Pharmacokinetics of the Protein Microbicide 5P12-RANTES in Sheep following Single-Dose Vaginal Gel Administration

Baseline and time-updated factors in preclinical development of anionic dendrimers as successful anti-HIV-1 vaginal microbicides

Although a wide variety of topical microbicides provide promising in vitro and in vivo efficacy, most of them failed to prevent sexual transmission of human immunodeficiency virus type 1 (HIV-1) in human clinical trials. In vitro, ex vivo, and in vivo models must be optimized, considering the knowledge acquired from unsuccessful and successful clinical trials to improve the current gaps and the preclinical development protocols. To date, dendrimers are the only nanotool that has advanced to human clinical trials as topical microbicides to prevent HIV-1 transmission. This fact demonstrates the importance and the potential of these molecules as microbicides. Polyanionic dendrimers are highly branched nanocompounds with potent activity against HIV-1 that disturb HIV-1 entry. Herein, the most significant advancements in topical microbicide development, trying to mimic the real-life conditions as closely as possible, are discussed. This review also provides the preclinical assays that anionic dendrimers have passed as microbicides because they can improve current antiviral treatments' efficacy. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Evaluation of the Safety, Acceptability, and Pharmacokinetic Profile of a Gel Formulation of OB-002 in Healthy Volunteers

OB-002 is an extremely potent CCR5 antagonist that has previously been shown to completely block transmission in a nonhuman primate model of HIV infection. The purpose of this study was to characterize the safety, acceptability, and pharmacokinetic profile of a gel formulation of OB-002 (OB-002H). The trial had two phases, an open label single dose exposure (vaginal and rectal) and a randomized placebo controlled multiple dose phase during which study participants received five vaginal daily doses of OB-002H gel or matched placebo in a 2:1 ratio. Serum OB-002 levels were quantified at multiple time points up to 24 h after the first dose. A total of thirty female and male participants were enrolled in the study (12 in the single dose phase and 18 in the multiple dose phase). All adverse events were Grade 1 or 2, and the majority was unrelated to study product. Only two product-related transient Grade 2 events (both vulval dryness) occurred in the study, both in the OB-002H gel randomized multiple dose arm. All colposcopic and anoscopic assessments following product exposure were normal. There was no evidence of systemic absorption of OB-002. Overall, the product had a positive acceptability profile, and most study participants would consider using the product for protection against HIV or pregnancy. Future studies are needed to assess the extended safety and acceptability of OB-002H gel in sexually active participants. Clinical Trial Registration Number: NCT04791007.

Anti-α4β7 monoclonal antibody-conjugated nanoparticles block integrin α4β7 on intravaginal T cells in rhesus macaques

Intravenous administration of anti-α₄β₇ monoclonal antibody in macaques decreases simian immunodeficiency virus (SIV) vaginal infection and reduces gut SIV loads. Because of potential side effects of systemic administration, a prophylactic strategy based on mucosal administration of anti-α₄β₇ antibody may be safer and more effective. With this in mind, we developed a novel intravaginal formulation consisting of anti-α₄β₇ monoclonal antibody-conjugated nanoparticles (NPs) loaded in a 1% hydroxyethylcellulose (HEC) gel (NP-α₄β₇ gel). When intravaginally administered as a single dose in a rhesus macaque model, the formulation preferentially bound to CD4⁺ or CD3⁺ T cells expressing high levels of α₄β₇, and occupied ~40% of α₄β₇ expressed by these subsets and ~25% of all cells expressing α₄β₇ Blocking of the α₄β₇ was restricted to the vaginal tract without any changes detected systemically.

In vitro release testing methods for drug-releasing vaginal rings

Drug-releasing vaginal rings are torus-shaped devices, generally fabricated from thermoplastic polymers or silicone elastomers, used to administer pharmaceutical drugs to the human vagina for periods typically ranging from three weeks to twelve months. One of the most important product performance tests for vaginal rings is the in vitro release test. Although it has been fifty years since a vaginal ring device was first described in the scientific literature, and despite seven drug-releasing vaginal rings having been approved for market, there is no universally accepted method for testing in vitro drug release, and only one non-compendial shaking incubator method (for the estradiol-releasing ring Estring®) is described in the US Food and Drug Administration's Dissolution Methods Database. Here, for the first time, we critically review the diverse range of test methods that have been described in the scientific literature for testing in vitro release of drug-releasing vaginal rings. Issues around in vitro-in vivo correlation and modelling of in vitro release data are also discussed.

Development and pharmacokinetics of a combination vaginal ring for sustained release of dapivirine and the protein microbicide 5P12-RANTES

The past fifteen years have witnessed a resurgence of interest in vaginal ring technologies for drug delivery applications, mostly driven by the impetus for development of vaginally-administered antiretroviral microbicides to help reduce the high acquisition rates for human immunodeficiency virus (HIV) among Sub-Saharan African women. Currently, the lead candidate microbicide is a 28-day silicone elastomer vaginal ring releasing dapivirine (Ring-004), an experimental non-nucleoside reverse transcriptase inhibitor. The ring was tested in two pivotal Phase III clinical studies in 2016 and is currently undergoing review by the European Medicines Agency. Recently, we described a new type of silicone elastomer vaginal ring offering sustained release of the protein molecule 5P12-RANTES, a potent experimental chemokine analogue that potently blocks the HIV CCR5 coreceptor. Building on our previous work, here we report the preclinical development of a new combination vaginal ring that offers sustained release of both 5P12-RANTES and dapivirine, in which the 5P12-RANTES is incorporated into an exposed core within the ring body and the dapivirine in the sheath. In this way, in vitro release of dapivirine matches closely that for Ring-004. Also, we report the pharmacokinetic testing of this combination ring formulation in sheep, where vaginal concentrations of both drugs are maintained over 28 days at levels potentially useful for preventing HIV infection in women.

