an alternative platform, an injectable in situ forming hydrogel implant to deliver a model antiretroviral drug (zidovudine [AZT]) over 28 days. The formulation is a self-assembling ultrashort d or l-α peptide hydrogelator, namely phosphorylated (naphthalene-2-ly)-acetyl-diphenylalanine-lysine-tyrosine-OH (NapFFKY[p]-OH), covalently conjugated to zidovudine via an ester linkage. Rheological analysis demonstrates phosphatase enzyme instructed self-assembly, with hydrogels forming within minutes. Small angle neutron scattering data suggest hydrogels form narrow radius (≈2 nm), large length fibers closely fitting the flexible cylinder elliptical model. d-Peptides are particularly promising for long-acting delivery, displaying protease resistance for 28 days. Drug release, via hydrolysis of the ester linkage, progress under physiological conditions (37 °C, pH 7.4, H2 O). Subcutaneous administration of Napffk(AZT)Y[p]G-OH in Sprague Dawley rats demonstrate zidovudine blood plasma concentrations within the half maximal inhibitory concentration (IC50 ) range (30-130 ng mL-1 ) for 35 days. This work is a proof-of-concept for the development of a long-acting combined injectable in situ forming peptide hydrogel implant. These products are imperative given their potential impact on society.

Preferences for pre-exposure prophylaxis (PrEP) among sexual and gender minorities: a discrete choice experiment in Brazil

Background

Men who have sex with men (MSM) and transgender women (TGW) are disproportionally affected by HIV infection in Latin America. This study aims to assess pre-exposure prophylaxis (PrEP) preferences among sexual and gender minorities (SGM) and identify attributes and levels that are related to PrEP uptake and adherence, both crucial for PrEP success.

Methods

We conducted a discrete choice experiment (DCE) among SGM from all Brazilian regions (September-December/2020). The survey was administered face-to-face (five Brazilian capitals) and online (entire country). We used a D-efficient zero-prior blocked experimental design to select 60 paired-profile DCE choice tasks.

Findings

The total sample size was 3924 (90.5% MSM; 7.2% TGW and 2.3% non-binary or gender diverse persons). In random-effects logit models, highest levels of protection and "no side effects" were the most important attribute levels. For "presentation", injectable and implant were preferred over oral. Participants were willing to accept a 4.1% protection reduction to receive injectable PrEP or a 4.2% reduction if PrEP were taken monthly. The largest class in the latent class models was defined predominantly by the preference for the highest HIV protection level (p < 0.005). Respondents in this class also preferred no side effects, injectable and implant presentations.

Interpretation

Higher HIV protection, no side effects, and presentation, whether injectable or implant, were the most important attributes in PrEP preferences. Protection against HIV was the most important attribute. PrEP programs should make available technologies such as long-acting presentations that could reunite the most desired attributes, thus maximizing acceptability and user-appropriateness.

Funding

Unitaid.

Preferences for Long-Acting and Alternative Modalities for PrEP among Military Men Who Have Sex with Men: Segmentation Results of an Adaptive Choice-Based Conjoint Analysis Study

The use of pre-exposure prophylaxis (PrEP) for HIV prevention within the U.S. military is low. Implementing preference-based alternative modalities of PrEP delivery, however, can be an innovative strategy to address the specific barriers to PrEP uptake among military MSM. We sought to identify population-based, segment-specific preferences for longer-acting and alternative PrEP delivery modalities to guide patient-centered strategies to optimize uptake within military-serving healthcare systems. HIV-negative military men who have sex with men (MSM) completed an anonymous, adaptive choice-based conjoint (ACBC) analysis survey consisting of five key attributes of interest (dosing method, provider type, visit location, lab work evaluation location, and dispensing venue). Relative importance and part-worth utility scores were generated using Hierarchical Bayes (HB) estimation, and cluster ensemble analysis grouped participants into "phenotype" segments by preference similarity. The randomized first-choice model was then used to examine changes in program interest rates among segments through market simulation. The 429 participants were segmented into five preference groups. The dosing method attribute was found to be the most important to nearly all segments. Simulations revealed that PrEP program interest among two segments with low interest levels increased when smartphone, civilian-based, and long-acting injectable PrEP options were involved. Findings also suggested a need for clinics to be responsive and sensitive to sexual practices, risk perception, and functional PrEP knowledge. Responsiveness to segment-specific preferences in the design of military PrEP programs and acting on the importance of clinical relationships within the context of PrEP engagement within a military setting may contribute to increasing PrEP uptake.

