Effectiveness of Cellulose Sulfate Vaginal Gel for the
Prevention of HIV Infection: Results of a Phase III Trial in
Vera Halpern1*, Folasade Ogunsola2, Orikomaba Obunge3, Chin-Hua Wang1, Nneka Onyejepu3, Oyinola
Oduyebo2, Doug Taylor1, Linda McNeil1, Neha Mehta1, John Umo-Otong3, Sakiru Otusanya2, Tania
Crucitti4, Said Abdellati4
1Family Health International, Research Triangle Park, North Carolina, United States of America, 2College of Medicine, University of Lagos, Lagos, Nigeria, 3Teaching
Hospital, University of Port Harcourt, Port Harcourt, Nigeria, 4HIV/STI Epidemiology and Control Unit, Institute of Tropical Medicine, Antwerp, Belgium
Background: This trial evaluated the safety and effectiveness of 6% cellulose sulfate vaginal gel in preventing male-to-
female vaginal transmission of HIV, gonorrhea and chlamydial infection.
Methods: This Phase III, double-blind, randomized, placebo-controlled trial was conducted between November 2004 and
March 2007 in Lagos and Port Harcourt, Nigeria. We enrolled 1644 HIV-antibody negative women at high risk of HIV
acquisition. Study participants were randomized 1:1 to cellulose sulfate or placebo and asked to use gel plus a condom for
each act of vaginal intercourse over one year of follow-up. The participants were evaluated monthly for HIV, gonorrhea and
chlamydial infection, and for adverse events.
Results: The trial was stopped prematurely after the data safety monitoring board of a parallel trial concluded that cellulose
sulfate might be increasing the risk of HIV. In contrast, we observed fewer infections in the active arm (10) than on placebo
(13), a difference that was nonetheless not statistically significant (HR=0.8, 95% CI 0.3–1.8; p=0.56). Rates of gonorrhea and
chlamydial infection were lower in the CS group but the difference was likewise not statistically significant (HR=0.8, 95% CI
0.5–1.1; p=0.19 for the combined STI outcome). Rates of adverse events were similar across study arms. No serious adverse
events related to cellulose sulfate use were reported.
Conclusions: Cellulose sulfate gel appeared to be safe in the evaluated study population but we found insufficient evidence
that it prevented male-to-female vaginal transmission of HIV, gonorrhea or chlamydial infection. The early closure of the trial
compromised the ability to draw definitive conclusions about the effectiveness of cellulose sulfate against HIV.
Trial Registration: ClinicalTrials.gov NCT00120770
Citation: Halpern V, Ogunsola F, Obunge O, Wang C-H, Onyejepu N, et al. (2008) Effectiveness of Cellulose Sulfate Vaginal Gel for the Prevention of HIV Infection:
Results of a Phase III Trial in Nigeria. PLoS ONE 3(11): e3784. doi:10.1371/journal.pone.0003784
Editor: Patricia Kissinger, Tulane University, United States of America
Received July 17, 2008; Accepted October 29, 2008; Published November 21, 2008
Copyright: ? 2008 Halpern et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This study was funded by the United States Agency for International Development and sponsored by CONRAD. The funder and sponsor monitored the
progress of the trial through regular reports, meetings and technical consultations. CONRAD provided the study product (CS and placebo-gel applicators), held
the IND, reviewed and approved the manuscript. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: firstname.lastname@example.org
As HIV has no cure, prevention technologies are needed to
control the epidemic. The most effective current methods of HIV
prophylaxis, including abstinence, male condoms and male
circumcision, are partially or wholly controlled by men. The need
for female-initiated methods for HIV prevention is all the more
urgent, given the recent disappointing results from several HIV
prevention trials among women [1–3] and the HIV vaccine field
. A safe, effective, and affordable topical microbicide could offer
women a method to prevent sexual transmission of HIV in cases
where other methods of protection cannot be used.
