Phase 1 Pharmacokinetic Trial of 2 Intravaginal Rings Containing Different Dose Strengths of Vicriviroc (MK-4176) and MK-2048.

BACKGROUND: Vaginal rings (VRs) are a promising approach for sustained delivery of antiretroviral (ARV) medication to prevent human immunodeficiency virus (HIV) infection in women. Combination ARV VRs could increase efficacy. METHODS: MTN-028, a phase 1 trial in 19 HIV-uninfected women, evaluated 2 VRs containing vicriviroc (VCV) and MK-2048. Participants were randomized 2:1 to a low-dose (VCV, 91 mg; MK-2048, 10 mg) or original-dose (VCV, 182 mg; MK-2048, 30 mg) ring used for 28 days. Safety was assessed by documenting adverse events (AEs). Drug concentrations were evaluated in plasma, cervicovaginal fluid (CVF), and cervical tissue samples. RESULTS: All AEs reported were grade 1 or 2, with no statistically significant differences in related genitourinary AEs or grade ≥2 AEs observed between arms (P = >.99). VCV/MK-2048 concentrations rose rapidly, with higher plasma area under the concentration-time curve (AUC) in the original-dose arm (geometric mean ratio, 3.29 for VCV and 1.49 for MK-2048) and similar AUCs across arms for CVF samples. Cervical tissue concentrations were higher in the original-dose arm (geometric mean ratio, 7.94 for VCV and 6.45 for MK-2048), with greater drug released based on residual drug levels. Plasma and CVF concentrations for both drugs fell rapidly after ring removal. CONCLUSIONS: In this first study evaluating 2 doses of a combination VCV/MK-2048 VR, both rings were found to be safe and well tolerated. VCV and MK-2048 were detectable in plasma, CVF, and cervical tissue samples, and drug release and plasma drug exposure were higher for the original-dose than for the low-dose ring.

Tenofovir-based preexposure prophylaxis for HIV infection among African women.

BACKGROUND: Reproductive-age women need effective interventions to prevent the acquisition of human immunodeficiency virus type 1 (HIV-1) infection. METHODS: We conducted a randomized, placebo-controlled trial to assess daily treatment with oral tenofovir disoproxil fumarate (TDF), oral tenofovir-emtricitabine (TDF-FTC), or 1% tenofovir (TFV) vaginal gel as preexposure prophylaxis against HIV-1 infection in women in South Africa, Uganda, and Zimbabwe. HIV-1 testing was performed monthly, and plasma TFV levels were assessed quarterly. RESULTS: Of 12,320 women who were screened, 5029 were enrolled in the study. The rate of retention in the study was 91% during 5509 person-years of follow-up. A total of 312 HIV-1 infections occurred; the incidence of HIV-1 infection was 5.7 per 100 person-years. In the modified intention-to-treat analysis, the effectiveness was -49.0% with TDF (hazard ratio for infection, 1.49; 95% confidence interval [CI], 0.97 to 2.29), -4.4% with TDF-FTC (hazard ratio, 1.04; 95% CI, 0.73 to 1.49), and 14.5% with TFV gel (hazard ratio, 0.85; 95% CI, 0.61 to 1.21). In a random sample, TFV was detected in 30%, 29%, and 25% of available plasma samples from participants randomly assigned to receive TDF, TDF-FTC, and TFV gel, respectively. Independent predictors of TFV detection included being married, being older than 25 years of age, and being multiparous. Detection of TFV in plasma was negatively associated with characteristics predictive of HIV-1 acquisition. Elevations of serum creatinine levels were seen more frequently among participants randomly assigned to receive oral TDF-FTC than among those assigned to receive oral placebo (1.3% vs. 0.2%, P=0.004). We observed no significant differences in the frequencies of other adverse events. CONCLUSIONS: None of the drug regimens we evaluated reduced the rates of HIV-1 acquisition in an intention-to-treat analysis. Adherence to study drugs was low. (Funded by the National Institutes of Health; VOICE ClinicalTrials.gov number, NCT00705679.).

Reporting of Adherence in the VOICE Trial: Did Disclosure of Product Nonuse Increase at the Termination Visit?

