Safety and tolerability of BufferGel, a novel vaginal microbicide, in women in the United States

Microbicides and other topical agents in the prevention of HIV and sexually transmitted infections

According to information from UNAIDS, more than 42 million individuals are living with HIV worldwide. Most infected individuals live in developing countries where the availability of antiretroviral agents is still limited. As this pandemic is increasing largely through mucosal transmission, new methods of prevention are urgently needed. If available, agents that block HIV prior to or early after contact with mucosal epithelia would decrease the incidence of HIV infection and, therefore, potentially save millions of lives over the next few decades. Topically applied microbicides acting against HIV-1 can be subdivided into four subgroups, including agents directly inhibiting pathogens, agents acting on genital pH, agents blocking pathogen entry and replication inhibitors. In addition, microbicides might also allow fighting against other sexually transmitted infections, such as herpes simplex viruses. With concerted efforts directed towards developing efficient microbicides, topical anti-infective compounds may well become a new weapon against sexually transmitted infections, including HIV, in everyday clinical practice.

Microbicides: a new frontier in HIV prevention

Microbicides are products that can be applied to vaginal or rectal mucosal surfaces with the goal of preventing, or at least significantly reducing, the transmission of sexually transmitted infections (STIs) including HIV-1. Despite more than two decades of HIV-1 vaccine research, there is still no efficacious HIV-1 vaccine, and the scientific community appears skeptical about the short or long-term feasibility of developing a vaccine that has the ability to induce sterilizing immunity against HIV-1. In this setting, microbicide research has gathered momentum. Currently, 16 candidate microbicides are in clinical development and five products are being evaluated in large-scale Phase 2B/3 effectiveness studies. Initial data from these trials will be available within the next 2-3 years, and it is feasible that there could be one or more licensed microbicides by the end of the decade. The first generation of surfactant microbicides had a non-specific mechanism of action. However, subsequent candidate microbicides have been developed to target specific steps in the process of viral transmission. The purpose of this article is to provide an overview of microbicide development and an update on the candidate pipeline.

Microbicides and other topical strategies to prevent vaginal transmission of HIV

The HIV epidemic is, by many criteria, the worst outbreak of infectious disease in history. The rate of new infections is now approximately 5 million per year, mainly in the developing world, and is increasing. Women are now substantially more at risk of infection with HIV than men. With no cure or effective vaccine in sight, a huge effort is required to develop topical agents (often called microbicides) that, applied to the vaginal mucosa, would prevent infection of these high-risk individuals. We discuss the targets for topical agents that have been identified by studies of the biology of HIV infection and provide an overview of the progress towards the development of a usable agent.

Vaginal safety after use of a bioadhesive, acid-buffering, microbicidal contraceptive gel (ACIDFORM) and a 2% nonoxynol-9 product

BACKGROUND

ACIDFORM is a microbicidal and contraceptive candidate with strong buffering capacity.

METHODS

This was a Phase I blinded, randomized and crossover clinical study on two products, ACIDFORM and a commercial nonoxynol-9 (N-9) product (2%), evaluating their vaginal safety in 20 couples aged between 19 and 45 years. The women had regular menses, underwent previous tubal ligation, were not breast-feeding, had no vaginal sign and symptom and were in a stable partnership; both partners had no previous STI. Colposcopy, vaginal microbiology, inflammation markers and subject complaints were studied after coitus. Women were randomly assigned sequentially to receive ACIDFORM 0-30 min (0-30 min before intercourse), ACIDFORM 8-10 h (8-10 h before intercourse) or N-9 0-30 min after a control cycle.

RESULTS

Mild/moderate vulvar irritation was observed in five postcoital test colposcopies, burning and pruritus were reported in six treated cycles and non-irritation-related symptoms were found in five cycles with different treatments. No difference in vaginal pH, Nugent scores, H2O2-producing lactobacillus or leukocytes and interleukin 6 in the cervicovaginal lavage was found between the treatment and control cycles.

CONCLUSIONS

ACIDFORM appears to be safe for clinical use once a day. There is a potential spermicidal-microbicidal role for ACIDFORM as a vaginal flora helper or as a vehicle for products, except N-9.

