Matrix and reservoir-type multipurpose vaginal rings for controlled release of dapivirine and levonorgestrel

Two into one does go: Formulation development of a multipurpose combination vaginal ring releasing dapivirine and metronidazole for prevention of HIV infection and treatment of bacterial vaginosis

Bacterial vaginosis (BV) is a common but often asymptomatic dysbiosis of the human vagina characterized by an imbalance in the normal vaginal microbiota due to loss of lactobacilli and an overgrowth of certain anaerobic bacteria. While BV itself is not a sexually transmitted infection, it is associated with an increased risk in women of various sexually acquired infections, including human immunodeficiency virus (HIV) infection. There is, therefore, a strong rationale for pursuing new multipurpose products that seek to treat or prevent BV alongside preventing HIV infection. With the dapivirine-releasing vaginal ring for HIV prevention now approved in several African countries, here we report formulation development of a next-generation ring product that releases both dapivirine (DPV) and the antibiotic drug metronidazole (MET). Following thermal analysis studies to characterize the phase behaviour of DPV-MET mixtures and rheological analysis to assess the cure characteristics of the active silicone elastomer mixes, matrix-type rings were manufactured containing 25 or 200 mg DPV in combination with 100, 250, 500, 1000 or 2000 mg MET. The results for drug content, in vitro release, mechanical testing, and Gardnerella vaginalis time-kill experiments demonstrate the feasibility of incorporating both DPV and MET in a matrix-type ring formulation and indicate that clinically effective release rates may be possible.

Physicochemical considerations in the formulation development of silicone elastomer vaginal rings releasing 5-nitroimidazole drugs for the treatment of bacterial vaginosis

Bacterial vaginosis (BV) is a common dysbiosis of the human vaginal microbiota characterized by depletion of hydrogen peroxide and lactic acid-producing Lactobacillus bacteria and an overgrowth of certain facultative anaerobic bacteria. Although short-term cure rates following treatment with frontline antibiotics (most notably oral metronidazole (MNZ), clindamycin vaginal cream, and MNZ vaginal gel) are generally high, longer-term recurrence rates are an issue. The development of vaginal formulations offering continuous/sustained administration of antibiotic drugs over one or more weeks might prove useful in reducing recurrence. Here, we report the manufacture and preclinical testing of matrix-type vaginal rings offering sustained release of four 5-nitroimidazole antimicrobial drugs either being used clinically or having potential in treatment of BV - MNZ, tinidazole (TNZ), secnidazole (SNZ) and ornidazole (ONZ). All four drugs showed good compatibility with a medical-grade addition-cure silicone elastomer based upon thermal analysis experiments, and matrix-type rings containing 250 mg (3.125 %w/w) of each drug were successfully manufactured by reaction injection molding. 28-day in vitro drug release studies demonstrated root-time kinetics, with daily release rates of 25, 22, 9 and 6 mg/day½ for SNZ, ONZ, MNZ and TNZ, respectively. The rank order of drug release from rings correlated with the simple molecular permeability parameter S/V, where S is the measured drug solubility in silicone fluid and V is the drug molecular volume. The relative merits of SNZ and ONZ over MNZ (the current reference treatment) are discussed. The data support development of vaginal rings for sustained release of 5-nitroimidazole compounds for treatment of BV.

Co-delivery of an HIV prophylactic and contraceptive using PGSU as a long-acting multipurpose prevention technology

OBJECTIVES

Poly(glycerol sebacate) urethane (PGSU) elastomers formulated with 4'-ethynyl-2-fluoro-2'-deoxyadenosine (EFdA), levonorgestrel (LNG), or a combination thereof can function as multipurpose prevention technology implants for prophylaxis against HIV and unintended pregnancies. For these public health challenges, long-acting drug delivery technologies may improve patient experience and adherence. Traditional polymers encounter challenges delivering multiple drugs with dissimilar physiochemical properties. PGSU offers an alternative option that successfully delivers hydrophilic EFdA alongside hydrophobic LNG.

METHODS

This article presents the formulation, design, and characterization of PGSU implants, highlighting the impact of API loading, dimensions, and individual- versus combination-loading on release rates.