Sustained release silk fibroin discs: Antibody and protein delivery for HIV prevention

With almost 2 million new HIV infections worldwide each year, the prevention of HIV infection is critical for stopping the pandemic. The only approved form of pre-exposure prophylaxis is a costly daily pill, and it is recognized that several options will be needed to provide protection to the various affected communities around the world. In particular, many at-risk people would benefit from a prevention method that is simple to use and does not require medical intervention or a strict daily regimen. We show that silk fibroin protein can be formulated into insertable discs that encapsulate either an antibody (IgG) or the potent HIV inhibitor 5P12-RANTES. Several formulations were studied, including silk layering, water vapor annealing and methanol treatment to stabilize the protein cargo and impact the release kinetics over weeks. In the case of IgG, high concentrations were released over a short time using methanol treatment, with more sustained results with the use of water vapor annealing and layering during device fabrication. For 5P12-RANTES, sustained release was obtained for 31 days using water vapor annealing. Further, we show that the released inhibitor 5P12-RANTES was functional both in vitro and in ex vivo colorectal tissue. This work shows that silk fibroin discs can be developed into formidable tools to prevent HIV infection.

Vaginal rings with exposed cores for sustained delivery of the HIV CCR5 inhibitor 5P12-RANTES

Antiretroviral-releasing vaginal rings are at the forefront of ongoing efforts to develop microbicide-based strategies for prevention of heterosexual transmission of the human immunodeficiency virus (HIV). However, traditional ring designs are generally only useful for vaginal administration of relatively potent, lipophilic, and small molecular weight drug molecules that have sufficient permeability in the non-biodegradable silicone elastomer or thermoplastic polymers. Here, we report a novel, easy-to-manufacture 'exposed-core' vaginal ring that provides sustained release of the protein microbicide candidate 5P12-RANTES, an experimental chemokine analogue that potently blocks the HIV CCR5 coreceptor. In vitro release, mechanical, and stability testing demonstrated the utility and practicality of this novel ring design. In a sheep pharmacokinetic model, a ring containing two ¼-length excipient-modified silicone elastomer cores - each containing lyophilised 5P12-RANTES and exposed to the external environment by two large windows - provided sustained concentrations of 5P12-RANTES in vaginal fluid and vaginal tissue between 10 and 10,000 ng/g over 28days, at least 50 and up to 50,000 times the reported in vitro IC50 value.

Pharmaceutical Approaches to HIV Treatment and Prevention

Human immunodeficiency virus (HIV) infection continues to pose a major infectious disease threat worldwide. It is characterized by the depletion of CD4+ T cells, persistent immune activation, and increased susceptibility to secondary infections. Advances in the development of antiretroviral drugs and combination antiretroviral therapy have resulted in a remarkable reduction in HIV-associated morbidity and mortality. Antiretroviral therapy (ART) leads to effective suppression of HIV replication with partial recovery of host immune system and has successfully transformed HIV infection from a fatal disease to a chronic condition. Additionally, antiretroviral drugs have shown promise for prevention in HIV pre-exposure prophylaxis and treatment as prevention. However, ART is unable to cure HIV. Other limitations include drug-drug interactions, drug resistance, cytotoxic side effects, cost, and adherence. Alternative treatment options are being investigated to overcome these challenges including discovery of new molecules with increased anti-viral activity and development of easily administrable drug formulations. In light of the difficulties associated with current HIV treatment measures, and in the continuing absence of a cure, the prevention of new infections has also arisen as a prominent goal among efforts to curtail the worldwide HIV pandemic. In this review, the authors summarize currently available anti-HIV drugs and their combinations for treatment, new molecules under clinical development and prevention methods, and discuss drug delivery formats as well as associated challenges and alternative approaches for the future.

HIV Entry and Its Inhibition by Bifunctional Antiviral Proteins

HIV entry is a highly specific and time-sensitive process that can be divided into receptor binding, coreceptor binding, and membrane fusion. Bifunctional antiviral proteins (bAVPs) exploit the multi-step nature of the HIV entry process by binding to two different extracellular targets. They are generated by expressing a fusion protein containing two entry inhibitors with a flexible linker. The resulting fusion proteins exhibit exceptional neutralization potency and broad cross-clade inhibition. In this review, we summarize the HIV entry process and provide an overview of the design, antiviral potency, and methods of delivery of bAVPs. Additionally, we discuss the advantages and limitations of bAVPs for HIV prevention and treatment.

Rational CCL5 mutagenesis integration in a lactobacilli platform generates extremely potent HIV-1 blockers

Efforts to improve existing anti-HIV-1 therapies or develop preventatives have identified CCR5 as an important target and CCL5 as an ideal scaffold to sculpt potent HIV-1 entry inhibitors. We created novel human CCL5 variants that exhibit exceptional anti-HIV-1 features using recombinant lactobacilli (exploited for live microbicide development) as a screening platform. Protein design, expression and anti-HIV-1 activity flowed in iterative cycles, with a stepwise integration of successful mutations and refinement of an initial CCL5 mutant battery towards the generation of two ultimate CCL5 derivatives, a CCR5 agonist and a CCR5 antagonist with similar anti-HIV-1 potency. The CCR5 antagonist was tested in human macrophages and against primary R5 HIV-1 strains, exhibiting cross-clade low picomolar IC50 activity. Moreover, its successful combination with several HIV-1 inhibitors provided the ground for conceiving therapeutic and preventative anti-HIV-1 cocktails. Beyond HIV-1 infection, these CCL5 derivatives may now be tested against several inflammation-related pathologies where the CCL5:CCR5 axis plays a relevant role.