VOICE-a phase 2B, placebo-controlled, randomized trial testing daily use of an antiretroviral tablet (tenofovir or Truvada) or daily use of tenofovir gel in 5029 women from South Africa, Uganda, and Zimbabwe-found none of the drug regimens effective in reducing HIV-1 acquisition in the intent-to-treat analysis. More than half of women assigned to active products in a case cohort sample had no drug detected in any plasma specimens tested during the trial. Yet, in response to questions asked of participants during the trial, ≥90 % of doses were reportedly taken. To explore factors associated with low adherence, a behavioral termination visit questionnaire was developed after early closure of the oral tenofovir and vaginal gel arms. We hypothesized that participants would be more forthcoming about nonuse after they exited the trial than during monthly/quarterly follow-up visits. Comparison of adherence reporting at routine follow-up visits with reporting at trial termination, however, indicates that disclosure of product nonadherence did not increase at the termination visit as anticipated. In resource-limited settings where women value the ancillary benefits provided by trial participation and are concerned that disclosure of nonuse may jeopardize trial participation, objective measures of adherence may yield more meaningful data regarding the inability or reluctance to use than measures of product use derived from self-report.

Characteristics Associated with HIV Drug Resistance Among Women Screening for an HIV Prevention Trial in KwaZulu-Natal, South Africa.

While the expansion of antiretroviral therapy (ART) in sub-Saharan Africa has reduced morbidity and mortality from HIV/AIDS, it has increased concern about drug resistance. The Microbicide Trials Network 009 study assessed the prevalence of drug-resistance mutations among women at clinical sites in Durban, South Africa who tested seropositive for HIV-1 at screening for the VOICE trial. The objective of this paper was to identify characteristics and behaviors associated with drug resistance. Factors found to be significantly associated with increased resistance were high perceived risk of getting HIV and prior participation in a microbicide trial, a likely proxy for familiarity with the health care system. Two factors were found to be significantly associated with reduced resistance: having a primary sex partner and testing negative for HIV in the past year. Other variables hypothesized to be important in identifying women with resistant virus, including partner or friend on ART who shared with the participant and being given antiretrovirals during pregnancy or labor, or the proxy variable-number of times given birth in a health facility-were not significantly associated. The small number of participants with resistant virus and the probable underreporting of sensitive behaviors likely affected our ability to construct a comprehensive profile of the type of HIV-positive women at greatest risk of developing resistance mutations.

HPTN 035 phase II/IIb randomised safety and effectiveness study of the vaginal microbicides BufferGel and 0.5% PRO 2000 for the prevention of sexually transmitted infections in women.

OBJECTIVES: To estimate the effectiveness of candidate microbicides BufferGel and 0.5% PRO 2000 Gel (P) (PRO 2000) for prevention of non-ulcerative sexually transmitted infections (STIs). METHODS: Between 2005 and 2007, 3099 women were enrolled in HIV Prevention Trials Network (HPTN) protocol 035, a phase II/IIb evaluation of the safety and effectiveness of BufferGel and PRO 2000 for prevention of STIs, including Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT) and Trichomonas vaginalis (TV). Incidences of STIs were determined by study arm, and HRs of BufferGel and PRO 2000 versus placebo gel or no gel control groups were computed using discrete time Andersen-Gill proportional hazards model. RESULTS: The overall incidence rates were 1.6/100 person-years at risk (PYAR) for NG, 3.9/100 PYAR for CT and 15.3/100 PYAR for TV. For BufferGel versus placebo gel, HRs were 0.99 (95% CI 0.49 to 2.00), 1.00 (95% CI 0.64 to 1.57) and 0.95 (95% CI 0.71 to 1.25) for prevention of NG, CT and TV, respectively. For PRO 2000, HRs were 1.66 (95% CI 0.90 to 3.06), 1.16 (95% CI 0.76 to 1.79) and 1.18 (95% CI 0.90 to 1.53) for prevention of NG, CT and TV, respectively. CONCLUSIONS: The incidence of STIs was high during HIV Prevention Trials Network 035 despite provision of free condoms and comprehensive risk-reduction counselling, highlighting the need for effective STI prevention programmes in this population. Unfortunately, candidate microbicides BufferGel and PRO2000 had no protective effect against gonorrhoea, chlamydia or trichomoniasis. TRIAL REGISTRATION NUMBER: NCT00074425.

Adherence and acceptability in MTN 001: a randomized cross-over trial of daily oral and topical tenofovir for HIV prevention in women.