Cellulose sulfate (CS) has antimicrobial activity in vitro against
various sexually transmitted pathogens, including HIV, Neisseria
gonorrhoeae and Chlamydia trachomatis . Prompted by the promising
laboratory data and a good safety profile demonstrated in early-
phase clinical trials [6–9], we proceeded to a Phase III study to
evaluate the effectiveness of CS gel in preventing male-to-female
vaginal transmission of HIV, gonorrhea and chlamydial infection
among sexually active women perceived to be at high risk of HIV
Materials and Methods
The protocol for this trial and supporting CONSORT checklist
are available as supporting information (see Checklist S1 and
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This Phase III, double-blind, randomized, placebo-controlled
trial was conducted in Lagos and Port Harcourt, Nigeria between
November 2004 and March 2007. Three Institutional Review
Boards approved the study: those of the College of Medicine,
University of Lagos; the University of Port Harcourt Teaching
Hospital; and Family Health International (FHI).
To be enrolled in the study women had to be HIV-seronegative,
non-pregnant, 18–35-years-old and have, on average, three or
more acts of intercourse per week and more than one sexual
partner in the last three months. We excluded women who were
injection drug users, were currently participating in another
microbicide trial, were less than three months since their last
pregnancy, or desired pregnancy in the next 12 months. Most
study participants were low-income women who exchanged sex for
money to supplement their incomes, although they did not self-
identify exclusively as sex workers. All participants signed written
informed consent form before screening and enrollment. Measures
were put in place to ensure that the informed consent process was
adequate for illiterate participants.
Each of the two study sites had two clinics with up to 15 outreach
posts located in areas with densely concentrated, low-income
populations where HIV transmission was thought to be high. The
informal results of previous research among high risk populations as
well as condom distribution programs conducted by local investiga-
tors and non-government organizations helped to identify suchareas
in Lagos and Port Harcourt. Outreach workers recruited women
from bars, markets, and other common gathering areas and referred
potential study participants to the study clinics for screening. After
receiving detailed information about the study and signing the
screening informed consent, women were screened for eligibility. An
interview, general physical examination, pelvic examination, and
testing for HIV, other sexually transmitted and reproductive tract
infections (STIs and RTIs) and pregnancy were performed. During
the interview baseline demographic data and information on
medical history, contraceptive practices and sexual behavior were
also collected. Risk reduction counseling, condom demonstration
and freelubricated latex condomsnot coated with nonoxynol-9 were
provided to all participants. Eligible women were asked to return
within 30 days for enrollment.
On return, participants signed an enrollment consent form and
were then tested for HIV, syphilis, gonorrhea, chlamydial infection
and pregnancy. Women who were pregnant or HIV positive were
not enrolled. Women diagnosed with gonorrhea, chlamydial
infection, trichomoniasis, syphilis, candidiasis or bacterial vaginosis
during screening or enrollment were treated per the Centers for
Disease Control and Prevention (CDC) treatment guidelines 
and admitted to the study. Upon confirmation of eligibility,
participants were randomized to the CS or placebo group and
supplied with study gels and condoms. Study staff instructed
participants to insert the contents of one full applicator of their
assigned study gel into the vagina immediately prior to each act of
sexual intercourse throughout the 12 months of study participation
and reapply the gel if intercourse did not take place within one hour
after application. Participants were instructed to use condoms for all
acts of sexual intercourse regardless of gel use, not to douch after sex,
not touse any other vaginalproducts, and not to use thestudy gelfor
anal intercourse. Participants were provided with referral informa-
contraceptives other than condoms.
Follow-up visits were held at the outreach post most conveniently
located for each participant. Procedures included an interview,
testing for HIV, gonorrhea, chlamydial infection and pregnancy, re-
supply and demonstration - if required - of gel and condom use, and
risk reduction and adherence counseling. As part of the interview
process participants were asked about their health, any adverse
experiences and concomitant medication use since their last visit,
and coital frequency, gel and condom adherence in the last 7 days.
gelsiftheyran outbetweentheirscheduled visits.Women presenting
with an adverse event were referred to the study clinic for evaluation
and treatment. Due to the investigational nature of the gel women
who became pregnant stopped using product until the pregnancy
had ended. To avoid social stigma, women that seroconverted were
not discontinued from the study, nor did we require them to stop gel
use so they could continue contributing to the STI and safety
outcomes. All HIV-infected participants were referred to appropri-
ate local facilities for social support and clinical management,
including antiretroviral drugs if indicated.
