An intravaginal ring for the simultaneous delivery of multiple drugs

Chitosan and Kappa-Carrageenan Vaginal Acyclovir Formulations for Prevention of Genital Herpes. In Vitro and Ex Vivo Evaluation

Vaginal formulations for the prevention of sexually transmitted infections are currently gaining importance in drug development. Polysaccharides, such as chitosan and carrageenan, which have good binding capacity with mucosal tissues, are now included in vaginal delivery systems. Marine polymer-based vaginal mucoadhesive solid formulations have been developed for the controlled release of acyclovir, which may prevent the sexual transmission of the herpes simplex virus. Drug release studies were carried out in two media: simulated vaginal fluid and simulated vaginal fluid/simulated seminal fluid mixture. The bioadhesive capacity and permanence time of the bioadhesion, the prepared compacts, and compacted granules were determined ex vivo using bovine vaginal mucosa as substrate. Swelling processes were quantified to confirm the release data. Biocompatibility was evaluated through in vitro cellular toxicity assays, and the results showed that acyclovir and the rest of the materials had no cytotoxicity at the maximum concentration tested. The mixture of hydroxyl-propyl-methyl-cellulose with chitosan- or kappa-carrageenan-originated mucoadhesive systems that presented a complete and sustained release of acyclovir for a period of 8–9 days in both media. Swelling data revealed the formation of optimal mixed chitosan/hydroxyl-propyl-methyl-cellulose gels which could be appropriated for the prevention of sexual transmission of HSV.

An intravaginal ring for the sustained delivery of tenofovir disoproxil fumarate

Recent clinical trials have demonstrated that pre-exposure prophylaxis (PrEP) may prevent HIV infection in a significant number of HIV-1 negative individuals in venerable populations; however, trial efficacy has been highly variable, with notable successes and failures. Poor adherence to PrEP regimens has been implicated as a primary factor in determining efficacy of these trials. With the exception of CAPRISA 004 where use of a pericoital tenofovir gel led to a 39% reduction in HIV infection, all successful PrEP regimens to date have used the fumarate salt of the tenofovir disoproxil ester prodrug of tenofovir (TDF) alone or in combination with emtricitabine (FTC). A sustained-release, intravaginal ring (IVR) formulation of TDF holds promise for improving adherence and, thus, increasing the effectiveness of PrEP. Here, a novel IVR delivering TDF with sustained zero-order release characteristics that may be controlled over nearly two orders of magnitude is described. Pod-IVRs containing 1-10 pods delivering TDF at 0.01-10 mg d(-1) were fabricated and their release characteristics evaluated in vitro. The pod-IVRs stabilized TDF against hydrolytic degradation both in storage and during in vitro release experiments. Successful translation of the TDF pod-IVR from laboratory evaluation to large-scale clinical trials requires the ability to manufacture the devices at low cost and in high quantity. Methods for manufacturing and scale-up were developed and applied to pilot-scale production of TDF pod-IVRs that maintained the IVR's release characteristics while significantly decreasing the variability in release rate observed between pod-IVRs. This pod-IVR enables for the first time the dose-ranging clinical studies that are required to optimize topical TDF PrEP in terms of efficacy and safety.

Vaginal gene therapy

In the last years, vaginal gene therapy has gained increasing attention mainly for the treatment and control of sexually transmitted infections. DNA delivery has been also suggested to improve reproductive outcomes for women with deficiencies in the female reproductive tract. Although no product has reached clinical phase, preclinical investigations reveal the potential of the vaginal tract as an effective administration route for gene delivery. This review focuses on the main advantages and challenges of vaginal gene therapy, and on the most used nucleic acid delivery systems, including viral and non-viral vectors. Additionally, the advances in the application of vaginal gene therapy for the treatment and/or prevention of infectious diseases such as the human immunodeficiency virus (HIV), the human papillomavirus (HPV) or the herpes simplex virus (HSV) are presented.

