Phase 1 Pharmacokinetic Trial of 2 Intravaginal Rings Containing Different Dose Strengths of Vicriviroc (MK-4176) and MK-2048.

BACKGROUND: Vaginal rings (VRs) are a promising approach for sustained delivery of antiretroviral (ARV) medication to prevent human immunodeficiency virus (HIV) infection in women. Combination ARV VRs could increase efficacy. METHODS: MTN-028, a phase 1 trial in 19 HIV-uninfected women, evaluated 2 VRs containing vicriviroc (VCV) and MK-2048. Participants were randomized 2:1 to a low-dose (VCV, 91 mg; MK-2048, 10 mg) or original-dose (VCV, 182 mg; MK-2048, 30 mg) ring used for 28 days. Safety was assessed by documenting adverse events (AEs). Drug concentrations were evaluated in plasma, cervicovaginal fluid (CVF), and cervical tissue samples. RESULTS: All AEs reported were grade 1 or 2, with no statistically significant differences in related genitourinary AEs or grade ≥2 AEs observed between arms (P = >.99). VCV/MK-2048 concentrations rose rapidly, with higher plasma area under the concentration-time curve (AUC) in the original-dose arm (geometric mean ratio, 3.29 for VCV and 1.49 for MK-2048) and similar AUCs across arms for CVF samples. Cervical tissue concentrations were higher in the original-dose arm (geometric mean ratio, 7.94 for VCV and 6.45 for MK-2048), with greater drug released based on residual drug levels. Plasma and CVF concentrations for both drugs fell rapidly after ring removal. CONCLUSIONS: In this first study evaluating 2 doses of a combination VCV/MK-2048 VR, both rings were found to be safe and well tolerated. VCV and MK-2048 were detectable in plasma, CVF, and cervical tissue samples, and drug release and plasma drug exposure were higher for the original-dose than for the low-dose ring.

Phase 2a Safety, Pharmacokinetics, and Acceptability of Dapivirine Vaginal Rings in US Postmenopausal Women.

BACKGROUND: Postmenopausal women have unique sociobiological human immunodeficiency virus (HIV) risks. We evaluated the safety, pharmacokinetics, and acceptability of a microbicide dapivirine (DPV) vaginal ring (VR) versus placebo in postmenopausal women. METHODS: We enrolled 96 HIV-negative postmenopausal US women in a phase 2a double-blind, randomized (3:1) trial of monthly VRs containing 25 mg DPV or placebo used continuously for 12 weeks. We assessed safety by adverse events (AEs). DPV concentrations were quantified in plasma and vaginal fluid. Steady-state concentrations were analyzed at 4, 8, and 12 weeks using repeated measures ANOVA. We assessed acceptability by self-report. RESULTS: We found no differences in the proportion of women with related grade 2 or higher reproductive system AEs (DPV: 6/72 (8%), placebo: 3/24 (13%), P = .68) or grade 3 or higher AEs (DPV: 4/72 (6%), placebo: 0/24 (0%), P = .57). In the DPV arm, 2/72 (3%) declined to resume product use due to AEs. Median DPV concentrations in plasma (262.0 pg/mL at week 12) and vaginal fluid (40.6 ng/mg at week 12) were constant over 12 weeks and exceeded the in vitro 50% effective concentration by 5000-fold in vaginal fluid by week 4. VR acceptability was high; 84/93 (90%) "very much liked or liked" the VR. CONCLUSIONS: DPV VRs were safe, well tolerated, and acceptable in postmenopausal women. Plasma concentrations were comparable to published data on DPV use in reproductive-age women (median plasma concentration: 264 pg/mL). Given the reassuring safety and pharmacokinetic data, the DPV VR is promising for preexposure prophylaxis in postmenopausal women. CLINICAL TRIALS REGISTRATION: NCT02010593.

Current and Future PrEP Medications and Modalities: On-demand, Injectables, and Topicals.