Both CS and placebo gels were identical in packaging and
labeling and were administered in a 3.5 ml dose via a plastic
single-use applicator. Each 3.5 ml application of 6% CS gel
contained 231 mg of the active ingredient, sodium cellulose
sulfate. The CS gel had a pH of 7.5. The placebo gel contained
hydroxyethylcellulose (HEC) as a gelling agent, had no cell toxicity
or anti-HIV properties, and had a pH of 4.4. The HEC placebo
was previously deemed safe and sufficiently inactive for use in
clinical studies of investigational microbicides .
The primary outcome was incident HIV-1 or HIV-2 infection, as
determined by antibodies in oral mucosal transudate using
OraQuickH Advance Rapid HIV-1/2 Antibody test (OraSure
Technologies, Inc., Bethlehem, PA, USA) and confirmed by Western
blot (Genetic SystemsTMHIV-1 Western Blot, Bio-Rad, Hercules,
CA, USA). Western blot testing for HIV was carried out by the study
laboratories in Nigeria. For women who seroconverted during first
three months of follow-up, qualitative RNA-based polymerase chain
reaction (PCR) testing for HIV with the AmpliScreen HIV-1 test
(Roche Diagnostics, Branchburg, NJ, USA) was performed on stored
enrollment plasma to assess whether the infection was pre-existing.
to identify recent infections in the absence of antibodies. HIV PCR
testing was conducted by a laboratory of the Institute of Tropical
Medicine (ITM, Antwerp, Belgium).
The secondary outcome was incident STI (gonorrhea or
chlamydial infection), measured by detecting DNA material in
self-administered vaginal swabs using the strand displacement
amplification (SDA) BDProbeTecTMET CT/NG assay (Becton
Dickinson, Erembodegem, Belgium). The quality of SDA testing
performed by the study laboratories in Nigeria was assured by
repeat testing of all positive and 10% of all negative results from
enrollment and quarterly follow-up visits at the ITM; in the event
of a discrepancy the ITM result was used for data analysis. Storage
and shipment of all biological samples were conducted in
accordance with the ITM instructions, manufacturer’s recom-
mendations and requirements of a shipping company (World
Courier, Allentown, PA, USA).
The trial and its reporting complied with the CONSORT
Guidelines . We conducted the study under an Investigational
New Drug application (IND) to the U.S. Food and Drug
Administration and in accordance with Good Clinical Practice
Randomized Trial of CS Gel
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as established by the International Conference on Harmonisation
. The trial was registered with the ClinicalTrials.gov registry
under #NCT00120770. The National Agency for Food and Drug
Administration and Control of Nigeria approved the study prior to
We aimed to enroll a total of 2,160 participants (1,080 in each
treatment group) to observe 66 total HIV infections. This study size
was designed toprovide 80%powerto detecta 50% reduction inthe
riskofHIV infection among CSgel users,controlling the type I error
for falsely concluding a reduction in risk at the 0.025 level (an
independent data and safety monitoring committee was to evaluate
any potentially harmful effect of CS using less stringent criteria). A
50% reduction in typical use risk was considered to be a meaningful
effect for impacting the epidemic. Such an assumption required that
CS be more than 50% efficacious during consistent and correct use,
since womenwould notuse gel for all acts during the trial (e.g. due to
withdrawal of product during pregnancy, missed product supply
visits, and other non-adherence).
The sample size calculation assumed that loss to follow-up
would not exceed 20% and that the incidence rate in the control
group would be 5 per 100 woman-years. This rate of HIV
infection was estimated based on HIV prevalence data available
prior to study initiation [14–16], as well as incidence-to-prevalence
ratios from previous research conducted by FHI among similar
study populations in West Africa . To compensate for the lack
of directly measured incidence, we planned to monitor the overall
infection rate during the study to determine if the sample size had
to be adjusted to achieve the target number of events (66).
