Feasibility, safety and tolerability of estrogen and/or probiotics for improving vaginal health in Canadian African, Caribbean, and Black women: A pilot phase 1 clinical trial

Abstract

Background: A dysbiotic vaginal microbiome (VMB) is associated with clinical conditions such as bacterial vaginosis (BV) and an increased risk of human immunodeficiency virus (HIV-1) infection. Considering the high prevalence of BV among African, Caribbean and Black (ACB) women, we conducted a prospective, randomized, open-label phase 1 clinical trial to determine the feasibility, safety and tolerability of administering low-dose estrogen, probiotics or both in combination to improve vaginal health and decrease HIV-1 susceptibility.

Methods: ACB women aged 18-49 from the Greater Toronto Area (GTA) were randomized to one of four study arms: intravaginal estradiol (Estring©; 7.5mg/day); a vaginal probiotic (RepHresh™ Pro-B™) administered twice daily; a combination of Estring© and vaginal RepHresh™ Pro-B™ (twice daily); or the Estring© and oral RepHresh™ Pro-B™ (twice daily), for a duration of 30 days. Feasibility was evaluated through enrolment, retention, and adherence rates, while safety and tolerability were determined by a pre- and post-treatment blood panel and reported adverse events (AEs).

Results: Overall, 63 ACB women were screened, 50 were enrolled and received the intervention while 41 completed the study, resulting in 80% enrollment and 82% retention rates. Overall adherence to the study protocol was high at 93%, with an adherence of 92% for RepHresh™ Pro-B™ and 97% for Estring©. A total of 88 AEs were reported by 29 participants which were mild (66/88; 75%) and largely resolved (82/88;93%) by the end of the study, with no serious AEs (SAEs) noted. In addition, a panel of safety blood markers measured pre- and post-intervention confirmed no clinically significant changes in blood chemistry or blood cell count.

Conclusion: Overall, the administration of intravaginal estrogen and/or probiotics in pre-menopausal ACB women is feasible, safe, and well tolerated.

Trial registration: The trial was registered with Clinicaltrials.gov (NCT03837015) and CIHR HIV Clinical Trials (CTN308).

Fig 1. Participant flowchart.

A flow diagram outlining study recruitment and completion rates. A total of 63 women were assessed for eligibility and 50 women received intervention. One woman was lost to follow up, four withdrew consent and an additional four were non-adherent to the study protocol. Overall, 41 women completed the study with group sizes between 9–13 participants for each study arm.

Fig 2. Study design.

This schematic outlines the design and study timeline used to evaluate the feasibility, safety and tolerability of administering low dose estrogen and/or a probiotic to premenopausal African, Caribbean, and Black (ACB) women. Eligible participants were randomized in a 1:1:1:1 ratio to receive one of four interventions including 1) the Estring alone 2) the Estring in combination with the probiotic L. rhamnosus GR-1 and L. reuteri RC-14 RepHresh Pro-B (administered vaginally), 3) the Estring together with the RepHresh Pro-B (administered orally) or the RepHresh (administered vaginally) alone. The duration of the intervention was 30 days with a 7-day follow up (visit 5) safety check. The study was designed to compare outcomes in each woman at baseline (visit 2) to the end of treatment (visit 4) with each participant serving as their own control.

Fig 3. Intervention protocol adherence.

Adherence was determined for Estring and probiotic intervention protocols (IP) both individually and overall. The bar plots indicate adherence for all participants who received the intervention including those who prematurely terminated the study. Women who did not complete the protocol were considered as nonadherent and assigned a value of zero. Each data point represents a participant, and the bars depict the median ± IQR. A. Overall participants showed a high adherence to the study protocols regardless of the study. B-C. Similarly, participants demonstrated high adherence for both Estring and probiotic administration with no significant differences observed between intervention type or route of probiotic administration.

Fig 4. Adverse events (AEs).

A total of 88 AEs were reported by 37 participants for each intervention. This bar plot summarizes the types of AEs based on their reported frequency and intensity. AEs reported with a mild intensity are represented in green while a moderate intensity is indicated in orange and severe AEs are highlighted in red. The number of reports according to event type is outlined based on the frequency of reports. Most reported AEs were mild (66/88; 75%), with only 7% (6/88) showing a severe intensity and no serious AEs (SAEs) reported. Vaginal irritation/itching/burning followed by cramps/abdominal pain were the most frequently reported AEs. In additional most AEs were short lived and non-recurring with 7% (6/88) ongoing after study completion.

Fig 5. Safety blood markers.

Blood collected at baseline (visit 2) and at the end of the intervention (visit 4) was used to measure metabolic, lipid and complete blood count panels pre and post intervention to evaluate safety. The safety blood marker panel consisted of 12 markers depicted by representative dot plots to monitor changes in health. Each data point is representative of a participant which has a paired sample taken at visit two and four. The four colours black, orange, blue, and red in each graph represent the treatment arm of each participant. In addition, the dotted lines in each graph indicate the clinically relevant thresholds representative of a healthy reference range for each safety marker. Overall, no clinically significant change was observed pre and post intervention suggesting that 30 days of the Estring© and/or probiotic RepHresh™ Pro-B™ does not induce changes to overall health. Moreover, the data is evenly distributed across intervention arms and thereby does not indicate an association to the type of intervention.