Topical Delivery of Tenofovir Disoproxil Fumarate and Emtricitabine from Pod-Intravaginal Rings Protects Macaques from Multiple SHIV Exposures

Development and characterization of formulations based on combinatorial potential of antivirals against genital herpes

Herpes simplex virus type 2 (HSV-2) treatment faces challenges due to antiviral resistance and systemic side effects of oral therapies. Local delivery of antiviral agents, such as tenofovir (TDF) and zinc acetate dihydrate (ZAD), may offer improved efficacy and reduced systemic toxicity. This study's objective is to develop and evaluate local unit dose formulations of TDF and ZAD combination for local treatment of HSV-2 infection and exploring their individual and combinatory effects in vitro. The study involved the development of immediate-release film and pessary formulations containing TDF and ZAD. These formulations were characterized for physicochemical properties and in vitro drug release profiles. Cytotoxicity and antiviral activity assays were conducted to evaluate the individual and combinatory effects of TDF and ZAD. Film formulations released over 90% of the drugs within 1 h, and pessary formulations within 90 min, ensuring effective local drug delivery. ZAD showed moderate antiviral activity while TDF exhibited significant antiviral activity at non-cytotoxic concentrations. The combination of TDF and ZAD demonstrated synergistic effects in co-infection treatments, reducing the concentration required for 50% inhibition of HSV-2. Developed film and pessary formulations offer consistent and predictable local drug delivery, enhancing antiviral efficacy while minimizing systemic side effects. The combination of TDF and ZAD showed potential synergy against HSV-2, particularly in co-infection treatments. Further preclinical studies on pharmacokinetics, safety, and efficacy are necessary to advance these formulations toward clinical application.

Acute antagonism in three-drug combinations for vaginal HIV prevention in humanized mice

Adolescent girls and young women in low- to middle-income countries are disproportionately at risk of becoming HIV-1 infected. New non-vaccine biomedical products aimed at overcoming this global health challenge need to provide a range of safe, effective, and discreet dosage forms based on the delivery of one or more antiviral compounds. An overarching strategy involves vaginal drug administration through inserts/tablets, gels, films, and intravaginal rings. The approach derives its appeal from being women-controlled and topical, there-by potentially minimizing systemic exposure to the agents and their metabolites. Oral regimens based on tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) are established and effective in HIV-1 pre-exposure prophylaxis (PrEP), and form a promising basis for vaginal PrEP. Here, we used bone marrow/liver/thymus humanized mice to measure the in vivo efficacy against HIV-1 of single and combination antiviral compounds applied vaginally, coupled with data analysis using the Chou-Talalay mathematical model to study the dose-effect characteristics. Unexpectedly, strong antagonism was observed in drug combinations composed of TDF-FTC coupled with a third agent using a different mode of action against HIV-1. The antagonistic effect was remedied when TDF was omitted from the regimen. Our approach provides a translational template for the preclinical, rational, and systematic evaluation of drug combinations for the prevention of HIV-1, and other viral diseases.

Drug-releasing vaginal rings for HIV/STI and pregnancy prevention: A review of recent advances and clinical applications

INTRODUCTION

Adolescent girls and young women (AGYW), as well as pre- and post-menopausal women globally would benefit from expanded choice to address their sexual and reproductive health (SRH) needs related to Human Immunodeficiency Virus (HIV), sexually transmitted infections (STIs) and pregnancy prevention. Lack of adequate preventative vaccines for HIV/STIs reinforces public health prioritization for options women may use independently to mitigate risk for infectious disease and unplanned pregnancy. Drug releasing intravaginal rings (IVR) represent one such technology that has garnered attention based on the modality's success recently as a pre-exposure prophylaxis (PrEP) delivery option and its impact on reduction in HIV risk.

AREAS COVERED

: This article provides a synopsis of three IVR technologies in active clinical development for prevention of HIV, STI, and unintended pregnancy demonstrating advancements in terms of compatibility with a wide range of drug types with a focus on dapivirine-based silicone rings (International Partnership for Microbicides (IPM), tenofovir-based polyurethane rings (CONRAD), and pod-based rings (Oak Crest Institute of Science).

EXPERT OPINION

The goals of IVR research are to reduce burdens of HIV/STIs and unplanned pregnancies. Through the evolution of IVR technologies, the potential exists to trigger integration of healthcare services through formulation of products with multiple indications.

