Antiretroviral implants for treatment and prevention of HIV infection

Changes in local tissue microenvironment in response to subcutaneous long-acting delivery of tenofovir alafenamide in rats and non-human primates

Several implantable long-acting (LA) delivery systems have been developed for sustained subcutaneous administration of tenofovir alafenamide (TAF), a potent and effective nucleotide reverse transcriptase inhibitor used for HIV pre-exposure prophylaxis (PrEP). LA platforms aim to address the lack of adherence to oral regimens, which has impaired PrEP efficacy. Despite extensive investigations in this field, tissue response to sustained subcutaneous TAF delivery remains to be elucidated as contrasting preclinical results have been reported in the literature. To this end, here we studied the local foreign body response (FBR) to sustained subdermal delivery of three forms of TAF, namely TAF free base (TAFfb), TAF fumarate salt (TAFfs), and TAFfb with urocanic acid (TAF-UA). Sustained constant drug release was achieved via titanium-silicon carbide nanofluidic implants previously shown to be bioinert. The analysis was conducted in both Sprague-Dawley (SD) rats and rhesus macaques over 1.5 and 3 months, respectively. While visual observation did not reveal abnormal adverse tissue reaction at the implantation site, histopathology and Imaging Mass Cytometry (IMC) analyses exposed a local chronic inflammatory response to TAF. In rats, UA mitigated foreign body response to TAF in a concentration-dependent manner. This was not observed in macaques where TAFfb was better tolerated than TAFfs and TAF-UA. Notably, the level of FBR was tightly correlated with local TAF tissue concentration. Further, regardless of the degree of FBR, the fibrotic capsule (FC) surrounding the implants did not interfere with drug diffusion and systemic delivery, as evidenced by TAF PK results and fluorescence recovery after photobleaching (FRAP).

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.

The LEAP Process: Streamlining the Development of Long-Acting Products and Formulations for Infectious Diseases

Developing long-acting products and formulations for infectious diseases is a nontrivial undertaking that is frequently classified as high risk and low reward by the pharmaceutical industry. The Long-Acting/Extended Release Antiretroviral Research Resource Program (LEAP) was founded in 2015 with the support of the National Institutes of Health to encourage, promote, and accelerate the development of such products. Assessment methodology for any new proposal brought to this group is part of a framework-the LEAP Process-that includes a landscape analysis of what is currently available in the public domain. This is followed by in silico modeling and simulation offered as a service to the relevant scientific community. A variety of preclinical and clinical outcome metrics are applied to each new agent as part of a continuous feedback loop to improve product characteristics. This allows us to catalog knowledge gaps and barriers that can be addressed by engaged stakeholders. Results are communicated in scientific articles, reviews, and position papers. This undertaking serves to de-risk discovery, development, and implementation by bridging the gaps between academic, regulatory, and industrial investigators, and by engaging those in the community who will be the eventual users of these medicines. The LEAP Process has supported formulations now approved for human immunodeficiency virus, as well as products in clinical and preclinical development for tuberculosis and hepatitis viruses B and C.

Antiretroviral therapy experience, satisfaction, and preferences among a diverse sample of young adults living with HIV

Youth and young adults living with HIV (YLWH) have a high HIV infection rate and suboptimal oral medication adherence. Biomedical researchers hope that long-acting antiretroviral therapy (LAART) modalities can help those who struggle with daily oral adherence. While adults living with HIV have expressed interest in LAART, little research has explored perspectives of YLWH. This study explores ART experiences and perspectives on LAART through qualitative interviews with twenty diverse YLWH (18-29) in the United States. Data were analyzed using framework analysis. Most participants were satisfied with their current ART yet had experienced side effects or had struggled with daily adherence. Preferences for improving daily oral ART included making pills smaller and reformulating ART into flavored chewable gummies. Most expressed enthusiasm for LAART, although needle aversion and previous injection drug use were potential barriers for some. Approximately half were interested in an ART patch, though its visibility and fear of stigmatization was concerning. Few expressed interest in implantable ART, calling it unappealing. Although younger people are most likely to benefit from these advancements in HIV treatment, additional research is needed to identify gaps in uptake and to further explore perspectives of YLWH to improve the success of new treatment modalities.