RESULTS

Co-delivery of hydrophilic EFdA alongside hydrophobic LNG acted as a porogen to accelerate LNG release. Increasing the surface area of LNG-only implants increased LNG release. All EFdA-LNG, EFdA-only, and LNG-only formulated implants demonstrated low burst release and linear release kinetics over 245 or 122 days studied to date.

CONCLUSION

PGSU co-delivers two APIs for HIV prevention and contraception at therapeutically relevant concentrations in vitro from a single bioresorbable, elastomeric implant. A new long-acting polymer technology, PGSU demonstrates linear-release kinetics, dual delivery of APIs with disparate physiochemical properties, and biocompatibility through long-term subcutaneous implantation. PGSU can potentially meet the demands of complex MPT or fixed-dose combination products, where better solutions can serve and empower patients.

In vitro drug release, mechanical performance and stability testing of a custom silicone elastomer vaginal ring releasing dapivirine and levonorgestrel

We have previously reported a multipurpose silicone elastomer vaginal ring providing sustained release of dapivirine (an antiretroviral) and levonorgestrel (a progestin) for HIV prevention and hormonal contraception. During initial development, issues arose due to reaction between the ethynyl group in the levonorgestrel molecule and the hydride-functionalised polydimethylsiloxane components in the silicone elastomer formulation. This unwanted reaction occurred both during and to a lesser extent after ring manufacture, impacting the curing process, the mechanical properties of the ring, and the in vitro release of levonorgestrel. Recently, we reported custom silicone elastomer grades that minimise this reaction. In this follow-on study, we describe the manufacture, in vitro drug release, mechanical, and pharmaceutical stability testing of ring formulations prepared from a custom silicone elastomer and containing 200 mg dapivirine and 80, 160, 240 or 320 mg levonorgestrel. The rings showed mechanical properties similar to marketed ring products, sustained in vitro release of both drugs over 30 days in quantities deemed clinically relevant, offered acceptable assay values, and provided good product stability over 15 weeks at 40 °C and 75% relative humidity.

Pharmacological Approaches for the Prevention of Breast Implant Capsular Contracture

Capsular contracture is a common complication associated with breast implants following reconstructive or aesthetic surgery in which a tight or constricting scar tissue capsule forms around the implant, often distorting the breast shape and resulting in chronic pain. Capsulectomy (involving full removal of the capsule surrounding the implant) and capsulotomy (where the capsule is released and/or partly removed to create more space for the implant) are the most common surgical procedures used to treat capsular contracture. Various structural modifications of the implant device (including use of textured implants, submuscular placement of the implant, and the use of polyurethane-coated implants) and surgical strategies (including pre-operative skin washing and irrigation of the implant pocket with antibiotics) have been and/or are currently used to help reduce the incidence of capsular contracture. In this article, we review the pharmacological approaches-both commonly practiced in the clinic and experimental-reported in the scientific and clinical literature aimed at either preventing or treating capsular contracture, including (i) pre- and post-operative intravenous administration of drug substances, (ii) systemic (usually oral) administration of drugs before and after surgery, (iii) modification of the implant surface with grafted drug substances, (iv) irrigation of the implant or peri-implant tissue with drugs prior to implantation, and (v) incorporation of drugs into the implant shell or filler prior to surgery followed by drug release in situ after implantation.

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.

[New frontiers in contraception research]

Improving current contraceptives and discover novel methods easy to use with added health benefits would meet the needs of couples who seek alternatives to current methods. New delivery systems target user-controlled, longer-acting options to provide choice, user's autonomy and improve compliance. Self-injections, microarray patches, pod rings able to deliver several molecules aim to prevent both pregnancies and sexually transmitted infections. Improved intrauterine systems and non-surgical permanent methods are also on the research agenda. The search for novel methods must continue, to curb maternal mortality led by multiple pregnancies and unsafe abortion, still a burden in many countries.