Manufacturing and Examination of Vaginal Drug Delivery System by FDM 3D Printing

Vaginal drug delivery systems can provide a long-term and constant liberation of the active pharmaceutical ingredient even for months. For our experiment, FDM 3D printing was used to manufacture the vaginal ring samples from thermoplastic polyurethane filament, which enables fast manufacturing of complex, personalized medications. 3D printing can be an excellent alternative instead of industrial manufacturing, which is complicated and time-consuming. In our work, the 3D printed vaginal rings were filled manually with jellified metronidazole or chloramphenicol for the treatment of bacterial vaginosis. The need for manual filling was certified by the thermogravimetric and heatflow assay results. The manufactured samples were analyzed by an Erweka USP type II Dissolution Apparatus, and the dissolution profile can be distinguished based on the applied jellifying agents and the API's. All samples were considered non-similar based on the pairwise comparison. The biocompatibility properties were determined by prolonged MTT assay on HeLa cells, and the polymer could be considered non-toxic. Based on the microbiological assay on E. coli metronidazole and chitosan containing samples had bactericidal effects while just metronidazole or just chitosan containing samples bacteriostatic effect. None of these samples showed a fungistatic or fungicide effect against C. albicans. Based on our results, we successfully manufactured 3D printed vaginal rings filled with jellified metronidazole.

Electrospun fibers for vaginal administration of tenofovir disoproxil fumarate and emtricitabine in the context of topical pre-exposure prophylaxis

Women are particularly vulnerable to sexual HIV-1 transmission. Oral pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate and emtricitabine (TDF/FTC) is highly effective in avoiding new infections in men, but protection has only been shown to be moderate in women. Such differences have been associated, at least partially, to poor drug penetration of the lower female genital tract and the need for strict adherence to continuous daily oral intake of TDF/FTC. On-demand topical microbicide products could help circumvent these limitations. We developed electrospun fibers based on polycaprolactone (PCL fibers) or liposomes associated to poly(vinyl alcohol) (liposomes-in-PVA fibers) for the vaginal co-delivery of TDF and FTC, and assessed their pharmacokinetics in mice. PCL fibers and liposomes-in-PVA fibers were tested for morphological and physicochemical properties using scanning electron microscopy, differential scanning calorimetry and X-ray diffractometry. Fibers featured organoleptic and mechanical properties compatible with their suitable handling and vaginal administration. Fluorescent quenching of mucin in vitro - used as a proxy for mucoadhesion - was intense for PCL fibers, but mild for liposomes-in-PVA fibers. Both fibers were shown safe in vitro and able to rapidly release drug content (15-30 min) under sink conditions. Liposomes-in-PVA fibers allowed increasing genital drug concentrations after a single intravaginal administration when compared to continuous daily treatment for five days with 25-times higher oral doses. For instance, the levels of tenofovir and FTC in vaginal lavage were around 4- and 29-fold higher, respectively. PCL fibers were also superior to oral treatment, although to a minor extent (approximately 2-fold higher drug concentrations in lavage). Vaginal tissue drug levels were generally low for all treatments, while systemic drug exposure was negligible in the case of fibers. These data suggest that proposed fibers may provide an interesting alternative or an ancillary option to oral PrEP in women.

A Summary of the Fifth Annual Virology Education HIV Microbiome Workshop

In October of 2019, researchers and community members from around the world met at the NIH for the fifth annual International Workshop on Microbiome in HIV. New research was presented on the role of the microbiome on chronic inflammation and vaccine design, interactions of genetics, environment, sexual practice and HIV infection with the microbiome and the development and clinical trials of microbiome-based therapeutic approaches intended to decrease the probability of HIV acquisition/transmission or ameliorate sequelae of HIV. The keynote address by Dr. Jacques Ravel focused on his work on the vaginal microbiome and efforts to improve the analysis and resolution of microbiome data.

Highly synergistic drug combination prevents vaginal HIV infection in humanized mice

The HIV-1 epidemic remains an urgent global health concern. Young women are disproportionately at risk of acquiring the virus. A range of highly effective, female-controlled, discrete vaginal products therefore is needed to help curb the epidemic. Oral tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) are effective in HIV-1 pre-exposure prophylaxis (PrEP) and form a promising basis for a vaginal product. Here, we evaluate TDF and FTC in combination with the broadly neutralizing antibody VRC01-N using a highly reproducible humanized mouse model. The agents were vaginally dosed individually and in combination, and the efficacy of HIV-1 prevention was analyzed using the established, rigorous median-effect model. Surprisingly, the triple combination showed a high degree of synergism, unprecedented for in vivo HIV-1 PrEP, leading to a possible fivefold dose reduction for some of the agents. Vaginal administration of the TDF-FTC-VRC01-N combination holds significant promise for HIV-1 PrEP.