PURPOSE OF REVIEW: Pre-exposure prophylaxis (PrEP) is a potent HIV prevention strategy, but uptake of daily oral PrEP remains low. This review covers PrEP agents currently available and agents and modalities under investigation. RECENT FINDINGS: Injectable ARV preparations have high acceptability among users but are likely to require adherence to 8-week interval injections. Topical microbicide gels and vaginal rings have underperformed by intention-to-treat analyses in efficacy studies, at least in large part due to challenges with adherence and/or sustained use. However, daily oral TDF-FTC also underperformed in randomized, placebo-controlled trials compared to expectations and subsequent real-world pragmatic use. On-demand (2-1-1 dosing strategy for MSM) and injectable PrEP appear to be acceptable among participants in clinical trials. These modalities are particularly compelling alternatives for individuals who either do not want to take a daily medication (both on-demand and injectable) and/or want to take PrEP without a long commitment (on-demand). Emerging modalities such as vaginal films, microneedles, and subdermal implants have numerous advantages but are still in early stages of development.

Current contraceptive trends among married Egyptian women: a cross-sectional survey.

OBJECTIVE: The aim of our study was to assess the knowledge and attitudes of married Egyptian women towards the different methods of contraception, examining the role of employment and education in modulating contraceptive behaviour. METHODS: A cross-sectional survey was conducted among 2360 Egyptian women between 15 and 45 years of age who were attending outpatient clinics at a university hospital in Cairo between August 2017 and January 2018. The survey collected sociodemographic data as well as information on education, employment, knowledge about contraceptive methods, current and previous use of contraception, source of family planning advice and side effects from previous contraceptive use. RESULTS: The response rate was 90.2%. Current use of a contraceptive method was 38.3%. The intrauterine device (IUD) was the leading contraceptive method (50.7%), followed by oral contraceptives (OCs) (23.6%). Contraceptive prevalence was significantly higher among working women (p < .001), whose primary choice was OCs, while IUD use was significantly higher among non-working women (p < .001). Contraceptive prevalence was highest among women with secondary school education or higher (41.6%). CONCLUSION: Both employment status and educational level of the surveyed women played a significant role in their contraceptive behaviour.

Acceptability of microbicidal vaginal rings and oral pre-exposure prophylaxis for HIV prevention among female sex workers in a high-prevalence US city.

Biomedical HIV prevention tools including oral pre-exposure prophylaxis (PrEP) and vaginal microbicidal rings hold unique value for high-risk women who may have limited capacity for condom negotiation, including the key populations of sex workers and drug users. Commercial sex is a PrEP indicator in CDC guidelines, yet little is known about female sex workers' (FSWs) knowledge of and attitudes toward PrEP or the recently developed monthly vaginal microbicide rings. We describe knowledge and attitudes toward PrEP and microbicide rings in a sample of 60 mostly drug-using FSWs in Baltimore, Maryland, a high HIV-prevalence US city. Just 33% had heard of PrEP, but 65% were interested in taking daily oral PrEP and 76% were interested in a microbicide vaginal ring; 87% were interested in at least one of the two methods. Results suggest method mix will be important as biomedical tools for HIV prophylaxis are implemented and scaled up in this population, as 12% were interested in PrEP but not vaginal rings, while 19% were interested in vaginal rings but not in PrEP. Self-efficacy for daily oral adherence was high (79%) and 78% were interested in using PrEP even if condoms were still necessary. Women who had experienced recent client-perpetrated violence were significantly more interested in PrEP (86% vs 53%, p = 0.009) and microbicidal rings (91% vs 65%, p = 0.028) than women who had not recently experienced violence. No differences were observed by demographics nor HIV risk behaviors, suggesting broad potential interest in daily PrEP and monthly-use vaginal microbicides in this high-risk population.

Prevalence of combined contraceptive vaginal rings in Norway.

INTRODUCTION: Little is known about vaginal ring (VR) prescribers and user patterns in Norway and internationally. With data from the Norwegian Prescription Database, we explore user and prescriber characteristics of women initiating VR use. MATERIAL AND METHODS: In a cross-sectional study design, we analyzed 47 127 first-time VR users from 1 January 2006 to 31 December 2012. Follow up ended on 30 June 2013. We applied strict definitions for switching from any other hormonal contraceptive before and at the end of VR use. All analyses were performed using SPSS, with chi-squared test, t-test, and survival analysis. RESULTS: At study end, the prevalent use of VR reached 10 per 1000 women of fertile age, which amounted to 3% of all hormonal contraceptive use. The number of first-time VR users increased from 2006 to 2008 only among women under the age of 20. Nearly three out of four new users discontinued after 3 months. Physicians without specialist status and general practitioners accounted for over 70% of the prescriptions, whereas gynecologists accounted for 17% of the prescriptions. Gynecologists were significant prescribers of VR to women aged 35 or more. CONCLUSIONS: Gynecologists are important providers of VR to first-time users above 30 years of age. When prescribing VR to first-time users, it is important to discuss the need for contraception in a longer time perspective. Authorizing public health nurses/midwives as VR prescribers to teenagers, from 1 March 2006, may explain the relative increase in VR usage at a younger age.