Pharmacokinetics of long-acting tenofovir alafenamide (GS-7340) subdermal implant for HIV prophylaxis

Oral or topical daily administration of antiretroviral (ARV) drugs to HIV-1-negative individuals in vulnerable populations is a promising strategy for HIV-1 prevention. Adherence to the dosing regimen has emerged as a critical factor determining efficacy outcomes of clinical trials. Because adherence to therapy is inversely related to the dosing period, sustained release or long-acting ARV formulations hold significant promise for increasing the effectiveness of HIV-1 preexposure prophylaxis (PrEP) by reducing dosing frequency. A novel, subdermal implant delivering the potent prodrug tenofovir alafenamide (TAF) with controlled, sustained, zero-order (linear) release characteristics is described. A candidate device delivering TAF at 0.92 mg day(-1) in vitro was evaluated in beagle dogs over 40 days for pharmacokinetics and preliminary safety. No adverse events related to treatment with the test article were noted during the course of the study, and no significant, unusual abnormalities were observed. The implant maintained a low systemic exposure to TAF (median, 0.85 ng ml(-1); interquartile range [IQR], 0.60 to 1.50 ng ml(-1)) and tenofovir (TFV; median, 15.0 ng ml(-1); IQR, 8.8 to 23.3 ng ml(-1)), the product of in vivo TAF hydrolysis. High concentrations (median, 512 fmol/10(6) cells over the first 35 days) of the pharmacologically active metabolite, TFV diphosphate, were observed in peripheral blood mononuclear cells at levels over 30 times higher than those associated with HIV-1 PrEP efficacy in humans. Our report on the first sustained-release nucleoside reverse transcriptase inhibitor (NRTI) for systemic delivery demonstrates a successful proof of principle and holds significant promise as a candidate for HIV-1 prophylaxis in vulnerable populations.

A novel intravaginal ring to prevent HIV-1, HSV-2, HPV, and unintended pregnancy

Women urgently need a self-initiated, multipurpose prevention technology (MPT) that simultaneously reduces their risk of acquiring HIV-1, HSV-2, and HPV (latter two associated with increased risk of HIV-1 acquisition) and prevents unintended pregnancy. Here, we describe a novel core-matrix intravaginal ring (IVR), the MZCL IVR, which effectively delivered the MZC combination microbicide and a contraceptive. The MZCL IVR contains four active pharmaceutical ingredients (APIs): MIV-150 (targets HIV-1), zinc acetate (ZA; targets HIV-1 and HSV-2), carrageenan (CG; targets HPV and HSV-2), and levonorgestrel (LNG; targets unintended pregnancy). The elastomeric IVR body (matrix) was produced by hot melt extrusion of the non-water swellable elastomer, ethylene vinyl acetate (EVA-28), containing the hydrophobic small molecules, MIV-150 and LNG. The solid hydrophilic core, embedded within the IVR by compression, contained the small molecule ZA and the macromolecule CG. Hydrated ZA/CG from the core was released by diffusion via a pore on the IVR while the MIV-150/LNG diffused from the matrix continuously for 94 days (d) in vitro and up to 28 d (study period) in macaques. The APIs released in vitro and in vivo were active against HIV-1ADA-M, HSV-2, and HPV16 PsV in cell-based assays. Serum LNG was at levels associated with local contraceptive effects. The results demonstrate proof-of-concept of a novel core-matrix IVR for sustained and simultaneous delivery of diverse molecules for the prevention of HIV, HSV-2 and HPV acquisition, as well as unintended pregnancy.