Effect of crosslinking on the physicochemical properties of polydimethylsiloxane-based levonorgestrel intrauterine systems

Polydimethylsiloxane (PDMS)-based levonorgestrel intrauterine systems (LNG-IUSs) such as Mirena® are long-acting drug-device combination products designed to release LNG for contraceptive purposes up to 6 years. LNG-IUSs consist of a hollow cylindrical drug-PDMS reservoir mounted with a polyethylene frame and covered by an outer PDMS membrane. PDMS is the release-controlling excipient present in both the matrix and the outer membrane. The degree of PDMS crosslinking is a key parameter in LNG-IUS manufacturing, dictating the elasticity and mechanical strength (which are critical parameters in molding and demolding of the cylindrical reservoirs). In addition, elasticity and mechanical strength are also important to prevent deformation during insertion into the uterine cavity. The objectives of this study were to investigate the impact of PDMS crosslinking on the physicochemical properties of LNG-IUSs and to develop appropriate testing methods for characterization of their mechanical strength. Formulations with different degrees of crosslinking were prepared by varying the ratio of the PDMS elastomer base and the crosslinking agent. A novel solvent swelling and extraction method was developed to determine the degree of PDMS crosslinking. The extent of crosslinking was also characterized via FTIR, Raman, ¹H NMR, DSC, TGA and dynamic mechanical analysis. As expected, formulations with higher degrees of crosslinking showed lower crystallinity. Interestingly, the less crystalline formulations showed higher Tg values and storage moduli compared to the high crystalline formulations, implying that crosslinking is the predominant parameter governing the physicochemical and mechanical properties in LNG-IUSs. Correlations were established between PDMS crosslinking and the physicochemical properties of LNG-IUSs which will be useful for quality control purposes during formulation screening and development. A better understanding of the physicochemical characteristics of these complex products will facilitate drug product development.

Recent advances in electrospun nanofiber vaginal formulations for women's sexual and reproductive health

Electrospinning is an innovative technique that allows production of nanofibers and microfibers by applying a high voltage to polymer solutions of melts. The properties of these fibers - which include high surface area, high drug loading capacity, and ability to be manufactured from mucoadhesive polymers - may be particularly useful in a myriad of drug delivery and tissue engineering applications. The last decade has witnessed a surge of interest in the application of electrospinning technology for the fabrication of vaginal drug delivery systems for the treatment and prevention of diseases associated with women's sexual and reproductive health, including sexually transmitted infections (e.g. infection with human immunodeficiency virus and herpes simplex virus) vaginitis, preterm birth, contraception, multipurpose prevention technology strategies, cervicovaginal cancer, and general maintenance of vaginal health. Due to their excellent mechanical properties, electrospun scaffolds are also being investigated as next-generation materials in the surgical treatment of pelvic organ prolapse. In this article, we review the latest advances in the field.

Contraceptive Technologies: Looking Ahead to New Approaches to Increase Options for Family Planning

With persistently high global rates of unintended pregnancy and contraceptive nonuse, nonadherence and discontinuation, new contraceptive methods must address the needs of women and men who seek alternatives to their current options. Methods under development aim to reduce potential side effects, improve access and ease of use, ensure safety, increase secondary benefits associated with method use and expand options for both women and men. Developmental approaches employed to enhance current methods utilize new delivery systems and novel active pharmaceutical ingredients. This will improve overall user satisfaction with the methods used while expanding the number of options available to provide choice and value user autonomy in the highly diverse contraceptive markets around the world.

Advances in long-acting injectables, implants, and vaginal rings for contraception and HIV prevention

Worldwide, women face compounding reproductive health risks, including human immunodeficiency virus (HIV), sexually-transmitted infections (STIs), and unintended pregnancy. Multipurpose prevention technologies (MPTs) offer combined protection against these overlapping risks in singular prevention products that offer potential for simplified use, lower burden, higher acceptability, and increased public health benefits. Over the past decade, substantial progress has been made in development of extended-release MPTs, which have further potential to grant sexual and reproductive health autonomy to women globally and to offer choice for women to accommodate varying needs during their reproductive lives. Here, we highlight the advances made in injectable, implant, and ring delivery forms, and the importance of incorporating end-user preferences early in the research and development of these products.

