CROI 2025 Abstract eBook

Abstract eBook

Poster Abstracts

Conclusions: DoxyPEP was well accepted within routine PrEP care, significantly reducing STI incidence with good tolerance. Our data show its efficacy and safety in real-world settings. The emergence of MRB or resistant NG was not observed. However, its impact on bacterial resistance and microbiota requires further evaluation. 1276 Doxycycline Post-Exposure Prophylaxis Continuum of Care Among MSM in Philadelphia, 2023 Tanner Nassau, Kathleen Brady Philadelphia Department of Public Health, Philadelphia, PA, USA Background: Doxycycline post-exposure prophylaxis (Doxy-PEP) is an effective tool for reducing bacterial sexually transmitted infection (STI) incidence among men who have sex with men (MSM). We sought to understand current rates of bacterial STIs (gonorrhea, chlamydia, syphilis) among MSM and generate Philadelphia’s first doxy-PEP continuum among MSM. Methods: We used 2023 National HIV Behavioral Surveillance data collected through venue-based sampling among MSM in Philadelphia, with Philadelphia specific local questions around the doxy-PEP continuum. We used Chi-square and Fisher’s exact tests to compare differences in demographics at each step of the doxy-PEP continuum. We also describe reported reasons for not wanting to take doxy-PEP. Results: Of the 452 eligible respondents, 326 (72.1%) answered questions on doxy-PEP and were included in analyses. One in four (25.8%) MSM reported being diagnosed with a bacterial STI in the previous 12 months. Slightly more than one-third (n=119; 36.5%) of all MSM had heard of doxy-PEP, 12.6% had discussed doxy-PEP with a provider, and 5.5% had used doxy-PEP in the previous 12 months. Knowledge of doxy-PEP was significantly greater among those with more than a high school education and a recent gonorrhea or chlamydia diagnosis, compared to those with a high school education or less and those without a recent gonorrhea or chlamydia diagnosis, respectively. Discussing doxy-PEP with a provider was associated with having been recently tested for STIs (p=0.027), recently diagnosed with gonorrhea or chlamydia (p<0.001 for both), and being on HIV PrEP (p=0.047). Interest in doxy-PEP was significantly greater among non-Hispanic White MSM (81.5%) (compared to both non-Hispanic Black (63.5%) and Hispanic/Latino (52.4%) MSM), as well as those with a recent gonorrhea or chlamydia diagnosis. Among those uninterested in doxy-PEP, the most frequently reported reasons were not feeling like they need doxy-PEP (45.2%), needing more information (30.1%), and concern about side effects or feeling sick (11.8%). Conclusions: Doxy-PEP awareness among MSM is low and few providers are discussing doxy-PEP as an option with their patients with recent bacterial STIs. Given the high level of interest in doxy-PEP among MSM, developing and distributing clear, culturally competent doxy-PEP guidance for providers has the potential for significantly increasing doxy-PEP awareness and uptake among MSM.