An intravaginal ring for the sustained delivery of antibodies

Human monoclonal antibodies (mAbs) based on IgG and IgA have shown promise as topical microbicide candidates to protect women from HIV infection. Application of mAbs has been limited, however, by the inability of vaginal gels and conventional intravaginal ring (IVR) designs, the predominant vaginal product formulations, to effectively deliver biomolecules in a coitally independent fashion with retention of bioactivity. We have developed a novel pod-IVR platform that delivers ovine IgG (ov-IgG) as a model for IgG and IgA human mAbs. In vitro release of ov-IgG from the pod-IVRs was sustained for 14 days. Facile control of release rate was achieved by changing the size of delivery channels in the ring structure, and the feasibility of ov-IgG delivery in the range 0.5-30 mg day(-1) from a 10-pod IVR was demonstrated. The activity of ov-IgG in pod-IVR formulations was maintained as confirmed by ELISA binding assay. Pod-IVRs delivering ov-IgG show promise for the effective sustained topical delivery of antibody-based microbicides. This significantly broadens the range of microbicides that can be delivered in a sustained fashion from IVRs and enables a new arsenal of topical biologic microbicide candidates beyond small molecule antiretrovirals.

Prophylactic treatment with a novel bioadhesive gel formulation containing aciclovir and tenofovir protects from HSV-2 infection

OBJECTIVES

Over-the-counter access to an inexpensive, effective topical microbicide could reduce the transmission of HIV and would increase women's control over their health and eliminate the need to obtain their partners' consent for prophylaxis. Chronic infection with herpes simplex virus 2 (HSV-2), also known as human herpes virus 2, has been shown to facilitate HIV infection and speed the progression to immunodeficiency disease. Our objective is to develop a drug formulation that protects against both HSV-2 and HIV infection and adheres to the vaginal surface with extended residence time.

METHODS

We developed a formulation using two approved antiviral active pharmaceutical ingredients, aciclovir and tenofovir, in a novel bioadhesive vaginal delivery platform (designated SR-2P) composed of two polymers, poloxamer 407 NF (Pluronic(®) F-127) and polycarbophil USP (Noveon(®) AA-1). The efficacy of the formulation to protect from HSV-2 infection was tested in vitro and in vivo. In addition to its efficacy, it is essential for a successful microbicide to be non-irritating to the vaginal mucosa. We therefore tested our SR-2P platform gel in the FDA gold-standard microbicide safety model in rabbits and also in a rat vaginal irritation model.

RESULTS

Our studies indicated that SR-2P containing 1% aciclovir and 5% tenofovir protects (i) Vero cells from HSV-2 infection in vitro and (ii) mice from HSV-2 infection in vivo. Our results further demonstrated that SR-2P was not irritating in either vaginal irritation model.

CONCLUSIONS

We conclude that SR-2P containing aciclovir and tenofovir may be a suitable candidate microbicide to protect humans from vaginal HSV-2 infection.

Pharmacokinetics and preliminary safety study of pod-intravaginal rings delivering antiretroviral combinations for HIV prophylaxis in a macaque model

Preexposure prophylaxis using oral regimens involving the HIV nucleoside reverse transcriptase inhibitors tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) demonstrated efficacy in three clinical trials. Adherence was determined to be a key parameter for success. Incorporation of the TDF-FTC combination into intravaginal rings (IVRs) for sustained mucosal delivery could increase product adherence and efficacy compared with those of oral and vaginal gel formulations. A novel pod-IVR technology capable of delivering multiple drugs is described; this constitutes the first report of an IVR delivering TDF and FTC, as well as a triple-combination IVR delivering TDF, FTC, and the entry inhibitor maraviroc (MVC). The pharmacokinetics and preliminary local safety of the two combination pod-IVRs were evaluated in the pig-tailed macaque model. The devices exhibited sustained release at controlled rates over the 28-day study period. Median steady-state drug levels in vaginal tissues in the TDF-FTC group were 30 μg g(-1) (tenofovir [TFV], in vivo hydrolysis product of TDF) and 500 μg g(-1) (FTC) and in the TDF-FTC-MVC group were 10 μg g(-1) (TFV), 150 μg g(-1) (FTC), and 20 μg g(-1) (MVC). No adverse events were observed, and there were no toxicological findings. Mild-to-moderate increases in inflammatory infiltrates were observed in the vaginal tissues of some animals in both the presence and the absence of the IVRs. The IVRs did not disturb the vaginal microbiota, and levels of proinflammatory cytokines remained stable throughout the study. Pod-IVR candidates based on the TDF-FTC combination have potential for the prevention of vaginal HIV acquisition and merit clinical investigation.