Development of Hormonal Intravaginal Rings: Technology and Challenges

Intravaginal rings (IVRs) are minimally invasive polymeric devices specifically designed to be used for the sustained and prolonged release of various type of drugs such as hormones. One of the benefits of using topical drug delivery systems (e.g., IVRs) is the fact that systemic drug delivery may cause drug resistance due to elevated drug levels. Topical drug delivery also provides higher concentrations of the drug to the target site and has fewer side effects. In addition, when a drug is administered vaginally, the hepatic first-pass effect is avoided, resulting in higher absorption. Contraception and treatments for specific diseases such as endometriosis and hormone deficiencies can be improved by the administration of hormones via an IVR. This article aims to classify and compare various designs of commercially available and non-commercial hormonal IVRs and to analyze their performance. Current challenges affecting the development of IVRs are investigated, and proposed solutions are discussed. A comprehensive search of publications in MEDLINE/PubMed and of commercial product data of IVRs was performed, and the materials, designs, performance, and applications (e.g., contraception, endometriosis, estrogen deficiency and urogenital atrophy) of hormonal IVRs were thoroughly evaluated. Most hormonal IVRs administer female sex hormones, i.e., estrogen and progestogens. In terms of material, IVRs are divided into 3 main groups: silicone, polyurethane, and polyethylene-co-vinyl acetate IVRs. As regards their design, there are 4 major designs for IVRs which strongly affect their performance and the timing and rate of hormone release. Important challenges include reducing the burst release and maintaining the bioavailability of hormones at their site of action over a prolonged period of administration as well as lowering production costs. Hormonal IVRs are a promising method which could be used to facilitate combination therapies by administering multiple drugs in a single IVR while eliminating the side effects of conventional drug administration methods. IVRs could considerably improve womenʼs quality of life all over the world within a short period of time.

Use of simulated vaginal and menstrual fluids to model in vivo discolouration of silicone elastomer vaginal rings

Vaginal rings releasing antiretrovirals – either alone or in combination with contraceptive progestins – are being developed for prevention of human immunodeficiency virus (HIV) transmission via vaginal sex. Following Phase I trials, significant discolouration was observed on the surface of investigational silicone elastomer antiretroviral-contraceptive matrix-type vaginal rings containing either 25 mg dapivirine or 200 mg dapivirine plus levonorgestrel. In this study, potential causes of the discolouration have been assessed in vitro using simulated vaginal and menstrual fluids (SVF and SMF, respectively) to model in vivo exposure. The fluid compositions also included hydrogen peroxide (H₂O₂), hydrogen peroxide plus a copper intrauterine device (IUD), or synthetic dyes (representing personal care and household cleaning products). No discolouration was observed for rings exposed to SVF + hydrogen peroxide (with or without an IUD). However, the SVF + dye compositions showed significant ring discolouration, with staining patterns similar to those observed with rings that had been exposed to highly-coloured personal care and household cleaning products during clinical trial use. Exposure of rings to SMF compositions invariably caused yellow surface discolouration, dark spotting and markings, similar to the staining patterns observed following clinical use. The darker marks on the ring surface were identified as blood debris derived from the SMF. The study indicates that surface discolouration of rings in vivo can be attributed to exposure to menstrual fluid or highly coloured personal care or household cleaning products. Discolouration of the rings was not associated with any specific safety risks for the user, though severe discolouration could potentially impact acceptability and adherence.

Drug eluting implants in pharmaceutical development and clinical practice

Introduction: Drug eluting implants offer patient convenience and improved compliance through less frequent dosing, eliminating repeated, painful injections and providing localized, site specific delivery with applications in contraception, ophthalmology, and oncology.Areas covered: This review provides an overview of available implant products, design approaches, biodegradable and non-biodegradable polymeric materials, and fabrication techniques with a focus on commercial applications and industrial drug product development. Developing trends in the field, including expanded availability of suitable excipients, development of novel materials, scaled down manufacturing process, and a wider understanding of the implant development process are discussed and point to opportunities for differentiated drug eluting implant products.Expert opinion: In the future, long-acting implants will be important clinical tools for prophylaxis and treatment of global health challenges, especially for infectious diseases, to reduce the cost and difficulty of treating chronic indications, and to prolong local delivery in difficult to administer parts of the body. These products will help improve patient safety, adherence, and comfort.