Impact of long-acting therapies on the global HIV epidemic

Long-acting antiretroviral drugs have emerged as exciting treatment and preexposure prophylaxis (PrEP) options for people with HIV and at risk of HIV. Long-acting regimens may improve dosing convenience, tolerability and cost compared with current daily-based oral therapy. They can also circumvent stigma associated with oral therapy for both treatment and PrEP, thereby improving adherence and outcomes. Yet, multiple challenges remain, many specific to low-income and middle-income countries (LMICs), where the epidemic is most concentrated and HIV prevention and treatment options are limited. To optimize the use of long-acting formulations, key outstanding questions must be addressed. Uncertain costing, scale-up manufacturing, complex delivery systems and implementation challenges are potential barriers when considering the scalability of long-acting ARVs for global use.

The Role of Alcohol-Related Behavioral Research in the Design of HIV Secondary Prevention Interventions in the Era of Antiretroviral Therapy: Targeted Research Priorities Moving Forward

HIV secondary prevention focuses on averting onward HIV transmission, which can be realized when people living with HIV enact requisite HIV care continuum-related behaviors to achieve viral suppression, and engage in condom-protected sex when virally unsuppressed. Alcohol has been detrimentally linked to all aspects of HIV secondary prevention, and although a growing number of behavioral interventions account for and address alcohol use within this realm, further efforts are needed to fully realize the potential of such initiatives. The present article proposes a series of targeted priorities to inform the future design, implementation, and evaluation of alcohol-related behavioral intervention research within the scope of HIV secondary prevention. These priorities and corresponding approaches account for the challenges of resource-constrained clinic environments; capitalize on technology; and address key comorbidities. This framework provides the foundation for a range of alcohol-related behavioral interventions that could potentially enhance global HIV secondary prevention efforts in the years ahead.

Experiences of Accessing and Providing Contraceptive Implant Removal Services in Gaborone, Botswana: A Qualitative Study Among Implant Users and Healthcare Providers

Introduction: This study explored implant user and healthcare provider experiences of accessing and providing contraceptive implant removal services in Gaborone, Botswana, following introduction of the implant in the public sector in 2016. We sought to understand reasons for satisfaction and dissatisfaction with services and their potential impact on wider perceptions of the implant, including influence on future uptake.

Methods: Qualitative data were collected through in-depth interviews. Participants comprised ten women who had previously undergone implant removal, and ten providers whose work included provision of implant insertion and removal. Data were analyzed using thematic content analysis.

Results: Seven of the ten users in this study had experienced a delay between initial request and undergoing implant removal. This interval ranged from <1 week to 3 months. Users identified the principal barriers to accessing implant removal services as lack of access to trained removal providers, inconvenient appointment times, and provider resistance to performing removal. Nine of the ten providers in this study had experienced barriers to providing implant removal, including insufficient training, lack of equipment, lack of time, and lack of a referral pathway for difficult removals. Despite experiencing barriers in accessing removal, users' perceptions of the implant remained generally positive. Providers were concerned that ongoing negative user experiences of removal services would damage wider perceptions of the implant.

Conclusion: Introduction of the contraceptive implant in Botswana has been an important strategy in increasing contraceptive choice. Following an initial focus on provision of insertion services, the development of comparable, accessible removal services is critical to ensuring that the implant remains a desirable contraceptive option and is vital to upholding women's reproductive health rights. The experiences of users and providers in this study can inform the ongoing development of services for implant insertion and removal in Botswana and other lower-resource settings.

Use of long-acting injectable antiretroviral agents for human immunodeficiency Virus: A review

The development of potent antiretroviral drugs has significantly reduced morbidity and mortality associated with human immunodeficiency virus infection, however, the effectiveness of these medications depends upon consistent daily oral intake. Non-adherence can lead to the emergence of resistance, treatment failure and disease progression. This has necessitated the development of long-acting antiretroviral formulations administrable via an infrequent dosing regimen. Long-acting injectable forms of cabotegravir and rilpivirine have reached various stages in clinical trials both for the treatment and prevention of HIV. Other long-acting agents are at various stages of development. This review evaluates the current research on the development of long-acting injectable antiretroviral agents for the treatment and prevention of HIV.