In Vitro Methods for Evaluating Drug Release of Vaginal Ring Formulations-A Critical Review

The vagina is a promising site for both local and systemic drug delivery and represents an interesting administration route for compounds with poor oral bioavailability. Whereas most of the currently marketed dosage forms were designed as immediate release formulations, intravaginal rings (IVRs) offer the possibility of a controlled vaginal drug delivery over several weeks or months. For a long time, the development of IVRs was limited to steroid-releasing formulations. Recently, IVRs have witnessed a surge of new interest as promising delivery systems for microbicides. Therefore, various novel IVR designs have been introduced. To ensure that only safe and effective IVRs will be administered to patients, it is important to properly distinguish between IVRs with desired and undesired release performance. In vitro methods for evaluating drug release of IVRs that present with sufficient predictive capacity for in vivo drug release, and discriminatory power with regard to IVRs quality, are an essential tool for this purpose. The objective of the present review article is to present the current status of in vitro drug release testing of IVRs and to critically discuss current compendial and non-official in vitro drug release methods with regard to their discriminatory power and in vivo predictivity.

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.

Rational Development of Liposomal Hydrogels: A Strategy for Topical Vaginal Antiretroviral Drug Delivery in the Context of HIV Prevention

HIV/AIDS stands as a global burden, and vaginal microbicides constitute a promising strategy for topical pre-exposure prophylaxis. Preceding the development of a microbicide containing tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC), in silico and in vitro studies were performed to evaluate the physicochemical characteristics of both drugs, and to study their biophysical impact in lipid model systems. Results from these pre-formulation studies defined hydrogels as adequate vehicles to incorporate TDF-loaded liposomes and FTC. After studying interactions with mucin, zwitterionic liposomes with a mean diameter of 134 ± 13 nm, an encapsulation TDF efficiency of approximately 84%, and a transition temperature of 41 °C were selected. The chosen liposomal formulation was non-cytotoxic to HEC-1-A and CaSki cells, and was able to favor TDF permeation across polysulfone membranes (J_ss = 9.9 μg·cm^-2·h^-1). After the incorporation of TDF-loaded liposomes and FTC in carbomer hydrogels, the drug release profile was sustained over time, reaching around 60% for both drugs within 3-6 h, and best fitting the Weibull model. Moreover, liposomal hydrogels featured pseudoplastic profiles that were deemed suitable for topical application. Overall, the proposed liposomal hydrogels may constitute a promising formulation for the vaginal co-delivery of TDF/FTC.

Antiretroviral agents in pre-exposure prophylaxis: emerging and advanced trends in HIV prevention

OBJECTIVES

Antiretroviral agents (ARVs) have been the most promising line of therapy in the management of human immunodeficiency virus (HIV) infections. Some of these ARVs are used in the pre-exposure prophylaxis (PrEP) to suppress the transmission of HIV. Prophylaxis is primarily used in uninfected people, before exposure, to effectively prevent HIV infection. Several studies have shown that ART PrEP prevents HIV acquisition from sexual, blood and mother-to-child transmissions. However, there are also several challenges and limitations to PrEP. This review focuses on the current antiretroviral therapies used in PrEP.

KEY FINDINGS

Among ARVs, the most common drugs employed from the class of entry inhibitors are maraviroc (MVC), which is a CCR5 receptor antagonist. Other entry inhibitors like emtricitabine (FTC) and tenofovir (TFV) are also used. Rilpivirine (RPV) and dapivirine (DPV) are the most common drugs employed from the Non-nucleoside reverse transcriptase inhibitor (NNRTIs) class, whereas, tenofovir disoproxil fumarate (TDF) is primarily used in the Nucleoside Reverse Transcriptase Inhibitor (NRTIs) class. Cabotegravir (CAB) is an analog of dolutegravir, and it is an integrase inhibitor. Some of these drugs are also used in combination with other drugs from the same class.

SUMMARY

Some of the most common pre-exposure prophylactic strategies employed currently are the use of inhibitors, namely entry inhibitors, non-nucleoside reverse transcriptase inhibitors, nucleoside reverse transcriptase inhibitors, integrase and protease inhibitors. In addition, we have also discussed on the adverse effects caused by ART in PrEP, pharmacoeconomics factors and the use of antiretroviral prophylaxis in serodiscordant couples.