Pre-clinical development of a combination microbicide vaginal ring containing dapivirine and darunavir.

OBJECTIVES: Combination microbicide vaginal rings may be more effective than single microbicide rings at reducing/preventing sexual transmission of HIV. Here, we report the pre-clinical development and macaque pharmacokinetics of matrix-type silicone elastomer vaginal rings containing dapivirine and darunavir. METHODS: Macaque rings containing 25 mg dapivirine, 100 mg dapivirine, 300 mg darunavir or 100 mg dapivirine+300 mg darunavir were manufactured and characterized by differential scanning calorimetry. In vitro release was assessed into isopropanol/water and simulated vaginal fluid. Macaque vaginal fluid and blood serum concentrations for both antiretrovirals were measured during 28 day ring use. Tissue levels were measured on day 28. Ex vivo challenge studies were performed on vaginal fluid samples and IC50 values were calculated. RESULTS: Darunavir caused a concentration-dependent reduction in the dapivirine melting temperature in both solid drug mixes and in the combination ring. In vitro release from rings was dependent on drug loading, the number of drugs present and the release medium. In macaques, serum concentrations of both microbicides were maintained between 10(1) and 10(2) pg/mL. Vaginal fluid levels ranged between 10(3) and 10(4) ng/g and between 10(4) and 10(5) ng/g for dapivirine and darunavir, respectively. Both dapivirine and darunavir showed very similar concentrations in each tissue type; the range of drug tissue concentrations followed the general rank order: vagina (1.8 × 10(3)-3.8 × 10(3) ng/g)  > cervix (9.4 × 10(1)-3.9 × 10(2) ng/g)  > uterus (0-108 ng/g)  > rectum (0-40 ng/g). Measured IC50 values were >2 ng/mL for both compounds. CONCLUSIONS: Based on these results, and in light of recent clinical progress of the 25 mg dapivirine ring, a combination vaginal ring containing dapivirine and darunavir is a viable second-generation HIV microbicide candidate.

Pharmacokinetics of a CCR5 inhibitor in rhesus macaques following vaginal, rectal and oral application.

OBJECTIVES: This study measured and compared the pharmacokinetics of CMPD167, a small molecule antiretroviral CCR5 inhibitor with potential as an HIV microbicide, following vaginal, rectal and oral administration in rhesus macaques. METHODS: A vaginal hydroxyethylcellulose (HEC) gel, a rectal HEC gel, a silicone elastomer matrix-type vaginal ring and an oral solution, each containing CMPD167, were prepared and administered to rhesus macaques pretreated with Depo-Provera. CMPD167 concentrations in vaginal fluid, vaginal tissue (ring only), rectal fluid and blood plasma were quantified by HPLC-mass spectrometry. RESULTS: CMPD167 concentrations measured in rectal fluid, vaginal fluid and blood plasma were highly dependent on both the route of administration and the formulation type. Although rectal and vaginal fluid concentrations were highest when CMPD167 was administered locally (via either gel or ring), lower concentrations of the drug were also measured in these compartments following administration at the remote mucosal site or orally. CMPD167 levels in the vaginal and rectal fluid following oral administration were relatively low compared with local administration. CONCLUSIONS: The study provides clear evidence for vaginal-rectal and rectal-vaginal drug transfer pathways and suggests that oral pre-exposure prophylaxis with CMPD167 may be less efficacious at preventing sexual transmission of HIV-1 than topically applied products.

Polymer Delivery Systems for Long-Acting Antiretroviral Drugs.

The success of long-acting (LA) drug delivery systems (DDSs) is linked to their biocompatible polymers. These are used for extended therapeutic release. For treatment or prevention of human immune deficiency virus type one (HIV-1) infection, LA DDSs hold promise for improved regimen adherence and reduced toxicities. Current examples include Cabenuva, Apretude, and Sunlenca. Each is safe and effective. Alternative promising DDSs include implants, prodrugs, vaginal rings, and microarray patches. Each can further meet patients' needs. We posit that the physicochemical properties of the formulation chemical design can optimize drug release profiles. We posit that the strategic design of LA DDS polymers will further improve controlled drug release to simplify dosing schedules and improve regimen adherence.

