CROI 2025 Abstract eBook

Abstract eBook

Poster Abstracts

Methods: We collected oral fluids from HIV-negative adults randomized to 2 or 4 or 7 doses/week with FTC/Tenofovir Disoproxil Fumarate for directly observed oral PrEP. Drug concentrations were measured using liquid chromatography tandem mass spectrometry. Drug levels below the limit of detection (LOD: 5 ng/mL) were considered as undetectable (0 ng/mL). Readouts below the limit of quantification (LOQ: 10 ng/mL) but above the LOD were imputed as half of the LOQ. Generalized Estimating Equations were used to examine associations between FTC/TFV detectability and the three dimensions of PrEP adherence: dosing recency (hours since last dose taken), cumulative dosing time (weeks since first dose), and dosing frequency (number of doses per week). We also assessed the diagnostic accuracy of FTC levels in oral fluids for predicting daily oral PrEP non-adherence(defined as having a time since last dose >24 hours). Results: 241 oral fluid specimens from 22 participants (41% female) were included. Among 165 oral fluid specimens with a time since last dose within 48 hours, 15 (9.0%) had detectable TFV, and 88 (53.3%) had detectable FTC. Median (interquartile range) FTC concentrations were 15 (0-141) ng/mL for 115 oral fluid specimens with time since the last dose ≤24 hours, and 0 (0-11) ng/ mL for 50 oral fluid specimens with time since the last dose between 24 and 48 hours. Oral specimens collected between 24 and 48 hours since the last oral PrEP dose had significantly lower odds of having detectable FTC (odds ratio: 0.21, 95% CI: 0.11-0.38), as compared to specimens collected within 24 hours since the last oral PrEP dose. An FTC threshold of <7.5 ng/mL achieved a sensitivity of 90% (95% CI: 84%-94%) and a specificity of 65% (95% CI: 57%-74%) to identify recent PrEP non-adherence with one daily dose missed. Conclusions: FTC can be detected in oral fluids and its absence may provide a reliable pharmacologic marker identifying non-adherence to daily PrEP dosing. TFV concentrations in oral fluids were low making it unsuitable for PrEP adherence monitoring. The figure, table, or graphic for this abstract has been removed. 1214 Are Sex-Specific Cutoffs Needed With a Next-Gen Urine Tenofovir Assay for Adherence Monitoring? Xin Niu 1 , Derin Sevenler 2 , Sandy Dossantos 2 , Mehmet Toner 2 , Rebecca Sandlin 2 , Oraphan Siriprakaisil 3 , Pra-Ornsuda Sukrakanchana 4 , Tim Cressey 4 , Paul Drain 1 1 University of Washington, Seattle, WA, USA, 2 Massachusetts General Hospital, Boston, MA, USA, 3 Sanpatong Hospital, Chiang Mai, Thailand, 4 Chiang Mai University, Chiang Mai, Thailand Background: Females may require higher oral Pre-exposure Prophylaxis (PrEP) adherence to achieve equivalent therapeutic drug concentrations compared to males, suggesting the need for sex-specific cutoffs for rapid urine tenofovir (TFV) assays. We developed a next-gen urine TFV Lateral Flow Assay (LFA) without a predefined threshold to (1) determine if the quantified LFA readouts differ between females and males with the same adherence levels, and (2) to evaluate its diagnostic performance for detecting non-adherence across sexes. Methods: Using a next-gen urine TFV LFA, we tested urine samples from HIV-negative adults randomized to 2 or 4 or 7 doses/week of Emtricitabine/ Tenofovir Disoproxil Fumarate for directly-observed oral PrEP. We obtained the averaged visual scores of the LFA test line from two operators using a graded color intensity reference card. Optical readings of the test and control line were objectively measured by an LFA reader. We assessed the effect of sex on LFA readouts among adherent samples with a dose taken in the prior day using Generalized Estimating Equations. We calculated the overall and sex-specific sensitivities/specificities for recent non-adherence defined as no dosing in the prior day. Results: A total of 586 urine specimens were evaluated from 28 participants. Among 139 urine samples with a dose taken in the prior day, males had 33% lower ( p <0.01) optical readings, and a 1.82 unit lower ( p <0.01) averaged visual score of the LFA test line, when compared to females. With the same cutoffs (>705) for the test line optical reading, we found similar sensitivities (86% vs 86%) and specificity (100% vs 95%) among males versus females. With similar specificities (97% vs 92%), the sensitivity among females (82%, 95% confidence interval (CI): 77-88%) was slightly higher than that among males (76%, 95% CI: 71-81%) when using the same cutoff (>1.25) for the averaged visual score. The ratio of the LFA test/control line optical readings (>0.095) was highly sensitive (93%, 95% CI: 91-95%) for detecting non-adherence as early as missing one dose, while maintaining a high specificity (96%, 95% CI: 93-99%) in the total population. Conclusions: While females showed higher LFA readouts (indicating lower urine TFV levels) than males, sex-specific cutoffs for a next-gen TFV LFA

