Dilution of microbicide gels with vaginal fluid and semen simulants: effect on rheological properties and coating flow.

Microbicides are agents applied topically to the vagina to prevent HIV transmission. Microbicide products formulated as semi-solid dosage forms or "gels" coat vulnerable tissue to deliver active ingredients. Effective microbicide delivery vehicles must have appropriate rheological properties to ensure appropriate deployment in vivo. Microbicide products become diluted by fluids in the vagina after application; dilution affects vehicle rheological properties and mechanics of vaginal distribution, thus affecting efficacy. To simulate the changes that might occur after application, this study analyzed the effects of small dilutions (10-30%) with vaginal fluid and semen simulants on three semi-solid vaginal formulations: a cellulose lubricant (KY Jelly), a polyacrylic acid moisturizer (Replens), and a carrageenan prototype microbicide (Carraguard). Rheological behavior was characterized using cone-and-plate rheometry. Data were fitted to either the power-law, Carreau, or Herschel-Bulkley model. Rheological parameters from these fits were input to models of coating flow due squeezing, and the simulated area coated output from these models was used to compare the responses of the different formulations to the two diluents for varying degrees of dilution. There were differences in the responses of the three materials to dilution. Even small dilutions altered the rank order of vaginal coating rates compared to the undiluted formulations.

Biophysical analysis of prototype microbicidal gels.

The objective of this study was to evaluate the distribution and retention (deployment) of four prototype vehicles for delivery of prophylactic microbicides against vaginal HIV transmission. Study gels were created with different molecular compositions, producing different biophysical properties governing vaginal deployment. The study employed three techniques: direct rheological measurement of gel properties, direct observation of gel surface coating erosion, and dissolution by a vaginal fluid simulant, and mathematical modeling of gel squeezing flow processes. Results suggest significant differences in extent of vaginal coating after gel application and in erosion of these gel layers due to contact with ambient vaginal fluid and shearing. The relationships between gel rheological properties, coating flow and erosion of coating were not always anticipated from differences in gel molecular composition.

Temperature and pH sensitive hydrogels: an approach towards smart semen-triggered vaginal microbicidal vehicles.

Microbicides are drug delivery systems (DDSs) for the prevention of sexual transmission of HIV and other STDs. A topically applied vaginal microbicidal gel should provide uniform coating of vaginal tissue, retention of this gel layer prior to intercourse, and controlled release kinetics of antivirals to inactivate the viral load potentially introduced during sexual activity. Here, we describe the microbicide-oriented characterization of a DDS made with a dual pH sensitive and thermosensitive smart polymer gel composed of a random terpolymer of N-isopropyl acrylamide, butyl methacrylate, and acrylic acid. The system was engineered to coat vaginal tissue with a stable gel layer and to release entrapped model agents in a burst release profile in response to the presence of the infecting agent: semen. The gel rheology, layer erosion properties, model drug release kinetics, and cytocompatibility of the terpolymer system were studied. Negligible erosion of the gel in the presence of vaginal fluid simulant suggests prolonged retention. Burst release of molecular and macromolecular model compounds was observed when the system's pH changed from the vaginal pH to the pH of semen, and cytotoxicity studies showed that the terpolymer is equally cytocompatible as a commonly used polymeric vaginal carrier.

Optical imaging and analysis of human vaginal coating by drug delivery gels.

OBJECTIVE: We used a new optical imaging technique to compare human intravaginal coating distributions of Conceptrol (Advanced Care Products, Brunswick, NJ) and Advantage (Columbia Laboratories, Aventuna, FL). These gels are surrogates for future microbicidal gels, differing in molecular structures and biophysical properties. METHODS: For each protocol, a 3-mL gel bolus was inserted to the posterior fornix while the woman was in the supine position. She then either (1) remained supine (10 min); or (2) sat up (1 min), stood up (1 min), sat down (1 min) and returned to supine for a net elapsed time of 10 min. The imaging device is sized/shaped like a phallus, and measurements while the device was inserted provide data that simulate peri-intromission coating. RESULTS: Coating by Advantage was more extensive and uniform than coating by Conceptrol, with smaller bare spots of uncoated epithelium. Change in posture tended to increase extent and uniformity of coating, details differing between gels. CONCLUSIONS: Results are consistent with predictions of mechanistic coating theory, using gel rheological data as inputs.

Attitudes and perceptions towards novel objective measures of ARV-based vaginal ring use: Results from a global stakeholder survey.