Vaginal multipurpose prevention technologies: promising approaches for enhancing women's sexual and reproductive health

Introduction: Multipurpose prevention technologies (MPTs) have the potential to avert multiple concomitant sexual and reproductive health issues in women such as sexually transmitted infections and unintended pregnancy. MPTs incorporate one or more active pharmaceutical ingredients in a single product, which adds more convenience for users and may promote increased adherence. Various vaginal dosage forms/delivery systems have been studied for designing MPTs. However, several challenges remain that are mainly related to requirements of individual drugs or intended multiple applications.Areas covered: This review focuses on the emerging need and development of vaginal MPTs. It illustrates numerous examples that are currently in the preclinical and clinical development pipeline, highlighting the concept behind vaginal MPTs. The article also highlights the challenges associated with formulation design and development, including regulatory issues that need to be addressed.Expert opinion: Vaginal MPTs present great potential to empower women with novel, efficient, and safe products for protection against sexually transmitted infections and unintended pregnancy. However, several technological issues and regulatory gaps still need to be addressed in order to meet real-world needs.

Montmorillonite-based polyacrylamide hydrogel rings for controlled vaginal drug delivery

Vaginal drug delivery is regarded as a promising route against women-related health issues such as unwanted pregnancies and sexually transmitted infections. However, only a very few studies have been reported on the use of hydrogel rings with low cytotoxicity for vaginal drug delivery applications. Moreover, the effect of nanoparticles on hydrogel vaginal rings has not been clearly evaluated. To overcome these challenges, we hereby developed nanocomposite hydrogel rings based on polyacrylamide-sodium carboxymethyl cellulose-montmorillonite nanoparticles in the ring-shaped aluminum mold for controlled drug delivery. The hydrogel rings were synthesized by using N,N'-methylene bisacrylamide, N,N,N',N'-tetramethyl ethylene diamine, and ammonium persulfate, as a crosslinker, accelerator, and initiator, respectively. The obtained rings were 5.5 cm in diameters and 0.5 cm in rims. Chemical structures of the nanocomposite rings were confirmed by Fourier transform infrared, and Nuclear Magnetic Resonance spectroscopies. Additionally, the swelling ratio of hydrogels was appeared to be adjusted by the introduction of nanoparticles. In vitro release experiment of methylene blue, as a hydrophilic model drug, revealed that the nanocomposite rings could not only reduce burst effect (almost more than twice), but also achieve prolonged release for 15 days in the vaginal fluid simulant which mimic the vaginal conditions at pH of almost 4.2, and a temperature of 37 °C. Importantly, the resultant hydrogel rings with or without various concentrations of montmorillonite showed low cytotoxicity toward human skin fibroblasts. Furthermore, different antibacterial activities against Escherichia coli were observed for various concentrations of montmorillonite in hydrogels. These results suggest the great potential of montmorillonite-based hydrogel rings for vaginal drug delivery.

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.

Towards a dapivirine and levonorgestrel multipurpose vaginal ring: Investigations into the reaction between levonorgestrel and addition-cure silicone elastomers

With a dapivirine-releasing vaginal ring having successfully completed late-stage clinical testing for HIV prevention and currently undergoing regulatory review, there is now growing interest in next-generation multipurpose prevention technologies that seek to combine antiretroviral and contraceptive drugs within a single product. Here, we focus on ongoing efforts to develop a silicone elastomer vaginal ring releasing both dapivirine and levonorgestrel. Specifically, we evaluate various strategies aimed at both better understanding and reducing the tendency of levonorgestrel to bind with the elastomer, including: (i) formulation and post-manufacturing strategies aimed at reducing the extent of levonorgestrel reaction with addition-cure silicone elastomers; (ii) evaluation of a simple silicone system to model the complex elastomer; (iii) use of model compounds representing the enone and ethinyl moieties of levonorgestrel to probe the mode of addition of levonorgestrel to addition-cure silicone elastomers; and (iv) solution and solid-state ¹³C NMR analysis to probe the structural features of the levonorgestrel-silicone system. The results demonstrate that both the enone and ethinyl groups within levonorgestrel undergo hydrosilylation reactions with the hydrosiloxane groups in the silicone elastomer leading to covalent binding. The results also highlight potential strategies for further optimising the dapivirine + levonorgestrel silicone vaginal ring formulation to ensure that the levonorgestrel is available for release.

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.