The Anti-Human Immunodeficiency Virus Drug Tenofovir, a Reverse Transcriptase Inhibitor, Also Targets the Herpes Simplex Virus DNA Polymerase

Background

Genital herpes is an important cofactor for acquisition of human immunodeficiency virus (HIV) infection, and effective prophylaxis is a helpful strategy to halt both HIV and herpes simplex virus (HSV) transmission. The antiretroviral agent tenofovir, formulated as a vaginal microbicide gel, was shown to reduce the risk of HIV and HSV type 2 (HSV-2) acquisition.

Methods

HSV type 1 (HSV-1) and HSV-2 mutants were selected for resistance to tenofovir and PMEO-DAPy (6-phosphonylmethoxyethoxy-2,4-diaminopyrimidine, an acyclic nucleoside phosphonate with dual anti-HSV and anti-HIV activity) by stepwise dose escalation. Several plaque-purified viruses were characterized phenotypically (drug resistance profiling) and genotypically (sequencing of the viral DNA polymerase gene).

Results

Tenofovir resistant and PMEO-DAPy-resistant viruses harbored specific amino acid substitutions associated with resistance not only to tenofovir and PMEO-DAPy but also to acyclovir and foscarnet. These amino acid changes (A719V, S724N, and L802F [HSV-1] and M789T and A724V [HSV-2]) were also found in clinical isolates recovered from patients refractory to acyclovir and/or foscarnet therapy or in laboratory-derived strains. A total of 10 (HSV-1) and 18 (HSV-2) well-characterized DNA polymerase mutants had decreased susceptibility to tenofovir and PMEO-DAPy.

Conclusions

Tenofovir and PMEO-DAPy target the HSV DNA polymerase, and clinical isolates with DNA polymerase mutations emerging under acyclovir and/or foscarnet therapy showed cross-resistance to tenofovir and PMEO-DAPy.

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.

Safety and pharmacokinetics of single, dual, and triple antiretroviral drug formulations delivered by pod-intravaginal rings designed for HIV-1 prevention: A Phase I trial

BACKGROUND

Intravaginal rings (IVRs) for HIV pre-exposure prophylaxis (PrEP) theoretically overcome some adherence concerns associated with frequent dosing that can occur with oral or vaginal film/gel regimens. An innovative pod-IVR, composed of an elastomer scaffold that can hold up to 10 polymer-coated drug cores (or "pods"), is distinct from other IVR designs as drug release from each pod can be controlled independently. A pod-IVR has been developed for the delivery of tenofovir (TFV) disoproxil fumarate (TDF) in combination with emtricitabine (FTC), as daily oral TDF-FTC is the only Food and Drug Administration (FDA)-approved regimen for HIV PrEP. A triple combination IVR building on this platform and delivering TDF-FTC along with the antiretroviral (ARV) agent maraviroc (MVC) also is under development.

METHODOLOGY AND FINDINGS

This pilot Phase I trial conducted between June 23, 2015, and July 15, 2016, evaluated the safety, pharmacokinetics (PKs), and acceptability of pod-IVRs delivering 3 different ARV regimens: 1) TDF only, 2) TDF-FTC, and 3) TDF-FTC-MVC over 7 d. The crossover, open-label portion of the trial (N = 6) consisted of 7 d of continuous TDF pod-IVR use, a wash-out phase, and 7 d of continuous TDF-FTC pod-IVR use. After a 3-mo pause to evaluate safety and PK of the TDF and TDF-FTC pod-IVRs, TDF-FTC-MVC pod-IVRs (N = 6) were evaluated over 7 d of continuous use. Safety was assessed by adverse events (AEs), colposcopy, and culture-independent analysis of the vaginal microbiome (VMB). Drug and drug metabolite concentrations in plasma, cervicovaginal fluids (CVFs), cervicovaginal lavages (CVLs), and vaginal tissue (VT) biopsies were determined via liquid chromatographic-tandem mass spectrometry (LC-MS/MS). Perceptibility and acceptability were assessed by surveys and interviews. Median participant age was as follows: TDF/TDF-FTC group, 26 y (range 24-35 y), 2 White, 2 Hispanic, and 2 African American; TDF-FTC-MVC group, 24.5 y (range 21-41 y), 3 White, 1 Hispanic, and 2 African American. Reported acceptability was high for all 3 products, and pod-IVR use was confirmed by residual drug levels in used IVRs. There were no serious adverse events (SAEs) during the study. There were 26 AEs reported during TDF/TDF-FTC IVR use (itching, discharge, discomfort), with no differences between TDF alone or in combination with FTC observed. In the TDF-FTC-MVC IVR group, there were 12 AEs (itching, discharge, discomfort) during IVR use regardless of attribution to study product. No epithelial disruption/thinning was seen by colposcopy, and no systematic VMB shifts were observed. Median (IQR) tenofovir diphosphate (TFV-DP) tissue concentrations of 303 (277-938) fmol/10(6) cells (TDF), 289 (110-603) fmol/10(6) cells (TDF-FTC), and 302 (177.1-823.8) fmol/10(6) cells (TDF-FTC-MVC) were sustained for 7 d, exceeding theoretical target concentrations for vaginal HIV prevention. The study's main limitations include the small sample size, short duration (7 d versus 28 d), and the lack of FTC triphosphate measurements in VT biopsies.