We compared adherence to and acceptability of daily topical and oral formulations of tenofovir (TFV) used as pre-exposure prophylaxis (PrEP) for HIV prevention among women in South Africa, Uganda and the United States. 144 sexually active, HIV-uninfected women participated in a cross-over study of three regimens: oral tablet, vaginal gel, or both. We tested for differences in adherence and evaluated product acceptability. Self-reported adherence for all regimens was high (94 %), but serum TFV concentrations indicated only 64 % of participants used tablets consistently. Most women in the U.S. (72 %) favored tablets over gel; while preferences varied at the African sites (42 % preferred gel and 40 % tablets). Findings indicate a role for oral and vaginal PrEP formulations and highlight the importance of integrating pharmacokinetics-based adherence assessment in future trials. Biomedical HIV prevention interventions should consider geographic and cultural experience with product formulations, partner involvement, and sexual health benefits that ultimately influence use.

Prevalence and Incidence of Sexually Transmitted Infection in Injectable Progestin Contraception Users in South Africa.

Introduction: Whether intramuscular depot medroxyprogesterone acetate (DMPA-IM) and norethisterone enanthate (NET-EN) have a differential impact on the incidence of sexually transmitted infection (STI) remains unclear. In the Vaginal and Oral Interventions to Control the Epidemic (VOICE) trial, HIV-1 acquisition was higher for DMPA-IM users vs. NET-EN users. We compared DMPA-IM and NET-EN users with regard to chlamydia, gonorrhea, trichomoniasis, syphilis, and herpes simplex virus type 2 (HSV-2) infection. Materials and Methods: Prospective data were analyzed from VOICE, a randomized trial of HIV-1 chemoprophylaxis. Participants were evaluated annually and as indicated for chlamydia, gonorrhea, trichomoniasis, and syphilis. Stored specimens were tested for HSV-2. Proportional hazards models compared the risk of STI between DMPA-IM and NET-EN users. Results: Among 2,911 injectable contraception users in South Africa, 1,800 (61.8%) used DMPA-IM and 1,111 used NET-EN (38.2%). DMPA-IM and NET-EN users did not differ in baseline chlamydia: 15.1 vs. 14.3%, p= 0.54; gonorrhea: 3.4 vs. 3.7%, p= 0.70; trichomoniasis: 5.7 vs.5.0%, p= 0.40; or syphilis: 1.5 vs. 0.7%, p= 0.08; but differed for baseline HSV-2: (51.3 vs. 38.6%, p < 0.001). Four hundred forty-eight incident chlamydia, 103 gonorrhea, 150 trichomonas, 17 syphilis, and 48 HSV-2 infections were detected over 2,742, 2,742, 2,783, 2,945, and 756 person-years (py), respectively (chlamydia 16.3/100 py; gonorrhea 3.8/100 py; trichomoniasis 5.4/100 py; syphilis 0.6/100 py; HSV-2 6.4/100 py). Comparing DMPA-IM with NET-EN users, no difference was noted in the incidence of chlamydia, gonorrhea, trichomoniasis, syphilis, or HSV2 infections, including when adjusted for confounders [chlamydia (aHR 1.03, 95% CI 0.85-1.25), gonorrhea (aHR 0.88, 95% CI 0.60-1.31), trichomoniasis (aHR 1.07, 95% CI 0.74-1.54), syphilis (aHR 0.41, 95% CI 0.15-1.10), and HSV-2 (aHR 0.83, 95% CI 0.45-1.54, p= 0.56)]. Discussion: Among South African participants enrolled in VOICE, DMPA-IM and NETEN users differed in prevalence of HSV-2 at baseline but did not differ in the incidence of chlamydia, gonorrhea, trichomoniasis, syphilis, or HSV-2 infection. Differential HIV-1 acquisition, previously demonstrated in this cohort, does not appear to be explained by differential STI acquisition. However, the high incidence of multiple STIs reinforces the need to accelerate access to comprehensive sexual and reproductive health services.

Prevalence and determinants of anal human papillomavirus infection in men who have sex with men and transgender women.

Human papillomavirus (HPV) prevalence varies by population. This study investigated anal HPV type detection risk by country in a population of men who have sex with men (MSM) and transgender women (TW) at risk of HIV. Sexually active HIV-1-uninfected MSM and TW were enrolled at eight sites: four in the United States (US), two in Thailand, one in Peru, and one in South Africa. Baseline anal HPV swabs were collected, and DNA typing was performed. One hundred and ninety-five participants, 76 (42%) from the US, had a mean age of 30.9 years (range 18-64). In 182 participants with results available, anal HPV infection was common with 169 (93%) with ≥1 type, 132 (73%) with ≥1 nine-valent vaccine types, and 66 (36%) with HPV 16. Participants in the US had a higher prevalence of HPV 16 (56%, p = 0.004) and HPV 6 (69%, p < 0.001) compared to the other regions. Stimulant drug use was significantly associated with HPV 6 detection. Anal HPV is highly prevalent in this population of MSM and TW sampled from four countries, with HPV 16 the most commonly detected type. The nine-valent HPV vaccine has the potential to provide significant protection if given prior to exposure.