Preferences for pre-exposure prophylaxis (PrEP) among men who have sex with men and transgender women at risk of HIV infection: a multicentre protocol for a discrete choice experiment in Brazil

INTRODUCTION

Pre-exposure prophylaxis (PrEP) is an important and well-established prevention strategy for sexual acquisition of HIV. In Brazil, transgender women (TGW) and men who have sex with men (MSM) bear the largest burden among key populations. Little is known about preferences for PrEP characteristics in these vulnerable populations in Latin America. The goal of this study is to investigate preferences of TGW and MSM with respect to PrEP characteristics, whether current user or not, and to assess any attributes and levels that may improve the decision to start using PrEP (uptake) and optimal continuity of use (adherence), which are important dimensions for PrEP success.

METHODS AND ANALYSIS

We hereby outline the protocol of a discrete choice experiment (DCE) to be conducted among TGW and MSM in Brazil. The study will be carried out in two phases. The first phase involves literature review and qualitative approaches including in-depth interviews to inform the development of the DCE (attributes and levels). The second phase entails the DCE survey and supporting questions pertaining to sociodemographic and risk behaviour information. The survey is aimed at current PrEP users and non-users, consisting of two modes of administration: face to face in five Brazilian capitals (Rio de Janeiro, Brasília, Manaus, Porto Alegre and Salvador) and online targeting the entire country. A D-efficient zero-prior blocked experimental design will be used to select 60 paired-profile DCE choice tasks, in which participants will be randomly assigned to one of four groups and presented with a set of 15 choice tasks. The planned sample size is 1000 volunteers.

ETHICS, TIMELINE AND DISSEMINATION

The study was approved by Comitê de Ética em Pesquisa-Instituto Nacional de Infectologia Evandro Chagas-INI/FIOCRUZ, CEP/INI, CAAE 28416220.2.1001.5262, approval number 3.979.759 in accordance with the Comissão Nacional de Ética em Pesquisa (CONEP-Brazilian National Board of Research Ethics). The study will be conducted between 2020 and 2021. The results will be disseminated to the scientific community and to the public in general through publications in published in peer-reviewed journals and in scientific conferences.

Preferences for pre-exposure prophylaxis among U.S. military men who have sex with men: results of an adaptive choice based conjoint analysis study

BACKGROUND

Pre-exposure prophylaxis (PrEP) prevents human immunodeficiency virus (HIV) infection, but its use remains low among U.S. military men who have sex with men (MSM), likely due to mis-matching with personal preferences. We conducted a study to characterize preferences to PrEP measures within this population.

METHODS

HIV-negative military MSM were recruited through a closed, Lesbian, Gay, Bisexual, and Transgendered (LGBT) military social media group. The survey was anonymous, and consisted of five experimentally varied attributes in service delivery: dosing method, provider type, visit location, lab work evaluation location, and dispensing venue. Relative importance and part-worth utility scores were generated using hierarchical bayes (HB) estimation, and the randomized first choice model was used to examine participation interest across eight possible PrEP program scenarios.

RESULTS

A total of 429 participants completed the survey. Among the eight scenarios with varying attributes, the most preferred scenario featured a daily tablet, PrEP injection or implant, along with a military provider, smartphone/telehealth visit, and on-base locations for lab evaluation and medication pick-up. The results also emphasized the importance for providers to be familiar with PrEP prescription knowledge, and to provide interactions sensitive to sexual identity and mental health.

CONCLUSION

A PrEP program consisting of daily tablet is preferred in military healthcare settings is preferred. Long-acting implants and injections are also desired.