CONCLUSIONS

An innovative pod-IVR delivery device with 3 different formulations delivering different regimens of ARV drugs vaginally appeared to be safe and acceptable and provided drug concentrations in CVFs and tissues exceeding concentrations achieved by highly protective oral dosing, suggesting that efficacy for vaginal HIV PrEP is achievable. These results show that an alternate, more adherence-independent, longer-acting prevention device based on the only FDA-approved PrEP combination regimen can be advanced to safety and efficacy testing.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02431273.

Impact of ring size and drug loading on the pharmacokinetics of a combination dapivirine-darunavir vaginal ring in cynomolgus macaques

This work investigates the impact of vaginal ring size and drug loading on the in vitro release, safety, ease of fit, and pharmacokinetics in cynomolgus macaques of matrix-type silicone elastomer vaginal rings containing a combination of the non-nucleoside reverse transcriptase inhibitor dapivirine and the protease inhibitor darunavir. Drug-free and drug-loaded vaginal rings having three different geometries were manufactured by reaction injection molding. In vitro drug release was assessed using both a solvent/water mixture and a vaginal fluid simulant. Macaques fitted with drug-free vaginal rings for 28 days were assessed by colposcopy, cytological evaluation of cervico-vaginal lavage and histological evaluation of tissue after ring removal. The 20 × 4.5 mm combination ring, deemed most appropriate for vaginal fit and comfort in the macaques, was evaluated for pharmacokinetics over 28 days. Substantial differences were observed in the in vitro release profiles between the three ring sizes. However, these differences were not manifest in vivo, where measured drug concentrations after 20 × 4.5 mm ring use were not significantly different from those reported previously with a 25 × 6 mm ring. These results suggest that ring placement and fit is an important species-specific study parameter that should be optimised prior to pharmacokinetic testing.

Composite films for vaginal delivery of tenofovir disoproxil fumarate and emtricitabine

Prevention of male-to-female HIV transmission remains a huge challenge and topical pre-exposure prophylaxis (PrEP) using microbicides may help overcoming the problem. In this work, different types of films containing the antiretroviral drugs tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) were developed. Formulations based in poly(vinyl alcohol) and pectin were produced as single- or double-layered films. Films containing TDF/FTC or TDF/FTC-loaded Eudragit® L 100 nanoparticles (NPs) obtained by nano spray-drying were tested for physicochemical, technological and biological properties relevant to microbicide development. All systems featured organoleptic and mechanical properties considered suitable for vaginal use and potentially favoring users' acceptability. Film design (single- or double-layered, and the incorporation or not of NPs) had a greater impact on disintegration time and drug release in a simulated vaginal fluid. Upon film disintegration, pH and osmolality of the fluid remained within values considered compatible with the vaginal environment. Double-layered films significantly reduced burst effect and the overall release of both drugs as compared to fast releasing, single-layered films. The effect on delaying drug release was most noticeable when TDF/FTC-loaded NPs were incorporated into double-layered films. This last design seems particularly advantageous for the development of a coitus-independent, on-demand microbicide product. Moreover, all film types were shown potentially safe when evaluated by the MTT metabolic activity and lactate dehydrogenase release assays using HeLa and CaSki cervical cell lines. Overall, results support that proposed films may be suitable for the vaginal delivery of TDF/FTC in the context of topical PrEP.

Comparison of the Pharmacokinetics and Pharmacodynamics of Single-Dose Tenofovir Vaginal Film and Gel Formulation (FAME 05)

OBJECTIVE

Although preexposure prophylaxis with oral tenofovir (TFV) disoproxil fumarate/emtricitabine reduces HIV acquisition rates, poor adherence to and acceptability of daily vaginal gels have led to development of vaginal film formulations to improve adherence and, potentially, to enable episodic use.