Results of recent microbicide and pre-exposure prophylaxis clinical trials have shown adherence to be a significant challenge with new HIV prevention technologies. As the vaginal ring containing dapivirine moves into two open label follow-on studies (HOPE/MTN-025 and DREAM) and other antiretroviral-based and multi-purpose prevention technology ring products advance through the development pipeline, there is a need for more accurate and reliable measures of adherence to microbicide ring products. We previously conducted a comprehensive landscape analysis to identify new technologies that could be applied to adherence measurement of vaginal rings containing antiretrovirals. To explore attitudes and perceptions towards the approaches that we identified, we conducted a survey of stakeholders with experience and expertise in microbicide and HIV prevention clinical trials. From May to July 2015 an electronic survey was distributed via email to 894 stakeholders; a total of 206 eligible individuals responded to at least one question and were included in the data analysis. Survey respondents were presented with various objective measures and asked about their perceived acceptability to trial participants, feasibility of implementation by study staff, usefulness for measuring adherence and ethical concerns. Methods that require no additional input from the participant and require no modifications to the existing ring product (i.e., measurement of residual drug or excipient, or a vaginal analyte that enters the ring) were viewed as being more acceptable to trial participants and more feasible to implement in the field. Respondents saw value in using objective measures to provide real-time feedback on adherence. However, approaches that involve unannounced home visits for sample collection or spot checks of ring use, which could provide significant value to adherence feedback efforts, were met with skepticism. Additional research on the acceptability of these methods to potential trial participants and trial staff is recommended.

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.

A review of the physical and chemical properties of human semen and the formulation of a semen simulant.

A fluid medium was developed to simulate the salient physical and chemical properties of human semen. The composition of the medium was based upon an extensive review of the literature on constituents of human semen. In choosing the ingredients for this medium, the goal was to emphasize properties that influence interactions of human semen with topical contraceptive, prophylactic, or therapeutic products. Among these properties, pH and buffering capacity, osmolarity, ionic strength, and rheological properties play dominant roles in the physico-chemical processes that govern drug release kinetics and delivery vehicle distribution.

Towards the development of a longer-acting injectable contraceptive: past research and current trends.

OBJECTIVES: A longer-acting injectable contraceptive that lasts for 6 months would be a valuable addition to the contraceptive method mix and ideal for women who are interested in spacing births and/or uncertain about their future reproductive plans. Here we review past applications of drug delivery technologies to injectable contraceptives as well as recent advancements in sustained drug delivery technologies that hold promise for the development of a new longer-acting injectable contraceptive product. STUDY DESIGN: A global landscape analysis was conducted, promising sustained drug delivery technologies, and research opportunities and partnerships were established with experts in the fields of contraception and drug delivery to identify new approaches in developing a longer-acting injectable contraceptive product. RESULTS: The landscape analysis confirmed that a number of existing polymer systems, such as poly-lactic-co-glycolic acid and poly(epsilon-caprolactone), remain promising candidates for application to a longer-acting injectable product. Novel polymers and materials also hold promise for achieving longer release profiles and/or having other advantages over existing polymer systems, but products using these materials could potentially have longer roads to regulatory approval. Additionally, recent advancements in the manufacturing process of microspheres may benefit the development of a longer-acting injectable contraceptive. CONCLUSION: The design of any new injectable product must take into account the limitations of current injectable contraceptives and address concerns that women may have for a longer-acting product. FHI 360 is supporting several research collaborations for proof of concept of various drug delivery approaches for achieving longer-acting product that fits an established target product profile.

In vivo release of levonorgestrel from Sino-implant (II) ­ an innovative comparison of explant data.

OBJECTIVES: Measuring the amount of progestin remaining in contraceptive implants used for different lengths of time provides useful information on in vivo release kinetics including change over time. We compared estimated in vivo levonorgestrel (LNG) release rates derived from Sino-implant (II) explants with similar data from removed Jadelle. STUDY DESIGN: We measured LNG remaining in 44 sets of Sino-implant (II) used for up to 7 years and removed in four Chinese clinics. Results were compared with published data for Jadelle explants used for up to 36 months. We estimated and compared monthly and daily LNG release rates for the two products using prediction models for drug release. We also estimated the dissolution profile similarity factor, f2, for LNG release. RESULTS: Both Sino-implant (II) and Jadelle release approximately 30% of total LNG load after 3 years. Results of fitting the data to a biologically plausible modified Higuchi prediction model indicate comparable release through 3 years. An estimated similarity factor of 80.6 (90% confidence interval: 70.8-85.7) indicates similarity in the dissolution profiles of the two implants. CONCLUSIONS: LNG release in vivo measured through explant analysis suggest that Sino-implant (II) and Jadelle may perform similarly through 3 years of use and could remain highly effective beyond this time point. These results align with published data for Jadelle and Sino-implant (II) showing high effectiveness for 5 years. Ongoing clinical studies comparing the products over 5 years present an opportunity to verify this supportive measure of clinical effectiveness. IMPLICATIONS: This innovative approach provides evidence that Sino-implant (II) may perform clinically similarly to Jadelle over 3 years and remain a highly effective contraceptive beyond this time point. Data from explant analyses show promise for investigating the equivalence of elusion profiles of contraceptive implants.

Effect of temperature and pH on contraceptive gel viscosity.