Polymeric long-acting drug delivery systems (LADDS) for treatment of chronic diseases: Inserts, patches, wafers, and implants

Non-oral long-acting drug delivery systems (LADDS) encompass a range of technologies for precisely delivering drug molecules into target tissues either through the systemic circulation or via localized injections for treating chronic diseases like diabetes, cancer, and brain disorders as well as for age-related eye diseases. LADDS have been shown to prolong drug release from 24 h up to 3 years depending on characteristics of the drug and delivery system. LADDS can offer potentially safer, more effective, and patient friendly treatment options compared to more invasive modes of drug administration such as repeated injections or minor surgical intervention. Whilst there is no single technology or definition that can comprehensively embrace LADDS; for the purposes of this review, these systems include solid implants, inserts, transdermal patches, wafers and in situ forming delivery systems. This review covers common chronic illnesses, where candidate drugs have been incorporated into LADDS, examples of marketed long-acting pharmaceuticals, as well as newly emerging technologies, used in the fabrication of LADDS.

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.

Long-acting antiretrovirals: a new era for the management and prevention of HIV infection

The long-acting antiretroviral cabotegravir and rilpivirine combination has just received FDA, EMA and Health Canada approval. This novel drug delivery approach is about to revolutionize the therapy of people living with HIV, decreasing the 365 daily pill burden to only six intramuscular injections per year. In addition, islatravir, a first-in-class nucleoside reverse transcriptase translocation inhibitor, is intended to be formulated as an implant with a dosing interval of 1 year or more. At present, long-acting antiretroviral therapies (LA-ARTs) are given at fixed standard doses, irrespectively of the patient's weight and BMI, and without consideration for host genetic and non-genetic factors likely influencing their systemic disposition. Despite a few remaining challenges related to administration (e.g. pain, dedicated medical procedure), the development and implementation of LA-ARTs can overcome long-term adherence issues by improving patients' privacy and reducing social stigma associated with the daily oral intake of anti-HIV treatments. Yet, the current 'one-size-fits-all' approach does not account for the recognized significant inter-individual variability in LA-ART pharmacokinetics. Therapeutic drug monitoring (TDM), an important tool for precision medicine, may provide physicians with valuable information on actual drug exposure in patients, contributing to improve their management in real life. The present review aims to update the current state of knowledge on these novel promising LA-ARTs and discusses their implications, particularly from a clinical pharmacokinetics perspective, for the future management and prevention of HIV infection, issues of ongoing importance in the absence of curative treatment or an effective vaccine.

"Lighten This Burden of Ours": Acceptability and Preferences Regarding Injectable Antiretroviral Treatment Among Adults and Youth Living With HIV in Coastal Kenya

Background:

Long-acting injectable (LAI) antiretroviral therapy (ART) may offer persons living with HIV (PLWH) an attractive alternative to pill-based treatment options, yet acceptability data remain scant, especially in sub-Saharan Africa.

Methods:

We conducted 6 focus group discussions with PLWH, including key stake holder groups, and analyzed data with content analysis.

Results:

Initial reactions to the idea of LAI-ART were often positive. The primary advantages voiced were potential to facilitate improved adherence and alleviate the burden of daily pill-taking while avoiding inadvertent disclosure and HIV stigma. Potential side effects were a particular concern of the women. Most participants preferred clinic-based administration over self-injections at home due to concerns about safety, privacy, and potential need for refrigeration.

Conclusions:

LAI-ART may be acceptable in Kenya, provided injections are infrequent and delivered in a clinic setting. However, HIV stigma, fear of potential side effects, and limited clinical capacity would need to be addressed.

An amphipathic peptide targeting the gp41 cytoplasmic tail kills HIV-1 virions and infected cells

HIV-associated morbidity and mortality have markedly declined because of combinational antiretroviral therapy, but HIV readily mutates to develop drug resistance. Developing antivirals against previously undefined targets is essential to treat existing drug-resistant HIV strains. Some peptides derived from HIV-1 envelope glycoprotein (Env, gp120-gp41) have been shown to be effective in inhibiting HIV-1 infection. Therefore, we screened a peptide library from HIV-1 Env and identified a peptide from the cytoplasmic region, designated F9170, able to effectively inactivate HIV-1 virions and induce necrosis of HIV-1-infected cells, and reactivated latently infected cells. F9170 specifically targeted the conserved cytoplasmic tail of HIV-1 Env and effectively disrupted the integrity of the viral membrane. Short-term monoadministration of F9170 controlled viral loads to below the limit of detection in chronically SHIV-infected macaques. F9170 can enter the brain and lymph nodes, anatomic reservoirs for HIV latency. Therefore, F9170 shows promise as a drug candidate for HIV treatment.

