A Trial to Compare Antibacterial vs. Placebo Mouthwash to Reduce the Incidence of Sexually Transmitted Infections (STIs) in Men Who Have Sex With Men (MSM) Taking HIV Pre-Exposure Prophylaxis (PrEP)

Study Overview
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Brief Summary
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The study involves a randomized placebo controlled trial that aims to assess if a mouthwash (Listerine cool mint, LCM) is able to reduce the cumulative incidence of gonorrhoea (Ng), chlamydia (Ct) and syphilis in men who have sex with men and receiving preexposure prophylaxis (PrEP) at the Institute of Tropical Medicine (ITM).

Detailed Description
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The study aims to assess if there is a difference in the incidence rate of gonorrhea, chlamydia and syphilis detected at any site whilst individuals are on daily and pre/post sex Listerine cool mint (LCM) vs. placebo mouthwash. The study has a double-blind, cross-over design, in which subjects will be screened at the ITM and, if eligible, will be enrolled and randomized to group 1 (LCM) or group 2 (placebo). After 3 months, a crossover will occur and subjects will switch to the other intervention. Each participant will therefore be enrolled for 6 months (2 x 3 months, no wash out period). Subjects will be recruited from the existing PrEP cohort at the Institute of Tropical Medicine Antwerp. A total of 320 subjects will be recruited (160 in each arm).

Official Title
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A Double-blind Single Center, Crossover, Randomized Controlled Trial of Antibacterial vs. Placebo Mouthwash to Reduce the Incidence of Gonorrhea/Chlamydia/Syphilis in MSM Taking HIV Pre-exposure Prophylaxis (PrEP)

Conditions
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Sexually Transmitted Diseases

Intervention / Treatment
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* Other: Mouthwash with LCM
* Other: Mouthwash with placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Men aged 18 or more Enrolled in Belgian PrEP program at ITM Has had sex with another man in the previous year Has had a symptomatic or asymptomatic STI (Ct/Ng/syphilis) in the previous 2 years Willing to be enrolled in the cohort for 6 months and attend 3 monthly follow up visits Willing to comply with the mouthwash study schema and willing to ask their casual partners to mouthwash pre- and post-sex Prepared to fill out the online diary once a week Able and willing to provide written informed consent Exclusion Criteria: Currently using a mouthwash and unwilling to cease use of this mouthwash Enrolment in another interventional trial Tests HIV positive at screening

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: LCM, then placebo<br>Mouthwash with LCM for 3 months followed by mouthwash with placebo for 3 months. | Other: Mouthwash with LCM<br>* Subjects will mouthwash daily with LCM and before/after sex<br>Other: Mouthwash with placebo<br>* Subjects will mouthwash daily with placebo and before/after sex<br>|
| Experimental: Placebo, then LCM<br>Mouthwash with placebo for 3 months followed by mouthwash with LCM for 3 months | Other: Mouthwash with LCM<br>* Subjects will mouthwash daily with LCM and before/after sex<br>Other: Mouthwash with placebo<br>* Subjects will mouthwash daily with placebo and before/after sex<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Patient Counts of Ng Plus Ct Plus Syphilis in Each Study Arm for Each Period | The sum of new diagnoses of Gonnorhea (Ng), Chlamydia (Ct) and syphilis in a 3 month period on LCM/placebo. Each participant can only contribute one diagnosis of Ct and one diagnosis of Ng per visit - regardless of number of sites infected. Thus each participant can contribute up to 3 diagnoses (Ct/Ng/syphilis) at each visit. The diagnosis of Ng and Ct will be made via molecular testing and syphilis via Rapid Plasma Reagin test (RPR) and Treponema Pallidum Antibodies tests (TPA) according to currently used European case definitions. | 3-month period following each intervention | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Difference in Incidence Rate of Pharyngeal Ng Between Each Study Arm for Each Period | Incidence rate of new pharyngeal Ng cases in each allocation arm for each study period of 3 months. | 3-month period following each intervention | 
| Difference in Incidence Rate of Ct (Combined Pharyngeal, Urethral and Rectal) Between Each Study Arm for Each Period | Incidence rate of new Ct cases in each allocation arm (LCM and placebo) for each study period of 3 months. | 3-month period following each intervention | 
| Difference in Incidence Rate of Syphilis Between Periods on LCM vs. Placebo | Incidence rate of new syphilis cases in each allocation arm (LCM and placebo) for each study period of 3 months. | 3-month period following each intervention | 
| Proportion of Days That Mouthwash is Used on a Daily Basis and Proportion of Casual Sex Contacts When Mouthwash is Used Pre or Post Sex | Daily: Proportion of days in study used mouthwash at least daily Post sex: Proportion of casual sexual contacts in study when mouthwash used post sex. Pre sex: proportion of casual sexual contacts in study when mouthwash used pre sex | 6-month period | 
| Difference in Incidence Rate of Ng Plus Ct Plus Syphilis Between LCM and Placebo After Controlling for Adherence With Daily and Pre/Post Sex Mouthwash | Incidence rate of Ng, Ct and syphilis between both groups (LCM and placebo) post controlling for adherence to mouthwash | 3-month period following each intervention | 
| Difference in Cumulative Numbers of Antibiotics Used Between Periods on LCM vs. Placebo | Cumulative number of antibiotics used between both groups (LCM and placebo) for each period | 3-month period following each intervention | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Gonorrhea, Syphilis, Chlamydia, Listerine, STI