The rheological properties of four commercially available spermicidal gels (two polyacrylic acid derivatives and two carboxymethylcellulose based) and their dilutions with a vaginal fluid simulant (pH 4.2) and a semen simulant (pH 7.7) were measured at 25 degrees C and 37 degrees C over a biologically relevant range of shear rates. All four gels were shear thinning with temperature-dependent rheological properties. The two types of gels responded differently to dilution. The rheological properties of the polyacrylic acid derivative gels were strongly dependent on the type of diluent used. Their viscosities after dilution with the semen simulant were 100 times greater than after comparable dilutions with the vaginal fluid simulant, this effect being due primarily to the higher pH. The cellulose gels did not exhibit such an effect. These results suggest that the polyacrylic acid and cellulose gels interact differently with the vaginal environment in vivo. Such differences could lead to differences in the extent and durability of epithelial coating.

An interdisciplinary framework for measuring and supporting adherence in HIV prevention trials of ARV-based vaginal rings.

INTRODUCTION: Product adherence and its measurement have emerged as a critical challenge in the evaluation of new HIV prevention technologies. Long-acting ARV-based vaginal rings may simplify use instructions and require less user behaviour, thereby facilitating adherence. One ARV-based ring is in efficacy trials and others, including multipurpose rings, are in the pipeline. Participant motivations, counselling support and measurement challenges during ring trials must still be addressed. In previous HIV prevention trials, this has been done largely using descriptive and post-hoc methods that are highly variable and minimally evaluated. We outline an interdisciplinary framework for systematically investigating promising strategies to support product uptake and adherence, and to measure adherence in the context of randomized, blinded clinical trials. DISCUSSION: The interdisciplinary framework highlights the dual use of adherence measurement (i.e. to provide feedback during trial implementation and to inform interpretation of trial findings) and underscores the complex pathways that connect measurement, adherence support and enacted adherence behaviour. Three inter-related approaches are highlighted: 1) adherence support - sequential efforts to define motivators of study product adherence and to develop, test, refine and evaluate adherence support messages; 2) self-reported psychometric measures - creation of valid and generalizable measures based in easily administered scales that capture vaginal ring use with improved predictive ability at screening, baseline and follow-up that better engage participants in reporting adherence; and 3) more objective measurement of adherence - real-time adherence monitoring and cumulative measurement to correlate adherence with overall product effectiveness through innovative designs, models and prototypes using electronic and biometric technologies to detect ring insertion and/or removal or expulsion. Coordinating research along these three pathways will result in a comprehensive approach to product adherence within clinical trials. CONCLUSIONS: Better measurement of adherence will not, by itself, ensure that future effectiveness trials will be able to address the most basic question: if the product is used per instructions, will it prevent HIV transmission? The challenges to adherence measurement must be addressed as one component of a more integrated system that has as its central focus adherence as a behaviour emerging from the social context of the user.

Designing a multipurpose technology for acceptability and adherence.

Multipurpose Prevention Technologies (MPTs) are new tools aimed at reducing or preventing multiple and overlapping sexual and reproductive health risks faced by women and couples around the globe. While MPTs could prove more acceptable and easier to adhere to than single-purpose prevention products, continuing high rates of HIV and unintended pregnancy remind us that these new products will need to be efficacious, acceptable and effectively used to achieve a public health impact. In this paper, we describe how a range of research methods can be applied during the pre-clinical phase of product development to inform decisions related to formulation and vehicle or product delivery mechanisms, and consider how choices in product-related characteristics may influence future demand for, delivery and use of future products. We draw on examples from the development of new single-purpose HIV and contraceptive products and then extend our discussion to the development of MPTs, including vaginal rings and injections. This article is based on a presentation at the "Product Development Workshop 2013: HIV and Multipurpose Prevention Technologies," held in Arlington, Virginia on February 21-22, 2013. It forms part of a special supplement to Antiviral Research.

Development and implementation of a quality assurance program for a hormonal contraceptive implant.

BACKGROUND: The importance of the distribution of safe, effective and cost-effective pharmaceutical products in resource-constrained countries is the subject of increasing attention. FHI 360 has developed a program aimed at evaluating the quality of a contraceptive implant manufactured in China, while the product is being registered in an increasing number of countries and distributed by international procurement agencies. The program consists of (1) independent product testing; (2) ongoing evaluation of the manufacturing facility through audits and inspections; and (3) post-marketing surveillance. STUDY DESIGN: This article focuses on the laboratory testing of the product. The various test methods were chosen from the following test method compendia, the United States Pharmacopeia (USP), British Pharmacopeia (BP), International Organization for Standardization (ISO), the American Society for Testing and Materials (ASTM), or lot release tests mandated by Chinese regulatory requirements. Each manufactured lot is independently tested prior to its distribution to countries supported by this program. In addition, a more detailed annual testing program includes evaluation of the active ingredient (levonorgestrel), the final product and the packaging material. RESULTS: Over the first 4 years of this 5-year project, all tested lots met the established quality criteria. CONCLUSIONS: The quality assurance program developed for this contraceptive implant has helped ensure that a safe product was being introduced into developing country family planning programs. This program provides a template for establishing quality assurance programs for other cost-effective pharmaceutical products that have not yet received stringent regulatory approval and are being distributed in resource-poor settings.