Emerging Trends and Potential Prospects in Vaginal Drug Delivery.

The vagina is an essential part of the female reproductive system and offers many potential benefits over conventional drug delivery, including a large surface area for drug absorption, relatively low enzymatic activity, avoiding first-pass effects, and ease of administration. The vaginal mucosal cavity is an effective route for administering therapeutic agents that are intended both for local and systemic administration. The present review provides a comprehensive overview of recent trends and developments in vaginal drug delivery. Marketed formulations and products under clinical study are also reviewed. Various novel vaginal delivery systems have been studied in recent years as effective tools for delivering a range of therapeutic agents to the vagina. These systems offer numerous benefits, including sustained delivery, improved bioavailability, effective permeation, and higher efficacy. The recent focus of the scientific community is on the development of safe and efficient drug delivery systems, such as nanoparticles, microparticles, vesicular systems, vaginal rings, microneedles, etc., for vaginal application. Various factors, such as the physicochemical properties of the drugs, the volume and composition of the vaginal fluid, the pH of the vaginal fluid, the thickness of the vaginal epithelium, and the influence of sexual intercourse may influence the release of drugs from the delivery system and subsequent absorption from the vaginal route. To date, only a limited number of in vivo studies on novel vaginal DDS have been reported. Additionally, drug release kinetics under varying vaginal environments is also not well understood. More research is needed to ensure the suitability, biocompatibility, and therapeutic effectiveness of novel DDS for vaginal delivery. Although numerous strategies and interventions have been developed, clinical translation of these systems remains a challenge. The toxicity of the carrier system is also an important consideration for future clinical applications.

Acceptability and Preference for 3-Month Versus 1-Month Vaginal Rings for HIV-1 Risk Reduction Among Participants in a Phase 1 Trial.

Background: The monthly dapivirine vaginal ring provides partial protection against HIV, and a longer duration ring may reduce user burden and improve adherence. We examined acceptability and preference for 3-month versus 1-month rings for HIV-1 risk reduction in a phase 1 clinical trial. Materials and Methods: In Microbicide Trials Network-036/International Partnership for Microbicides 047, 49 HIV-negative participants aged 18-45 were randomized to one of two 3-month rings or the 1-month ring. Acceptability ratings were collected at enrollment, week 4, and study exit (week 13). At exit, ring preference was assessed quantitatively among all participants and a randomly selected subset of 24 participants completed in-depth interviews. Quantitative and qualitative findings were integrated to explore factors influencing acceptability and preference. Results: Acceptability of each ring was initially moderate and increased during the trial. Ratings were lower in the 3-month ring arms than the 1-month arm at each time point, including baseline. Most participants (34/47; 72%) preferred a 3-month ring at exit; however, this proportion was significantly lower within some subgroups characterized by site, education, race/ethnicity, and experiences with ring use. Qualitative interviews revealed reservations about hygiene and safety of the 3-month ring, including discomfort with use during menses, but these were usually outweighed by its increased convenience. Conclusions: Both ring durations were highly acceptable at study exit. Although most participants preferred a 3-month ring, preference was more divided in certain subgroups, highlighting the benefit of offering different duration options. Providing additional support to address concerns about hygiene and safety may improve acceptability of a 3-month vaginal ring.

Users' Preferred Characteristics of Vaginal Rings for HIV Prevention: A Qualitative Analysis of Two Phase I Trials.

Vaginal rings address a critical need for an independently initiated, long-acting HIV prevention method, but their design must be acceptable to promote uptake and adherence. Human-centered design (HCD) may help address design preference questions. In two Phase I studies of vaginal rings for HIV prevention conducted in the United States, we used qualitative interviews to assess participants' perceptions and opinions of the physical characteristics of the ring they used and of a ring's physical characteristics after comparing four ring designs presented via a visual tool. Users were found to prefer ring designs that appear easy to use, are physically comfortable, that function well, and are aesthetically pleasing. The parameters for these features varied widely. Product developers and marketers should consider marketing messages in which the target users feel this product is made to meet their needs and desires. Product developers are encouraged to design using HCD early in ring development (Clinical Trial Registration number: NCT03234400 and NCT03670355).

Contraception During Perimenopause: Practical Guidance.