Randomization and Blinding
Participants were randomly assigned to either the CS or placebo
arm using a 1:1 allocation ratio. A statistician not otherwise
involved in the study developed the allocation sequence using a
stratified (by study site), randomly permuted block design with
block sizes 12, 18, and 24. Six product label colors (3 for CS and 3
for placebo) were used to improve blinding (revealing one color
would not un-blind the entire study). Sequentially numbered,
sealed opaque envelopes were used to assign participants to one of
the six color groups after they signed the enrollment consent form
and were determined eligible for the study. There was no
indication that any unblinding occurred during the study.
We compared the distribution of time to HIV infection between
groups using an exact log-rank test, stratified by site. We calculated
Kaplan-Meier estimates of HIV infection probabilities by treat-
ment group, pooled across sites. Time to HIV infection, in days,
was computed as the difference between the estimated date of HIV
infection (based on the midpoint between the dates of the first
confirmed positive HIV test visit and the preceding HIV negative
visit) and the enrollment date, plus one. Data from participants who
were lost to follow-up were included in the primary analysis but
were censored on the date of their last HIV test visit. In secondary
analyses, we used a proportional hazards regression model to
estimate the hazard ratio (HR) for HIV infection, controlling for
pre-specified baseline prognostic variables. The effect of CS gel in
preventing transmission of gonorrhea and chlamydial infection was
primarily evaluated by a proportional hazards model that
controlled for site and other pre-specified baseline prognostic
variables including age, history of pregnancy and anal intercourse,
previous use of spermicides, number of male partners and sexual
acts not protected by condoms, and positive results for gonorrhea
or chlamydial infection at enrollment. We calculated exact
confidence intervals for the relative risk of adverse events within
system organ classes under a Poisson assumption for the event rates
in each treatment group.
All primary analyses were performed on an intent-to-treat (ITT)
basis, with the following modifications: randomized participants
later found to be positive for HIV at enrollment (via HIV PCR
testing) were excluded from analysis; and - for gonorrhea and
chlamydial outcomes - women who were positive for STI at
enrollment started their time in analysis on the date of their first
negative SDA test following treatment.
We also performed pre-planned, exploratory on-product
analyses of HIV, gonorrhea and chlamydial infection that
excluded data collected from participants after their first
documented interruption of product use (e.g. due to a positive
pregnancy test, a lack of gel supplies following a missed visit, or
safety concerns raised by the study clinician). Non-use of available
product (e.g. choosing not to use available gel) was considered part
of typical use and was not documented as a product interruption.
Data were collected at the sites on two-ply data collection forms
and subsequently entered into FHI’s 21 CFR Part 11 compliant
Clintrial 4.5 database management system (Phase Forward, Inc.,
Waltham, MA, USA) by local data entry staff through a secure
Internet server. Data analyses were implemented using version 9.1
of SAS statistical software (SAS Institute, Cary, NC, USA) and
StatXact (Cytel Software, Cambridge, MA, USA).
Two interim analyses were planned. The first analysis took
place after 16 HIV infections had occurred and focused exclusively
on the safety profile of CS (i.e. there was no test of effectiveness).
The second interim analysis was planned to occur after 33
infections to evaluate both safety and preliminary effectiveness
data. We planned to use the Lan-Demets spending function 
with O’Brien-Fleming type boundaries  to control the type I
error for concluding effectiveness at the one-sided 0.025 level. In
contrast, a fixed, one-sided p-value less than 0.10 in the direction
of harm was used as the criteria to stop for potential harm or
futility. Since the study was stopped prematurely due to external
factors, no type I error adjustment was required when reporting
the final results using two-sided p-values.
Study screening began in November 2004, and the last follow-
up visit took place in March 2007. An independent Data
Monitoring Committee (DMC) conducted the first planned
interim safety analysis in September 2006 and their recommen-
dation was to continue the study. An unplanned interim safety
analysis was conducted on January 29, 2007 after an apparent
increased risk of HIV in the CS arm was found in a parallel trial
conducted by CONRAD, a cooperating agency of the United
States Agency for International Development . The DMC
found no increased risk in the FHI study but recommended to stop
due to the CONRAD study results.