Preventive efficacy of a tenofovir alafenamide fumarate nanofluidic implant in SHIV-challenged nonhuman primates

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

Perspectives on and preferences for on-demand and long-acting PrEP among sexual and gender minority adolescents assigned male at birth

INTRODUCTION

Sexual and gender minority (SGM) adolescents assigned male at birth who have sex with male partners are at increased risk for HIV. Daily oral pre-exposure prophylaxis (PrEP) is available for minor adolescents in the United States, who may have difficulty with adherence. Adolescents' perspectives toward emerging PrEP delivery methods that would not require daily pill-taking have not been well-explored.

METHODS

We conducted online surveys and focus groups in November 2018-February 2019 with 59 SGM adolescents assigned male at birth who reported sex with or attraction to male partners. Questions assessed their perspectives on and preferences for biomedical (on-demand, injection, implant) and non-biomedical HIV prevention options (condoms). Data were analyzed thematically.

RESULTS

Of all prevention options, the implant and condoms were rated highest, and participants preferred the implant over other biomedical options. Convenience, duration, and ease of access played important roles in adolescents' preferences. Parents were viewed as a barrier to taking PrEP regardless of delivery method due to their role in adolescents' ability to access healthcare.

CONCLUSIONS

SGM adolescents are interested in long-acting PrEP, yet also perceive substantial obstacles to using biomedical prevention that reflect adolescents' developmental contexts.

POLICY IMPLICATIONS

State laws expanding adolescents' access to HIV preventive services, sex education inclusive of PrEP information, and parent- and provider-initiated PrEP conversations can reduce barriers regardless of PrEP delivery method. Research to accelerate the availability of long-acting implants for adolescents is needed.

Emerging Trends in the Long-Acting Antiretroviral Therapy: Current Status and Therapeutic Challenges

Antiretroviral drug therapy has significantly improved the prognosis and life expectancy of people living with HIV over the years. But this progress comes with an important caveat that antiretroviral regimens generally require adherence to life-long, daily dosing, to keep viral multiplication under check. Non-adherence to such dosing leads to decreased efficacy and increased drug resistance against antiretroviral drugs. Besides, poor drug penetration to certain tissues like CNS and lymph nodes leads to the build-up of viral reservoirs in these sites. To combat some of these challenges and improve patient compliance, long-acting antiretroviral drugs, are a new weapon in the arsenal, in the fight against HIV. Few long-acting preparations have been approved, and several others are in various clinical and preclinical stages of development. However, long-acting formulations also have their share of clinical issues like limited drug distribution, long term adverse drug reactions, drug-drug interactions, and gradual development of drug resistance. Modern technological premises are being tested to mitigate some of these problems. One such promising approach involves nanotechnological methods, which are being used to develop ultra-long acting formulations and drug delivery systems, targeting tissues with residual HIV concentration. Long-Acting Slow Effective Release Antiretroviral Therapy aka LASER ART, also builds on nanotechnology and prodrug modifications to design preparations with tailor-made favorable pharmacokinetics and wider drug distribution. These recent advances are fueling the progression of antiretroviral therapy towards eliminating the disease.

Design strategies for long-acting anti-HIV pharmaceuticals

Current combination antiretroviral therapy (cART) for human immunodeficiency virus (HIV) is limited by the frequent dosing and unfavorable adherence, and the rapid appearance of resistant mutants. Thus, there is a continuous need to improve and optimize the present therapies. The clinical phase III trials of FLAIR and ATLAS, showed two-drug injectable cabotegravir (CAB) and rilpivirine (RPV) formulation is potent, safe, and tolerable in HIV-infected patients. The recent approval of cabenuva (CAB+RPV) by Health Canada is a milestone in the development of long-term therapies for HIV infection. Broadly neutralizing antibodies (bNAbs) with excellent breath and efficiency against HIV have been investigated as LA antiviral weapons. Several modern modalities capable of sustained drug release for long-term treatment and prevention of HIV infection are also in development, such as implants, vaginal rings, and nanotherapies.

Biomedical Implants for Regenerative Therapies

Regenerative therapies aim to develop novel treatments to restore tissue function. Several strategies have been investigated including the use of biomedical implants as three-dimensional artificial matrices to fill the defect side, to replace damaged tissues or for drug delivery. Bioactive implants are used to provide growth environments for tissue formation for a variety of applications including nerve, lung, skin and orthopaedic tissues. Implants can either be biodegradable or non-degradable, should be nontoxic and biocompatible, and should not trigger an immunological response. Implants can be designed to provide suitable surface area-to-volume ratios, ranges of porosities, pore interconnectivities and adequate mechanical strengths. Due to their broad range of properties, numerous biomaterials have been used for implant manufacture. To enhance an implant’s bioactivity, materials can be functionalised in several ways, including surface modification using proteins, incorporation of bioactive drugs, growth factors and/or cells. These strategies have been employed to create local bioactive microenvironments to direct cellular responses and to promote tissue regeneration and controlled drug release. This chapter provides an overview of current bioactive biomedical implants, their fabrication and applications, as well as implant materials used in drug delivery and tissue regeneration. Additionally, cell- and drug-based bioactivity, manufacturing considerations and future trends will be discussed.

