Efficacy and safety of a new vaginal contraceptive antimicrobial formulation containing high molecular weight poly(sodium 4-styrenesulfonate)

Effects of candidate vaginally-applied microbicide compounds on innate immune cells

Ideally, a vaginally-applied microbicide would be effective against a broad range of pathogens but would have minimal effects on the female genital tract. The aim of this study was to determine if representative candidate detergent-type and sulfated/sulfonated polymer-type microbicides altered the composition or function of innate immune cells normally found in the vaginal mucosa. The effect of microbicide on the composition of vaginal leukocytes was tested using a flow cytometric approach. Application of the detergent cholic acid, but not the sulfated polysaccharide lambda carrageenan, resulted in a significant increase in macrophages at the vaginal epithelial surface compared to control treatment (19.3% macrophages compared to 2.8%; p<0.0004). Phagocytosis of fluorochrome-labeled bacteria by macrophages was inhibited greater than 50% in the presence of 1.0mg/ml of the sulfonated polymer PRO 2000 but was not inhibited by the same concentration of lambda carrageenan. PRO 2000-pulsed macrophages regained phagocytic function after being washed free of the compound. Culture of macrophages with PRO 2000 also resulted in diminished detection of the surface proteins CD11b and CD18. After treated cells were washed free of PRO 2000, these proteins were detected at levels similar to control treated cells. In conclusion, application of a detergent-type microbicide, but not a sulfated polymer, resulted in the infiltration of inflammatory cells at the vaginal epithelial surface. Phagocytic function of macrophages was lost in the presence of 1mg/ml PRO 2000 which may have reflected masking of important cell surface proteins by the microbicide; however, there was no evidence of permanent loss of function upon removal of the compound.

Discovery of substituted isoxazolecarbaldehydes as potent spermicides, acrosin inhibitors and mild anti-fungal agents

BACKGROUND

The continued endeavour to design novel, non-detergent molecules that can be useful as topical, prophylactic contraceptives has led to the discovery of substituted isoxazolecarbaldehydes as a new class of compounds exhibiting both spermicidal and acrosin inhibitory activities simultaneously.

METHODS

Normal human semen samples were used to detect the spermicidal and acrosin inhibitory activities of the new compounds. Lactobacillus, HeLa and Candida cultures were used to determine the safety of compounds towards normal vaginal flora, their cytotoxicity and anti-fungal activity. Supravital staining and the hypo-osmotic swelling test (HOST) were used to detect the effect on sperm membrane integrity. Nonoxynol-9 (N-9) was used as a reference standard.

RESULTS

The 5- and 3-substituted isoxazolecarbaldehydes showed significant spermicidal [minimum effective concentration (MEC)=0.005-2.5%] and acrosin inhibitory (IC50=3.9-58 x 10(-4) mol/l) activities in several molecules along with weak fungicidal activity against Candida albicans. Lineweaver-Burk and Dixon plot analysis of a representative structure showed non-competitive inhibition of human acrosin enzyme, and the most potent acrosin inhibitors also considerably diminished the induction of the acrosome reaction by Ca2+ ionophore. Some compounds were found to be significantly safer than N-9 towards Lactobacillus acidophilus in vitro at their respective spermicidal MECs. In the cytotoxicity assay, the IC50 of these compounds towards the HeLa cell line was of the same order as N-9 (0.9-0.1 mmol/l); however, in contrast, the compounds exhibited only a moderate effect on sperm membrane integrity.

CONCLUSIONS

This study indicates that 5- and 3-substituted isoxazolecarbaldehydes are 'first generation' multifunctional, spermicidal molecules that hold promise for development as topical contraceptives with useful associated activities that can add considerably to their effectiveness, safety and prophylaxis.

Development and characterization of bioadhesive vaginal films of sodium polystyrene sulfonate (PSS), a novel contraceptive antimicrobial agent

PURPOSE

Polystyrene sulfonate (PSS) is a novel noncytotoxic antimicrobial contraceptive agent. A gel formulation of PSS was found safe for vaginal administration in phase I clinical trials. The purpose of the current study was to develop and evaluate novel bioadhesive vaginal film formulations of PSS.