Safety and tolerability of tenofovir vaginal gel in abstinent and sexually active HIV-infected and uninfected women

OBJECTIVES

To establish the highest practical dose and frequency (HPDF) of 0.3% or 1% tenofovir vaginal gel applied once or twice daily by sexually abstinent HIV-uninfected women, and to evaluate the safety, tolerability and systemic pharmacokinetics of the HPDF in abstinent and sexually active HIV-negative and HIV-infected women.

METHODS

Eighty-four women, enrolled in sequential cohorts, used the study product for 14 consecutive intermenstrual days. Safety laboratory assessments and pelvic examinations were carried out during five study visits, with colposcopy at enrollment and on day 14. Samples for pharmacokinetics were collected before and after the initial tenofovir gel use and at day 13.

RESULTS

The 1% tenofovir gel used twice daily was as well tolerated as other regimens used by the 48 HIV-negative sexually abstinent women, establishing the HPDF. Although 92% of the women reported at least one adverse event, the majority were mild (87%) and involved the genitourinary tract (70%). One possibly product-related severe adverse event involving lower abdominal cramping was reported by a sexually abstinent woman who used 0.3% gel twice daily. Serum tenofovir levels were low but detectable in 14 of the 25 women. No new HIV RNA resistance mutations were detected after 2 weeks of tenofovir gel in the 24 HIV-infected participants. No significant systemic toxicity was detected.

CONCLUSION

A 2-week course of 1% tenofovir vaginal gel used twice daily was well tolerated in sexually abstinent and sexually active HIV-negative and HIV-positive women. Systemic tenofovir absorption occurred. Expanded safety and effectiveness testing is warranted.

Evaluating the clinical safety of three vaginal applicators: a pilot study conducted in the Dominican Republic

BACKGROUND

Targeted research on applicator safety has not been conducted as part of microbicide clinical trials and was considered necessary for ensuring safe and effective product use. Colposcopy, regarded as a standard method for assessing the safety of vaginal products, including microbicides, was used in this study to assess the external genitalia, vaginal epithelium and cervical epithelium after a single applicator use.

OBJECTIVES

The objectives of this study were to assess and compare the effects of three vaginal applicators on symptoms and signs of irritation of the external genitalia, vagina and cervix as seen by colposcopy after applicator use.

METHODS

Twenty women used three different vaginal applicators over three separate clinic visits 7-14 days apart and underwent a colposcopic examination before and after each applicator use. In total, the safety of each applicator was assessed over 20 product uses.

RESULTS

No severe colposcopic finding was reported. Four minor colposcopic findings (petechiae) were considered possibly related to product use. No difference was found between applicators.

CONCLUSIONS

This study provides reassuring data on the safety of the three applicator products from the perspective of causing vaginal trauma or irritation. Epithelial changes that could be more important for risk of disease transmission were not observed.

Low pH immobilizes and kills human leukocytes and prevents transmission of cell-associated HIV in a mouse model

Background

Both cell-associated and cell-free HIV virions are present in semen and cervical secretions of HIV-infected individuals. Thus, topical microbicides may need to inactivate both cell-associated and cell-free HIV to prevent sexual transmission of HIV/AIDS. To determine if the mild acidity of the healthy vagina and acid buffering microbicides would prevent transmission by HIV-infected leukocytes, we measured the effect of pH on leukocyte motility, viability and intracellular pH and tested the ability of an acidic buffering microbicide (BufferGel^®) to prevent the transmission of cell-associated HIV in a HuPBL-SCID mouse model.

Methods

Human lymphocyte, monocyte, and macrophage motilities were measured as a function of time and pH using various acidifying agents. Lymphocyte and macrophage motilities were measured using video microscopy. Monocyte motility was measured using video microscopy and chemotactic chambers. Peripheral blood mononuclear cell (PBMC) viability and intracellular pH were determined as a function of time and pH using fluorescent dyes. HuPBL-SCID mice were pretreated with BufferGel, saline, or a control gel and challenged with HIV-1-infected human PBMCs.