Performance and Stability of Tenofovir Alafenamide Formulations within Subcutaneous Biodegradable Implants for HIV Pre-Exposure Prophylaxis (PrEP)

A critical need exists to develop diverse biomedical strategies for the widespread use of HIV Pre-Exposure Prophylaxis (HIV PrEP). This manuscript describes a subcutaneous reservoir-style implant for long-acting delivery of tenofovir alafenamide (TAF) for HIV PrEP. We detail key parameters of the TAF formulation that affect implant performance, including TAF ionization form, the selection of excipient and the exposure to aqueous conditions. Both in-vitro studies and shelf stability tests demonstrate enhanced performance for TAF freebase (TAFFB) in this long-acting implant platform, as TAFFB maintains higher chemical stability than the TAF hemifumarate salt (TAFHF). We also examined the hydrolytic degradation profiles of various formulations of TAF and identified inflection points for the onset of the accelerated drug hydrolysis within the implant using a two-line model. The compositions of unstable formulations are characterized by liquid chromatography-mass spectrometry (LC-MS) and are correlated to predominant products of the TAF hydrolytic pathways. The hydrolysis rate of TAF is affected by pH and water content in the implant microenvironment. We further demonstrate the ability to substantially delay the degradation of TAF by reducing the rates of drug release and thus lowering the water ingress rate. Using this approach, we achieved sustained release of TAFFB formulations over 240 days and maintained > 93% TAF purity under simulated physiological conditions. The opportunities for optimization of TAF formulations in this biodegradable implant supports further advancement of strategies to address long-acting HIV PrEP.

Trans-urocanic acid enhances tenofovir alafenamide stability for long-acting HIV applications

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

Long-acting approaches for delivery of antiretroviral drugs for prevention and treatment of HIV: a review of recent research

INTRODUCTION

Despite significant advances in treatment and prevention of HIV-1 infection, poor adherence to daily combination antiretroviral therapy (ART) regimens remains a major obstacle toward achieving sustained viral suppression and prevention. Adherence to ART could also be compromised by adverse drug reactions and societal factors that limit access to therapy. Therefore, medicines that aim to improve adherence by limiting ART side effects, frequency of dosing and socially acceptable regimens are becoming more attractive.

AREAS COVERED

This review highlights recent advances and challenges in the development of long-acting drug delivery strategies for HIV prevention and treatment. Approaches for extended oral and transdermal deliveries, microbicides, broadly neutralizing antibodies, and long-acting implantable and injectable deliveries are reviewed.

EXPERT OPINION

Emerging approaches on long-acting antiretroviral therapies and broadly neutralizing antibody technologies are currently at various stages of development. Such efforts, if successful and become broadly accepted by clinicians and users, will provide newer and simpler options for prevention and treatment of HIV infection.

A year-long extended release nanoformulated cabotegravir prodrug

Long-acting cabotegravir (CAB) extends antiretroviral drug administration from daily to monthly. However, dosing volumes, injection site reactions and health-care oversight are obstacles towards a broad usage. The creation of poloxamer-coated hydrophobic and lipophilic CAB prodrugs with controlled hydrolysis and tissue penetrance can overcome these obstacles. To such ends, fatty acid ester CAB nanocrystal prodrugs with 14, 18 and 22 added carbon chains were encased in biocompatible surfactants named NMCAB, NM2CAB and NM3CAB and tested for drug release, activation, cytotoxicity, antiretroviral activities, pharmacokinetics and biodistribution. Pharmacokinetics studies, performed in mice and rhesus macaques, with the lead 18-carbon ester chain NM2CAB, showed plasma CAB levels above the protein-adjusted 90% inhibitory concentration for up to a year. NM2CAB, compared with NMCAB and NM3CAB, demonstrated a prolonged drug release, plasma circulation time and tissue drug concentrations after a single 45 mg per kg body weight intramuscular injection. These prodrug modifications could substantially improve CAB's effectiveness.