Climacteric is by no means in itself a contraindication to safe contraception. On the contrary, there are several conditions related to the perimenopause that could benefit from the use of modern contraceptives, mainly hormonal, with the goals of avoiding unintended pregnancies and giving further possible benefits beyond contraception (menstrual cycle control, a reduction of vasomotor symptoms and menstrual migraines, a protection against bone loss, a positive oncological risk/benefit balance). This narrative review aims to provide practical guidance on their possible use in this particular life stage, both short- and long-acting reversible contraceptives, and to assist clinicians for women transitioning from contraception to their menopausal years, including the possible initiation of postmenopausal hormone therapy. Comprehensive contraceptive counselling is an essential aspect of the overall health and wellbeing of women and should be addressed with each such patient irrespective of age.

The effect of different contraceptive methods on the vaginal microbiome.

Introduction: Following a historical overview, the effect of different contraceptive methods on vaginal microbiome has been reviewed and summarized.Areas covered: Effects of combined hormonal contraceptives (oral or vaginal) and of progestin only (injectable and implantable), intrauterine devices/systems (copper- or levonorgestrel-releasing), on vaginal microbiome. In addition, mention is made of vaginal rings releasing antiviral drugs and lactic acid.Expert opinion: The vaginal microbiota (VM) is unique in that it is normally dominated by Lactobacillus species providing a degree of protection against infections; this however may vary, depending on the species and strains of Lactobacillus. Bacterial Vaginosis represents the most common dysbiosis of the VM and its prevalence can be influenced by use of contraception. Available evidence indicates that, under the influence of oral or systemically administered female sex hormones, there is apromotion of vaginal eubiosis, with aprevalence of ahealthy VM in which Lactobacilli predominate.

Silicone elastomer formulations for improved performance of a multipurpose vaginal ring releasing dapivirine and levonorgestrel.

A dapivirine-releasing silicone elastomer vaginal ring for reducing women's risk of HIV acquisition has recently been approved. A next-generation multipurpose vaginal ring releasing dapivirine and levonorgestrel is currently in development, offering hormonal contraception and HIV prevention from a single device. Previously, we reported challenges with incorporating levonorgestrel into rings manufactured from addition-cure silicone elastomers due to an irreversible chemical reaction between the levonorgestrel molecule and the hydride-functionalised crosslinker component of the silicone elastomer formulation, leading to low drug content assay, cure inhibition, and reduced ring mechanical properties (which may account for the increased incidence of ring expulsion in vivo). Here, we report on the development and testing of various custom silicone elastomer materials specifically formulated to circumvent these issues. After extensive testing of the custom silicones and subsequent manufacture and testing (Shore M hardness, pot life, content assay, oscillatory rheology, mechanical testing) of rings containing both dapivirine and levonorgestrel, a lead candidate formulation was selected that was amenable to practical ring manufacture via injection molding, exhibited no substantial levonorgestrel binding, and offered suitable mechanical properties.

In Vitro-In Vivo Correlation (IVIVC) Population Modeling for the In Silico Bioequivalence of a Long-Acting Release Formulation of Progesterone.

Health authorities carefully evaluate any change in the batch manufacturing process of a drug before and after regulatory approval. In the absence of an adequate in vitro-in vivo correlation (Level A IVIVC), an in vivo bioequivalence (BE) study is frequently required, increasing the cost and time of drug development. This study focused on developing a Level A IVIVC for progesterone vaginal rings (PVRs), a dosage form designed for the continuous delivery in vivo. The pharmacokinetics (PK) of four batches of rings charged with 125, 375, 750 and 1500 mg of progesterone and characterized by different in vitro release rates were evaluated in two clinical studies. In vivo serum concentrations and in vitro release profiles were used to develop a population IVIVC progesterone ring (P-ring) model through a direct differential-equation-based method and a nonlinear-mixed-effect approach. The in vivo release, Rvivo(t), was predicted from the in vitro profile through a nonlinear relationship. Rvivo(t) was used as the input of a compartmental PK model describing the in vivo serum concentration dynamics of progesterone. The proposed IVIVC P-ring model was able to correctly predict the in vivo concentration-time profiles of progesterone starting from the in vitro PVR release profiles. Its internal and external predictability was carefully evaluated considering the FDA acceptance criteria for IVIVC assessment of extended-release oral drugs. Obtained results justified the use of the in vitro release testing in lieu of clinical studies for the BE assessment of any new PVRs batches. Finally, the possible use of the developed population IVIVC model as a simulator of virtual BE trials was explored through a case study.

