CAPRISA 004, a two-arm, double-blind, randomized, placebo-controlled trial, was conducted from May 2007 to March 2010. Women were enrolled at an urban and a rural clinic in KwaZulu-Natal, South Africa, but the study was not designed to assess the effectiveness of tenofovir in each clinic separately. Urban women were enrolled at the CAPRISA eThekwini Research Clinic, adjacent to an STI clinic located in the Durban city centre. Rural women were enrolled at the CAPRISA Vulindlela Research Clinic, adjacent to a comprehensive primary health care clinic in Vulindlela, a rural community of approximately 90,000 people, about 150km north-west of Durban. Prior to the CAPRISA 004 trial, feasibility studies were conducted to assess HIV incidence and sexual behavior at both sites. Extrapolated HIV incidence rates from prevalence studies in the urban (19
) and rural (20
) sites were 15.6% and 11.2% respectively. Reported anal sex rates were substantially lower at these two sites than we had observed in previous microbicide trials (21
) in female sex workers in this region. Data from these feasibility studies were used as the basis for selecting these sites for the trial as well as for the design and sample size calculations for the CAPRISA 004 trial.
HIV negative women, from 18 to 40 years, who were sexually active (defined as having engaged in vaginal sex at least twice in the 30 days prior to screening), not pregnant, and using a non-barrier form of contraceptive were eligible for enrolment. Participants who had a history of adverse reactions to latex, planned to either travel away from the study site for more than 30 consecutive days, relocate away from the study site, become pregnant, or enroll in any other behavioral or investigational product study were excluded. Participants who had a creatinine clearance <50ml/min, (22
), had evidence of genital deep epithelial disruption, had in the past year participated in any research related to any vaginally applied product/s, or had an untreated STI or reproductive tract infection were also excluded. Women who met eligibility criteria and demonstrated adequate understanding of the trial (through a comprehension checklist) were enrolled after providing written informed consent. From May 2007 to January 2009, 2160 women were screened, 1085 were enrolled, of whom 889 were included in the analysis (). Further information on the enrollment process and exclusions can be found in SOM
Screening, enrolment, randomization and follow-up of the study participants in the CAPRISA 004 tenofovir gel trial.
Enrolled women were randomly assigned in equal proportions to one of two study arms; tenofovir gel or placebo gel. Tenofovir gel comprised 40mg of 9- [(R)-2-phosphonomethoxy)propyl]adenine monohydrate (PMPA) in a solution of purified water with edetate disodium, citric acid, glycerin, methylparaben, propylparaben, and hydroxyethycellulose (HEC). The placebo gel was the “universal” HEC placebo gel which has been shown to have minimal anti-HIV activity (23
). Tenofovir and placebo gels appeared identical and were dispensed in the same pre-filled vaginal applicators with identical packaging.
A coitally-related dosing strategy was selected to achieve high adherence, based on in-depth consultations with the communities involved. Sexual behavior data showed that women in the key study population had infrequent high-risk sex with migrant partners. Monkey challenge data and perinatal transmission studies informed the timing of doses in relation to sex. The “before and after” sex doses were modeled on the timing of nevirapine in its proven strategy for preventing mother-to-child HIV transmission (24
). Women were requested to insert one dose of gel within 12 hours b
efore sex and a second dose of gel as soon as possible within 12 hours a
fter sex and no more than t
wo doses of gel in a 24
-hour period. Hence the dosing strategy is referred to as “BAT24”. The latter restriction was imposed due to the lack of human safety data on more than two doses of gel per day.
Gel adherence was defined as the estimated proportion of reported sex acts covered by two gel doses and calculated for each woman by dividing half the number of returned used applicators each month by the number of reported sex acts that month. Applicators that were not returned were regarded as unused for the purposes of calculating adherence. When we conducted a sensitivity analysis treating unreturned applicators as used, the results did not change materially. The median of each woman's monthly adherence estimates was assigned as her overall gel adherence. This approach assumed that every reported sex act utilized two doses of gel. While this assumption was not always applicable, adjusting for multiple sex acts within 24 hours made no material difference.
At enrolment and monthly follow-up visits, participants were provided with comprehensive HIV prevention services (HIV pre- and post-test counseling, HIV risk reduction counseling, condoms, and STI treatment), reproductive health services, and assigned study gel.
Participants were requested to return their used (from October 2007 onwards) and unused applicators at every visit. Each month the applicators returned by women as used and unused were counted, reconciled against number dispensed, and thereafter discarded, in accordance with standard requirements for medical waste.
A comprehensive adherence support program assisted participants with the mechanics of applicator use, timing and dosing, avoidance of gel sharing, and incorporation of gel use into their daily routines. From October 2008, individualized, motivational interviewing (25
) was introduced to assist participants to overcome obstacles to gel use and set goals for optimal adherence in the upcoming month. This included individualized adherence support and counseling, customized on the previous month's experience of gel use, which was provided throughout the study. The women in this study were specifically and repeatedly counseled to only use the gel vaginally and the lack of safety with rectal use was highlighted.
Each participant had monthly HIV and urine pregnancy testing (QuickVue One-Step hCG Urine Test Quidel Corporation, San Diego, USA) performed before gel was dispensed. Due to a lack of pregnancy safety data, gel use was temporarily discontinued after a positive pregnancy test and resumed when the pregnancy test returned to negative. Self-reported data on gel use and sexual frequency during the last 30 days were collected at monthly visits, together with gel and condom use on the day of the last sex act, by means of a brief interviewer-administered questionnaire. Two months after study exit, participants attended a post-trial visit to assess HIV status and safety after product withdrawal.
Drug safety was assessed at every study visit by evaluating, grading and recording adverse events experienced by participants. Participants underwent quarterly pelvic examinations and, if needed, colposcopy. Serology was performed for hepatitis B virus (Abbott Architect C8200, Abbott Laboratories, Detroit, MI) and herpes simplex type 2 virus (Kalon Enzyme Immunoassay, Kalon Biologicals, Ashgate, UK). Hematological, hepatic and renal abnormalities were assessed at study months 3, 12 and 24, additionally when clinically indicated, and at study exit. Adverse events were graded for severity via the Division of AIDS Table for Grading Adult and Pediatric Adverse Events, 2004. Product use was temporarily discontinued for an adverse event at the discretion of the study clinician. The trial (NCT00441298) was approved by the University of KwaZulu-Natal's Biomedical Research Ethics Committee (E111/06), Family Health International's Protection of Human Subjects Committee (#9946) and the South African Medicines Control Council (#20060835).