Antiretroviral adherence for adolescents growing up with HIV: understanding real life, drug delivery and forgiveness

Poorer adherence to medication is normal in adolescence and is one of a range of risk-taking behaviours common during a developmental stage that encompasses enormous cognitive, physical, sexual, social and emotional change. For adolescents living with human immunodeficiency virus (HIV) infection, poor adherence to antiretroviral therapy (ART) confers two significant challenges: poor health, but also the specific additional burden of onward transmission to partners. Late adolescence (15-19 years) is the only age group where HIV-associated mortality is rising, driven by poor adherence to ART and lack of access to second-line therapy, particularly amongst surviving perinatally infected young people. A previous lack of well-powered randomised multimodal behavioural ART adherence interventions specifically targeting adolescents is now being addressed and ongoing studies registered to ClinicalTrials.gov are described in the context of previous data. Accepting that despite enhanced support, some adolescents will continue to struggle with adherence, we must address how best to use existing ART agents to reduce mortality and allow adolescents the time to mature into adult life. Single-tablet regimens with a high genetic barrier to resistance based on integrase inhibitors and boosted protease inhibitors exist, but global access, in resource limited settings of young people living with HIV reside, is limited. Pragmatically, such regimens tolerate the intermittent adherence so characteristic of adolescence, preserving immune function, without the rapid evolution of resistance. The potential role of long-acting injectable ART, specifically cabotegravir and rilpivirine, is discussed and future strategies including ultra-long-acting drug-delivery systems and broadly neutralising monoclonal antibodies explored.

A Conjoint Analysis of the Acceptability of Targeted Long-Acting Injectable Antiretroviral Therapy Among Persons Living with HIV in the U.S

With long-acting injectable antiretroviral therapy likely to be a treatment option for people living with HIV (PLWH), it is critical to assess its acceptability among potential end-users. Based on formative qualitative work and our own ongoing development of targeted long-acting products in nanosuspension formulations, we created eight hypothetical medication scenarios varying along six dichotomous attributes: administration location (home versus [vs.] clinic), dosing frequency (every 2 weeks vs. 1 week), injections per dose (one vs. two), injection pain (mild vs. moderate), injection site reaction (mild vs. moderate), and effectiveness (better vs. same as pills). PLWH from three outpatient care clinics in Seattle, WA and Riverside, CA rated acceptability (i.e., willingness to try each hypothetical medication) from 0 (very unlikely) to 100 (very likely). In conjoint analyses, we examined level and correlates of acceptability, the impact of each attribute on overall acceptability, and moderators of this effect. Participants (median age 52 years; 71% male, 34% White, 36% Black/African American, 20% Hispanic) rated acceptability of the 8 scenarios from 47.8 (standard deviation [SD] = 37.0) to 68.8 (SD = 34.1), with effectiveness (impact score = 7.3, SD = 18.7, p = 0.005) and dosing frequency (impact score = 5.7, SD = 19.6, p = 0.034) the only attributes with a significant impact on acceptability. There were no statistically significant differences in overall acceptability according to any participant socio-demographic or other characteristic; however, gender, education, employment status, and experience with and hatred/avoidance of injections moderated some effects. Overall acceptability for targeted long-acting antiretroviral treatment as proposed was modest, with superior effectiveness and lower dosing frequency most impactful on acceptability. Future acceptability research should continue to evaluate specific products in development with a full range of conjoint analytic and other techniques.

Addressing the global burden of hepatitis B virus while developing long-acting injectables for the prevention and treatment of HIV

The first long-acting formulations of HIV drugs are undergoing regulatory review for use in maintenance of viral suppression in people with HIV. Although these novel drug formulations could contribute greatly to HIV treatment and prevention efforts, their lack of activity against hepatitis B virus (HBV) could limit their global impact, particularly in populations with high burdens of both HIV and HBV. An urgent need for greater investment in research and development of long-acting drugs with dual activity against HIV and HBV exists. Access to long-acting HIV drug formulations with dual activity against HBV would be transformative and have a great impact on efforts to prevent, treat, and eradicate both of these important global epidemics.