Results

Progressive motility was completely abolished in all cell types between pH 5.5 and 6.0. Concomitantly, at and below pH 5.5, the intracellular pH of PBMCs dropped precipitously to match the extracellular medium and did not recover. After acidification with hydrochloric acid to pH 4.5 for 60 min, although completely immotile, 58% of PBMCs excluded ethidium homodimer-1 (dead-cell dye). In contrast, when acidified to this pH with BufferGel, a microbicide designed to maintain vaginal acidity in the presence of semen, only 4% excluded dye at 10 min and none excluded dye after 30 min. BufferGel significantly reduced transmission of HIV-1 in HuPBL-SCID mice (1 of 12 infected) compared to saline (12 of 12 infected) and a control gel (5 of 7 infected).

Conclusion

These results suggest that physiologic or microbicide-induced acid immobilization and killing of infected white blood cells may be effective in preventing sexual transmission of cell-associated HIV.

Combination of candidate microbicides cellulose acetate 1,2-benzenedicarboxylate and UC781 has synergistic and complementary effects against human immunodeficiency virus type 1 infection

The combination of two candidate microbicides, cellulose acetate 1,2-benzenedicarboxylate (CAP), a polymer that blocks human immunodeficiency virus type 1 (HIV-1) entry by targeting gp120 and gp41, and UC781, a tight-binding HIV-1 reverse transcriptase inhibitor (RTI), resulted in effective synergy for inhibition of MT-2 cell infection by HIV-1(IIIB), a laboratory-adapted virus strain. The 95% effective concentration values for the combination were reduced about 15- to 20-fold compared with those corresponding to the single compounds. The combination of CAP and UC781 is also synergistic in inhibiting infection of peripheral blood mononuclear cells by a primary HIV-1 isolate, 92US657. Combinations of CAP with other RTIs, such as efavirenz or zidovudine, also had significant synergistic effects on the inhibition of HIV-1 infection. In addition, CAP and UC781 had complementary effects against HIV-1 infection since (i) CAP inhibited infection by the UC781-resistant strain HIV-1(IIIB) A17 and (ii) pretreatment of MT-2 cells with UC781, but not CAP, abolished subsequent infection after removal of the compound. This suggests that the combination of CAP and UC781 represents a promising candidate microbicide for prevention of sexual transmission of HIV-1.

The development of vaginal microbicides for the prevention of HIV transmission

Given that we still do not have an effective vaccine against HIV, the development of novel biomedical methods for preventing HIV transmission remains a top priority in controlling the HIV pandemic.

Clinical microbicide research: an overview

At the end of 2003, 42 million people were HIV infected and the epidemic continues to spread, despite the availability and effectiveness of male condoms. For many women negotiating condom use is not feasible. Therefore there is an urgent need for a female controlled method for HIV prevention. This article gives an overview of the clinical research done with microbicides, chemicals with the potential to prevent an HIV infection. In the 1990s most research was done with spermicides, mainly nonoxynol-9. Since the results of the COL-1492 trial became available, new products were evaluated and some of them are now in phase III trials.

[Vaginal virucides against HIV]

Despite intensive efforts to promote condoms as a means of preventing the spread of HIV, the rate at which the epidemic is expanding, highlights the need for additional prevention technologies, and in particular methods controlled by women. Virucides are anti-infective substances, formulated as gels, foams, creams, and suppositories and impregnated sponges, for vaginal application. Women will be able to insert them prior to sexual intercourse to protect themselves and their partners from infection with HIV. Unlike condoms, the woman will control them, and their use can be with or without her partner's consent or even knowledge. They will not create a physical barrier to reduce sexual pleasure, and it will be possible to apply them considerably in advance of sex so that there is no interruption to the natural course of events. Virucides will not necessarily be contraceptive; ideally, they will be available in a choice of contraceptive and non-contraceptive versions. Virucides are not intended to replace other prevention measures such as those based on male and female condoms-or vaccines when they become available-but will give people a wider choice of potentially life-saving methods of protection. About 60 candidate virucides are in the development pipeline, representing many different chemical categories and different mechanisms of action against infection. About half a dozen are scheduled to enter large-scale clinical trials in the near future. Virucides offer the prospect of a low-cost, woman-controlled option for self-administered, broad-spectrum protection against multiple HIV strains, other sexually transmitted pathogens and unwanted pregnancy.

Acceptability of a microbicide among women and their partners in a 4-country phase I trial

OBJECTIVES

We analyzed qualitative and quantitative data for 98 HIV-negative, low-risk women in Malawi, Zimbabwe, India, and Thailand who participated in a safety and acceptability study of BufferGel, a vaginal microbicide to determine the across-country acceptability of vaginal microbicides among women and their partners.