Participant Flow and Baseline Characteristics
By the time of the early closure 3619 women had been screened,
of whom 1644 (45%) were enrolled in the trial. Screening failures
included women who did not return (26%), had a positive rapid
HIV test (16%), were pregnant (7%) or met other exclusion criteria
(6%). Participant’s final status was similar in the two groups: 70%
of women completed the study, 30% were lost to follow-up and an
additional one woman in each group discontinued early (Figure 1).
Eighteen percent of women missed one study visit, 9% missed two
visits, and 38% missed 3 or more study visits. A mean of 293 days
Randomized Trial of CS Gel
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(median 357, range 16–380) were contributed to the effectiveness
analysis, among those women with any follow-up. Demographic
and baseline characteristics are presented in Table 1. The majority
of the study participants were young, not married and relatively
well educated. More than half of all women relied on condoms for
pregnancy prevention prior to the trial, and more than half were
diagnosed with bacterial vaginosis at baseline. The two groups
appeared similar in all respects at baseline except for a slightly
higher prevalence of chlamydial infection among those random-
ized to CS (4% vs. 2% on placebo; p=0.045).
Sexual Behavior and Product use
Self-reported sexual behaviors were similar between groups
(Table 2). The average coital frequency increased slightly during
the first month of the study but returned to enrollment levels at
month 12, whereas the average reported number of sexual partners
and new partners in the last 30 days decreased from enrollment to
month12.Self-reportedcondom useincreased fromscreening (60%)
toenrollment (89%),and fluctuatedlittle during follow-up(84–90%).
On average, gel was reportedly used in 81% of all sexual acts, and in
approximately 50% of sexual acts not protected by condoms.
A total of 645 product interruptions were documented during
the trial (323 on CS and 322 on placebo). In both groups
pregnancy was the primary reason for product discontinuation
(54%), followed by a lack of supplies due to missed visits (45%).
Despite the high pregnancy rates (29 and 28 per 100 woman-years
in the CS and placebo groups, respectively; Table 3), only 4.8% of
total observed person-time was off product due to pregnancy
(5.1% for CS and 4.5% for placebo) because most women did not
carry their pregnancy to term.
Viewed by site, women in Port Harcourt were better educated,
more likely to be students, less likely to be married, and reported
more oral sex and less contraceptive use at baseline than in Lagos.
In addition, participants in Port Harcourt reported higher risk of
sexual behavior and used more gel than women in Lagos. They
also were more adherent with gel use and more compliant with the
protocol (data not shown).
Figure 1. Participant Flow.
Table 1. Selected Baseline Characteristics by Treatment
Age in years (mean6SDb) 23.463.7 23.363.5
Not married (n, %)780 (95%) 784 (95%)
Years of education (mean6SD) 10.263.8 10.463.6
Ever been pregnant (n, %)654 (80%)673 (82%)
Contraceptive method (n, %)
none 170 (21%)161 (20%)
hormonal 149 (18%) 143 (17%)
condom 451 (55%)469 (57%)
other 50 (6%)51 (6%)
Previous use of spermicide (n, %)19 (2%)26 (3%)
Douching (n, %)578 (71%) 595 (72%)
Baseline STIscand RTIsd(n, %)
gonorrhea57 (7%) 44 (5%)
chlamydial infection32 (4%)18 (2%)
syphilis8 (1%)6 (1%)
bacterial vaginosis470 (57%) 461 (56%)
trichomoniasis53 (6%)45 (5%)
candidiasis183 (22%)204 (25%)
Number of different male sexual partners in the
last 3 months (mean6SD)
20.8 (59.6)17.8 (42.7)
Number of new male partners in the last
3 months (mean6SD)
17.4 (56.1)14.5 (42.0)
anone of the differences between the study groups were statistically significant
except for prevalence of chlamydial infection (p=0.045, unadjusted for
cSexually Transmitted Infections.
dReproductive Tract Infections.
