CROI 2025 Abstract eBook

Abstract eBook

Poster Abstracts

1217 Factors Associated With PrEP Uptake, Persistence, and Adherence Among Incarcerated People in Zambia Brianna R. Lindsay-Renninger 1 , Cassidy W. Claassen 1 , Muyunda Siyambango 2 , Linah K. Mwango 3 , Caitlin Baumhart 1 , Nasho Nyirongo 3 , Morley Mujansi 3 , Clement Moonga 2 , Godfrey Muchanga 4 , Chiti Bwalya 5 , Monica Gandhi 6 , Maurice Musheke 2 , Michael E. Herce 7 1 University of Maryland, Baltimore, MD, USA, 2 Center for Infectious Disease Research in Zambia, Lusaka, Zambia, 3 Ciheb Zambia, Lusaka, Zambia, 4 Maryland Global Initiatives Corporation, Lusaka, Zambia, 5 University of Maryland, College Park, College Park, MD, USA, 6 University of California San Francisco, San Francisco, CA, USA, 7 CIDRZ / University of North Carolina, Chapel Hill, NC, USA Background: For justice-involved people, the times during and immediately after incarceration can be high-risk periods for HIV acquisition since these periods afford limited access/adherence to effective HIV prevention. We report results from one of the first longitudinal studies to characterize PrEP use among justice-involved people in sub-Saharan Africa. Methods: From August 2023—March 2024, we enrolled a cohort of PrEP users and non-users across four correctional facilities in Lusaka, Zambia. HIV-negative incarcerated persons were offered oral tenofovir (TFV)-based PrEP by the health system, and then approached by study staff for participation. Consenting participants were followed from incarceration through community release for HIV seroconversion and PrEP outcomes, including uptake, persistence, and adherence. Follow-up visits were scheduled at 1, 3, 6, 9 and 12 months after enrollment and a randomly selected sub-cohort of participants on PrEP underwent urine TFV screening for objective adherence monitoring. We used logistic regression to examine factors associated with PrEP outcomes. Results: A total of 706 participants enrolled, with an average age of 28.6 years, majority (672; 95%) male and less than a third (200; 28%) with secondary education. Of 531 (75%) eligible to start PrEP, 326 (61%) initiated PrEP at enrollment. Participants were significantly more likely to initiate PrEP at enrollment if they were sentenced (OR: 1.8, 95% CI:1.3-2.5) vs awaiting trial, had heard of PrEP (OR: 2.3, 95% CI:1.6-3.3) or had greater worry about acquiring HIV in prison (OR 1.1, 95% CI:1.0-1.3). Of 101 persons initiating PrEP at enrollment with a 6-month follow-up visit, 54 (54%) were on PrEP. A total of 59 (29%) of 202 urine TFV screening tests at follow-up indicated adequate adherence. Self-reported PrEP adherence had a positive predictive value of 0.71 (95% CI:0.59-0.80) and negative predictive value of 0.97 (95% CI:0.92-0.99) compared to urine TFV. Two participants seroconverted (0.3%)—one in a PrEP user who had discontinued—and were linked to treatment. Women were 15.7 (95% CI:2.5-304) times as likely than men to persist on PrEP at 6 months. Conclusions: Initial results suggest high PrEP uptake among incarcerated people in Zambia, particularly among those who had heard of PrEP before. PrEP adherence adjudicated objectively was low (29%) as was persistence, which was higher among women. Our preliminary findings point to the need for differentiated prevention services in this group, especially for men. The figure, table, or graphic for this abstract has been removed. 1218 Trends in 2016 CDC-Recommended PEP Regimens and Bictegravir for HIV PEP: United States, 2015-2023 John Le, Weiming Zhu, Ya-Lin A. Huang, Jesse O'Shea, Laura M. Mann, Karen W. Hoover, Athena Kourtis, Mary Tanner Centers for Disease Control and Prevention, Atlanta, GA, USA Background: Postexposure prophylaxis (PEP) is critical for HIV prevention because it is the only intervention that can prevent HIV acquisition following an exposure. 2016 CDC PEP guidelines recommend specific regimens for PEP. A recent report found increasing off-label use of bictegravir for PEP. Bictegravir is a second-generation integrase inhibitor approved for HIV treatment in 2018 that is not one of the CDC PEP guidelines recommended regimens. Our objective was to analyze national trends in the use of 2016 CDC recommended regimens and bictegravir for PEP and to describe PEP user characteristics. Methods: We analyzed data from the IQVIA Real World Data—Longitudinal Prescriptions database and updated a validated algorithm to identify persons aged ≥16 years prescribed PEP from 2015−2023. Among those prescribed an antiretroviral (ARV) medication, we used the validated algorithm to exclude persons with prescriptions for PrEP or hepatitis B treatment. We also excluded persons with a prior or concurrent HIV diagnosis from 2015–2023, an ARV prescription with >30 days of supply, or any prior ARV prescription record. Two clinicians independently reviewed the regimens and determined probable PEP