HIV Antiretroviral Treatment and Pre-exposure Prophylaxis in Transgender Individuals

HIV prevalence is elevated among transgender populations with an estimated 13.7% of transgender adults living with HIV in the USA. In addition, transgender people experience significant disparities in biomedical HIV prevention and treatment. The efficacy of topical microbicides for prevention of HIV acquisition have not been tested among transgender people and may be impacted by hormonal therapies and/or surgeries undertaken by some transgender people to align their anatomy with their gender identity. Low pre-exposure prophylaxis (PrEP) uptake and adherence as well as potential drug-hormone interactions impact the efficacy of PrEP among transgender women. Few transgender men have been engaged in the PrEP continuum, and they have been largely excluded from PrEP research until very recently. Prioritisation of hormone therapy over HIV treatment as well as concerns about drug-hormone interactions may impact transgender women's adherence to antiretroviral therapy. More research is needed to clarify the clinical significance of identified drug-hormone interactions and better inform interventions to improve HIV prevention and care for transgender people.

Multispecies Evaluation of a Long-Acting Tenofovir Alafenamide Subdermal Implant for HIV Prophylaxis

New HIV-1 infection rates far outpace the targets set by global health organizations, despite important progress in curbing the progression of the epidemic. Long-acting (LA) formulations delivering antiretroviral (ARV) agents for HIV-1 pre-exposure prophylaxis (PrEP) hold significant promise, potentially facilitating adherence due to reduced dosing frequency compared to oral regimens. We have developed a subdermal implant delivering the potent ARV drug tenofovir alafenamide that could provide protection from HIV-1 infection for 6 months, or longer. Implants from the same lot were investigated in mice and sheep for local safety and pharmacokinetics (PKs). Ours is the first report using these animal models to evaluate subdermal implants for HIV-1 PrEP. The devices appeared safe, and the plasma PKs as well as the drug and metabolite concentrations in dermal tissue adjacent to the implants were studied and contrasted in two models spanning the extremes of the body weight spectrum. Drug and drug metabolite concentrations in dermal tissue are key in assessing local exposure and any toxicity related to the active agent. Based on our analysis, both animal models were shown to hold significant promise in LA product development.

Fully synthetic injectable depots with high drug content and tunable pharmacokinetics for long-acting drug delivery

Clinical studies have validated that antiretroviral (ARV) drugs can serve as an HIV pre-exposure prophylactic (PrEP) strategy. Dosing adherence remains a crucial factor determining the final efficacy outcomes, and both long-acting implants and injectable depot systems are being developed to improve patient adherence. Here, we describe an injectable depot platform that exploits a new mechanism for both formation and controlled release. The depot is a polymeric prodrug synthesized from monomers that incorporate an ARV drug tenofovir alafenamide (TAF) with degradable linkers that can be designed to control release rates. The prodrug monomers are synthetically incorporated into homopolymer or block designs that exhibit high drug weight percent (wt%) and also are hydrophobized in these prodrug segments to drive depot formation upon injection. Drug release converts those monomers to more hydrophilic pendant groups via linker cleavage, and as this drug release proceeds, the polymer chains losing hydrophobicity are then disassociated from the depot and released over time to provide a depot dissolution mechanism. We show that long-acting TAF depots can be designed as block copolymers or as homopolymers. They can also be designed with different linkers, for example with faster or slower degrading p-hydroxybenzyloxycarbonyl (Benzyl) and ethyloxycarbonyl (Alkyl) linkers, respectively. Diblock designs of p(glycerol monomethacrylate)-b-p(Alkyl-TAF-methacrylate) and p(glycerol monomethacrylate)-b-p(Benzyl-TAF-methacrylate) were first characterized in a mouse subcutaneous injection model. The alkylcarbamate linker design (TAF 51 wt%) showed excellent sustained release profiles of the key metabolite tenofovir (TFV) in skin and plasma over a 50-day period. Next, the homopolymer design with a high TAF drug wt% of 73% was characterized in the same model. The homopolymer depots with p(Alkyl-TAFMA) exhibited sustained TFV and TAF release profiles in skin and blood over 60 days, and TFV-DP concentrations in peripheral blood mononuclear cells (PBMC) were found to be at least 10-fold higher than the clinically suggested minimally EC90 protective concentration of 24 fmol/10⁶ cells. These are the first reports of sustained parent TAF dosing observed in mouse and TFV-DP in mouse PBMC. IVIS imaging of rhodamine labeled homopolymer depots showed that degradation and release of the depot coincided with the sustained TAF release. Finally, these polymers showed excellent stability in accelerated stability studies over a six-month time period, and exceptional solubility of over 700 mg/mL in the DMSO formulation solvent. The homopolymer designs have a drug reservoir potential of well over a year at mg/day dosing and may not require cold chain storage for global health and developed world long-acting drug delivery applications.