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.

Treatment and prevention of HIV infection with long-acting antiretrovirals.

INTRODUCTION: Current antiretroviral therapy allows to achieve and sustain maximal suppression of HIV replication in most treated patients. As result, the life expectancy of HIV-infected persons has improved dramatically and is nowadays similar to that of the HIV-negative population. However, oral antiretrovirals have to be taken daily and indefinitely to avoid resumption of HIV replication and selection of drug resistance. Unfortunately, drug adherence is often suboptimal and tends to decline over time. Areas covered: New drugs, formulations and delivery systems are being developed for extended-release of antiretrovirals. At this time, intramuscular cabotegravir and rilpivirine, dapivirine vaginal rings and tenofovir alafenamide subdermal implants are the products in more advanced stages of clinical development. Their pharmacokinetics/dynamics and safety/efficacy are reviewed. Expert commentary: In the absence of eradicative therapy for individuals with HIV infection and protective vaccines for persons at risk, long-term antiretroviral therapy is the best approach for preventing disease progression in patients and halting transmissions, either as result of 'treatment as prevention' for HIV carriers or 'pre-exposure prophylaxis' for uninfected individuals at risk. In all these scenarios, the advent of long-acting antiretrovirals will expand options for overcoming the challenge of suboptimal drug adherence and reduce the burden of HIV infection.

Biomarkers and biometric measures of adherence to use of ARV-based vaginal rings.

INTRODUCTION: Poor adherence to product use has been observed in recent trials of antiretroviral (ARV)-based oral and vaginal gel HIV prevention products, resulting in an inability to determine product efficacy. The delivery of microbicides through vaginal rings is widely perceived as a way to achieve better adherence but vaginal rings do not eliminate the adherence challenges exhibited in clinical trials. Improved objective measures of adherence are needed as new ARV-based vaginal ring products enter the clinical trial stage. METHODS: To identify technologies that have potential future application for vaginal ring adherence measurement, a comprehensive literature search was conducted that covered a number of biomedical and public health databases, including PubMed, Embase, POPLINE and the Web of Science. Published patents and patent applications were also searched. Technical experts were also consulted to gather more information and help evaluate identified technologies. Approaches were evaluated as to feasibility of development and clinical trial implementation, cost and technical strength. RESULTS: Numerous approaches were identified through our landscape analysis and classified as either point measures or cumulative measures of vaginal ring adherence. Point measurements are those that give a measure of adherence at a particular point in time. Cumulative measures attempt to measure ring adherence over a period of time. DISCUSSION: Approaches that require modifications to an existing ring product are at a significant disadvantage, as this will likely introduce additional regulatory barriers to the development process and increase manufacturing costs. From the point of view of clinical trial implementation, desirable attributes would be high acceptance by trial participants, and little or no additional time or training requirements on the part of participants or clinic staff. We have identified four promising approaches as being high priority for further development based on the following measurements: intracellular drug levels, drug levels in hair, the accumulation of a vaginal analyte that diffuses into the ring, and the depletion of an intrinsic ring constituent. CONCLUSIONS: While some approaches show significant promise over others, it is recommended that a strategy of using complementary biometric and behavioural approaches be adopted to best understand participants' adherence to ARV-based ring products in clinical trials.

Microbicide vaginal rings: Technological challenges and clinical development.

Vaginal rings (VRs) are flexible, torus-shaped, polymeric devices designed to sustain delivery of pharmaceutical drugs to the vagina for clinical benefit. Following first report in a 1970 patent application, several steroid-releasing VR products have since been marketed for use in hormone replacement therapy and contraception. Since 2002, there has been growing interest in the use of VR technology for delivery of drugs that can reduce the risk of sexual acquisition of human immunodeficiency virus type 1 (HIV-1), the causative agent of acquired immunodeficiency syndrome (AIDS). Although no vaginally-administered product has yet been approved for HIV reduction/prevention, extensive research efforts are continuing and a number of VR devices offering sustained release of so-called 'HIV microbicide' compounds are currently being evaluated in late-stage clinical studies. This review article provides an overview of the published scientific literature within this important field of research, focusing primarily on articles published within peer-reviewed journal publications. Many important aspects of microbicide-releasing VR technology are discussed, with a particular emphasis on the technological, manufacturing and clinical challenges that have emerged in recent years.