STUDY DESIGN

In this 2-arm, cross-over study of a fast-dissolving tenofovir film (40 mg) compared with a previously studied semisolid tenofovir 1% gel (40 mg), 10 healthy women received a single vaginal dose of each study product. Clinical, pharmacokinetic, and antiviral assessments were performed over 1 week after dose.

RESULTS

Nine of 10 participants experienced mild to moderate adverse effects, similar between products, with no severe adverse events or events attributed to study products. TFV concentrations after film dosing exceeded concentrations after gel dosing in plasma between 8 and 24 hours (P ≤ 0.02). TFV concentrations in cervicovaginal fluid and both TFV and TFV diphosphate concentrations in cervical tissue homogenates were higher after film dosing (all P values < 0.04). The differences ranged from median (interquartile range) 2.9-fold (1.1, 9.0; midvaginal cervicovaginal fluid) to 4.4-fold (2.9, 7.7; plasma). Neither film nor gel demonstrated reduced cervical tissue biopsy infectivity after ex vivo HIV challenge.

CONCLUSION

Single-dose tenofovir film demonstrated consistently higher concentrations in plasma and cervicovaginal samples when compared with gel during the first day after dosing. Single-dose cervical tissue TFV-diphosphate concentrations at 5 hours exceeded steady-state concentrations previously reported with daily oral Truvada dosing. Tenofovir film may provide an alternative to tenofovir oral and gel formulations. Clinical efficacy remains to be tested.

An intravaginal ring that releases three antiviral agents and a contraceptive blocks SHIV-RT infection, reduces HSV-2 shedding, and suppresses hormonal cycling in rhesus macaques

Women globally need access to multipurpose prevention technologies (MPTs) that prevent human immunodeficiency virus (HIV), sexually transmitted infections that increase HIV acquisition/transmission risk, and unintended pregnancy. Seeking an MPT with activity against HIV, herpes simplex virus-2 (HSV-2), and human papillomavirus (HPV), we developed a prototype intravaginal ring (IVR), the MZCL IVR, which released the antiviral agents MIV-150, zinc acetate, and carrageenan (MZC for short) and the contraceptive levonorgestrel (LNG). Previously, we showed that an MZC gel has potent activity against immunodeficiency viruses, HSV-2, and HPV and that the MZCL (MZC with LNG) IVR releases all four components in macaques in vivo at levels associated with efficacy. Vaginal fluid from treated macaques has in vitro activity against HIV, HSV-2, and HPV. Herein, we assessed the ability of the MZCL IVR to protect macaques against repeated co-challenge with HSV-2 and SHIV-RT (simian immunodeficiency virus [SIV] containing the reverse transcriptase gene from HIV) and prevent hormonal cycling. We evaluated in vivo drug release in co-challenged macaques by measuring drug levels in blood and vaginal fluid and residual drug levels in used IVRs. The MZCL IVR significantly prevented SHIV-RT infection, reduced HSV-2 vaginal shedding, and prevented cycling. No non-nucleoside HIV reverse transcriptase inhibitor (NNRTI)-resistant SHIV was detected in macaques that became infected after continuous exposure to MZC from the IVR. Macaques wearing the MZCL IVR also had carrageenan levels in vaginal fluid expected to protect from HPV (extrapolated from mice) and LNG levels in blood associated with contraceptive efficacy. The MZCL IVR is a promising MPT candidate that warrants further development.

Novel multipurpose pod-intravaginal ring for the prevention of HIV, HSV, and unintended pregnancy: Pharmacokinetic evaluation in a macaque model