Integrating Economic Evaluation and Implementation Science to Advance the Global HIV Response

BACKGROUND

Numerous cost-effectiveness analyses have indicated good value for money from a wide array of interventions for treatment and prevention of HIV/AIDS. There is limited evidence, however, regarding how cost-effectiveness information contributes to better decision-making around investment and action in the global HIV response.

METHODS

We review challenges for economic evaluation relevant to the global HIV response and consider how the practice of cost-effectiveness analysis could integrate approaches and insights from implementation science to enhance the impact and efficiency of HIV investments.

RESULTS

In light of signals that cost-effectiveness analyses may be vulnerable to systematic bias toward overly optimistic conclusions, we emphasize two priorities for advancing the field of economic evaluation in HIV/AIDS and more broadly in global health: (1) systematic reevaluation of the cost-effectiveness literature with reference to ex-post empirical evidence on costs and effects in real-world programs and (2) development and adoption of good-practice guidelines for incorporating implementation and delivery aspects into economic evaluations. Toward the latter aim, we propose an integrative approach that focuses on comparative evaluation of strategies, which specify both technologies/interventions as well as the delivery platforms, complementary interventions, and actions needed to increase coverage, quality, and uptake of those technologies/interventions. Specific recommendations draw on several existing implementation science models that provide systematic frameworks for understanding implementation barriers and enablers, designing and choosing specific implementation and policy actions, and evaluating outcomes.

DISCUSSION

These preliminary steps aimed at bridging the divide between economic evaluation and implementation science can help to advance the practice of economic evaluation toward a science of comparative strategy evaluation.

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.

Interpreting In Vitro Release Performance from Long-Acting Parenteral Nanosuspensions Using USP-4 Dissolution and Spectroscopic Techniques

Injectable sustained release dosage forms have emerged as desirable therapeutic routes for patients that require life-long treatments. The prevalence of drug molecules with low aqueous solubility and bioavailability has added momentum toward the development of suspension-based long-acting parenteral (LAP) formulations; the previously undesirable physicochemical properties of Biopharmaceutics Classification System (BCS) Class II/IV compounds are best suited for extended release applications. Effective in vitro release (IVR) testing of crystalline suspensions affirms product quality during early-stage development and provides connections with in vivo performance. However, before in vitro-in vivo correlations (IVIVCs) can be established, it is necessary to evaluate formulation attributes that directly affect IVR properties. In this work, a series of crystalline LAP nanosuspensions were formulated with different stabilizing polymers and applied to a continuous flow-through (USP-4) dissolution method. This technique confirmed the role of salt effects on the stability of polymer-coated nanoparticles through the detection of disparate active pharmaceutical ingredient (API) release profiles. The polymer stabilizers with extended hydrophilic chains exhibited elevated intrapolymer activity from the loss of hydrogen-bond cushioning in dissolution media with heightened ionic strength, confirmed through one-dimensional (1D) ¹H NMR and two-dimensional nuclear Overhauser effect spectroscopy (2D NOESY) experiments. Thus, steric repulsion within the affected nanosuspensions was limited and release rates decreased. Additionally, the strength of interaction between hydrophobic polymer components and the API crystalline surface contributed to suspension dissolution properties, confirmed through solution- and solid-state spectroscopic analyses. This study provides a unique perspective on the dynamic interface between the crystalline drug and aqueous microenvironment during dissolution.