Randomized Trial of CS Gel
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Effect on HIV, Gonorrhea and Chlamydial infection
A total of 1506 women contributed data to the primary HIV
analysis, of whom 23 had an incident infection (pooled incidence
rate of 1.9 per 100 woman-years). All incident infections were
diagnosed as HIV-1. Fewer infections occurred in the CS group
(10) than on placebo (13), but the difference was not statistically
significant (HR=0.8, 95% CI 0.3–1.8, p=0.56; Table 3).
Premature closure of the trial greatly curtailed the power of the
study to detect an effect on HIV (23 events provided only ,40%
power to detect a 50% reduction in risk). In contrast, we observed
a total of 126 incident gonorrhea and chlamydial infections which
provided greater than 90% power to detect a 50% reduction in the
risk of acquiring an STI among women randomized to CS.
Although the rates of both STIs were lower in the CS group, the
difference was not statistically significant (HR=0.8, 95% CI 0.5–
1.1; p=0.19 for the combined STI outcome; Table 3).
We excluded data from participants after a documented product
interruption in planned secondary analyses in order to estimate
not exclude self-reported imperfect use because self-reported
adherence is subject to unknown levels and directions of bias). This
exclusion resulted in only a slight change to the HIV result (HR 0.9,
95% CI 0.4–2.3; p=0.86), the combined STI result (HR=0.7, 95%
CI 0.5–1.1; p=0.15) and the chlamydial infection result (HR 0.8,
the CS group (HR 0.6, 95% CI 0.4–1.0; p=0.058). Additional,
unplanned exploratoryanalyses suggested that CS use mayhave been
women who reported above median coital frequency at baseline (HR
0.4, 95% CI 0.2–0.8; p=0.01) and above median average number of
partners during follow up (HR 0.6, 95% CI 0.4–1.0; p=0.05).
We also explored the effects of other covariates on the risk of HIV
infection, irrespective of treatment group. Previous experience using
spermicides was associated with higher risk of HIV (HR 6.7, 95% CI
1.8–4.7;p,0.01),although lessthan 3%ofwomen reported previous
spermicide use. Similarly, a positive gonorrhea or chlamydial
infection result at baseline was associated with higher risk of both
HIV (HR 3.6, 95% CI 1.2–10.8; p=0.02) and gonorrhea or
chlamydial infection (HR 2.5, 95% CI 1.2–5.2; p=0.01).
A total of 47 serious adverse events (SAEs) were identified, but
none were related to gel use. Hospitalization due to malaria and
typhoid were the most frequent SAEs. Overall adverse event rates,
Table 2. Self-reported Sexual Behavior, Gel and Condom Use by Treatment Group*.
In the previous 30 days In the previous 7 days
Number of male
partners Mean (SEa)
Number of new
partners Mean (SE)
acts Mean (SE)
% of sex acts
% of sex acts
% of condom-
free sex acts
CS (N=820)Screening Data not collected Data not collected6.0 (0.3) 61.2c
Not applicable Not applicable
Enrollment 10.1 (0.8)5.8 (0.8) 6.2 (0.3)88.7Not applicable Not applicable
Month 1 10.8 (0.7)4.7 (0.4) 8.5 (0.4) 89.084.2 52.0
Month 6 9.4 (0.6)4.1 (0.4)7.8 (0.4) 89.680.645.4
Month 127.0 (0.9) 2.9 (0.7) 5.1 (0.3) 84.376.051.4
Placebo (N=824)ScreeningData not collectedData not collected 5.4 (0.2)60.2c
Not applicable Not applicable
Enrollment 9.4 (0.9)4.3 (0.5) 5.9 (0.2)88.6 Not applicableNot applicable
Month 1 12.2 (1.2)4.7 (0.5) 8.0 (0.4)87.681.3 52.9
Month 610.6 (1.0)4.7 (0.5)8.2 (0.4)87.280.4 47.1
Month 12 7.8 (0.9)3.6 (0.7) 5.8 (0.3)88.8 77.956.5
*none of the differences between the study groups were statistically significant.
bestimated based on self-reported adherence data.
cestimated as % of condom use in the last vaginal sex at screening.
Table 3. Incidence of HIV, Gonorrhea and Chlamydial Infection by Treatment Group.
