Efficacy of nonhormonal vaginal contraceptives from a hydrogel delivery system

A nine-month repeat-dose intravaginal ring (Ovaprene) irritation study in sheep

OBJECTIVES

Ovaprene is a novel, investigational, intravaginal hormone-free monthly ring contraceptive designed for use in women of reproductive age to be worn over multiple weeks (one menstrual cycle). The objective of this work was to evaluate the safety of Ovaprene during a nine-month repeat-dose sheep study.

STUDY DESIGN

In addition to traditional safety endpoints such as histopathological evaluation of the sheep female reproductive tract, vaginal fluids were collected and tested for released iron over time. Also, the amount of iron in the rings was assessed following removal, and serum iron levels were measured. There were four sheep in each group (Ovaprene group and sham group).

RESULTS

There were no macroscopic clinical findings. There was minimal to mild, mixed or mononuclear cell infiltration present in all levels of vagina (cranial, mid, and caudal) from all animals including sham controls based on post-study necropsy. The female reproductive tract from animals treated with the Ovaprene ring was comparable to the sham controls. The concentrations of serum iron in sheep treated with Ovaprene ring were similar compared to a sham treated animal. The average amount of ferrous gluconate released from Ovaprene over the 29-day period of use was 175 mg of the approximately 512 mg nominally loaded into the rings.

CONCLUSIONS

Overall, the Ovaprene devices were well-tolerated in female sheep.

IMPLICATIONS

This study should support a chronic (e.g., one year) contraceptive efficacy study in women.

Successful postcoital testing of Ovaprene: An investigational non-hormonal monthly vaginal contraceptive

OBJECTIVE

Evaluate reduction in progressively motile sperm per high power field (HPF) in midcycle cervical mucus after intercourse with Ovaprene: an investigational monthly non-hormonal vaginal contraceptive consisting of a vaginal ring and mechanical barrier, releasing spermiostatic ferrous gluconate.

STUDY DESIGN

Open-label, multicenter study enrolling heterosexually-active women with previous permanent contraception. Participants underwent a baseline postcoital test cycle with no device to confirm the presence of sperm, followed by one diaphragm postcoital test cycle, one Ovaprene safety cycle, and two Ovaprene postcoital test cycles. In each postcoital test cycle, participants underwent a midcycle cervical mucus evaluation to confirm an Insler score ≥10 and absence of sperm, and then returned two to four hours after vaginal intercourse for repeat cervical mucus evaluation. We considered <5 progressively motile sperm/HPF indicative of preliminary contraceptive effectiveness.

RESULTS

We enrolled 38 participants; 23 completed the study. All participants had ≥5 progressively motile sperm/HPF in the baseline cycle and <5 progressively motile sperm/HPF in all 49 Ovaprene cycles and all 35 diaphragm cycles, meeting the definition of a successful postcoital test. This was true regardless of examiner blinding, prior vaginal delivery or vaginal ring use, body mass index, or dislodgements noted by the participant or investigator. The mean of 27.2 (±17.9) progressively motile sperm/HPF in baseline postcoital test cycles was reduced to 0.5 (±1.1) and 0.5 (±1.3) progressively motile sperm/HPF in the first and second Ovaprene cycles, respectively. Ovaprene fit all participants and all could insert, position, and remove it.

CONCLUSION

Use of Ovaprene resulted in meeting the prespecified criterion for contraceptive effect by all participants during all postcoital test cycles.

IMPLICATIONS

The finding that use of Ovaprene, an investigational monthly non-hormonal vaginal contraceptive, resulted in postcoital testing of cervical mucus that met the pre-specified definition of success (<5 progressively motile sperm/HPF) supports further evaluation of contraceptive efficacy of the device in users at risk for pregnancy.