Design of a Drug-Eluting Subcutaneous Implant of the Antiretroviral Tenofovir Alafenamide Fumarate

PURPOSE

Sexual transmission of HIV has been clinically proven to be preventable with a once-daily oral tablet; however, missed doses dramatically increase the risk of HIV infection. Long-acting subcutaneous implants do not allow the user to miss a dose. A desirable long-acting drug-eluting implant can deliver a constant amount of drug, adjust the delivered dose, and be readily manufactured. We present a long-acting, subcutaneous implant design composed of tenofovir alafenamide hemifumarate (TAF) pellets loaded in a sealed polyether urethane tube for the prevention of HIV transmission.

METHODS

Implants were prepared with pressed drug pellets and extruded polyurethane tubing. In vitro release rate of implants using different pellet formulations, rate-controlling membranes, and geometries were measured.

RESULTS

Tenofovir alafenamide release appeared to be governed by a pseudo-steady state and followed a mass transport model of release from a cylindrical drug reservoir. Implant seal integrity was tested and confirmed using mechanical testing. The inclusion of sodium chloride in the pellet increased the release rate and reduced initial lag. The release was sustained for 100 days.

CONCLUSIONS

The release rate of tenofovir alafenamide mechanistically varied with geometry and rate controlling membrane composition. The polyether urethane implant presented herein is modular and tunable to adjust the release rate and duration of the TAF release.

The Invisible Product: Preferences for Sustained-Release, Long-Acting Pre-exposure Prophylaxis to HIV Among South African Youth

BACKGROUND

Long-acting injectable and implantable approaches aim to overcome some of the documented challenges with uptake and adherence to current HIV prevention methods. Youth are a key end-user population for these methods. We used qualitative methods to examine product attributes and preferences for current and future long-acting HIV prevention approaches.

METHODS

Ninety-five South African youth aged 18-24 years, of whom 62 were female and 33 male, completed 50 interviews and 6 focus groups. We purposively selected for previous product experience, including oral pre-exposure prophylaxis, injectable pre-exposure prophylaxis, or the vaginal ring, to ensure participants' opinions were rooted in actual experience.

RESULTS

Irrespective of previous method-use experience, gender, or sexual orientation, the majority expressed a preference for prevention methods formulated as injectables or implants. Several mentioned that their top priority in any product was efficacy, and for some, this overrode other concerns; for example, even if they feared pain, an implant or an injectable would be used if fully protective. Although efficacy was a top priority, there was also a clear desire across all subgroups for a product that would not interfere with sex, would stay in the system to provide protection, and that caused minimal burden, or was not apparent to others, and these characteristics were most salient for long-acting methods.

CONCLUSIONS

Narrative explanations for preferences converged thematically around different dimensions of "invisibility" including invisibility to oneself, one's partner and household members, and community members. End-user preferences can be used to inform product development of long-acting HIV prevention approaches formulated as injections or implants to optimize adherence and impact.

Next-Generation HIV Pre-Exposure Prophylaxis Preferences Among Men Who Have Sex with Men Taking Daily Oral Pre-Exposure Prophylaxis

Next-generation forms of HIV pre-exposure prophylaxis (PrEP) currently in development, including long-acting injectables (LAIs), rectal microbicides (RMs), antibody infusions (AIs), and subdermal implants (SIs), may address barriers to daily oral PrEP uptake and adherence. The purpose of this study was to evaluate barriers to oral PrEP, preferences for next-generation PrEP modalities, sociodemographic characteristics and sexual behaviors associated with preferences, and reasons for wanting or not wanting each formulation among a sample of men who have sex with men (MSM). We administered a cross-sectional survey to a diverse sample of MSM currently taking oral PrEP (n = 108) at two sexually transmitted disease clinics. We used logistic multivariate analyses to explore preferences, relative to oral PrEP, for each formulation across sociodemographic and sexual behaviors. The most commonly endorsed barriers were finding a PrEP provider and making appointments to get PrEP. Participants were most likely to prefer the SI (45%), followed by the LAI (31%), pill (21%), RM (1%), and AI (1%). Black/African American and Hispanic/Latino MSM were more likely to prefer the LAI over daily oral PrEP (odds ratio: 2.45, 95% confidence interval: 0.86-6.89), and sexual behaviors were most commonly associated with preference for the SI. Top reasons for wanting or not wanting each formulation were most commonly related to perceived ease of use. These findings demonstrate variations in preferences for next-generation PrEP modalities, highlighting a need to ensure comprehensive access to all formulations once they become available.