Hazard Ratio (95% CI)
HIV746 599101.7 760609 132.1 0.8 (0.3, 1.8)
Gonorrhea 67353337 6.9679 529529.8 0.7 (0.5, 1.1)
Chlamydia673547152.7686553 22 4.00.7 (0.4, 1.3)
Gonorrhea or Chlamydia670522 50 9.6675521 6412.3 0.8 (0.5, 1.1)
Pregnancy746531 15629 760541 15228 1.05 (0.8, 1.3)
*per 100 woman-years.
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including bacterial vaginosis and genital pruritus - the two most
common reproductive system disorders - were generally the same
among study groups (Table 4). Most of the adverse events were
mild and resolved with no sequelae. Rates of reported intermen-
strual bleeding were similar between groups.
Early termination of the trial compromised our ability to draw
definitive conclusions about the effectiveness of CS. However, our
final HIV result (HR=0.8, 95% CI 0.3–1.8) was inconsistent with
the size of the interim effect of a parallel trial conducted by
CONRAD that led to premature closure of both CS studies
(estimated HR=2.2)  as well as with the direction of the final
ITT result from that study (HR 1.6; 95% CI 0.9–3.0).  If CS is
indeed associated with increased risk of HIV, it may be so only at
high rates of gel use like those reported in two of the CONRAD trial
sites (mean of more than 20 times per week in Uganda and Benin),
 compared to only 8 per week on average in the Nigeria trial.
The potential for extremely high frequencies of gel use in some
populations may indicate the need for Phase I safety studies that go
beyond the standard once- or twice-daily application for 14 days.
Vaginal douching was reported at baseline by 70% of the study
participants in Nigeria. If CS does increase risk of acquiring HIV,
one could argue that vaginal cleansing might have removed the gel
and masked any ill effects in the Nigeria trial. However, all study
participants were instructed not to douche after gel application
and sex, and douching was only reported to have taken place at
6% of recorded follow-up visits.
Self-reported condom use was considerably higher during the
trial than at screening. While this may be entirely due to social
desirability bias, it may also suggest that our counseling messages,
among other factors, modified the sexual behavior of participants,
which could in turn explain the lower than expected incidence of
HIV in both treatment groups. Although effective risk reduction
counseling and condom promotion has positive public health
implications, substantially larger study sizes may be required to
achieve adequate numbers of HIV endpoints in a clinical trial.
Although less than expected when designing the study, the
overall incidence of HIV of 1.9 per 100 woman-years was
relatively high considering that the overall prevalence of HIV in
Nigeria does not exceed 6% . For comparison, Padian et al.
reported an HIV incidence of 2.7 per 100 woman-years in
Zimbabwe , a country where the HIV epidemic is more
generalized and national adult HIV prevalence exceeds 15% .
Targeting women at highest risk of HIV took a heavy toll on study
retention however: we compromised our follow up rates by
recruiting young women at highest risk of HIV infection,
residential mobility, and poor compliance with the protocol
procedures. Despite the rigorous efforts of in-country study teams,
one third of participants in each group were lost.
Since rates of loss to follow-up were non-differential between the
two study groups, and since baseline characteristics of women who
were lost to follow-up were similar between the CS and placebo
group (data not shown), there is no evidence that our estimate of
treatment effect was biased. Nonetheless, high loss to follow-up
compromises the interpretation of study findings. The fact that our
retention rates were in line with those reported in similar study
populations emphasizes the challenges associated with performing
clinical research among high risk women in resource poor settings
Although we observed very high pregnancy rates, relatively few
of the pregnancies were carried to term and only 5% of woman-
years of follow-up were off product due to pregnancy. Moreover,
Table 4. Adverse Experiences Reported in at least 5% of Women by Treatment Group.