this, paired with exposure to asymptomatic STIs from partners, exacerbates risks of transmission. MSM, perceiving marginalization within health services, typically limit STI symptom-reporting essential for initiation of treatment algorithms. Diagnostic STI testing and management are therefore critical to an effective STI prevention response, which in turn is essential for preventing HIV/ STI acquisition and re-infection. Methods: We conducted a 12-month, randomized crossover study (July 2022 June 2024) where MSW and MSM in Cape Town and Johannesburg, South Africa were administered three bimonthly gluteal placebo injections and at crossover, a six-month placebo subdermal implant each, as proxies for long-acting PrEP delivery modalities. At screening, Months 6, 12, and when indicated, clinical assessments included collection of urine and blood samples for HIV (Ag/ Ab rapids); syphilis (RPR/TPHA); Chlamydia trachomatis (CT) and Neisseria gonorrhea (GC) testing (GeneXpert). Men testing HIV-positive were referred for ART services and those with GC/CT/syphilis were treated on-site. Partner notification cards for accessing treatment were offered. Results: We screened 251 potential participants, of whom 184 were enrolled (median age 22, IQR 22-27). Men had a median of three sex partners in the past six months (IQR 2-5). Baseline testing identified 22 prevalent HIV infections (8.8%), 24 syphilis, 33 CT and 4 GC infections (22.7% prevalence of bacterial STIs [26.9%MSM, 17.9%MSW]). Over 12-months of follow-up, diagnostic testing detected a further six incident HIV infections among MSM, 26 syphilis infections in 15 men (12 MSM, 3 MSW); 24 CT infections in 19 men (6 MSM, 13 MSW), and 9 GC infections among 8 men (2 MSM, 6 MSW). Forty-one enrolled participants experienced at least one lab-diagnosed bacterial STI (22.2% incidence). Conclusions: We found high incidence of HIV and bacterial STIs among both groups of men, with higher incidence of HIV and syphilis among MSM and CT/ GC among MSW. Coinfection and recurring infections, combined with STIs preceding HIV acquisition, reinforce urgency around identifying a more effective STI response for men in South Africa. Innovative diagnostic and treatment strategies including use of testing paired with expedited partner therapy need further exploration. 1275 Postexposure Prophylaxis With Doxycycline (Doxy PEP) in a Cohort of High-Risk MSM: The PRIDOX Study Background: Clinical trials have shown high efficacy of doxycycline as STI preventive strategy, but real-world data are limited. We aimed to assess the impact of DoxyPEP on Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG) and syphilis (SPL) incidence in a high-risk MSM cohort in a real-world setting. Methods: PrEP users at our clinic, meeting high STI risk criteria similar to DOXYVAC and DoxyPEP trials, were offered DoxyPEP. This analysis includes PrEP users who initiated DoxyPEP between March/23 and August/24. The pre-DoxyPEP period was from PrEP initiation to DoxyPEP beginning, and the post-DoxyPEP period from DoxyPEP start to 30/August/24, or discontinuation. Participants were tested for CT/NG at baseline, every follow up visit and when symptomatic by PCR from pharynx, rectum, and urine, and serology test for SPL. NG cultures were also conducted. Multidrug-resistant bacteria (MRB) cultures from nasal and rectal samples were performed at DoxyPEP initiation and at week 48. The incidence of the first CT, NG, and SPL episode was compared between periods using Cox proportional hazard models. Statistical analysis: SPSS v25. Results: Among 876 active PrEP users, 197 (22.4%) initiated DoxyPEP; all were MSM with a mean age of 38.9±8.5 years. Median follow-up was 18.2±12.3 and 14.0±4.9 months for pre- and post-DoxyPEP periods. Incidence rates per 100 PY for the first STI episode in the pre- and post-DoxyPEP periods were: 31.4 and 7.81 (p=0.0001) for CT, 41.5 and 28.9 (p=0.1) for NG, and 21.5 and 3.20 (p=0.0001) for SPL. NG culture was positive in 14 (29.7%) of 47 NG infections detected by PCR in the post-DoxyPEP period. All isolates were sensitive to ceftriaxone, and 6 (42%) to tetracyclines similar as those not on DoxyPEP (42 vs 46,2%, p=0.23). DoxyPEP was discontinued in 9 (4.5%) participants (4 due to adverse events, 2 due to reduced STI risk, 1 lost to follow-up, 1 for medical reasons, 1 patient decision). Microbiologic cultures for MRB were available in 158 (80.2%) participants at baseline, with 17 (10.8%) positive (15 E. coli ESBL, 2 MRSA), and in 120 (60.9%) participants at week 48, with 10 (8.3%) showing MRB (4 E. coli ESBL, 2 MRSA). Cristina Gómez-Ayerbe, Jesús Santos, Maria Lopez Jodar, Salvador Martín Cortés, Isabel Pérez-Hernández, Andrés González, Rosario Palacios Hospital Universitario Virgen de la Victoria, Málaga, Spain

Poster Abstracts

1277 Characteristics of Breakthrough Chlamydia Cases Among Cisgender Women Assigned to Doxycycline PEP Jenell Stewart 1 , Lauren R. Violette 2 , Felix Ong'era Mogaka 3 , Victor Omollo 3 , Deborah J. Donnell 4 , Josephine Odoyo 5 , Elizabeth A. Bukusi 5 , Jared M. Baeten 6 , for the dPEP Kenya Study Team 1 Hennepin Healthcare Research Institute, Minneapolis, MN, USA, 2 Harvard Medical School, Boston, MA, USA, 3 Kenya Medical Research Institute-UCSF Infectious Disease Research Training Program, Kisumu, Kenya, 4 Fred Hutchinson Cancer Center, Seattle, WA, USA, 5 Kenya Medical Research Institute, Kilifi, Kenya, 6 University of Washington, Seattle, WA, USA Background: Doxycycline postexposure prophylaxis (PEP), taken within 72 hours of condomless sexual exposure, did not reduce incident bacterial STIs

CROI 2025 422