Dapivirine Bioadhesive Vaginal Tablets Based on Natural Polymers for the Prevention of Sexual Transmission of HIV

Young sub-Saharan women are a group that is vulnerable to the sexual transmission of HIV. Pre-exposure prophylaxis through vaginal microbicides could provide them an option for self-protection. Dapivirine has been demonstrated to have topical inhibitory effects in HIV, and to provide protection against the sexual transmission of this virus. This paper reports on the studies into swelling behaviour, bioadhesion and release carried out on dapivirine tablets based on chitosan, locust bean gum and pectin, to select the most suitable formulation. The modified simulated vaginal fluid led to a high solubility of dapivirine and allowed the dapivirine release profiles to be characterized in sink conditions; this aqueous medium is an alternative to organic solvents, which are not a realistic option when evaluating systems whose behaviour varies in aqueous and organic media. Of the formulations evaluated, dapivirine/pectin tablets containing 290 mg of polymer and 30 mg of dapivirine present the most moderate swelling, making them the most comfortable dosage forms. Their high bioadhesive capacity would also allow the formulation to remain in the action zone and release the drug in a sustained manner, pointing to this formulation as the most promising candidate for future evaluations of vaginal microbicides for the prevention of HIV.

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.

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.

Solid state 13C NMR spectroscopy provides direct evidence for reaction between ethinyl estradiol and a silicone elastomer vaginal ring drug delivery system

Steroid molecules have a long history of incorporation into silicone elastomer materials for controlled release drug delivery applications. Previously, based on in vitro release testing and drug content analysis, we demonstrated indirectly that the contraceptive progestin levonorgestrel (LNG) chemically and irreversibly binds to addition cure silicone elastomers, presumably via a hydrosilylation reaction between the levonorgestrel ethynyl group and the hydrosilane groups in the poly(dimethylsiloxane-co-methylhydrosiloxane) crosslinker of the silicone elastomer. Here, for the first time, we report that solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy provides direct evidence for the irreversible binding of ethinyl estradiol (EE) - an estrogenic steroid molecule also containing an ethynyl functional group - to an addition cure silicone elastomer. By preparing silicone elastomer samples containing ¹³C-labelled EE, signals in the NMR spectra could readily be assigned to both the free and bound EE. Additional depolymerisation studies, performed on an addition cure silicone elastomer system from which the unbound EE fraction was completely extracted, further confirmed the presence of bound EE through the formation of coloured reaction mixtures resulting from the reaction of bound EE and trifluoroacetic acid (TFA). These methods will be particularly useful in the ongoing development of new steroid-releasing silicone drug delivery devices, including various vaginal ring devices for contraception, HIV prevention and multipurpose prevention technology applications.

HIV and contraception

PURPOSE OF REVIEW

Contraception is a vital component of medical care for women with HIV or at high risk of acquiring HIV. Over the last several years, there has been emerging evidence regarding the safety and effectiveness of various contraceptive methods, ultimately leading to a revision in the WHO Medical Eligibility Criteria for contraceptive use.

RECENT FINDINGS

Progestogen-only injectables may be associated with an increased risk of HIV acquisition and its use has been revised to category 2 from category 1. Etonogestrel and levonorgestrel levels are lower in women who concurrently use contraceptive implant and efavirenz-based antiretroviral therapy. Multipurpose technology, aimed at providing antiretroviral medication and contraception, is an area of ongoing research but is not yet clinically available.

SUMMARY

It is important for providers who care for women with HIV or at high risk of HIV to inquire about pregnancy intentions. If contraception is desired, these women should be offered all available methods, with counseling regarding possible risks of contraceptive failure or HIV acquisition.

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.

