# Evaluation of doxycycline post-exposure prophylaxis to reduce sexually transmitted infections in PrEP users and HIV-infected men who have sex with men

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2021 · $1,431,796

## Abstract

Abstract
Sexually transmitted infections (STI) rates are at an all-time high in the US, with striking increases of gonorrhea
(GC), chlamydia (CT), and syphilis among men who have sex with men (MSM). Pre-exposure prophylaxis (PrEP)
against HIV is increasingly being used by at-risk MSM populations in the US; remarkably, this population has
bacterial STI incidence rates as high as >50% per year. MSM living with HIV are also disproportionately impacted
by STIs, with high incidence and reinfection rates of syphilis, 50% higher rates of GC and 30% higher rates of
CT compared to MSM without HIV. These data highlight the pressing need for innovative and effective strategies
to reduce STIs in high-risk MSM, both those living with HIV and HIV-negative MSM taking PrEP. One potential
STI control strategy is post-exposure prophylaxis (PEP) with doxycycline. This strategy demonstrated efficacy
in a recent randomized open-label trial in 232 HIV-negative MSM on event-driven PrEP in France (IPERGAY
study). Doxycycline PEP resulted in a 47% relative reduction in new bacterial STIs (GC, CT, or syphilis), with
rare adverse events and no difference in self-reported sexual behavior between arms. However, IPERGAY
participants were older, mostly Caucasian and college educated, and highly adherent to event driven PrEP (as
opposed to daily PrEP, the US norm). Thus, the results of the IPERGAY doxycycline PEP study may not reflect
the advantages and risks of this strategy in diverse populations, including MSM living with HIV, whose adherence,
sexual practices, and sexual networks may differ from HIV-uninfected MSM. Furthermore, a previously
unexplored and important concern about doxycycline PEP is selection of antibiotic resistance among the target
bacterial STI pathogens, colonizing bacteria that can cause disease (e.g., Staph aureus), commensal Neisseria
spp which could transmit tetracycline (TCN) resistance genes to GC, and in the gut microbiome which may serve
as a reservoir of transmissible TCN resistance to colonic microbiota. Based on the IPERGAY data, doxycycline
PEP appears to be a promising innovative strategy to address the STI epidemic, particularly among higher risk
MSM with a history of STIs and condomless sex. A sufficiently-powered, high-quality study is needed to evaluate
the effectiveness in both MSM living with HIV and MSM on PrEP and the impact on drug resistance in the target
bacterial STIs and normal host microbiota. We propose a randomized open label trial to assess the effectiveness
of doxycycline PEP and impact on antibiotic resistance in 380 MSM living with HIV and 380 MSM on PrEP at
public health clinics in San Francisco and Seattle. Our Specific Aims are to: 1) Evaluate the effectiveness,
tolerability, acceptability, and adherence profile of doxycycline PEP to reduce STI incidence among MSM
taking PrEP or living with HIV. 2) Assess the effect of doxycycline PEP on selection of tetracycline
resistance in Neisseria gonorrhoeae, Staphylocccus aureus...

## Key facts

- **NIH application ID:** 10129262
- **Project number:** 5R01AI143439-03
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** CONNIE L CELUM
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $1,431,796
- **Award type:** 5
- **Project period:** 2019-04-12 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10129262

## Citation

> US National Institutes of Health, RePORTER application 10129262, Evaluation of doxycycline post-exposure prophylaxis to reduce sexually transmitted infections in PrEP users and HIV-infected men who have sex with men (5R01AI143439-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10129262. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*