High levels of adherence to a rectal microbicide gel and to oral Pre-Exposure Prophylaxis (PrEP) achieved in MTN-017 among men who have sex with men (MSM) and transgender women.

Trials to assess microbicide safety require strict adherence to prescribed regimens. If adherence is suboptimal, safety cannot be adequately assessed. MTN-017 was a phase 2, randomized sequence, open-label, expanded safety and acceptability crossover study comparing 1) daily oral emtricitabine/tenofovir disoproxil fumarate (FTC/TDF), 2) daily use of reduced-glycerin 1% tenofovir (RG-TFV) gel applied rectally, and 3) RG-TFV gel applied before and after receptive anal intercourse (RAI)-if participants had no RAI in a week, they were asked to use two doses of gel within 24 hours. Product use was assessed by mixed methods including unused product return count, text messaging reports, and qualitative plasma TFV pharmacokinetic (PK) results. Convergence interviews engaged participants in determining the most accurate number of doses used based on product count and text messaging reports. Client-centered adherence counseling was also used. Participants (N = 187) were men who have sex with men and transgender women enrolled in the United States (42%), Thailand (29%), Peru (19%) and South Africa (10%). Mean age was 31.4 years (range 18-64 years). Based on convergence interviews, over an 8-week period, 94% of participants had ≥80% adherence to daily tablet, 41% having perfect adherence; 83% had ≥80% adherence to daily gel, 29% having perfect adherence; and 93% had ≥80% adherence to twice-weekly use during the RAI-associated gel regimen, 75% having perfect adherence and 77% having ≥80% adherence to gel use before and after RAI. Only 4.4% of all daily product PK results were undetectable and unexpected (TFV concentrations <0.31 ng/mL) given self-reported product use near sampling date. The mixed methods adherence measurement indicated high adherence to product use in all three regimens. Adherence to RAI-associated rectal gel use was as high as adherence to daily oral PrEP. A rectal microbicide gel, if efficacious, could be an alternative for individuals uninterested in daily oral PrEP.

Divergent adherence estimates with pharmacokinetic and behavioural measures in the MTN-003 (VOICE) study.

INTRODUCTION: In the Microbicide Trial Network MTN-003 (VOICE) study, a Phase IIB pre-exposure prophylaxis trial of daily oral or vaginal tenofovir (TFV), product adherence was poor based on pharmacokinetic (PK) drug detection in a random subsample. Here, we sought to compare behavioural and PK measures of adherence and examined correlates of adherence misreporting. METHODS: We included participants with PK and behavioural data from VOICE random subsample. Behavioural assessments included face-to-face interviews (FTFI), audio computer-assisted self-interviewing (ACASI) and pharmacy-returned product counts (PC). TFV concentrations < 0.31 ng/mL in plasma (oral group) and < 8.5 ng/swab in vaginal group were defined as "PK non-adherent." Logistic regression models were fit to calculate the combined predictive ability of the behavioural measures as summarized by area under the curve (AUC). Baseline characteristics associated with over-reporting daily product use relative to PK measures was assessed using a Generalized Linear Mixed Model. RESULTS: In this random adherence cohort of VOICE participants assigned to active products, (N = 472), PK non-adherence was 69% in the oral group (N = 314) and 65% in the vaginal group (N = 158). Behaviourally, ≤ 10% of the cohort reported low/none use with any behavioural measure and accuracy was low (≤ 43%). None of the regression models had an AUC > 0.65 for any single or combined behavioural measures. Significant (p < 0.05) correlates of over-reporting included being very worried about getting HIV and being unmarried for the oral group; whereas for the vaginal group, being somewhat worried about HIV was associated with lower risk of over-reporting. CONCLUSIONS: PK measures indicated similarly low adherence for the oral and vaginal groups. No behavioural measure accurately predicted PK non-adherence. Accurate real-time measures to monitor product adherence are urgently needed. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT00705679.

Risk of HIV-1 acquisition among women who use diff erent types of injectable progestin contraception in South Africa: a prospective cohort study.

