Dextrin sulfate as a vaginal microbicide: randomized, double-blind, placebo-controlled trial including healthy female volunteers and their male partners

Biotherapeutic agents and vaginal health

Treatment of vaginal infection requires different drugs although the recurrence rate post treatment remains high due to adverse effects on the beneficial microbiota. Thus, there are clear clinical advantages for the use of biotherapeutic agents (prebiotics and/or probiotics) for treating these infections. Pre- and probiotic beneficial effects can be delivered topically or systemically. In general, both approaches have the potential to optimize, maintain and restore the ecology of the vaginal ecosystem. Specific carbohydrates provide a therapeutic approach for controlling infections by stimulating the growth of the indigenous lactobacilli but inhibiting the growth and adhesion of pathogens to the vaginal epithelial cells. Overall, little evidence exists to promote the prevention or treatment of vaginal disease with prebiotic carbohydrates in formulations such as pessaries, creams or douches. However, recent reports have promoted prebiotic applications in ecosystems other than the gut and include the mouth, skin and vagina. This review focuses on the utilization of pre- and probiotics for vaginal health.

Transport theory for HIV diffusion through in vivo distributions of topical microbicide gels

Topical microbicide products are being developed for the prevention of sexually transmitted infections. These include vaginally-applied gels that deliver anti-HIV molecules. Gels may also provide partial barriers that slow virion diffusion from semen to vulnerable epithelium, increasing the time during which anti-HIV molecules can act. To explore the barrier function of microbicide gels, we developed a deterministic mathematical model for HIV diffusion through realistic gel distributions. We applied the model to experimental data for in vivo coating distributions of two vaginal gels in women. Time required for a threshold number of virions to reach the tissue surface was used as a metric for comparing different scenarios. Results delineated how time to threshold increased with increasing gel layer thickness and with decreasing diffusion coefficient. We note that for gel layers with average thickness > approximately 100 microm, the fractional area coated, rather than the gel layer thickness, was the primary determinant of time to threshold. For gel layers < approximately 100 microm, time to threshold was brief, regardless of fractional area coated. Application of the model to vaginal coating data showed little difference in time to threshold between the two gels tested. However, the protocol after gel application (i.e., with or without simulated coitus) had a much more significant effect. This study suggests that gel distribution in layers of thickness >100 microm and fractional area coated >0.8 is critical in determining the ability of the gel to serve as a barrier to HIV diffusion.

Australian men's experiences during a microbicide male tolerance study

Microbicides currently in development have the potential to provide new options for the prevention of sexually transmitted infections if proven safe and efficacious. We examined the experiences of healthy male volunteers in a male tolerance study in Victoria, Australia in relation to trial participation and product use. Men (N=36) enrolled in a seven-day, phase 1 clinical safety trial of SPL7013 were interviewed pre and post-use of the gel using a semi-structured interview guide. Interviews were digitally recorded and transcribed verbatim, and transcripts were analysed using a framework approach. All but one man completed the trial. The median age was 34 years (range 22-67 years). Most men had little pre-study knowledge of microbicides and almost all participated for altruistic or personal reasons. Men expressed few concerns about product safety during the trial and indicated trust in the information received through the consent process and from study staff. Three men were non-adherent to the request to be abstinent and an additional two did not refrain from masturbation. Most were positive about the gel, although they described it as "sticky" and found that it stuck to clothes, bed sheets and pubic hair. The type of applicator used was unfamiliar to the men, and some found it "clinical" in appearance. Men are willing to participate in male tolerance studies, often for altruistic reasons. However, counseling about ways to maintain abstinence and further research to inform anticipatory guidance regarding the "sticky" quality of gels, may be important.

Acceptability of tenofovir gel as a vaginal microbicide by US male participants in a Phase I clinical trial (HPTN 050)

We studied the acceptability of tenofovir gel among HIV-infected and uninfected men who were exposed to it during vaginal intercourse. The gel was found to be highly acceptable to most men, the large majority indicating they would probably use it in the future if they were concerned about HIV and the product were available. Men liked the gel's transparency and odorless qualities, although reactions to its viscosity were more varied. Men acknowledged women's rights to self-determination concerning HIV-prevention, yet considered that women's covert use of the product was more acceptable in the context of 'one-night-stands' than in stable relationships, for which dialogue on protection measures was preferred. Restrictions to couples' habitual sexual repertoire and the protocol requirement to use condoms resulted in complaints. Microbicide trials that do not require condom use from men who don't typically use them may provide a more accurate assessment of acceptability. Consistent microbicide use may be contingent on its ease of incorporation into typical sexual practices, type of sexual partnership and contextual issues.