Pre-exposure prophylaxis 2.0: new drugs and technologies in the pipeline

Pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate and emtricitabine was adopted by WHO as a strategy to reduce HIV incidence. Although shown to be highly effective in reducing HIV acquisition, the protective efficacy of oral tenofovir disoproxil fumarate and emtricitabine relies on optimal adherence, which poses a challenge for a key portion of the most at-risk populations (women, young individuals [15-24 years], racial and ethnic minority men who have sex with men, and transgender women). New PrEP agents in clinical development include novel oral agents (eg, tenofovir alafenamide and islatravir [also known as MK-8591]), long-acting injectables (eg, cabotegravir), vaginal rings, broadly neutralising monoclonal antibodies, topical products (including gels, films, and enemas), and multipurpose technologies. In addition, new drug delivery systems, such as implants and transdermal devices, are promising strategies that are being developed for HIV prevention. The ultimate goal of this new PrEP research agenda is to expand the available PrEP regimens and offer preventive technologies that will appeal to a wide variety of individuals with different needs over the course of their sexually active lifespan.

A Multiple Dose Phase 1 Assessment of Rilpivirine Long Acting in a Model of Preexposure Prophylaxis Against HIV

The MWRI-01 study characterized the safety, acceptability, pharmacokinetic (PK), and pharmacodynamic (PD) profile of rilpivirine (RPV) long acting (LA) in a model of preexposure prophylaxis (PrEP). Prospective, open-label Phase 1 study. The safety and acceptability of three repeated doses of RPV LA were monitored. Blood, tissue (rectal, cervical, and vaginal), and biological fluids (vaginal and endocervical) were collected at baseline and at 1- to 2-month intervals throughout the study for PK and PD assessment. Eight women and four men received three intramuscular doses of 1,200 mg of RPV LA given 8 weeks apart. There were a total of 195 adverse events (AEs) reported, of which 138 (70.8%) were Grade 1 and 55 (28.2%) were Grade 2. The most common AE was injection site pain. Geometric mean (90% confidence interval) plasma RPV concentrations at 56 days after the first and third doses were 39 (33-45) ng/mL (female)/29 (17-40) ng/mL (male) and 59 (45-62) ng/mL (female)/40 (30-51) ng/mL (male), respectively. Exposure to RPV LA was associated with significant inhibition of HIV-1_BaL viral replication in the ex vivo rectal explant model (p < .0001) that persisted for up to 4 months after the third dose of RPV LA. In contrast, no viral suppression was seen in cervicovaginal tissue. Multiple dose administration of RPV LA was safe and well tolerated, and was associated with prolonged suppression of viral replication in rectal explant tissue.

Representations of Pre-exposure Prophylaxis, Informal Antiretroviral Medication Use for HIV Prevention, and Diversion on Geosocial Networking Apps among Men Who Have Sex with Men

The use of geosocial networking applications (e.g., Grindr) among men who have sex with men (MSM) is common. Yet scant research has examined how antiretroviral medications (ARVs)-including informal use-diversion and pre-exposure prophylaxis (PrEP) are presented inside of the applications. The present study examines this phenomenon. Data are drawn from a qualitative study (N = 39) of the scope and magnitude of the informal market of ARV use for HIV prevention among MSM. Twenty-five participants reported seeing references to ARVs inside the applications. Men described geosocial networking application users' presentations of ARVs as being related to: PrEP use among HIV-negative MSM, the sale and/or use of illicit drugs (e.g., methamphetamine), informal trade/sale for HIV-prevention, and PrEP use among HIV-positive men. Findings suggest continued desire for and acceptability of PrEP as HIV prevention tool and that geosocial networking apps are being used to facilitate the exchange and informal use of ARVs for HIV-prevention. Geosocial networking applications represent a promising and important platform to educate MSM about safe and effective use of PrEP and the risks related to diversion and informal ARV use.