METHODS

PSS films were prepared by solvent evaporation and optimized for various physical, mechanical, and aesthetic properties. Further, films were evaluated for various biological activities and safety.

RESULTS

Vaginal films containing 300 mg PSS per unit have been developed, using generally regarded as safe (GRAS) listed excipients. The films are colorless, transparent, thin, soft, and tough, dissolve rapidly in physiologic fluid to form a smooth, viscous and bioadhesive solution that could be retained in the vagina for prolonged intervals. Sperm function inhibition (hyaluronidase and cervical mucus penetration) and antimicrobial activities against human immunodeficiency virus (HIV) and herpes simplex virus (HSV) by PSS films were found comparable to PSS. Also, films did not inhibit normal vaginal microflora (Lactobacillus) and were noncytotoxic as indicated by negligible sperm immobilization and cytotoxicity to host cell assays.

CONCLUSIONS

Rapidly dissolving bioadhesive vaginal film formulation of PSS with desired physical, mechanical, aesthetic, and biological properties is a suitable candidate vaginal microbicide for prevention of sexually transmitted disease (STDs) and is ready for toxicological and clinical evaluation.

Single and multiple exposure tolerance study of polystyrene sulfonate gel: a phase I safety and colposcopy study

OBJECTIVES

To evaluate symptoms and signs of genital irritation, vaginal leakage and acceptability of polystyrene sulfonate (PSS), which is being studied as a vaginal contraceptive and microbicide.

METHODS

Forty-nine women applied 2.5 mL of either 5% PSS, 10% PSS, PSS vehicle, or Conceptrol (a marketed spermicidal product containing 4% nonoxynol-9) for 6 consecutive days.

RESULTS

All women completed the study except one in the Conceptrol group who experienced vaginal symptoms after her first use and was discontinued. After both the first use and after all uses, irritation was seen among more women in the Conceptrol group than in the PSS groups, reaching statistical significance with regard to any evidence of irritation, signs of irritation and product-related irritation. There were no adverse events that were serious, unexpected and related to product use in any group. The 5% concentration of PSS may be preferable in terms of leakage and acceptability.

CONCLUSION

The results suggest that PSS has a safety profile comparable to that of the marketed nonoxynol-9 product, Conceptrol, and appears to be associated with less genital irritation.

Evaluation of antimicrobial peptide nisin as a safe vaginal contraceptive agent in rabbits: in vitro and in vivo studies

In the midst of the global epidemics of both unwanted pregnancies and sexually transmitted infections (STIs), options that provide protection are ideal. In the present study, nisin, a known antimicrobial peptide, was evaluated for safety and contraceptive potential in vitro and in vivo in the rabbit. A concentration of 400 microg nisin per ml was found to be spermicidal in vitro, and the effect was dose and time dependent. In vivo studies indicated that intravaginal application of 1 mg nisin blocked conception in rabbits. Repeated application of nisin (50 mg/animal per day) in rabbits for 14 consecutive days did not cause local inflammation or damage to the vaginal epithelium. In addition, the rate of diffusion of nisin into the blood via the vaginal mucosal epithelium, and its clearance from the circulation was found to be rapid. No treatment-related changes were observed in the reproductive performance of rabbits after cessation of treatment. Furthermore, no changes were observed in the gestation period, subsequent growth and survival of neonates in these animals. When male rats were given nisin orally for 13 consecutive weeks, no effect was observed on reproductive performance. The number of pups born, survival and growth of pups were unaltered. The affinity studies of nisin revealed that spermatozoa are more susceptible to nisin than red blood cells and vaginal epithelial cells. We suggest that nisin with spermicidal and antimicrobial properties could serve as a safe vaginal contraceptive for future therapeutic interventions in STIs.