"Set it and forget it": women's perceptions and opinions of long-acting topical vaginal gels

Women's initial understandings and anticipated acceptability of long-acting vaginal gels as potential anti-HIV microbicides was investigated by exploring the perceptibility variables associated with prototype formulations. Four focus groups with 29 women, aged 18-45, were conducted to consider gel prototypes with varied physicochemical and rheological properties. Participants responded favorably to the concept of long-acting vaginal gels as microbicides. Distinctions in understandings and stated needs regarding product dosing, characteristics, and effectiveness offer valuable insights into product design. Long-acting vaginal gels capable of protecting against HIV/STIs will be a viable option among potential users, with dosing frequency being an important factor in willingness to use.

Cultivated vaginal microbiomes alter HIV-1 infection and antiretroviral efficacy in colonized epithelial multilayer cultures

There is a pressing need for modeling of the symbiotic and at times dysbiotic relationship established between bacterial microbiomes and human mucosal surfaces. In particular clinical studies have indicated that the complex vaginal microbiome (VMB) contributes to the protection against sexually-transmitted pathogens including the life-threatening human immunodeficiency virus (HIV-1). The human microbiome project has substantially increased our understanding of the complex bacterial communities in the vagina however, as is the case for most microbiomes, very few of the community member species have been successfully cultivated in the laboratory limiting the types of studies that can be completed. A genetically controlled ex vivo model system is critically needed to study the complex interactions and associated molecular dialog. We present the first vaginal mucosal culture model that supports colonization by both healthy and dysbiotic VMB from vaginal swabs collected from routine gynecological patients. The immortalized vaginal epithelial cells used in the model and VMB cryopreservation methods provide the opportunity to reproducibly create replicates for lab-based evaluations of this important mucosal/bacterial community interface. The culture system also contains HIV-1 susceptible cells allowing us to study the impact of representative microbiomes on replication. Our results show that our culture system supports stable and reproducible colonization by VMB representing distinct community state types and that the selected representatives have significantly different effects on the replication of HIV-1. Further, we show the utility of the system to predict unwanted alterations in efficacy or bacterial community profiles following topical application of a front line antiretroviral.

Sustained delivery of commensal bacteria from pod-intravaginal rings

Topical administration of live commensal bacteria to the vaginal tract holds significant potential as a cost-effective strategy for the treatment of sexually transmitted infections and the delivery of mucosal vaccines. Probiotic-releasing intravaginal rings (IVRs) embody significant theoretical advantages over traditional daily-dosage forms, such as sustained and controlled delivery leading to improved adherence to therapy compared to that of frequent dosing. The conventional IVR designs, however, are not amenable to the delivery of live bacteria. We have developed a novel pod-IVR technology where polymer-coated tablets ("pods") of Lactobacillus gasseri strain ATCC 33323, a commensal microorganism of human origin, are embedded in silicone IVRs. The release rate of bacterial cells is controlled by the diameter of a delivery channel that exposes a portion of the pod to external fluids. In vitro studies demonstrated that the prototype devices released between 1.1×10(7) and 14×10(7) cells per day for up to 21 days in a controlled sustained fashion with stable burst-free release kinetics. The daily release rates were correlated with the cross-sectional area of the delivery channel. Bacteria in the IVR pods remained viable throughout the in vitro studies and formed biofilms on the surfaces of the devices. This proof-of-principle study represents the first demonstration of a prolonged, sustained release of bacteria from an intravaginal device and warrants further investigation of this device as a nonchemotherapeutic agent for the restoration and maintenance of normal urogenital flora.