Delay of cell growth and loss of stemness by inhibition of reverse transcription in human mesenchymal stem cells derived from dental tissue

The present study investigated the cellular properties in the dental tissue-derived mesenchymal stem cells (DSCs) exposed to nevirapine (NVP), an inhibitor of reverse transcriptase (RTase). After a prolonged exposure of DSCs for 2 weeks, the population doubling time (PDT) was significantly (P < .05) increased by delayed cell growth in the DSCs treated with 250 and 500 μM NVP, compared with untreated DSCs. Furthermore, the G1 phase of cell cycle with high activity of senescence-associated β-galactosidase was also significantly (P < .05) increased in the 250 μM NVP-treated DSCs, compared with untreated DSCs. The level of telomerase activity was unchanged between control and treatment. However, following the treatment of NVP, negative surface markers for mesenchymal stem cells (MSCs), such as CD34 and CD45, were significantly (P < .05) increased, while positive surface markers for MSCs, such as CD90 and CD105, were significantly (P < .05) decreased in the NVP-treated DSCs than those of untreated DSCs. Furthermore, the differentiation capacity into mesodermal lineage was gradually decreased, and a significant (P < .05) decrease of expression level of NANOG, OCT-4 and SOX-2 transcripts was observed in the DSCs treated with NVP, compared with untreated control DSCs. Taken together, the present results have revealed that inhibition of RTase by NVP induces delayed cell growth and loss of stemness.

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.

Creation of a long-acting rilpivirine prodrug nanoformulation

Antiretroviral therapy requires lifelong daily dosing to attain viral suppression, restore immune function, and improve quality of life. As a treatment alternative, long-acting (LA) antiretrovirals can sustain therapeutic drug concentrations in blood for prolonged time periods. The success of recent clinical trials for LA parenteral cabotegravir and rilpivirine highlight the emergence of these new therapeutic options. Further optimization can improve dosing frequency, lower injection volumes, and facilitate drug-tissue distributions. To this end, we report the synthesis of a library of RPV prodrugs designed to sustain drug plasma concentrations and improved tissue biodistribution. The lead prodrug M3RPV was nanoformulated into the stable LA injectable NM3RPV. NM3RPV treatment led to RPV plasma concentrations above the protein-adjusted 90% inhibitory concentration for 25 weeks with substantial tissue depots after a single intramuscular injection in BALB/cJ mice. NM3RPV elicited 13- and 26-fold increases in the RPV apparent half-life and mean residence time compared to native drug formulation. Taken together, proof-of-concept is provided that nanoformulated RPV prodrugs can extend the apparent drug half-life and improve tissue biodistribution. These results warrant further development for human use.

Long-acting or extended-release antiretroviral products for HIV treatment and prevention in infants, children, adolescents, and pregnant and breastfeeding women: knowledge gaps and research priorities

Antiretroviral agents with long-acting properties have potential to improve treatment outcomes substantially for people living with HIV. In November 2017, the Long acting/Extended Release Antiretroviral Resource Program (LEAP) convened a workshop with the aim of shaping the research agenda and promoting early development of long-acting or extended release products for key populations: pregnant and lactating women, children aged up to 10 years, and adolescents aged 10-19 years. Goals included strategies and principles to ensure that the needs of children, adolescents, and pregnant and lactating women are considered when developing long-acting formulations. Research should focus not only on how best to transition long-acting products to these populations, but also on early engagement across sectors and among stakeholders. A parallel rather than sequential approach is needed when establishing adult, adolescent, and paediatric clinical trials and seeking regulatory approval. Pregnant and lactating women should be included in adult clinical trials. Adolescent-friendly trial design is needed to improve recruitment and retention of young people.

Topical Inserts: A Versatile Delivery Form for HIV Prevention

The development of topical inserts for the prevention of sexually transmitted infections (STIs), particularly human immunodeficiency virus (HIV), represents a promising alternative to oral and parenteral pre-exposure prophylaxis (PrEP) dosage forms. They may be used for vaginal and/or rectal administration of a variety of agents with antiviral activity. Topical inserts deliver drugs to the portal of viral entry, i.e., the genital or rectal mucosa, with low systemic exposure, and therefore are safer and have fewer side effects than systemic PrEP agents. They may dissolve fast, releasing the active drugs within minutes of insertion, or slowly for long-acting drug delivery. Furthermore, they are user-friendly being easy to administer, discreet and highly portable. They are also economical and easy to manufacture at scale and to distribute, with excellent stability and shelf-life. Altogether, topical inserts represent a particularly promising form of drug delivery for HIV and STI prevention. Highlighted within this review are end-user acceptability research dedicated to understanding preferred attributes for this form of drug delivery, advantages and disadvantages of the formulation platform options, considerations for their development, clinical assessment of select placebo prototypes, future directions, and the potential impact of this dosage form on the HIV prevention landscape.