Contraceptive efficacy of antimicrobial peptide Nisin: in vitro and in vivo studies

Sexually transmitted infections and unplanned pregnancies present a great risk to the reproductive health of women. Therefore, female-controlled vaginal products directed toward disease prevention and contraception are needed urgently. In the present study, efforts were made to evaluate the contraceptive potential of Nisin. The effect of Nisin on sperm motility was assessed under in vitro and in vivo conditions. The results showed that sperm motility was completely inhibited with Nisin. The minimum effective concentration of Nisin required to immobilize sperm (80-100 x 10(6)) in vitro within 20 s was found to be 50 microg in rat, 200 microg in rabbit and 300-400 microg in monkey and human. The effect on sperm motility was observed to be dose- and time-dependent. Intravaginal administration of Nisin (200 microg) before mating during proestrus-estrous transition phase caused complete arrest of sperm motility and blockage of conception. Subacute toxicity studies in rats indicated that, repetitive intravaginal application of Nisin at the dose of 200 microg for 14 consecutive days induced no abnormalities either in the length of estrous cycle or in the morphology of vaginal epithelial cells. No histopathological abnormalities in vaginal tissue or any change in blood and serum biochemical profiles were observed. Furthermore, no adverse effects were observed on subsequent reproductive performance, neonate survival and development of pups. It is suggested that Nisin, with its antibacterial and spermicidal activities, could be developed as a potent vaginal contraceptive for future use in humans.

Preclinical evaluation of magainin-A as a contraceptive antimicrobial agent

OBJECTIVE

To evaluate the safety and contraceptive efficacy of magainin-A in monkeys.

DESIGN

Controlled laboratory study.

SETTING

Department of Immunology, National Institute for Research in Reproductive Health, Parel, Mumbai, India.

ANIMAL(S)

Male and female bonnet monkeys (Macaca radiata).

INTERVENTION(S)

Animals were treated intravaginally with 1 mg of magainin-A before attempted conception, as well as daily for 14 days to assess local and systemic toxicity.

MAIN OUTCOME MEASURE(S)

Suitability of magainin-A for the control of pregnancy and sexually transmitted infections.

RESULT(S)

Complete sperm immobilization was observed within 20 seconds after the exposure to magainin-A (800-1,000 microg) in vitro. Intravaginal administration of 1 mg of magainin-A blocked conception in monkeys. When magainin-A was administered intravaginally for 14 consecutive days, no treatment-related abnormalities were observed in menstrual cycle length, vaginal epithelial cell morphology, and hematologic/serum biochemical profiles. The peptide inhibited the growth of sexually transmitted infection-causing pathogens but not HIV-1 and HIV-2.

CONCLUSION(S)

Magainin-A can be used as an effective and safe intravaginal contraceptive compound with additional protection against sexually transmitted infection-causing pathogens.

Poly(sodium 4-styrene sulfonate): evaluation of a topical microbicide gel against herpes simplex virus type 2 and Chlamydia trachomatis infections in mice

OBJECTIVE

To investigate the in vivo activity of poly(sodium 4-styrene sulfonate) (T-PSS) gel formulations as topical microbicides.

METHODS

The ability of the gel formulations to reduce the incidence of infection when applied prior to pathogen challenge was examined in mouse models of vaginal herpes simplex type 2 (HSV-2) and Chlamydia trachomatis infection, and rectal HSV-2 infection.

RESULTS

In the vaginal HSV-2 challenge studies, 10% T-PSS gel provided significant protection against infection, even when administered 60 min prior to virus challenge (P < 0.0001). Both 5% and 10% T-PSS gel formulations significantly reduced the incidence of upper genital tract C. trachomatis infection in animals treated up to 5 min before challenge (P < 0.001). However, no protection against C. trachomatis infection was seen in animals treated 30 min before challenge. In mice challenged rectally with HSV-2, both the 5% and 10% T-PSS gels significantly reduced infection at 20 s (P < 0.01 for both). However, only the 10% gel provided significant protection when administered 5 min before challenge (P < 0.01).