Comparison of the vaginal microbial communities in women with recurrent genital HSV receiving acyclovir intravaginal rings

Vaginally administered antiviral agents may reduce the risk of HIV and HSV acquisition. Delivery of these drugs using intravaginal rings (IVRs) holds the potential benefits of improving adherence and decreasing systemic exposure, while maintaining steady-state drug levels in the vaginal tract. Elucidating how IVRs interact with the vaginal microbiome constitutes a critical step in evaluating the safety of these devices, as shifts the vaginal microbiome have been linked with several disease states. To date, clinical IVR trials have relied on culture-dependent methods that omit the high diversity of unculturable microbial population. Longitudinal, culture-independent characterization of the microbiota in vaginal samples from 6 women with recurrent genital HSV who used an acyclovir IVR was carried out and compared to the communities developing in biofilms on the IVR surface. The analysis utilized Illumina MiSeq sequence datasets generated from bar-coded amplicons of 16S rRNA gene fragments. Specific taxa in the vaginal communities of the study participants were found to be associated with the duration of recurrent genital HSV status and the number of HSV outbreaks. Taxonomic comparison of the vaginal and IVR biofilm communities did not reveal any significant differences, suggesting that the IVRs were not systematically enriched with members of the vaginal microbiome. Device usage did not alter the participants' vaginal microbial communities, within the confines of the current study design. Rigorous, molecular analysis of the effects of intravaginal devices on the corresponding microbial communities shows promise for integration with traditional approaches in the clinical evaluation of candidate products.

Evaluation of microporous polycaprolactone matrices for controlled delivery of antiviral microbicides to the female genital tract

Acyclovir (ACV) as a model antiviral microbicide, was incorporated in controlled-release polycaprolactone (PCL) matrices designed for application as intra-vaginal ring inserts (IVRs). Microporous materials incorporating acyclovir up to a level of ~10 % w/w were produced by rapidly cooling suspensions of drug powder in PCL solution followed by solvent extraction from the hardened matrices. Around 21, 50 and 78 % of the drug content was gradually released from matrices over 30 days in simulated vaginal fluid at 37 °C, corresponding to drug loadings of 5.9, 7.0 and 9.6 % w/w. The release behaviour of matrices having the lowest drug loading followed a zero order model, whereas, the release kinetics of 7.0 and 9.6 % ACV-loaded PCL matrices could be described effectively by the Higuchi model, suggesting that Fickian diffusion is controlling drug release. Corresponding values of the diffusion co-efficient for ACV in the PCL matrices of 3.16 × 10(-9) and 1.07 × 10(-8) cm(2)/s were calculated. Plaque reduction assays provided an IC50 value of 1.09 μg/mL for acyclovir against HSV-2 and confirmed the antiviral activity of released acyclovir against HSV-2 replication in primate kidney cells (Vero) at levels ~70 % that of non-formulated acyclovir at day 30. Estimated minimum in vivo acyclovir concentrations produced by a PCL IVR (19 μg/mL) exceeded by a factor of 20 the IC50 value against HSV-2 and the reported ACV vaginal concentrations in women (0.5-1.0 μg/mL) following oral administration. These findings recommend further investigations of PCL matrices for vaginal delivery of antiviral agents in the treatment and prevention of sexually transmitted infections such as AIDS.

Pharmacokinetics of a multipurpose pod-intravaginal ring simultaneously delivering five drugs in an ovine model

Multipurpose technologies that simultaneously protect from sexually transmitted infections and unintended pregnancy are urgently needed. Pod-intravaginal rings (IVRs) formulated with the antiretroviral agents (ARVs) tenofovir, nevirapine, and saquinavir and the contraceptives etonogestrel and estradiol were evaluated in sheep. Steady-state concentrations were maintained for 28 days with controlled, sustained delivery. This proof-of-principle study demonstrates that pod IVRs can deliver three ARVs from different mechanistic classes and a progestin-estrogen combination over the wide range needed for putative preventative efficacy.