METHODS

Quantitative survey data were collected at 7 and 14 days after use among enrolled women, and exit interviews were conducted with women and their partners in separate focus group discussions.

RESULTS

Acceptability was high in all sites (73% of women approved of the microbicide). Women in Africa, where HIV infection rates are highest, were virtually unanimous in their desire for such a product, suggesting that an individual's perception of being at risk for HIV will outweigh concerns about side effects, problems applying a product, or other factors, when products are shown to be efficacious. But men and women reported that use, which was kept secret from an intimate partner, would be difficult and might "break the trust" of a relationship.

CONCLUSIONS

Acceptability research across diverse settings through all stages of microbicide research, development, and post-licensure dissemination can help maximize acceptability and use.

Safety and Efficacy Evaluations for Vaginal and Rectal Use of BufferGel in the Macaque Model

BACKGROUND

The nonhuman primate model allows for safety and efficacy testing of topical microbicide products.

GOAL

The goal of this study was to evaluate the safety and efficacy of vaginal and rectal applications of BufferGel (ReProtect, Inc.).

STUDY DESIGN

The safety of repeated product applications was evaluated by microflora, pH, vaginal colposcopy, and rectal lavage. To test efficacy in preventing chlamydia, infection was documented by culture and nucleic acid amplification tests.

RESULTS

Repeated vaginal or rectal applications of BufferGel were not associated with significant changes in microflora. BufferGel use had a transient acidifying effect on vaginal and rectal pH. Colposcopic observations remained relatively normal in all test animals. A slightly increased incidence of epithelial desquamation was noted after rectal product use compared with the control group. BufferGel did not prevent cervical or rectal chlamydial infection.

CONCLUSION

BufferGel has an acceptable safety profile after repeated vaginal and rectal use, but does not prevent chlamydial infection in the macaque models.

Vaginal microbicides and teenagers

PURPOSE OF REVIEW

Sexually active teens are at significant risk from sexually transmitted infections and girls and women bear the greatest burden of these infections. New methods, such as vaginal microbicides, would provide female controlled options. Microbicides are currently in development and thus it is timely to discuss the progress made and factors that may influence acceptability for teens.

RECENT FINDINGS

Microbicide development presents many challenges, and several different potential mechanisms of action are being explored. There is interest in these products from women and men, and specific preferences are being investigated. Adolescents, due to reproductive system immaturity, developing cognitive abilities and the psychosocial context of their relationships, present a special set of challenges in efforts to foster microbicide use.

SUMMARY

Vaginal microbicides are on the horizon. Further study into teen issues is required to develop successful strategies for marketing and encouraging adolescent use of microbicides.

Safety and acceptability of penile application of 2 candidate topical microbicides: BufferGel and PRO 2000 Gel: 3 randomized trials in healthy low-risk men and HIV-positive men

OBJECTIVES

To assess safety and acceptability of penile application of BufferGel (ReProtect, Baltimore, MD) and PRO 2000 Gel (Indevus Pharmaceuticals, Lexington, MA)compared with placebo among low-risk sexually abstinent men and HIV-positive sexually abstinent men.

DESIGN

Seventy-two healthy low-risk men (36 uncircumcised) and 25 HIV-positive men (12 uncircumcised) were enrolled in 3 double-blind, single-center studies as follows: 36 low-risk men in a study of BufferGel and K-Y Jelly (McNeil-PPC, Skillman, NJ) placebo; 36 low-risk men in a study of PRO 2000 Gel and vehicle placebo; and 25 HIV-positive men in a crossover study of BufferGel, PRO 2000 Gel, and K-Y Jelly placebo.

METHODS

Participants applied product to the penis on 7 consecutive nights, kept study diaries, and were then interviewed and examined. Urine was tested for inflammation by leukocyte esterase.

RESULTS

No serious adverse events (AEs) or urethral inflammation was detected. During use of BufferGel, 3 low-risk men (13%) reported 6 AEs and 2 HIV-positive men (8%) reported 3 AEs. During use of PRO 2000 Gel, 4 low-risk men (17%) reported 6 AEs and 1 HIV-positive participant (4%) had 1 AE. AE rates during use of BufferGel and PRO 2000 Gel use were not significantly different from rates observed during placebo. One low-risk man (4%) would object to his partners using BufferGel and 3 (13%) to PRO 2000 Gel. Two HIV-positive men (8%) reported they would object to partners using either BufferGel or PRO 2000 Gel.