The Vaginal Microbiota, Bacterial Biofilms and Polymeric Drug-Releasing Vaginal Rings

The diversity and dynamics of the microbial species populating the human vagina are increasingly understood to play a pivotal role in vaginal health. However, our knowledge about the potential interactions between the vaginal microbiota and vaginally administered drug delivery systems is still rather limited. Several drug-releasing vaginal ring products are currently marketed for hormonal contraception and estrogen replacement therapy, and many others are in preclinical and clinical development for these and other clinical indications. As with all implantable polymeric devices, drug-releasing vaginal rings are subject to surface bacterial adherence and biofilm formation, mostly associated with endogenous microorganisms present in the vagina. Despite more than 50 years since the vaginal ring concept was first described, there has been only limited study and reporting around bacterial adherence and biofilm formation on rings. With increasing interest in the vaginal microbiome and vaginal ring technology, this timely review article provides an overview of: (i) the vaginal microbiota, (ii) biofilm formation in the human vagina and its potential role in vaginal dysbiosis, (iii) mechanistic aspects of biofilm formation on polymeric surfaces, (iv) polymeric materials used in the manufacture of vaginal rings, (v) surface morphology characteristics of rings, (vi) biomass accumulation and biofilm formation on vaginal rings, and (vii) regulatory considerations.

Vaginal Administration of Contraceptives

While contraceptive drugs have enabled many people to decide when they want to have a baby, more than 100 million unintended pregnancies each year in the world may indicate the contraceptive requirement of many people has not been well addressed yet. The vagina is a well-established and practical route for the delivery of various pharmacological molecules, including contraceptives. This review aims to present an overview of different contraceptive methods focusing on the vaginal route of delivery for contraceptives, including current developments, discussing the potentials and limitations of the modern methods, designs, and how well each method performs for delivering the contraceptives and preventing pregnancy.

Injectable Vaginal Hydrogels as a Multi-Drug Carrier for Contraception

Injectable intravaginal hydrogels could deliver drugs systemically without hepatic first pass effect. This paper focuses on the contraceptive function of an injectable temperature-sensitive four-arm star-shaped poly(D,L-lactic-co-glycolic acid)-b-methoxy poly(ethylene glycol) (4sPLGA-mPEG) block copolymer hydrogels as a carrier of three drugs. In vitro controlled release profiles were investigated via HPLC, and it showed that the cumulative release amounts of indomethacin (IMC), gestodene (GSD), and ethinyl estradiol (EE) from copolymer hydrogels could be regulated by adjusting the lactide/glycolide (LA/GA) mol ratio. In addition, in vitro release profiles of IMC, GSD, and EE well corresponded to Higuchi model. The acute toxicity of copolymer hydrogels loaded with different dosage contents multi-drug was evaluated in vivo. As to the high dosage group, the uterus was hydropic at day 1 and ulcerated at day 5, followed with intestinal adhesion. Regarding the middle dosage group, no festering of tissues was observed and, blood coagulum existed in the uterus at different days. For low dosage group, no significant tissue necrosis was found. Finally, the antifertility experiments confirmed that hydrogels loaded with the multi-drug had an excellent contraceptive effect. The above results indicated that injectable copolymer hydrogel as a multi-drug carrier was promising as a novel contraception method.

In situ-forming and pH-responsive hydrogel based on chitosan for vaginal delivery of therapeutic agents

One of the important routes of drug administration for localized delivery of contraceptives and cervical cancer treatment agents is vaginal canal. Due to the low pH of vagina, a pH-responsive drug delivery system was developed. This hydrogel was synthesized based on a mucoadhesive biopolymer, chitosan (CS), that promotes the interaction between the hydrogel and mucosal surface of the vagina, potentially increasing the residence time of the system. This injectable hydrogel was formed via acid-labile Schiff-base linkages between free amine groups and aldehyde functionalities on modified chitosan. A novel approach was taken to add aldehyde functionalities to chitosan using a two-step reaction. Two types of slow and fast degrading hydrogels were prepared and loaded with iron (II) gluconate dihydrate, a non-hormonal spermicide, and doxorubicin hydrochloride, an anti-cancer drug. The release profiles of these drugs at different pH environments were assessed to determine the pH-dependent release mechanism. Mechanical properties, swell-ability and degradation rate of these matrices were studied. The cross-linking density of the hydrogel as well as pH changes played an important role in the characteristic of these hydrogels. The hydrogels degraded faster in lower pH, while the hydrogel with lower cross-linking density showed longer gelation time and faster degradation rate compared to the gel with higher cross-linking density. In vitro cytotoxicity assessment of these hydrogels in 48 h indicated the non-toxic effect of these hydrogels toward mesenchymal stem cells (MSCs) in the test period.