Design of an Implant for Long-Acting HIV Pre-Exposure Prophylaxis: Input from South African Health Care Providers

Implants are in the pre-clinical stage for long-acting HIV pre-exposure prophylaxis (PrEP), with an opportunity to solicit end-users' feedback early in development. Health care providers (HCPs) have been key gatekeepers for contraceptive implant uptake, and uniquely understand both technical considerations and the social context of use. Given their influential role, we gathered South African HCP perspectives on contraceptive implant implementation and features of PrEP implant prototypes that may influence future provider and patient acceptability. We conducted in-depth interviews with 30 HCPs (20 nurses and 10 doctors) in Cape Town and Soshanguve, South Africa. Interviews were conducted by a bioengineer and later transcribed, coded, and analyzed for key themes. HCPs described health system barriers such as understaffed clinics and inadequate training on contraceptive implant removal as major influences to their PrEP implant design preferences. They preferred a PrEP implant that is long lasting (>6 months) to minimize patient-clinic interactions, biodegradable to avoid need for removal, and flexible (but still palpable in case of removal). Commenting on negative experiences with contraceptive implant rollout, they recommended prioritizing both HCP and community education on the PrEP implant, with emphasis on expected side effects, and planning ahead for adequate training of HCPs before rollout. Challenges experienced with past contraceptive implant rollout may taint perspectives on future PrEP implants and must be carefully considered during product development and planning for clinical studies. Particular consideration should be given to the health system context of future distribution, including staff who would be providing and monitoring implants.

Pediatric Considerations for Postexposure Human Immunodeficiency Virus Prophylaxis

Exposures that carry risk of transmission of blood-borne disease are rare in pediatrics, but expose patients and families to great anxiety. Specialists in pediatric infectious diseases are often asked about initial antimicrobial prophylaxis in these cases. Guidelines for nonoccupational postexposure prophylaxis for human immunodeficiency virus have evolved as new formulations and medications become available and greater experience obtained in assessing relative risks of different exposures and relative costs and benefits for different interventions. This article discusses the evidence behind recent updates to Centers for Disease Control and Prevention guidelines for nonoccupational postexposure prophylaxis for human immunodeficiency virus, focusing on application in the pediatric population.

Extended-Duration MK-8591-Eluting Implant as a Candidate for HIV Treatment and Prevention

Regimen adherence remains a major hurdle to the success of daily oral drug regimens for the treatment and prevention of human immunodeficiency virus (HIV) infection. Long-acting drug formulations requiring less-frequent dosing offer an opportunity to improve adherence and allow for more forgiving options with regard to missed doses. The administration of long-acting formulations in a clinical setting enables health care providers to directly track adherence. MK-8591 (4'-ethynyl-2-fluoro-2'-deoxyadenosine [EFdA]) is an investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI) drug candidate under investigation as part of a regimen for HIV treatment, with potential utility as a single agent for preexposure prophylaxis (PrEP). The active triphosphate of MK-8591 (MK-8591-TP) exhibits protracted intracellular persistence and, together with the potency of MK-8591, supports its consideration for extended-duration dosing. Toward this end, drug-eluting implant devices were designed to provide prolonged MK-8591 release in vitro and in vivo Implants, administered subcutaneously, were studied in rodents and nonhuman primates to establish MK-8591 pharmacokinetics and intracellular levels of MK-8591-TP. These data were evaluated against pharmacokinetic and pharmacodynamic models, as well as data generated in phase 1a (Ph1a) and Ph1b clinical studies with once-weekly oral administration of MK-8591. After a single administration in animals, MK-8591 implants achieved clinically relevant drug exposures and sustained drug release, with plasma levels maintained for greater than 6 months that correspond to efficacious MK-8591-TP levels, resulting in a 1.6-log reduction in viral load. Additional studies of MK-8591 implants for HIV treatment and prevention are warranted.

