The missing partner in recurrent bacterial vaginosis
In 2025, a randomized trial published in NEJM (StepUp) found that treating the male partner — with antibiotics — reduced BV recurrence in women. We are working on the next question: whether a similar effect can be achieved without antibiotics.
This is a hypothesis. It has not been tested, and we have no product on the market.
BV keeps coming back
Bacterial vaginosis (BV) is one of the most common vaginal conditions in women of reproductive age. Antibiotics usually clear an episode, but recurrence is common: in the control arm of the StepUp trial, where only the woman was treated, 63% of women (43 of 68) had BV again within 12 weeks.
Standard care treats only the woman. A growing body of research suggests that BV-associated bacteria are shared between sexual partners, and that the male partner may be part of why BV returns.
Evidence on the male partner
StepUp: treating the partner reduced recurrence
In monogamous couples in Australia, treating the male partner with oral metronidazole plus topical 2% clindamycin cream for 7 days reduced BV recurrence within 12 weeks from 63% (43/68) to 35% (24/69); hazard ratio 0.37 (95% CI 0.22–0.61). The trial was stopped early for benefit. It tested antibiotics, not any non-antibiotic approach.
Earlier trials were not conclusive
Earlier partner-treatment trials, mostly using oral antibiotics, did not show a clear reduction in recurrence. StepUp also applied treatment directly to the penile skin.
The male genital microbiome and BV in his partner
Cohort studies in Kisumu, Kenya, found that the composition of a man's penile microbiome predicted incident BV in his female partner. In the Rakai, Uganda, circumcision trials, female partners of circumcised men had a lower prevalence of BV. These studies show association, not cause.
Our working hypothesis
Changing the male genital environment without antibiotics may reduce BV recurrence in the female partner. None of the studies above tested this. Our development program exists to test it.
Science →Two lines of work
Product development
We are selecting candidates for a non-antibiotic, partner-applied approach and designing the first study in couples. We are looking for investors, industry partners and a scientific co-founder.
For investors & partnersIndependent academic research
We support academic research on the male genital microbiome, including ADJUNCT-SYPH, a pilot study in preparation with partners in Rakai, Uganda (not yet funded; pending ethics review). Research partners keep full rights over data and publication.
ResearchMeet us at the Microbiome Times Partnering Forum USA
Manuel Becerril, our founder, will be at the South San Francisco Conference Center. Request a meeting through the partnering platform or write to research@circunaro.com.
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