Vaginal rings for delivery of HIV microbicides

Following the successful development of long-acting steroid-releasing vaginal ring devices for the treatment of menopausal symptoms and contraception, there is now considerable interest in applying similar devices to the controlled release of microbicides against HIV. In this review article, the vaginal ring concept is first considered within the wider context of the early advances in controlled-release technology, before describing the various types of ring device available today. The remainder of the article highlights the key developments in HIV microbicide-releasing vaginal rings, with a particular focus on the dapivirine ring that is presently in late-stage clinical testing.

A 90-day tenofovir reservoir intravaginal ring for mucosal HIV prophylaxis

A vaginal gel containing the antiretroviral tenofovir (TFV) recently demonstrated 39% protection against HIV infection in women. We designed and evaluated a novel reservoir TFV intravaginal ring (IVR) to potentially improve product effectiveness by providing a more controlled and sustained vaginal dose to maintain cervicovaginal concentrations. Polyurethane tubing of various hydrophilicities was filled with a high-density TFV/glycerol/water semisolid paste and then end-sealed to create IVRs. In vitro, TFV release increased with polyurethane hydrophilicity, with 35 weight percent water-swelling polyurethane IVRs achieving an approximately 10-mg/day release for 90 days with mechanical stiffness similar to that of the commercially available NuvaRing. This design was evaluated in two 90-day in vivo sheep studies for TFV pharmacokinetics and safety. Overall, TFV vaginal tissue, vaginal fluid, and plasma levels were relatively time independent over the 90-day duration at approximately 10(4) ng/g, 10(6) ng/g, and 10(1) ng/ml, respectively, near or exceeding the highest observed concentrations in a TFV 1% gel control group. TFV vaginal fluid concentrations were approximately 1,000-fold greater than levels shown to provide significant protection in women using the TFV 1% gel. There were no toxicological findings following placebo and TFV IVR treatment for 28 or 90 days, although slight to moderate increases in inflammatory infiltrates in the vaginal epithelia were observed in these animals compared to naïve animals. In summary, the controlled release of TFV from this reservoir IVR provided elevated sheep vaginal concentrations for 90 days to merit its further evaluation as an HIV prophylactic.

Safety and pharmacokinetics of intravaginal rings delivering tenofovir in pig-tailed macaques

Antiretroviral-based microbicides applied topically to the vagina may play an important role in protecting women from HIV infection. Incorporation of the nucleoside reverse transcriptase inhibitor tenofovir (TFV) into intravaginal rings (IVRs) for sustained mucosal delivery may lead to increased microbicide product adherence and efficacy compared with those of conventional vaginal formulations. Formulations of a novel "pod IVR" platform spanning a range of IVR drug loadings and daily release rates of TFV were evaluated in a pig-tailed macaque model. The rings were safe and exhibited sustained release at controlled rates over 28 days. Vaginal secretion TFV levels were independent of IVR drug loading and were able to be varied over 1.5 log units by changing the ring configuration. Mean TFV levels in vaginal secretions were 72.4 ± 109 μg ml(-1) (slow releasing) and 1.84 ± 1.97 mg ml(-1) (fast releasing). The mean TFV vaginal tissue concentration from the slow-releasing IVRs was 76.4 ± 54.8 μg g(-1) and remained at steady state 7 days after IVR removal, consistent with the long intracellular half-life of TFV. Intracellular tenofovir diphosphate (TFV-DP), the active moiety in defining efficacy, was measured in vaginal lymphocytes collected in the study using the fast-releasing IVR formulation. Mean intracellular TFV-DP levels of 446 ± 150 fmol/10(6) cells fall within a range that may be protective of simian-human immunodeficiency virus strain SF162p3 (SHIV(SF162p3)) infection in nonhuman primates. These data suggest that TFV-releasing IVRs based on the pod design have potential for the prevention of transmission of human immunodeficiency virus type 1 (HIV-1) and merit further clinical investigation.