Long-Acting Anti-HIV Drugs Targeting HIV-1 Reverse Transcriptase and Integrase

One of the major factors contributing to HIV-1 drug resistance is suboptimal adherence to combination antiretroviral therapy (cART). Currently, recommended cART for HIV-1 treatment is a three-drug combination, whereas the pre-exposure prophylaxis (PrEP) regimens consist of one or two antivirals. Treatment regimens require adherence to a once or twice (in a subset of patients) daily dose. Long-acting formulations such as injections administered monthly could improve adherence and convenience, and thereby have potential to enhance the chances of expected outcomes, although long-lasting drug concentrations can also contribute to clinical issues like adverse events and development of drug resistance. Globally, two long-acting antivirals have been approved, and fifteen are in clinical trials. More than half of investigational long-acting antivirals target HIV-1 reverse transcriptase (HIV-1 RT) and/or integrase (HIV-1 IN). Here, we discuss the status and potential of long-acting inhibitors, including rilpivirine (RPV), dapivirine (DPV), and 4-ethynyl-2-fluoro-2-deoxyadenosine (EFdA; also known as MK-8591), which target RT, and cabotegravir (CAB), which targets IN. The outcomes of various clinical trials appear quite satisfactory, and the future of long-acting HIV-1 regimens appears bright.

The Promise of Long-Acting Antiretroviral Therapies: From Need to Manufacture

Antiretroviral therapy has transformed human immunodeficiency virus infections from certain death to a manageable chronic disease. Achieving strict adherence to drug regimens that limit toxicities and viral resistance is an achievable goal. Success is defined by halting viral transmission and by continuous viral restriction. A step towards improving treatment outcomes is in long-acting antiretrovirals. While early results remain encouraging there remain opportunities for improvement. These rest, in part, on the required large drug dosing volumes, local injection-site reactions, and frequency of injections. Thus, implantable devices and long-acting parenteral prodrugs have emerged which may provide more effective clinical outcomes. The recent successes in transforming native antiretrovirals into lipophilic and hydrophobic prodrugs stabilized into biocompatible surfactants can positively affect both. Formulating antiretroviral prodrugs demonstrates improvements in cell and tissue targeting, in drug-dosing intervals, and in the administered volumes of nanosuspensions. As such, the newer formulations also hold the potential to suppress viral loads beyond more conventional therapies with the ultimate goal of HIV-1 elimination when combined with other modalities.

Long-Acting Injectable Antiretroviral Treatment Acceptability and Preferences: A Qualitative Study Among US Providers, Adults Living with HIV, and Parents of Youth Living with HIV

To better understand acceptability of long-acting injectable antiretroviral treatment (LAI-ART) regimens for HIV management, we conducted seven semi-structured focus group discussions with experienced HIV care providers and persons living with HIV (PLWH) and five individual interviews with parents of children living with HIV in the western United States. Although providers were wary about a potential negative impact on consistent engagement in care, they predicted that patients, especially those with adherence challenges, would be enthusiastic about LAI options. Many PLWH, especially young adults, welcomed the option of an LAI-ART regimen; however, others feared injections and expressed concerns about possible side effects, dosing more frequent than every 2 weeks, additional costs, and lower efficacy. Parents' interest varied according to their child's age and sensitivity to injections. In summary, potential users considered LAI-ART generally acceptable yet voiced possible concerns as well, especially if their current pill-based regimen was effective in achieving viral suppression.

Long-Acting HIV Drugs for Treatment and Prevention

Antiretroviral drugs have revolutionized the treatment and prevention of HIV infection; however, adherence is critical for sustained efficacy. Current HIV treatment consists of three-drug regimens, and current HIV pre-exposure prophylaxis (PrEP) consists of a two-drug regimen; both generally require adherence to once-daily dosing. Long-acting formulations are useful in the treatment and prevention of other conditions (e.g., contraceptives, antipsychotics) and help promote adherence. Newer long-acting formulations of approved and investigational antiretroviral drugs in existing and newer mechanistic classes are under study for HIV treatment and prevention, including some phase III trials. Although long-acting antiretroviral drugs hold promise, some clinical challenges exist, including managing side effects, drug-drug interactions, pregnancy, and long-lasting drug concentrations that could lead to the development of drug resistance. This review aims to summarize currently available information on long-acting antiretroviral drugs for HIV treatment and prevention.