System Organ Class Category*
CS vs. Placebo
Rate Ratio (95% CI)
Infections and infestations
1.1 (0.9, 1.4)
0.7 (0.5, 1.0)
Nervous system disorders
0.8 (0.6, 1.2)
General disorders and administration site
1.2 (0.8, 1.8)
Respiratory, thoracic and mediastinal disorders
Respiratory tract infection
0.8 (0.6, 1.2)
Reproductive system and breast disorders
1.0 (0.7, 1.3)
Genital pruritus female
1.1 (0.8, 1.6)
0.8 (0.6, 1.3)
0.8 (0.5, 1.3)
0.8 (0.5, 1.3)
*MedDRATMcoding terminology was used for coding adverse events.
**Incidence rate per 100 woman-years.
Randomized Trial of CS Gel
PLoS ONE | www.plosone.org6 November 2008 | Volume 3 | Issue 11 | e3784
excluding data collected after product interruptions did not Download full-text
influence the primary effectiveness result. Thus we have no
evidence that our estimate of treatment effect was confounded by
high pregnancy rates. Nonetheless, preventing pregnancies in
future trials remains an important task in mitigating safety
concerns and ensuring validity of results .
gel (more than 80% of sex acts covered in each group), we estimated
that gel was used for only 50% of acts when a condom was not used.
Had the study continued to the planned total of 66 endpoints, such a
level of adherence would have seriously compromised the power to
detect an effect of CS. Given the strong contraceptive profile of CS
, the lack of an observed difference in pregnancy rates between
groups is disappointing, and provides additional evidence of possible
poor adherence to study product. Previously reported differential use
of prevention methods with different partner types  might
account for the overall low use of gel among acts without condoms.
As we did not collect information on partner type, this question
Strengths of our trial included accurate detection of incident
infections, as well as close monitoring and proactive management of
the recruitment facilitated by remote data entry. Unfortunately the
early closure of the trial, poor retention, and possible low adherence
impaired our ability to detect an effect – positive or negative - of CS.
The trial highlighted many of the challenges associated with the
evaluation of candidate microbicides, but we hope that the
methodological lessons learned and knowledge gained in Nigeria
will be useful to researchers planning future HIV prevention trials.
Found at: doi:10.1371/journal.pone.0003784.s001 (0.06 MB
Found at: doi:10.1371/journal.pone.0003784.s002 (1.21 MB
We thank all study participants for entrusting their safety to us; the CS
teams in Lagos and Port Harcourt for their continuous dedication to the
project; the senior management of the Teaching Hospital, University of
Port Harcourt, and the College of Medicine, University of Lagos, for their
on-going support of the study; Stephanie Horn for the administrative
management of the trial; Vivian Bragg and Nicole Roberge for clinical
monitoring; Grace Wilson, Wes Rountree, Erik Jolles and Lisa Saylor for
managing the data; Suzanne Fleming for regulatory assistance; John
Preisser, Steven Meshnick, and Evan Myers for their work on the
independent data monitoring committee; Ronald Roddy for the innovative
study design; our colleagues at CONRAD for submitting the IND,
reporting to the U.S. Food and Drug Administration and reviewing the
manuscript; Be ´ne ´dicte De Deken, Vicky Cuylaerts and Hilde Smet at
Institute of Tropical Medicine for SDA and HIV PCR testing; Elizabeth
Raymond for her scrupulous work to ensure the safety of the study
participants and review of the manuscript.
Conceived and designed the experiments: VH DT TC. Performed the
experiments: FO OObunge JUO SO. Analyzed the data: VH CHW NO
OOduyebo DT TC SA. Wrote the paper: VH CHW DT. Provided overall
supervision of the trial: VH. Interpreted the data: FO OObunge NO
OOduyebo TC. Critically revised the paper for important intellectual
content: FO OObunge NO OOduyebo TC. Supervised all aspects of the
trial in Lagos: FO. Reviewed, approved and takes responsibility for the
manuscript: FO OObunge NO OOduyebo LM NM JUO SO TC SA.
Supervised all aspects of the trial in Port Harcourt: OObunge. Acquired
and facilitated management of the data: LM NM JUO SO SA. Monitored
the fieldwork: LM NM. Trained site staff: LM. Coordinated all site staff:
JUO SO. Led data querying and cleaning efforts: JUO SO.
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PLoS ONE | www.plosone.org7November 2008 | Volume 3 | Issue 11 | e3784