Antimicrobial Properties of Microparticles Based on Carmellose Cross-Linked by Cu(2+) Ions

Carmellose (CMC) is frequently used due to its high biocompatibility, biodegradability, and low immunogenicity for development of site-specific or controlled release drug delivery systems. In this experimental work, CMC dispersions in two different concentrations (1% and 2%) cross-linked by copper (II) ions (0.5, 1, 1.5, or 2.0 M CuCl₂) were used to prepare microspheres with antimicrobial activity against Escherichia coli and Candida albicans, both frequently occurring pathogens which cause vaginal infections. The microparticles were prepared by an ionotropic gelation technique which offers the unique possibility to entrap divalent copper ions in a CMC structure and thus ensure their antibacterial activity. Prepared CMC microspheres exhibited sufficient sphericity. Both equivalent diameter and copper content were influenced by CMC concentration, and the molarity of copper (II) solution affected only the copper content results. Selected samples exhibited stable but pH-responsive behaviour in environments which corresponded with natural (pH 4.5) and inflamed (pH 6.0) vaginal conditions. All the tested samples exhibited proven substantial antimicrobial activity against both Gram-negative bacteria Escherichia coli and yeast Candida albicans. Unexpectedly, a crucial parameter for microsphere antimicrobial activity was not found in the copper content but in the swelling capacity of the microparticles and in the degree of CMC surface shrinking.

Drug-eluting fibers for HIV-1 inhibition and contraception

Multipurpose prevention technologies (MPTs) that simultaneously prevent sexually transmitted infections (STIs) and unintended pregnancy are a global health priority. Combining chemical and physical barriers offers the greatest potential to design effective MPTs, but integrating both functional modalities into a single device has been challenging. Here we show that drug-eluting fiber meshes designed for topical drug delivery can function as a combination chemical and physical barrier MPT. Using FDA-approved polymers, we fabricated nanofiber meshes with tunable fiber size and controlled degradation kinetics that facilitate simultaneous release of multiple agents against HIV-1, HSV-2, and sperm. We observed that drug-loaded meshes inhibited HIV-1 infection in vitro and physically obstructed sperm penetration. Furthermore, we report on a previously unknown activity of glycerol monolaurate (GML) to potently inhibit sperm motility and viability. The application of drug-eluting nanofibers for HIV-1 prevention and sperm inhibition may serve as an innovative platform technology for drug delivery to the lower female reproductive tract.

Development of vaginal rings for sustained release of nonhormonal contraceptives and anti-HIV agents

OBJECTIVES

Construction of vaginal rings to deliver nonhormonal contraceptives and 3'-azido-3'-deoxythymidine (AZT) as an anti-HIV agent and determination of their daily release and efficacy in vitro.

MATERIALS AND METHODS

Intravaginal rings of 0.5-0.7 cm rim and 5-5.5 cm in diameter were cast in the molds. The rings were composed of biosoluble acacia gum or nonbiodegradable hydrogel of 2-hydroxyethyl methacrylate (HEMA) and sodium methacrylate (SMA) [P(HEMA-co-SMA)]. The rings were impregnated with nonhormonal contraceptives such as ferrous gluconate to cause spermiostasis, l-ascorbic acid to increase the viscosity of the cervical mucus, and pharmalytes of pH 4-5 or AZT.