Perspectives of South African youth in the development of an implant for HIV prevention

INTRODUCTION

Implants are a new dosage form in development for HIV pre-exposure prophylaxis (PrEP) with potential for high adherence given that they are provider-administered and are intended for long-acting protection. Integrating end-user preference into early stage product development may further overcome challenges with future product uptake and adherence. Hence, we sought to optimize the design of a PrEP implant in early-stage development by gathering opinions about implant attributes from potential end-users in South Africa.

METHODS

We conducted 14 focus group discussions (FGDs) with young women and men aged 18 to 24 in Cape Town and Soshanguve, South Africa, inviting participants into discussion as co-designers. FGDs were homogenous by gender and previous implant experience. During FGDs, we showed prototype devices and followed a semi-structured guide with questions on history of contraceptive implant use, preferences for physical characteristics of an implant, implant biodegradability, insertion process, participant-driven ideas for implant design, and social adoption considerations. FGDs were facilitated in English, isiXhosa, Tswana, isiZulu, or Tsonga, audio-recorded, transcribed into English, and qualitatively coded and analysed.

RESULTS

In this qualitative sample of 105 youth (68 women and 37 men), 58 participants were from Soshanguve and 47 from Cape Town, and 23% had previously used contraceptive implants. Participants expressed preferences for several implant design features; specifically, longer duration (≥6 months) was more important to most participants than the size or number of devices implanted. A majority preferred a flexible versus stiff implant to minimize palpability, thereby increasing discreetness and comfort. Nearly all participants favoured a biodegradable implant to avoid removal and thus reduce clinic visits. Concerns about the implant centred on its possible side effects and the "plastic" look of the prototype displayed for demonstration.

CONCLUSIONS

This study offers preliminary insights into an implant for HIV prevention that provides long-lasting protection may be well received among young South Africans. Additionally, flexibility, discreetness, and biodegradability may increase acceptability of the implant. Such end-user feedback is being incorporated into current implant designs in the hope of creating an effective long-acting PrEP product that is likely to achieve high uptake and adherence in target populations.

Recent developments of nanotherapeutics for targeted and long-acting, combination HIV chemotherapy

Combination antiretroviral therapy (cART) given orally has transformed HIV from a terminal illness to a manageable chronic disease. Yet despite the recent development of newer and more potent drugs for cART and suppression of virus in blood to undetectable levels, residual virus remains in tissues. Upon stopping cART, virus rebounds and progresses to AIDS. Current oral cART regimens have several drawbacks including (1) challenges in patient adherence due to pill fatigue or side-effects, (2) the requirement of life-long daily drug intake, and (3) limited penetration and retention in cells within lymph nodes. Appropriately designed injectable nano-drug combinations that are long-acting and retained in HIV susceptible cells within lymph nodes may address these challenges. While a number of nanomaterials have been investigated for delivery of HIV drugs and drug combinations, key challenges involve developing and scaling delivery systems that provide a drug combination targeted to HIV host cells and tissues where residual virus persists. With validation of the drug-insufficiency hypothesis in lymph nodes, progress has been made in the development of drug combination nanoparticles that are long-acting and targeted to lymph nodes and cells. Unique drug combination nanoparticles (DcNPs) composed of three HIV drugs-lopinavir, ritonavir, and tenofovir-have been shown to provide enhanced drug levels in lymph nodes; and elevated drug-combination levels in HIV-host cells in the blood and plasma for two weeks. This review summarizes the progress in the development of nanoparticle-based drug delivery systems for HIV therapy. It discusses how injectable nanocarriers may be designed to enable delivery of drug combinations that are long-lasting and target-selective in physiological contexts (in vivo) to provide safe and effective use. Consistent drug combination exposure in the sites of residual HIV in tissues and cells may overcome drug insufficiency observed in patients on oral cART.