Lime Juice as a Candidate Microbicide? An Open-Label Safety Trial of 10% and 20% Lime Juice Used Vaginally

OBJECTIVE

Lime has a long history as a contraceptive and vaginal hygiene douche, and ongoing use in Africa is documented. We report on the first safety study on diluted lime juice to assess its potential as a candidate microbicide.

METHODS

Twenty-five sexually abstinent women were randomly assigned to apply a 10% or 20% concentration of lime juice or 0% (water-only) through a soaked tampon once daily for 14 consecutive days. Tests for genital infections, measurement of inflammatory biomarkers, and a colposcopy were performed before and after treatment.

RESULTS

No participant showed severe vaginal irritation. Two women developed a yeast infection after using lime juice. More than 70% of women in all groups reported side effects, most being singular, mild, and transient events. The users of 20% diluted lime juice experienced a significantly higher frequency of burning and dryness. Vaginal inflammatory biomarkers showed no significant change between preexposure and postexposure levels. The naturally low vaginal pH showed little change, and lactobacilli colonization did not decrease.

CONCLUSIONS

Lime juice up to 20% concentration has an acceptable safety profile for vaginal use. However, as new in vitro research shows that the effectiveness of lime juice to prevent HIV transmission in concentrations lower than >or=50% is unlikely and concentrations of 50% have been shown to be toxic, women should be discouraged from commencing or continuing the vaginal use of lime juice.

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.

Safety and Acceptability of the Candidate Microbicide Carraguard in Thai Women

OBJECTIVE

To determine the safety and acceptability of vaginal application of Carraguard, a carrageenan-derived candidate microbicide gel.

DESIGN

A randomized, placebo-controlled, triple-blinded clinical trial was conducted in Chiang Rai, northern Thailand.

METHODS

Women were asked to insert one applicator of study gel vaginally at least three times per week (with or without sex) and to use gel with condoms every time they had sex. Safety was assessed by visual inspection of the vagina and cervix, changes in vaginal flora and self-reported symptoms at day 14, month 1 and then monthly for up to 1 year. Acceptability was assessed through reported use of the gel, return of used and unused applicators, and quarterly interviews.

RESULTS

One hundred sixty-five women were randomized: 83 to Carraguard and 82 to the placebo (methylcellulose gel) group. Study gel use was similarly high in both groups throughout the trial with an average of four applicators per week. Carraguard use was not associated with abnormal genital clinical findings, abnormal vaginal flora, Pap smear abnormalities or other abnormal clinical signs or symptoms. Adverse events were mostly mild, not attributed to gel use, and similarly distributed between groups. Participants in both groups reported high acceptability.

CONCLUSIONS

Carraguard can safely be used an average of four times per week with or without sex and is acceptable to Thai women. A Phase III efficacy trial of Carraguard is warranted and is currently ongoing in South Africa.

Microbicide preference among young women in California

BACKGROUND

Microbicides for HIV/sexually transmitted infection (STI) prevention are still in development. Microbicide acceptability studies have thus focused on soliciting input from individuals about hypothetical products using traditional epidemiological and behavioral research methodologies. Here, we integrate a well-established market research method, conjoint analysis, with more traditional epidemiological and behavioral research to examine potential users' preferences for different microbicide formulations.

METHODS

Focus group discussions (n = 67) were held with a diverse population of young men and women (aged 18-32 years) from Northern California. Then, young women participated in structured surveys (n = 321) that included a conjoint study, a methodology not yet used in microbicide acceptability. The main outcome measures were intentions for different microbicide formulations, inferred preferences for microbicide characteristics, and self-reported risk factors for HIV, other STIs, and pregnancy.

RESULTS

Risk of STIs and unwanted pregnancies is a concern within this population. Participants' responses suggest that the ideal microbicide would (1) offer protection from pregnancy, HIV, STIs, and vaginal infections, (2) offer as much protection as condoms, (3) allow insertion up to 8 hours prior to sexual activity, (4) be available over the counter (OTC), (5) be inserted with an applicator, and (6) have only slight leakage not requiring a panty liner. The average predicted purchase probability for this ideal microbicide was 69%.

CONCLUSIONS

Our findings help illustrate microbicide product preferences and demand among young women in California, and the methodological approach should lend itself to other populations as well as during clinical trials when understanding product use and nonuse is critical.