CONCLUSIONS

Daily application of BufferGel and PRO 2000 Gel directly to the penis consecutively for 7 days was generally safe and well tolerated among healthy low-risk men and HIV-positive men. These microbicides have acceptable safety profiles to proceed with planned phase 3 vaginal microbicide trials.

A pilot study of treatment of bacterial vaginosis with a buffering vaginal microbicide

BACKGROUND

Bacterial vaginosis (BV) is an extremely common problem for women and is associated with adverse pregnancy outcomes and HIV infection. Currently available antibiotic treatments are moderately effective but may need to be repeated frequently because of the recurrent nature of the disease. We undertook a pilot study of a buffering vaginal microbicide in the treatment of BV.

METHODS

Women with clinically diagnosed BV were recruited to receive seven applications (5 g per application) of BufferGel trade mark (ReProtect, LLC, Baltimore, MD), a topical vaginal microbicide, and had clinical and gram stain evaluation of response. Subjects were evaluated at 2-3 days after the last application of BufferGel as a test of cure and again at 1 month to assess for relapse. Subjects with BV at test of cure were offered oral metronidazole.

RESULTS

Thirty-one women were screened, 16 were offered enrollment, and 10 completed the study. Treatment with BufferGel was clinically effective in 70% of women at 2-3 days after treatment and in 40% of women by 1-month follow-up.

CONCLUSIONS

These results suggest that 5 g of BufferGel vaginally once a day appears to be a moderately effective treatment for BV.

Blocking of cell-free and cell-associated HIV-1 transmission through human cervix organ culture with UC781

OBJECTIVE

To determine the efficacy of UC781 in preventing HIV-1 transmission through cervical tissue.

DESIGN

Use of human cervical tissue organ culture, in which the cervix is in the upper chamber of a transwell and transmission of infective virus is quantified in the lower chamber.

METHODS

Five-millimeter pieces of cervical tissues are exposed to UC781. After thorough removal of the drug, the tissues are exposed to high doses of cell-free or cell-associated HIV-1. Transmission of HIV-1 through the cervix is measured by determining infection of target cells in the lower chamber.

RESULTS

Exposure of cervix to 0.5 microM UC781 for 30 min, followed by extensive washing away of the residual drug, resulted in 95% reduction of subsequent viral transmission. Exposure of the cervix to 1 microM UC781 for 20 min, or 10 microM UC781 for 2 min, resulted in neutralization of T- and M-tropic HIV-1 isolates of various clades, and prevention of cell-associated HIV-1 transmission. Moreover, a 20 min incubation with 10 microM UC781 abolished HIV-1 transmission through the cervix for 48 h after drug pretreatment. Importantly, UC781 was not toxic, even when the cervical tissues were exposed to 20 microM UC781 for 24 h. UC781 was effective against transmission of both cell-free and cell-associated HIV-1 also when formulated into a non-spermicidal (Replen) or spermicidal (BufferGel) gel.

CONCLUSIONS

Exposure of the cervix to UC781 results in blocking of subsequent HIV-1 transmission with no toxicity. Therefore, UC781 is an excellent candidate microbiocide.

Safety and tolerability of vaginal PRO 2000 gel in sexually active HIV-uninfected and abstinent HIV-infected women

OBJECTIVES

To evaluate once or twice daily vaginal exposure to 2 and 4% PRO 2000 Gel, a naphthalene sulfonate polymer microbicide, in sexually active HIV-uninfected women to determine the highest tolerated frequency and concentration combination, and to assess this in sexually abstinent HIV-infected women.

METHODS

Sixty three women from Providence, Philadelphia, Durban and Johannesburg were enrolled after being screened to exclude pre-existing illnesses and were instructed to use the product once or twice daily for 14 intermenstrual days. They underwent colposcopy prior to product use and after 14 days of product use, with a pelvic examination at day 7.