BACKGROUND: Several observational studies have reported that HIV-1 acquisition seems to be higher in women who use depot medroxyprogesterone acetate (DMPA) than in those who do not use hormonal contraception. We aimed to assess whether two injectable progestin-only contraceptives, DMPA and norethisterone enanthate (NET-EN), confer different risks of HIV-1 acquisition. METHODS: We included data from South African women who used injectable contraception while participating in theVOICE study, a multisite, randomised, placebo-controlled trial that investigated the safety and efficacy of three formulations of tenofovir for prevention of HIV-1 infection in women between Sept 9, 2009, and Aug 13, 2012. Women were assessed monthly for contraceptive use and incident infection. We estimated the difference in incident HIV-1infection between DMPA and NET-EN users by Cox proportional hazards regression analyses in this prospective cohort. The VOICE trial is registered with ClinicalTrials.gov, NCT00705679. FINDINGS: 3141 South African women using injectable contraception were included in the present analysis: 1788 (56·9%)solely used DMPA, 1097 (34·9%) solely used NET-EN, and 256 (8·2%) used both injectable types at different times during follow-up. During 2733·7 person-years of follow-up, 207 incident HIV-1 infections occurred (incidence7·57 per 100 person-years, 95% CI 6·61­8·68). Risk of HIV-1 acquisition was higher among DMPA users (incidence 8·62 per 100 person-years, 95% CI 7·35­10·11) than among NET-EN users (5·67 per 100 person-years, 4·35­7·38;hazard ratio 1·53, 95% CI 1·12­2·08; p=0·007). This association persisted when adjusted for potential confoundingvariables (adjusted hazard ratio [aHR] 1·41, 95% CI 1·06­1·89; p=0·02). Among women seropositive for herpes simplex virus type 2 (HSV-2) at enrolment, the aHR was 2·02 (95% CI 1·26­3·24) compared with 1·09 (0·78­1·52)for HSV-2-seronegative women (pinteraction=0·07). INTERPRETATION: Although moderate associations in observational analyses should be interpreted with caution, thesefi ndings suggest that NET-EN might be an alternative injectable drug with a lower HIV risk than DMPA in high HIV-1 incidence settings where NET-EN is available. FUNDING: National Institutes of Health, Mary Meyer Scholars Fund, and the Ruth Freeman Memorial Fund.

Prevalence of HIV-1 drug resistance among women screening for HIV prevention trials in KwaZulu-Natal, South Africa (MTN-009).

BACKGROUND: A major concern with using antiretroviral (ARV)-based products for HIV prevention is the potential spread of drug resistance, particularly from individuals who are HIV-infected but unaware of their status. Limited data exist on the prevalence of HIV infection or drug resistance among potential users of ARV-based prevention products. METHODS: A cross-sectional study of reproductive-aged women who presented to screen for an HIV prevention trial was conducted at 7 clinical sites in Durban, South Africa. CD4+T cell counts, HIV-1 RNA levels and population sequencing of the protease and reverse transcriptase genes were performed for all women with 2 positive HIV rapid tests. Resistance mutations were identified using the Stanford Calibrated Population Resistance Tool. RESULTS: Of the 1073 evaluable women, 400(37%) were confirmed as HIV-infected. Of those, plasma HIV-1 RNA was detectable in 365/400(91%) and undetectable(<40 copies/ml) in 35/400(9%) women. 156 women(39%) were eligible for antiretroviral therapy (CD4+T cell counts<350 cells/mm(3)) and 50(13%) met criteria for AIDS(CD4<200 cells/mm(3)). Of 352 plasma samples(>200 copies/ml) analyzed for drug resistance, 26(7.4%) had nucleoside reverse transcriptase inhibitor (NRTI), non-nucleoside reverse transcriptase inhibitor (NNRTI) or protease inhibitor (PI) drug resistance mutations. Among those with resistance, 18/26 participants(62%) had single-class NNRTI resistance and 5/26(19%) had dual-class NRTI/NNRTI. Major mutations in reverse transcriptase included K65R(n = 1), L74I(n = 1), K103N(n = 19), V106M(n = 4), Y181C(n = 2), M184V(n = 4), and K219E/R(n = 2). Major PI-resistance mutations were rare: M46L(n = 1) and I85V(n = 1). All participants were infected with subtype C virus, except one infected with subtype A. CONCLUSIONS: In women from Durban, South Africa screening for an HIV prevention trial, the HIV prevalence was high (37%) and HIV drug resistance prevalence was above 5%. This study highlights the potential challenges faced when implementing an ARV-based prevention product that overlaps with first-line antiretroviral therapy. Effective screening to exclude HIV infection among women interested in uptake of ARV-based HIV prevention will be essential in limiting the spread of ARV resistance.

