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HomeHIV ResearchDoxycycline slashes STI risk among MSM, trans women – US study

Doxycycline slashes STI risk among MSM, trans women – US study

New studies presented at AIDS 2022, the 24th International AIDS Conference (29 July-2 August) hosted by IAS – the International AIDS Society – demonstrated promising advances in the global HIV response.

Speaking at a virtual press conference, authors shared various insights with their colleagues and others, one being the successful results from a trial of the antibiotic doxycycline to prevent sexually transmitted infections (STIs).

The researchers found that doxycycline significantly reduces risk of STIs after condomless sex by 65%.

The DoxyPEP study found that taking 200mg of doxycycline within 72 hours of condomless sex significantly reduces the risk of gonorrhoea, chlamydia and syphilis among men who have sex with men and trans women. Among those randomised to take doxycycline, 65% fewer were diagnosed with an STI each quarter than those not taking doxycycline.

Participants in the study were male sex at birth, living with HIV or taking HIV pre-exposure prophylaxis (PrEP), and had a history of an STI and condomless sex with a male partner within the past year. They were randomised 2:1 to take open-label doxycycline after condomless sex versus continued standard of care without doxycycline.

Among the 327 participants taking PrEP, there was a 66% reduction in new STIs per quarter (doxycycline 10.7% versus control 31.9%, p<0.001). Of the 174 participants living with HIV, there was a 62% reduction per quarter with doxycycline (11.8% vs 30.5%, p<0.0001). Participants reported taking doxycycline 87% of the time after condomless sex; 54% reported taking fewer than 10 doses per month, 30% took 10-20 doses per month, and 16% took more than 20 doses per month. No serious or >Grade 2 adverse events were attributed to doxycycline.

Analyses of the impact of intermittent doxycycline on antimicrobial resistance and the gut microbiome are ongoing.

The DoxyPEP study was stopped early in May 2022 when a planned interim analysis showed that those randomised to take doxycycline had substantially fewer STIs.

Co-principal investigator Annie Luetkemeyer, Professor of Medicine at Zuckerberg San Francisco General Hospital at University of California, San Francisco, noted that doxycycline taken after sex is a promising prevention strategy for populations disproportionately impacted by high rates of STIs.

“DoxyPEP represents an important advance in reducing STIs within two vulnerable populations – men who have sex with men and transgender women,” she said. “I look forward to learning more about the implementation of this prevention measure and any long-term effects of using antibiotics for STI prevention.”

The trial was funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. It was conducted at the HIV clinic at Zuckerberg San Francisco General Hospital and the San Francisco City Clinic, both part of the San Francisco Department of Public Health, and the Madison Clinic and the Sexual Health Clinic at Harborview Medical Centre, both at the University of Washington.

Abstract, session and study details:

Doxycycline post-exposure prophylaxis for STI prevention among MSM and transgender women on HIV PrEP or living with HIV: high efficacy to reduce incident STI's in a randomised trial

A. Luetkemeyer, J. Dombrowski, S. Cohen, D. Donnell, C. Grabow, C. Brown, C. Malinski, R. Perkins, M. Nasser, C. Lopez, S. Buchbinder, H. Scott, E. Charlebois, D. Havlir, O. Soge, C. Celum.

With a sexually transmitted infection (STI) epidemic among men who have sex with men(MSM) and transgender women(TGW), interventions to reduce STIs are needed.

DoxyPEP is a randomised open-label trial among Seattle and San Francisco MSM/TGW living with HIV or on PrEP who had N. gonorroheae (GC), C. trachomatis (CT), or early syphilis in the past year. Randomisation was 2:1 to 200 mg doxycycline hyclate within 72 hours of condomless sex or no doxycycline with STI testing at enrollment, quarterly, and when symptomatic. An independent committee adjudicated STIs. The trial had >80% power to detect a 50% reduction in STI incidence, assuming a 10% quarterly STI incidence. The intent to treat analysis compared relative risk of an STI per quarter. A single interim analysis at ~50% of follow-up time occurred May 2022; the DSMB recommended stopping the control arm based on prespecified efficacy thresholds measured independently in PLWH and PrEP cohorts.

Of 554 enrolled, 360 were on PrEP, 194 PWLH, 65% white, 8% black, 10% Asian, 30% Latinx. 19 (3%) identified as TGW or nonbinary. Median sex partners in past 3 months was 9. In the past year 67% had GC, 58% CT, 20% syphilis; at enrollment, 18% had GC, 10% CT, 2% syphilis . Among 360 on PrEP, 65 STI endpoints (29.5%) occurred in controls and 47 (9.6%) in doxyPEP participants (RR 0.33; 95%CI 0.23-0.47; p<0.0001). Among 194 PLWH, 30 STI endpoints (27.8%) in controls and 31 (11.7%) in doxyPEP participants (RR 0.42; 95% CI 0.25-0.75; p=0.0014). GC, CT, and syphilis were each reduced. No serious or '¥ Grade 2 AEs were attributed to doxycycline.

Doxycycline 200 mg taken within 72 hours after condomless sex significantly reduced STIs in MSM/TGW. Effects on antimicrobial resistance, gut microbiome, and sexual behavior are being assessed as important considerations for this STI prevention strategy.


AIDS 2022 presentation (Open access)


See more from MedicalBrief archives:


More than 1m new curable STIs reported worldwide every day


Experimental STI prophylaxis in PrEP users


Self-sampling for STIs in rectum and throat just as accurate


WHO updates recommendation for PrEP as HIV prevention option for MSM


End of USAID funding puts MSM programme at risk



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