CONCLUSIONS

T-PSS gel formulations have promising in vivo activity as topical microbicides.

Development pharmaceutics of microbicide formulations. Part I: preformulation considerations and challenges

Microbicides, the compounds and formulations that can prevent transmission of sexually transmitted diseases (STDs)/HIV are being pursued actively as a promising AIDS intervention. The drug development chain for a topical microbicide differs significantly from that of any systemic or topical compound/formulation regarding to time line, cost, activities, and milestones. This is in part because of the lack of standard in vitro models to assess efficacy, and complex ethical issues in clinical trials of microbicides. Several factors, including changes in the physiology of the cervix and vagina with age and menstrual cycle, intercourse, as well as leakage of the formulation from the vagina may affect their design, development, and performance. Selection and development of optimal microbicide delivery systems (gel/cream, pessary, film, tablet, foam, etc.), their inactive ingredients, manufacturing details, and packaging system are dependent on the properties of active drug, or their preformulation parameters (PP). The PP of the active drug substance needs to be evaluated in initial stages of drug discovery and development so that the most suitable delivery system can be selected. Some PP of microbicide agents include physical state, organoleptic properties (color, odor, appearance, taste, etc.), molecular weight, aqueous solubility, hygroscopicity, acidity/alkalinity, permeability and absorption characteristics, stability in solid/solution state, and inherent bioadhesiveness. Thus, a well-coordinated, planned, and implemented preformulation program can help in not only accelerating microbicide formulation development, but also to minimize unforeseen failures in subsequent stages of the development. The objective of this review is to highlight the significance of PP, suggesting a systematic preformulation program.

Use of mandelic acid condensation polymer (SAMMA), a new antimicrobial contraceptive agent, for vaginal prophylaxis

OBJECTIVE

To assess the contraceptive properties, antimicrobial activity, and safety of mandelic acid condensation polymer (SAMMA).

DESIGN

Experimental study of SAMMA's in vitro and in vivo properties.

SETTING

Academic research laboratories.

PATIENT(S)

Healthy volunteers for semen donation in an academic research environment.

INTERVENTION(S)

Inhibition of sperm function indicators, conception, sexually transmitted infection-causing pathogens (including HIV), and lactobacilli was evaluated. Safety indicators were studied.

MAIN OUTCOME MEASURE(S)

Quantitation of SAMMA's effect on microbial infectivity or multiplication and on sperm function in vitro; evaluation of contraceptive efficacy in vivo; assessment of safety in vitro and in vivo.

RESULT(S)

Mandelic acid condensation polymer is not cytotoxic toward lactobacilli, microbial host cells, and spermatozoa. The compound inhibits hyaluronidase and acrosin, induces sperm acrosomal loss, and is contraceptive in the rabbit model. Mandelic acid condensation polymer prevents infectivity of HIV and herpesviruses 1 and 2 and, to a lesser extent, of Chlamydia trachomatis. It inhibits the multiplication of Neisseria gonorrhoeae. Mandelic acid condensation polymer is not mutagenic, has low acute oral toxicity, and is safe in the rabbit vaginal irritation assay.

CONCLUSION(S)

Mandelic acid condensation polymer inhibits sperm function, is contraceptive, has broad-spectrum antimicrobial activity, and is highly safe. Further development as a microbicide is warranted.

Two novel vaginal microbicides (polystyrene sulfonate and cellulose sulfate) inhibit Gardnerella vaginalis and anaerobes commonly associated with bacterial vaginosis

This is the first report demonstrating the in vitro inhibitory activity of two novel microbicides (cellulose sulfate and polystyrene sulfonate) against bacterial vaginosis (BV)-associated bacteria. Vaginal application of these microbicides not only may reduce the risk of acquisition of human immunodeficiency virus and other sexually transmitted infection-causing organisms but may also decrease the incidence of BV.