p<0.01). In longitudinal models, higher adherence score was associated with a greater likelihood of a positive urine assay (adjusted relative risk [aRR]: 1.12; 95% confidence interval [CI]: 1.08-1.17; p<0.01) and detectable TFV in hair (aRR: 1.02; 95% CI: 1.00-1.04; p=0.02). Conclusions: Associations between self-reported and biomarker-verified PrEP adherence indicate that women in this cohort were able to accurately report pill-taking. Self-reported adherence using validated items may be able to more accurately identify PrEP use patterns in contexts where women know their adherence is being monitored periodically with biomarkers. 1212 Point-of-Care Urine Tenofovir Feedback Counseling Improves PrEP Adherence for US MSM in Pilot RCT Matthew A. Spinelli 1 , Leah Davis Ewart 2 , Emily Ross 2 , Megan J. Heise 1 , Renata Buccheri 3 , Shivani Mahuvakar 1 , David Glidden 1 , K. Rivet Amico 4 , Emily Arnold 1 , Guohong Wang 5 , Hideaki Okochi 1 , Jennifer Manuel 1 , Susan Buchbinder 6 , Adam Carrico 2 , Monica Gandhi 1 1 University of California San Francisco, San Francisco, CA, USA, 2 Florida International University, Miami, FL, USA, 3 Vitalant Research Institute, San Francisco, CA, USA, 4 University of Michigan, Ann Arbor, MI, USA, 5 Abbott Laboratories, Green Oaks, IL, USA, 6 San Francisco Department of Public Health, San Francisco, CA, USA Background: Young men who have sex with men (YMSM) have high HIV incidence and challenges with PrEP adherence. Point-of-care (POC) urine tenofovir (TFV) testing permits real-time objective adherence monitoring at a low cost. A prior study with PrEP-using women in Kenya demonstrated improved long-term adherence when women had motivational interviewing (MI)-informed drug-level feedback using the POC test in the clinic. We adapted and pilot tested a 2-session, MI-informed intervention with POC self-testing and remote counseling. Methods: Participants (age<30; n=49) who reported daily oral PrEP (F/TDF or F/TAF) use were recruited remotely from the Grindr application and randomized 2:1 to a 2 session MI-informed POC drug-level feedback counseling intervention delivered remotely by psychologists versus standard of care over a 3-month period. Urine POC tests were mailed to participants and self-administered before each session, informing the counseling. Self-collected hair samples were analyzed for TFV at baseline and 3 months using liquid chromatography/tandem mass spectrometry. GEE models analyzed the change in hair TFV levels over time comparing the intervention and control groups. Results: Overall, the participants (n=49; 31 intervention/18 control) had a median age of 26 (IQR: 23-29) years; 30% were Hispanic, 26% were Black; and 46% used F/TAF. Of 31 intervention participants, 100% successfully self-administered the urine test and 100% reported the intervention was somewhat/very acceptable. Over the 3 months of the intervention, there was a 0.01 ng/mg increase in hair TFV levels in the intervention group when compared to the control group (95% CI: 0.00-0.18; p=0.04). This degree of change in hair TFV levels in the intervention group translates to ~1-2 more PrEP tablets per week. Among those with <4 doses/week adherence at baseline, 6 of 8 of the intervention participants increased above 4 doses/week compared to 0 of 4 participants in the control group. Conclusions: In a diverse sample of YMSM using daily oral F/TDF or F/TAF PrEP, a pilot RCT of a telehealth MI-informed POC urine TFV testing intervention demonstrated preliminary efficacy for biologically verified increases in long term adherence, assessed via hair TFV levels. Given the low-cost of the POC test, the remote nature of the intervention, and increasing use of telehealth to provide PrEP care, this approach could be scaled nationally and implemented outside of in-person clinic settings if more definitive RCTs provide evidence of efficacy. 1213 Oral Fluid Concentrations of Tenofovir and Emtricitabine for Antiretroviral Adherence Monitoring 1 University of Washington, Seattle, WA, USA, 2 Centers for Disease Control and Prevention, Atlanta, GA, USA, 3 Sanpatong Hospital, Chiang Mai, Thailand, 4 Chiang Mai University, Chiang Mai, Thailand Background: Adherence monitoring using drug concentrations for oral Pre exposure Prophylaxis (PrEP) can identify people who need additional adherence support interventions or a transition to long-acting injectable regimens. Oral fluids are widely accepted as a convenient and confidential specimen type for HIV self-testing. This study evaluated the feasibility of detecting emtricitabine (FTC) and tenofovir (TFV) in oral fluids to monitor daily oral PrEP adherence. Xin Niu 1 , Eric Edwards 2 , Jeannette Dienhart 2 , Richard Haaland 2 , Oraphan Siriprakaisil 3 , Pra-Ornsuda Sukrakanchana 4 , Tim Cressey 4 , Paul Drain 1

Poster Abstracts

CROI 2025 399