cases. We reported the annual number of PEP users, stratified by regimen type, days of supply, and PEP user demographic characteristics. Results: During 2015−2023, the annual number of persons prescribed PEP ranged from 38,059−49,525. In 2023, 88.1% of PEP prescriptions were a full course for 28−30 days and 12.0% for shorter durations. The number of persons prescribed bictegravir for PEP increased from 3,525 (7.3%) in 2018 to 15,048 (30.4%) in 2023. While CDC-recommended PEP regimens were prescribed equally for men and for women, bictegravir was prescribed predominantly for men (72.9%). Nearly half of individuals prescribed bictegravir for PEP were from the South (48.5%). Conclusions: The increasing use of bictegravir for PEP reflects a shift in prescribing behavior, likely because of its dosed once daily, tolerability, and efficacy in PEP. Our finding of increased bictegravir use can inform future recommendations for PEP medications. Not all PEP users were prescribed a full course of PEP. It is important to ensure that persons prescribed PEP starter-packs be supported to follow-up for a full course.

Poster Abstracts

1219 Impact of Initiation Delay, Duration, and Prior PrEP Usage on FTC/ TDF-Containing PEP Efficacy Max von Kleist 1 , Lanxin Zhang 1 , Julie Fox 2 , Simon Collins 3 1 Robert Koch Institute, Berlin, Germany, 2 King's College London, London, UK, 3 HIV i-Base, London, UK Background: Pre- and post-exposure prophylaxis (PrEP and PEP) are key strategies to prevent HIV infection. While the efficacy of PrEP has been elucidated in many randomized clinical trials, corresponding data for PEP is challenging to obtain in a controlled setting. Consequently, it is almost impossible to study the impact of PEP initiation delay and PEP duration on HIV risk reduction clinically to inform PEP recommendations. Methods: We employed pharmacokinetics, pharmacodynamics, and viral dynamics models, incorporating individual factors such as self-start PEP and PEP adherence to investigate the impact of initiation delay and PEP duration on HIV risk reduction. We evaluated PEP using two- and three-drug regimens with an FTC/TDF backbone. Moreover, we study PEP efficacy in the context of PrEP-to-PEP transitions. Results: Our simulations indicate that early initiation of PEP is critical for reducing HIV transmission risk. We found that 2-drug (FTC/TDF) PEP may offer insufficient protection when initiated >1hour post-exposure. When adding dolutegravir (DTG) as a third drug, early initiation was still a critical factor, however, ≈90% efficacy could be achieved when PEP was initiated within 48 hours post-exposure and taken for at least 28 days. If 2-drug (FTC/TDF) PEP was initiated within 24hours post-exposure, DTG may be added several days later to still achieve >90% protection. When investigating PrEP-to-PEP transitions, we observed that preceding PrEP can (i) contribute directly to prophylactic efficacy, and (ii) boost subsequent PEP efficacy by delaying initial viral dynamics and building-up drug concentrations, overall facilitating self-managed transitioning between PrEP and PEP. Conclusions: Our study confirms the critical role of early (<48hours) PEP initiation, preferably with three drugs taken for 28 days. Self-starting with TDF/FTC and later addition of a third drug is better than not self-starting. Furthermore, our study highlights the synergy between recent PrEP intake and PEP, where we find that two drug PEP may be possible in situations where PrEP had recently been taken by the exposed individual.

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