Safety and acceptability of cellulose sulfate as a vaginal microbicide in HIV-infected women

OBJECTIVES

Few studies of topical microbicides have assessed their safety in HIV-infected women. We conducted this study to evaluate the safety and acceptability of 6% cellulose sulfate (CS) gel as a vaginal microbicide in sexually abstinent and active HIV-infected women.

METHODS

Fifty-nine HIV-infected women were enrolled in a randomized double-blind placebo-controlled study comparing 6% CS to placebo gel used for 14 days. Sexually abstinent women applied gel once or twice daily and sexually active women used gel once daily.

RESULTS

CS gel was safe with no reported severe or life-threatening adverse events (AE). Thirty-nine (66%) of the participants experienced urogenital AE judged as probably or possibly related to gel. The majority (51%) of these participants reported only mild events. Fewer women (62%) who used CS experienced urogenital AE than those assigned to placebo gel (70%) (P = 0.59). Eleven (19%) women experienced intermenstrual bleeding judged to be probably or possibly related to gel use (four in the CS and seven in the placebo gel group). There was no increase in AE by frequency of gel use or sexual activity with the exception of abdominal/pelvic pain which was noted more frequently with twice daily use among sexually abstinent women. Women and men found the gel highly acceptable.

CONCLUSIONS

This Phase I study demonstrated that CS vaginal gel was safe, well tolerated and acceptable by HIV-infected women and their male partners. Thus, further development of CS is warranted as a potential method to prevent HIV transmission and acquisition.

A randomized controlled safety and acceptability trial of dextrin sulphate vaginal microbicide gel in sexually active women in Uganda

OBJECTIVE

To assess the safety of dextrin sulphate (DS) gel compared to placebo gel in terms of local and systemic adverse events, and to determine the acceptability of dextrin sulphate gel.

DESIGN

A 4-week randomized trial of DS intra-vaginal gel, partially blinded, with placebo and observation control arms. Participants were randomized to use DS gel twice daily, placebo gel twice daily, DS gel pre-sex, or into an observation only arm.

METHODS

Sexually active women were recruited from post natal and HIV clinics at Nsambya Hospital, Kampala, Uganda. Screening, enrollment and follow-up visits took place every 1 or 2 weeks over an 8-week period and consisted of questionnaire interviews, colposcopy examinations, sexually transmitted infection screen and routine laboratory testing.

RESULTS

Out of a total of 172 women screened, 109 were randomized to use DS gel twice daily (65 women), placebo gel twice daily (15 women), DS gel pre-sex (nine women) or into an observation only arm (20 women). Two individuals had abnormal colposcopy findings in the DS twice daily gel use arm. Vaginal bleeding was reported as frequently by participants in the active gel arm as by participants in the placebo and observation only arms. No clinically significant difference was observed between arms in terms of vaginal flora, Candida, haemoglobin, white cell count, platelets, thrombin time, activated partial thromboplastin time, creatinine and aspartate aminotransferase results after 4 weeks of gel use. DS gel appeared to be acceptable to over 95% of the users.

CONCLUSIONS

Results show a satisfactory safety and acceptability profile of dextrin sulphate gel.

A Dose-Ranging Phase I Study of Dextrin Sulphate, a Vaginal Microbicide, in HIV-Negative and HIV-Positive Female Volunteers

DESIGN

This phase I dose-ranging study of 2 weeks of twice-daily dextrin sulphate (DS), a sulphated polymer with in vitro activity against HIV, was designed in 2 parts. Part A was a randomized, placebo-controlled, double-blind, 3-arm trial (DS4%, DS1%, placebo) in HIV-negative women. In part B, HIV-positive women received DS4% and HIV-negative women were randomized to DS4% or no gel.

RESULTS

One hundred women were enrolled from 2 sites (London and Antwerp): DS4% (n = 50, 20 of whom were HIV-positive), DS1% (n = 20), placebo (n = 10) and no gel (n = 20). There were no withdrawals related to adverse events and no cases of epithelial disruption. Spotting was reported by 24 women and numbers were significantly higher in all the gel groups (23 of 80), including placebo, compared with no gel (one of 20) (Fisher exact test P = 0.037). There was no evidence of a dose effect. Safety tests showed no evidence of systemic absorption.

CONCLUSION

Although there was no clear explanation for the spotting, DS4% was well tolerated. It was decided to proceed with DS4% in an expanded safety study in Africa but to restrict entry to low-risk HIV-negative women, include a no-gel group, and monitor intermenstrual bleeding closely.