Globally, women bear an uneven burden for sexual HIV acquisition. Results from two clinical trials evaluating intravaginal rings (IVRs) delivering the antiretroviral agent dapivirine have shown that protection from HIV infection can be achieved with this modality, but high adherence is essential. Multipurpose prevention technologies (MPTs) can potentially increase product adherence by offering protection against multiple vaginally transmitted infections and unintended pregnancy. Here we describe a coitally independent, long-acting pod-IVR MPT that could potentially prevent HIV and HSV infection as well as unintended pregnancy. The pharmacokinetics of MPT pod-IVRs delivering tenofovir alafenamide hemifumarate (TAF2) to prevent HIV, acyclovir (ACV) to prevent HSV, and etonogestrel (ENG) in combination with ethinyl estradiol (EE), FDA-approved hormonal contraceptives, were evaluated in pigtailed macaques (N = 6) over 35 days. Pod IVRs were exchanged at 14 days with the only modification being lower ENG release rates in the second IVR. Plasma progesterone was monitored weekly to determine the effect of ENG/EE on menstrual cycle. The mean in vivo release rates (mg d-1) for the two formulations over 30 days ranged as follows: TAF2 0.35-0.40; ACV 0.56-0.70; EE 0.03-0.08; ENG (high releasing) 0.63; and ENG (low releasing) 0.05. Mean peak progesterone levels were 4.4 ± 1.8 ng mL-1 prior to IVR insertion and 0.075 ± 0.064 ng mL-1 for 5 weeks after insertion, suggesting that systemic EE/ENG levels were sufficient to suppress menstruation. The TAF2 and ACV release rates and resulting vaginal tissue drug concentrations (medians: TFV, 2.4 ng mg-1; ACV, 0.2 ng mg-1) may be sufficient to protect against HIV and HSV infection, respectively. This proof of principle study demonstrates that MPT-pod IVRs could serve as a potent biomedical prevention tool to protect women's sexual and reproductive health and may increase adherence to HIV PrEP even among younger high-risk populations.

Prevention of vaginal and rectal HIV transmission by antiretroviral combinations in humanized mice

With more than 7,000 new HIV infections daily worldwide, there is an urgent need for non-vaccine biomedical prevention (nBP) strategies that are safe, effective, and acceptable. Clinical trials have demonstrated that pre-exposure prophylaxis (PrEP) with antiretrovirals (ARVs) can be effective at preventing HIV infection. In contrast, other trials using the same ARVs failed to show consistent efficacy. Topical (vaginal and rectal) dosing is a promising regimen for HIV PrEP as it leads to low systematic drug exposure. A series of titration studies were carried out in bone marrow/liver/thymus (BLT) mice aimed at determining the adequate drug concentrations applied vaginally or rectally that offer protection against rectal or vaginal HIV challenge. The dose-response relationship of these agents was measured and showed that topical tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) can offer 100% protection against rectal or vaginal HIV challenges. From the challenge data, EC50 values of 4.6 μM for TDF and 0.6 μM for FTC for HIV vaginal administration and 6.1 μM TDF and 0.18 μM for FTC for rectal administration were obtained. These findings suggest that the BLT mouse model is highly suitable for studying the dose-response relationship in single and combination ARV studies of vaginal or rectal HIV exposure. Application of this sensitive HIV infection model to more complex binary and ternary ARV combinations, particularly where agents have different mechanisms of action, should allow selection of optimal ARV combinations to be advanced into pre-clinical and clinical development as nBP products.

Repeated administration of high-dose depot medroxyprogesterone acetate does not alter SHIVSF162p3 viral kinetics and tenofovir pharmacokinetics when delivered via intravaginal rings

BACKGROUND

Intravaginal rings (IVR) for HIV prevention will likely be used by women on depot medroxyprogesterone acetate (DMPA) hormonal contraception. We used pigtailed macaques to evaluate the effects of DMPA on tenofovir disoproxil fumarate (TDF) IVR pharmacokinetics and viral shedding.

METHODS

Mucosal tenofovir (TFV) levels were compared in SHIVSF162p3 -negative DMPA-treated (n=4) and normally cycling (n=6) macaques receiving TDF IVRs. Plasma viremia and vaginal shedding were determined in groups of SHIVSF162p3 -positive DMPA-treated (n=6) and normally cycling (n=5) macaques.

RESULTS

Similar median vaginal fluid TFV concentrations were observed in the DMPA-treated and cycling macaques over 4 weeks (1.2×105 and 1.1.×105  ng/mL, respectively). Median plasma viremia and vaginal shedding AUC of the DMPA-treated (2.73×107 and 8.15×104 copies/mL, respectively) and cycling macaques (3.98×107 and 1.47×103 copies/mL, respectively) were statistically similar.

CONCLUSIONS

DMPA does not affect TDF IVR pharmacokinetics or SHIV shedding.