RESULTS

The product was well tolerated, with no serious adverse events, even though 73% of the participants had at least one adverse experience: 82% of these were classified as mild, and over 90% of the findings and symptoms were localized to the genital tract. Women who used the 4% gel twice daily tended to have more adverse events than all the other groups. Three participants did not complete the study; one because of Herpes simplex virus cervicitis, the second because of epithelial disruption, and the third because she became pregnant. The remaining participants adhered to the study protocol and indicated that they would use the product if it were shown to be effective.

CONCLUSIONS

PRO 2000 Gel was safe and well tolerated in sexually active HIV-uninfected and sexually abstinent HIV-infected women, enabling the product to be considered for evaluation in efficacy trials.

Microbicides: a new approach to preventing HIV and other sexually transmitted infections

Many chemical agents can block human immunodeficiency virus (HIV) infection in the laboratory. Scientists are investigating which of these, used intravaginally by women, will safely prevent the sexual transmission of HIV in humans. Several such products - microbicides - will soon be tested in populations at high risk for HIV, and others are waiting in the wings. Microbicides will provide a low-cost method, controlled by women, for protection against HIV, other sexually transmitted pathogens and unwanted pregnancy, and will therefore have global public-health benefits.

Anti-HIV-1 activity of anionic polymers: a comparative study of candidate microbicides

BACKGROUND

Cellulose acetate phthalate (CAP) in soluble form blocks coreceptor binding sites on the virus envelope glycoprotein gp120 and elicits gp41 six-helix bundle formation, processes involved in virus inactivation. CAP is not soluble at pH < 5.5, normal for microbicide target sites. Therefore, the interaction between insoluble micronized CAP and HIV-1 was studied. Carbomer 974P/BufferGel; carrageenan; cellulose sulfate; dextran/dextrin sulfate, poly(napthalene sulfonate) and poly(styrene-4-sulfonate) are also being considered as anti-HIV-1 microbicides, and their antiviral properties were compared with those of CAP.

METHODS

Enzyme linked immunosorbent assays (ELISA) were used to (1) study HIV-1 IIIB and BaL binding to micronized CAP; (2) detect virus disintegration; and (3) measure gp41 six-helix bundle formation. Cells containing integrated HIV-1 LTR linked to the beta-gal gene and expressing CD4 and coreceptors CXCR4 or CCR5 were used to measure virus infectivity.

RESULTS

1) HIV-1 IIIB and BaL, respectively, effectively bound to micronized CAP. 2) The interaction between HIV-1 and micronized CAP led to: (a) gp41 six-helix bundle formation; (b) virus disintegration and shedding of envelope glycoproteins; and (c) rapid loss of infectivity. Polymers other than CAP, except Carbomer 974P, elicited gp41 six-helix bundle formation in HIV-1 IIIB but only poly(napthalene sulfonate), in addition to CAP, had this effect on HIV-1 BaL. These polymers differed with respect to their virucidal activities, the differences being more pronounced for HIV-1 BaL.

CONCLUSIONS

Micronized CAP is the only candidate topical microbicide with the capacity to remove rapidly by adsorption from physiological fluids HIV-1 of both the X4 and R5 biotypes and is likely to prevent virus contact with target cells. The interaction between micronized CAP and HIV-1 leads to rapid virus inactivation. Among other anionic polymers, cellulose sulfate, BufferGel and aryl sulfonates appear most effective in this respect.

Microbicide efficacy and toxicity tests in a mouse model for vaginal transmission of Chlamydia trachomatis

BACKGROUND

Microbicides are being developed for woman-controlled protection against sexually transmitted diseases (STDs).

GOAL

The goal of the study was to test candidate microbicides in a mouse model for preventing vaginal transmission of and for acute toxicity to columnar epithelium.

STUDY DESIGN

Progestin-sensitized CF-1 mice were treated vaginally with 50 microl of microbicide, followed either by vaginal inoculation with 10 ID(50) of serovar D or by examination of the epithelial surface for acute toxicity with a viability stain (ethidium homodimer-1).

RESULTS

Nonoxynol-9 (N9), sodium dodecyl sulfate (SDS), chlorhexidine digluconate, and BufferGel all provided significant though incomplete protection against vaginal transmission. Other candidates, all of which were effective in vitro, provided no vaginal protection: kappa-carrageenan, dextran sulfate, polystyrene sulfonate, Concanavalin A, wheat germ agglutinin, and agglutinin. The surface-active agents (N9, SDS, and chlorhexidine) caused significant acute epithelial toxicity: 3 days after chlorhexidine exposure, mice also had vaginal friability and markedly increased susceptibility to. BufferGel was the only candidate tested that was both protective and relatively nontoxic.