Naturally derived anti-HIV agents

The urgent need for new anti-HIV/AIDS drugs is a global concern. In addition to obvious economical and commercial hurdles, HIV/AIDS patients are faced with multifarious difficulties associated with the currently approved anti-HIV drugs. Adverse effects, the emergence of drug resistance and the narrow spectrum of activity have limited the therapeutic usefulness of the various reverse transcriptase and protease inhibitors that are currently available on the market. This has driven many scientists to look for new anti-retrovirals with better efficacy, safety and affordability. As has always been the case in the search for cures, natural sources offer great promise. Several natural products, mostly of plant origin have been shown to possess promising activities that could assist in the prevention and/or amelioration of the disease. Many of these anti-HIV agents have other medicinal values as well, which afford them further prospective as novel leads for the development of new drugs that can deal with both the virus and the various disorders that characterize HIV/AIDS. The aim of this review is to report new discoveries and updates pertaining to anti-HIV natural products. In the review anti-HIV agents have been classified according to their chemical classes rather than their target in the HIV replicative cycle, which is the most frequently encountered approach. Perusal of the literature revealed that most of these promising naturally derived anti-HIV compounds are flavonoids, coumarins, terpenoids, alkaloids, polyphenols, polysaccharides or proteins. It is our strong conviction that the results and experiences with many of the anti-HIV natural products will inspire and motivate even more researchers to look for new leads from plants and other natural sources.

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.

The appealing story of HIV entry inhibitors : from discovery of biological mechanisms to drug development

Current therapeutic intervention in HIV infection relies upon 20 different drugs. Despite the impressive efficacy shown by these drugs, we are confronted with an unexpected frequency of adverse effects, such as mitochondrial toxicity and lipodystrophy, and resistance, not only to individual drugs but to entire drug classes.Thus, there is now a great need for new antiretroviral drugs with reduced toxicity, increased activity against drug-resistant viruses and a greater capacity to reach tissue sanctuaries of the virus. Two different HIV molecules have been selected as targets of drug inhibition so far: reverse transcriptase and protease. Drugs that target the interactions between the HIV envelope and the cellular receptor complex are a 'new entry' into the scenario of HIV therapy and have recently raised great interest because of their activity against multidrug-resistant viruses. There are several compounds that are at different developmental stages in the pipeline to counter HIV entry, among them: (i) the attachment inhibitor dextrin-2-sulfate; (ii) the inhibitors of the glycoprotein (gp) 120/CD4 interaction PRO 542, TNX 355 and BMS 488043; (iii) the co-receptor inhibitors subdivided in those targeting CCR5 (SCH 417690 [SCH D], UK 427857 GW 873140, PRO 140, TAK 220, AMD 887) and those targeting CXCR4 (AMD 070, KRH 2731); and (iv) the fusion inhibitors enfuvirtide (T-20) and tifuvirtide (T-1249). The story of the first of these drugs, enfuvirtide, which has successfully completed phase III clinical trials, has been approved by the US FDA and by the European Medicines Agency, and is now commercially available worldwide, is an example of how the knowledge of basic molecular mechanisms can rapidly translate into the development of clinically effective molecules.

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.

Measurement of anti-HIV activity of marketed vaginal products and excipients using a PBMC-based in vitro assay

BACKGROUND AND OBJECTIVE

Because microbicides will be applied topically in the vagina, the active agent must be formulated as a gel or cream by combining the active agent with suitable excipients. Although a number of in vitro methods have been developed for testing anti-HIV activity of microbicides, most of these methods have not been used for testing microbicides as a gel or cream.

GOAL

The goal of this study was to measure anti-HIV activity of marketed vaginal gel or cream products and excipients.

STUDY DESIGN

A PBMC-based in vitro method has been developed for the evaluation of anti-HIV activity of gel or cream marketed products and formulated drug delivery systems. This method includes viral exposure to test compounds followed by differential centrifugation and filtration.

RESULTS

Using this methodology, a number of marketed vaginal products showed 83% to 100% inactivation of a variety of X4 and R5 HIV of different clades. Cell viability as determined by the MTT assay for all marketed products was greater than 90%. Some of the excipients also showed anti-HIV activity (20-90%) of their own.

CONCLUSION

This knowledge of baseline anti-HIV activity of vaginal products (cream/gel) and excipients is useful for the final formulation and development of anti-HIV microbicides.