CROI 2019 Abstract eBook

Abstract eBook

Poster Abstracts

464 VALIDATION OF A URINE TFV IMMUNOASSAY FOR REAL-TIME PrEP AND ART ADHERENCE TESTING Monica Gandhi 1 , Peter Bacchetti 1 , Hideaki Okochi 1 , Matthew A. Spinelli 1 , Jared Baeten 2 , Warren Rodrigues 3 , Guohong Wang 3 , Michael Vincent 3 , Rachel W. Kubiak 2 , Yardpiroon Tawon 4 , Virat Klinbuayaem 5 , Pra-ornsuda Sukrakanchana 4 , Oraphan Siriprakaisil 6 , Tim R. Cressey 7 , Paul K. Drain 2 1 University of California San Francisco, San Francisco, CA, USA, 2 University of Washington, Seattle, WA, USA, 3 Alere Rapid Diagnostics, Pomona, CA, USA, 4 Chiang Mai University, Chiang Mai, Thailand, 5 Sanpatong Hospital, Chiang Mai, Thailand, 6 Sanpasitthiprasong Hospital, Ubon Ratchathani, Thailand, 7 Harvard University, Boston, MA, USA Background: Pharmacologic measures are widely used to assess adherence to tenofovir (TFV) disoproxil fumarate (TDF)/emtricitabine (FTC)-based PrEP and ART. Currently-available measures in plasma, dried blood spots, hair and urine involve liquid chromatography/tandemmass spectrometry (LC-MS/MS), which is expensive and labor intensive. Only a point-of-care (POC) test can monitor and support adherence in real-time and TFV-specific antibody-based assays allow for POC adherence monitoring. We developed an immunoassay to quantify TFV in urine and validated it against the gold standard of LC-MS/MS in a large directly-observed therapy (DOT) pharmacokinetics study. Methods: The randomized TARGET study administered TDF 300mg/FTC 200mg directly-observed 7 (high adherence), 4 (moderate adherence) and 2 doses per week (low adherence) to 30 volunteers (10 per group) in Thailand, collecting urine samples over 6 weeks of administration and during wash-out. In total, 637 urine samples were collected (average 21 samples per participant). We measured urine TFV levels by the immunoassay using ELISA (lower limit of quantification LLOQ <1000 ng/ml) and by a validated LC-MS/MS-based method (LLOQ 500 ng/ml) and calculated the sensitivity and specificity of the novel assay compared to the gold standard. We calculated Spearman’s correlation between TFV levels via both assays. Results: Among all participants, median TFV urine levels were 12,000 ng/mL (IQR 7500-25,000) by the immunoassay 1 day after dosing; 5000 ng/mL (IQR 2500-8000) 2 days after dosing; 1500 ng/mL (IQR 500-2750) 3 days after dosing and below the immunoassay’s LLOQ thereafter (≥4 days). The specificity and sensitivity of the TFV immunoassay compared to the gold-standard of LC-MS/ MS were 98.8% and 87.3% respectively. The correlation between TFV levels measured by the immunoassay and LC-MS/MS in all 637 urine samples from TARGET was 0.92 (p<0.00001) (Figure). Conclusion: We have developed a novel TFV immunoassay that is highly specific (99%) and sensitive (87%), and correlates strongly with urine TFV concentrations measured by the gold standard of LC-MS/MS (rho=0.92) across a wide range of typical concentrations. TFV concentration cutoffs in urine for different degrees of adherence from this DOT study can now guide the development of an immunoassay into a POC rapid strip test. Real-time monitoring of TFV adherence using an easy-to-perform low-cost assay should allow for immediate intervention and optimization of outcomes for both HIV treatment and prevention.

Poster Abstracts

465 URINE FTC AND TFV CONCENTRATIONS AS POTENTIAL BIOMARKERS FOR ARV ADHERENCE Richard Haaland 1 , Tamee Livermont 1 , Jeffrey Fountain 1 , Chuong Dinh 1 , Amy Martin 1 , Davis Lupo 1 , LaShonda Hall 2 , Christopher Conway-Washington 2 , Colleen F. Kelley 2 1 CDC, Atlanta, GA, USA, 2 Emory Center for AIDS Research, Atlanta, GA, USA Background: Antiretroviral drug (ARV) efficacy in both treatment of chronic HIV infection and prevention of HIV infection in pre-exposure prophylaxis (PrEP) regimens is contingent on high levels of adherence to daily dosing regimens. Urine provides a potential noninvasive specimen that could be amenable to the development of rapid point of care (POC) tests to detect ARV adherence to track and improve individual adherence. This study sought to determine if urine could provide an accurate biomarker of plasma drug exposure for currently approved PrEP and HIV treatment regimens. Methods: Urine and peripheral blood were collected from 34 HIV-negative men who have sex with men aged 18-49 years enrolled in a clinical trial comparing pharmacokinetics of 2 ARV regimens. Specimens were collected 4 and 24 hours after a single oral dose of tenofovir disoproxil fumarate (TDF)/emtricitabine (FTC) (n=10) or tenofovir alafenamide (TAF)/FTC/cobicistat (COBI)/elvitegravir (EVG) (n=9), or after 4 and 10 days of daily oral TDF/FTC (n=8) or TAF/FTC/COBI/ EVG (n=7). Tenofovir (TFV), FTC, and EVG were measured by high performance liquid chromatography-mass spectrometry with a lower limit of quantification of 10 ng/mL and specific gravity was evaluated by urine dipstick analysis. Results: Median urine FTC concentrations at 4 and 24 hours were similar between men receiving TDF/FTC (4 hours 147 µg/mL; 24 hours 10 µg/mL) and men receiving TAF/FTC/COBI/EVG (4 hours 333 µg/mL, p=0.173; 24 hours 13 µg/ mL, p=0.681). However, median urine TFV concentrations were significantly reduced among men receiving TAF/FTC/COBI/EVG (4 hours 1.2 µg/mL; 24 hours 0.8 µg/mL) compared to men receiving TDF/FTC (4 hours 17 µg/mL, p<0.001; 24 hours 7 µg/mL, p=0.001). Urine FTC, but not TFV or EVG, concentrations suggested recent dosing among all men receiving daily dosing as values were greater than minimum concentrations observed 24 hours following a single dose. Urine FTC concentrations, but not TFV or EVG, were correlated with plasma concentrations for all study participants at all visits (r=0.766, p<0.001). Urine FTC (p=0.022) and TFV (p=0.039) concentrations were associated with specific gravity measures. Conclusion: Urine FTC levels, but not TFV or EVG, may provide a good surrogate for plasma FTC concentrations and could be useful in developing POC tests to assess adherence. These results suggest urine may provide an appropriate noninvasive specimen type for measuring adherence to FTC-containing regimens used in HIV treatment and prevention.

CROI 2019 171