CONCLUSION

Microbicides can provide vaginal protection against in highly susceptible progestin-sensitized mice. Since N9 does not inactivate, it likely protects by killing target cells in the vagina. Despite the ability to both potently inactivate and kill target cells, two surface-active agents, SDS and chlorhexidine, failed to provide complete protection, a circumstance which emphasizes the importance of distributing microbicides to all susceptible surfaces.

Considerations and development of topical microbicides to inhibit the sexual transmission of HIV

The increased incidence of HIV/AIDS disease in women aged 15 - 49 years has identified the urgent need for a female-controlled, efficacious and safe vaginal topical microbicide. To meet this challenge, new topical microbicide candidates consisting of molecules or formulations that modify the genital environment (BufferGel, engineered Lactobacillus, over-the-counter lubricants), surfactants (C31D/Savvy, sodium dodecyl sulfate, sodium lauryl sulfate), polyanionic polymers (PRO 2000, beta-cyclodextrin, Carraguard, CAP, D2S, SPL-7013), proteins (cyanovirin-N, monoclonal antibodies, thromspondin-1 peptides, Pokeweed antiviral protein and others), reverse transcription inhibitors (PMPA [Tenofovir ]), UC-781, SJ-3366, DABO and thiourea) and other molecules (NCp7-specific virucides, chemokine receptor agonists/antagonists, WHI-05 and WHI-07) are currently being investigated for activity, safety and efficacy. This review will assess the development of these molecules in the context of cervicovaginal defences and the clinical failure of nonoxynol-9.

Microflora changes with the use of a vaginal microbicide

BACKGROUND

The rate of HIV transmission is increasing more in women than in any other group. There is an urgent need for the development of microbicides with activity against this virus that women can use during intercourse. These products must be convenient, effective, and safe, and ideally they will cause minimal disruption in the normal vaginal ecosystem.

GOAL

The objective of this study was to evaluate changes in vaginal microflora, specifically Lactobacillus species, with the use of BufferGel.

STUDY DESIGN

A prospective cohort study was performed to evaluate the change in vaginal flora before and after BufferGel use. BufferGel was applied vaginally once or twice daily for 14 days by low-risk abstinent and monogamous women.

RESULTS

There was no change in frequency of Lactobacillus species after BufferGel use. However, there was a decrease in H2O2-producing lactobacilli (from 4.9 x 107 to 1.1 x 107 cfu; P = 0.001). The proportion of facultative gram-negative rods present increased from 27% to 65% after BufferGel use, whereas obligately anaerobic microbes decreased from 62% to 38%.

CONCLUSION

Use of BufferGel once or twice daily for 14 days resulted in no clinically significant change in Lactobacillus colonization.

Vaginal microbicides

The focus of this review will be to highlight articles from 2000 and up to August 2001 that demonstrate the challenges in the evaluation of candidate microbicides, and the ways in which investigators have approached these challenges.

Tests of Buffergel for contraception and prevention of sexually transmitted diseases in animal models

BACKGROUND

BufferGel is a novel spermicidal and microbicidal gel formulated to maintain the natural protective acidity of the vagina by acidifying semen, which otherwise alkalinizes the vagina.

GOAL

To test the efficacy of BufferGel for preventing sexually transmitted infections and pregnancy in animal models.

STUDY DESIGN

Animals were challenged with pathogens or sperm after pretreatment with both test and control agents, or after no pretreatment, then evaluated for infection or pregnancy using standard methods.

RESULTS

BufferGel provided significant contraceptive efficacy in the rabbit, and significant protection against vaginal and rectal transmission of herpes simplex virus type 2 (HSV-2) in the mouse, vaginal transmission of Chlamydia trachomatis in the mouse, and skin transmission of cottontail rabbit papillomavirus in the rabbit. It did not protect against vaginal transmission of Neisseria gonorrhoeae in the mouse.

CONCLUSIONS

The protective efficacy of BufferGel in five of the six animal models suggests that this microbicide warrants clinical evaluation for both contraception and disease prevention.