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

5P12-RANTES, a chemokine analogue that potently blocks the HIV CCR5 coreceptor, is being developed as both a vaginal and rectal microbicide for prevention of sexual transmission of HIV. Here, we report the first pharmacokinetic data for 5P12-RANTES following single-dose vaginal gel administration in sheep. Aqueous gel formulations containing low (1.24-mg/ml), intermediate (6.18-mg/ml), and high (32.0-mg/ml; suspension-type gel) concentrations of 5P12-RANTES were assessed via rheology, syringeability, and in vitro release testing. Following vaginal gel administration to sheep, 5P12-RANTES concentrations were measured in vaginal fluid, vaginal tissue, and serum over a 96-h period. All gels showed non-Newtonian pseudoplastic behavior, with the high-concentration gels exhibiting a greater viscosity and cohesive structure than the intermediate- and low-concentration gels. In in vitro release testing, >90% 5P12-RANTES was released from the low- and intermediate-concentration gels after 72 h. For the high-concentration gel, ∼50% 5P12-RANTES was detected, attributed to protein denaturation during lyophilization and/or subsequent solvation of the protein within the gel matrix. In sheep, 5P12-RANTES concentrations in vaginal fluid, vaginal tissue, and serum increased in a dose-dependent manner. The highest concentrations were measured in vaginal fluid (10⁵ to 10⁷ ng/ml), followed by vaginal tissue (10⁴ to 10⁶ ng/ml). Both of these concentration ranges are several orders of magnitude above the reported half-maximal inhibitory concentrations. The lowest concentration was measured in serum (<10² ng/ml). The 5P12-RANTES pharmacokinetic data are similar to those reported previously for other candidate microbicides. These data, coupled with 5P12-RANTES's potency at picomolar concentrations, its strong barrier to resistance, and the full protection that it was observed to provide in a rhesus macaque vaginal challenge model, support the continued development of 5P12-RANTES as a microbicide.

Thermoplastic polyurethane-based intravaginal rings for prophylaxis and treatment of (recurrent) bacterial vaginosis

The aim of the present study was to develop thermoplastic polyurethane (TPU)-based intravaginal rings (IVRs) for prophylaxis and treatment of bacterial vaginosis via hot melt extrusion/injection molding. Therefore, different TPU grades were processed in combination with lactic acid or metronidazole, targeting a sustained lactic acid release over a 28day-period and sustained metronidazole release over 4-7days. Hot melt extrusion of lactic acid/TPU combinations required a lower extrusion temperature due to the plasticizing properties of lactic acid, evidenced by the lower glass transition temperature (T_g) and cross-over point (T_tanδ=1) values. NIR-chemical imaging data showed a homogenous distribution of lactic acid in TPU matrices at drug loads up to 30% (w/w). The addition of metronidazole did not lower processing temperatures, as the active pharmaceutical ingredient remained crystalline in the TPU matrix. Hydrophobic TPUs with a low ratio between the soft and hard segments (SS/HS ratio) in the polymer structure were suitable carriers for the lactic acid-eluting device over a 28-day period, while hydrophilic TPUs were needed to achieve the required release rate of metronidazole-eluting IVRs. IVRs manufactured with a TPU grade having a higher SS/HS ratio and lactic acid/TPU ratio exhibited a more elastic behavior. The addition of 25% (w/w) metronidazole did not affect the mechanical properties of the IVRs. Hydrophilic TPUs were most prone to biofilm formation by Candida albicans and Staphylococcus aureus, but the incorporation of metronidazole in the device prevented biofilm formation. Based on the drug eluting performance and mechanical tests, a mixture of lactic acid and Tecoflex™ EG-93A (20/80, w/w) and a combination of metronidazole and Tecophilic™ SP-93A-100 (25/75, w/w) were selected to design IVRs for the prophylaxis and treatment of bacterial vaginosis, respectively. Slug mucosal irritation tests predicted low irritation potency for both devices.

Packing Polymorphism of Dapivirine and Its Impact on the Performance of a Dapivirine-Releasing Silicone Elastomer Vaginal Ring

A silicone elastomer vaginal ring providing sustained release over 28 days of the anti-retroviral microbicide dapivirine has recently completed phase III clinical testing and showed moderate protection against HIV acquisition. In support of the product licensure program, we report the impact of dapivirine packing polymorphism on the thermal and solubility characteristics of dapivirine and on the in vitro performance of the 25 mg dapivirine ring product. This is the first time that polymorphism has been reported for a drug-releasing vaginal ring product. Thermal, particle size, powder X-ray diffraction, and thermodynamic solubility analyses of dapivirine polymorphic forms I and IV, both of which are persistent at room temperature and with form I being the thermodynamically stable form, were conducted for both micronized and non-micronized materials. No significant differences in solubility between DPV forms I and IV were observed in media commonly used for in vitro release testing. Matrix-type silicone elastomer vaginal rings were manufactured and the impact of dapivirine polymorphism on key in vitro parameters (compression and tensile behavior; content assay; in vitro release; residual content assay) was investigated. The data demonstrate that dapivirine packing polymorphism has no significant impact on in vitro performance of the 25 mg dapivirine vaginal ring.

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.