MTN-001: randomized pharmacokinetic cross-over study comparing tenofovir vaginal gel and oral tablets in vaginal tissue and other compartments.

BACKGROUND: Oral and vaginal preparations of tenofovir as pre-exposure prophylaxis (PrEP) for human immunodeficiency virus (HIV) infection have demonstrated variable efficacy in men and women prompting assessment of variation in drug concentration as an explanation. Knowledge of tenofovir concentration and its active form, tenofovir diphosphate, at the putative vaginal and rectal site of action and its relationship to concentrations at multiple other anatomic locations may provide key information for both interpreting PrEP study outcomes and planning future PrEP drug development. OBJECTIVE: MTN-001 was designed to directly compare oral to vaginal steady-state tenofovir pharmacokinetics in blood, vaginal tissue, and vaginal and rectal fluid in a paired cross-over design. METHODS AND FINDINGS: We enrolled 144 HIV-uninfected women at 4 US and 3 African clinical research sites in an open label, 3-period crossover study of three different daily tenofovir regimens, each for 6 weeks (oral 300 mg tenofovir disoproxil fumarate, vaginal 1% tenofovir gel [40 mg], or both). Serum concentrations after vaginal dosing were 56-fold lower than after oral dosing (p<0.001). Vaginal tissue tenofovir diphosphate was quantifiable in ≥90% of women with vaginal dosing and only 19% of women with oral dosing. Vaginal tissue tenofovir diphosphate was ≥130-fold higher with vaginal compared to oral dosing (p<0.001). Rectal fluid tenofovir concentrations in vaginal dosing periods were higher than concentrations measured in the oral only dosing period (p<0.03). CONCLUSIONS: Compared to oral dosing, vaginal dosing achieved much lower serum concentrations and much higher vaginal tissue concentrations. Even allowing for 100-fold concentration differences due to poor adherence or less frequent prescribed dosing, vaginal dosing of tenofovir should provide higher active site concentrations and theoretically greater PrEP efficacy than oral dosing; randomized topical dosing PrEP trials to the contrary indicates that factors beyond tenofovir's antiviral effect substantially influence PrEP efficacy. TRIAL REGISTRATION: ClinicalTrials.gov NCT00592124.

Phase 1 randomized trial of the vaginal safety and acceptability of SPL7013 gel (VivaGel) in sexually active young women (MTN-004).

OBJECTIVES: The study was designed to assess the safety, adherence, acceptability, and effect on vaginal microflora of 3% SPL7013 Gel (VivaGel), a novel dendrimer topical microbicide that inhibits HIV, herpes simplex virus-2, and human papillomavirus in vitro and in animal models. DESIGN: Phase 1, randomized, double-blind, placebo-controlled study on sexually active women. METHODS: Sixty-one sexually active women aged 18-24 years were recruited from three sites in the United States. Participants were randomized 1: 1: 1 to receive VivaGel, VivaGel placebo, or a hydroxyethylcellulose (HEC) placebo twice daily for 14 consecutive days. Safety endpoints included genitourinary and/or other adverse events. Changes in vaginal flora were determined from Gram-stained vaginal smears and quantitative vaginal culture. RESULTS: No serious adverse events or withdrawals due to adverse events were reported. Genitourinary symptoms were reported as follows: VivaGel (n = 17/22; 77.3%), VivaGel placebo (n = 14/21; 66.7%), and HEC (n = eight of 18; 44.4%; not significant, P = 0.1). The incidence of abnormal pelvic examination findings was similar across all gel arms of the study. Using pairwise comparison, women in the VivaGel arm had a significantly higher incidence of related genitourinary adverse events compared with women in the HEC gel arm (0.297 versus 0.111 per 100 person-years, respectively; P = 0.003). Exposure to VivaGel and VivaGel placebo resulted in minor shifts in the vaginal microflora, but there was no overall impact on incidence of bacterial vaginosis as assessed by Nugent score. CONCLUSION: VivaGel was generally well tolerated and comparable with the VivaGel placebo, although there was a higher incidence of low-grade related genital adverse events compared to the HEC placebo gel.