RESULTS

The daily release rate of nonhormonal contraceptives as well as AZT from the rings was efficacious in vitro. Cumulative effect of nonhormonal contraceptives showed complete spermiostasis within 30 s up to 10 and 28 days, respectively. Daily release of AZT from both rings was also likely to be efficacious to inhibit HIV proliferation in vitro for 10 and 28 days, respectively.

CONCLUSION

The data indicate that the rings described here can be developed for intravaginal delivery of nonhormonal contraceptives and/or anti-HIV agents.

Synthesis of cell-adhesive dextran hydrogels and macroporous scaffolds

Dextran hydrogels have been previously investigated as drug delivery vehicles and more recently as macroporous scaffolds; however, the non-cell-adhesive nature of dextran has limited its utility for tissue engineering. To overcome this limitation, macroporous scaffolds of methacrylated dextran (Dex-MA) copolymerized with aminoethyl methacrylate (AEMA) were synthesized, thereby introducing primary amine groups for covalent immobilization of extracellular-matrix-derived peptides. The amino group density for hydrogels copolymerized with 0.5 wt% AEMA was found to be 36.1+/-0.4 micromol/cm(3) by elemental analysis. To further enhance cellular interaction, poly(Dex-MA-co-AEMA) hydrogels were modified with either CRGDS or a mixture of CDPGYIGSR and CQAASIKVAV (1:1, v/v) using sulfo-(N-maleimidomethyl)cyclohexane-1-carboxylate (sulfo-SMCC). The immobilized peptide concentration was determined using amino acid analysis at: 2.6+/-0.9 micromol/cm(3) for CRGDS-derived hydrogels and 2.2+/-0.3 micromol/cm(3) plus 1.9+/-0.2 micromol/cm(3) for CDPGYIGSR plus CQAASIKVAV-derived hydrogels, respectively. Cellular interactions of primary embryonic chick dorsal root ganglia (DRGs) were compared on the hydrogels. Cell adhesion and neurite outgrowth on poly(Dex-MA) increased with copolymerization of AEMA and further improved with peptide modification and significantly for CDPGYIGSR/CQAASIKVAV-derived poly(Dex-MA-co-AEMA) hydrogels. Moreover, DRGs penetrated within the first 600 microm of the scaffolds, thereby demonstrating the potential of this scaffold for guided cell and axonal regeneration in vivo.

Vaginal delivery of contraceptives

Although a steady increase in contraceptive use has been observed both in developed and less-developed countries, the large number of unplanned pregnancies may indicate that the contraceptive needs of a significant percentage of couples have so far not been met. Several new contraceptive products have reached the market during the last 2 years. Among these is a new contraceptive vaginal ring, which has become available for prescription. This new female method has been developed to expand the contraceptive choices available to couples. This review will address the specifics of the vaginal route for delivering contraceptive steroids and describe the various systems available or under evaluation.

Delivery options for contraceptives

Although a steady increase in contraceptive use has been observed in developed and less-developed countries, the contraceptive needs of a significant proportion of couples have not yet been met, resulting in an increase in unplanned pregnancies. Several new contraceptive products have reached the market during the past few years. Among these are new implants, a medicated intrauterine device, contraceptive vaginal rings, transdermal patches and several new regimen of combined oral contraceptives. These new or improved methods have been developed to expand the contraceptive choices available to women and men as well as to respond to the unmet need for contraceptives with long-term activity. New targets are being identified both in the ovary and the testes for a more specific non-hormonal contraception. This futuristic approach still keeps in mind the need for better access to existing contraceptive methods, as well as the discovery of new contraceptives that are simple to use, safe, reversible and inexpensive. In recent years, there has been great interest in agents that provide dual protection against pregnancy and sexually transmitted infections (STI), especially human immunodeficiency virus (HIV). A contraceptive method providing dual medical benefits might increase motivation for consistent use, thus reducing contraceptive failures and unwanted pregnancies.