Pharmacokinetics and Preliminary Safety of Pod-Intravaginal Rings Delivering the Monoclonal Antibody VRC01-N for HIV Prophylaxis in a Macaque Model

The broadly neutralizing antibody (bNAb) VRC01, capable of neutralizing 91% of known human immunodeficiency virus type 1 (HIV-1) isolates in vitro, is a promising candidate microbicide for preventing sexual HIV infection when administered topically to the vagina; however, accessibility to antibody-based prophylactic treatment by target populations in sub-Saharan Africa and other underdeveloped regions may be limited by the high cost of conventionally produced antibodies and the limited capacity to manufacture such antibodies. Intravaginal rings of the pod design (pod-IVRs) delivering Nicotiana-manufactured VRC01 (VRC01-N) over a range of release rates have been developed. The pharmacokinetics and preliminary safety of VRC01-N pod-IVRs were evaluated in a rhesus macaque model. The devices sustained VRC01-N release for up to 21 days at controlled rates, with mean steady-state VRC01-N levels in vaginal fluids in the range of 10² to 10³ μg g^-1 being correlated with in vitro release rates. No adverse safety indications were observed. These findings indicate that pod-IVRs are promising devices for the delivery of the candidate topical microbicide VRC01-N against HIV-1 infection and merit further preclinical evaluation.

The future of pre-exposure prophylaxis (PrEP) for human immunodeficiency virus (HIV) infection

INTRODUCTION

People at high risk for HIV acquisition should be offered pre-exposure prophylaxis (PrEP). Tenofovir disoproxil fumarate (TDF)/emtricitabine (FTC) is currently the only medication recommended for pre-exposure prophylaxis (PrEP) by the Centers for Disease Control and Prevention (CDC) in people at high risk for HIV acquisition. This article will review medications currently under investigation and the future landscape of PrEP therapy. Areas covered: This article will review clinical trials that have investigated nontraditional regimens of TDF/FTC, antiretroviral agents from different drug classes such as integrase strand transfer inhibitors (INSTI), nucleoside reverse transcriptase inhibitors (NRTI), and non-nucleoside reverse transcriptase inhibitors (NNRTI) as potential PrEP therapies. Expert commentary: Currently, there are several investigational drugs in the pipeline for PrEP against HIV infection. Increased utilization of PrEP therapy depends on provider identification of people at high risk for HIV transmission. Advances in PrEP development will expand options and access for people and reduce the risk of HIV acquisition.

Are you PEPped and PrEPped for travel? Risk mitigation of HIV infection for travelers

The HIV pandemic persists globally and travelers are at risk for infection by the Human Immunodeficiency Virus (HIV). While HIV-focused guidelines delineate risk stratification and mitigation strategies for people in their home communities, travel issues are not addressed. In this review, direct and indirect evidence on HIV risk among travelers is explored. The burgeoning practice of employing pre-exposure prophylaxis (PrEP) with anti-retroviral therapy in the non-travel setting is introduced, as well as the more established use of post-exposure prophylaxis (PEP). Challenges in applying these lessons to travelers are discussed, and a new guidelines process is scoped and recommended.

Combination Pod-Intravaginal Ring Delivers Antiretroviral Agents for HIV Prophylaxis: Pharmacokinetic Evaluation in an Ovine Model

Preexposure prophylaxis (PrEP) against HIV using oral regimens based on the nucleoside reverse transcriptase inhibitor tenofovir disoproxil fumarate (TDF) has been effective to various degrees in multiple clinical trials, and the CCR5 receptor antagonist maraviroc (MVC) holds potential for complementary efficacy. The effectiveness of HIV PrEP is highly dependent on adherence. Incorporation of the TDF-MVC combination into intravaginal rings (IVRs) for sustained mucosal delivery could increase product adherence and efficacy compared with oral and vaginal gel formulations. A novel pod-IVR technology capable of delivering multiple drugs is described. The pharmacokinetics and preliminary local safety characteristics of a novel pod-IVR delivering a combination of TDF and MVC were evaluated in the ovine model. The device exhibited sustained release at controlled rates over the 28-day study and maintained steady-state drug levels in cervicovaginal fluids (CVFs). Dilution of CVFs during lavage sample collection was measured by ion chromatography using an inert tracer, allowing corrected drug concentrations to be measured for the first time. Median, steady-state drug levels in vaginal tissue homogenate were as follows: for tenofovir (TFV; in vivo hydrolysis product of TDF), 7.3 × 10(2) ng g(-1) (interquartile range [IQR], 3.0 × 10(2), 4.0 × 10(3)); for TFV diphosphate (TFV-DP; active metabolite of TFV), 1.8 × 10(4) fmol g(-1) (IQR, 1.5 × 10(4), 4.8 × 10(4)); and for MVC, 8.2 × 10(2) ng g(-1) (IQR, 4.7 × 10(2), 2.0 × 10(3)). No adverse events were observed. These findings, together with previous pod-IVR studies, have allowed several lead candidates to advance into clinical evaluation.