Triaging dolutegravir resistance via a point-of-care urine tenofovir assay

PROJECT SUMMARY/ ABSTRACT Tenofovir (TFV)-lamivudine-dolutegravir (TLD) has been first line HIV therapy worldwide since 2018. TLD is also used as second line therapy more recently in those with a history of prior treatment experience. However, in 2024, there is evidence of increasing rates of dolutegravir (DTG) resistance globally (4-8%), with rates up to 20% among those with virologic failure and treatment experience. Integrase strand transferase inhibitor (INSTI) resistance screening worldwide is therefore an urgent global priority, although HIV drug resistance (HIVDR) is still severely rationed in most low-and-middle-income countries due to cost. HIVDR is higher among people living with HIV (PWH) with virologic failure and laboratory-confirmed exposure to ART, demonstrating that high viral loads combined with ART exposure are more likely to signal HIV drug resistance (HIVDR) due to selective drug pressure from the antiretroviral(s) on the virus to evolve. The 2023 South Africa treatment guidelines now state HIVDR testing should only be requested after 2 elevated viral loads on TLD are documented and adherence is established using one of five objective adherence metrics; 1) a urine assay to detect tenofovir (TFV); 2) DTG levels in plasma; 3) tenofovir-diphosphate (TFV-DP) levels in dried blood spots (DBS); 4) clinic attendance; 4) pharmacy refill data. Our laboratory group at UCSF recently developed a point-of-care urine TFV assay that can assess with high accuracy whether TFV was recently ingested. However, the urine assay has not been rigorously studied for the prediction of resistance in PWH failing TLD to date. We thereby propose to test the ability of the urine TFV assay to triage HIV drug resistance testing in South Africa, comparing it to other metrics and assessing cost. We will first compare the prevalence of DTG resistance among PWH with prior treatment experience failing TLD with a positive or negative urine TFV assay, with participants recruited from large HIV treatment clinics in Cape Town and Johannesburg (Aim 1). We will then compare the ability of the urine TFV assay to predict DTG resistance with other adherence measures (other drug level assays, pharmacy refills, clinic visits) listed in the South Africa treatment guidelines, hypothesizing that the harder-to-collect metrics (pharmacy refills/clinic visits) will be less predictive of DTG resistance than the three more precise drug level assays (Aim 2). We will then examine the feasibility and cost-effectiveness of the urine assay in triaging HIVDR testing, since a scalable, cost-effective tool to determine those at the highest risk of HIVDR is urgently needed. The urine TFV assay is an exciting point-of-care diagnostic test which has already shown to improve HIV prevention and treatment outcomes in high burden HIV settings. If the low-cost urine TFV assay (<$2/test) is found to be highly predictive of HIV drug resistance in our study, the assay should be added to provincial, national, and international guidelines as a cost-effective, scalable tool to triage HIV drug resistance testing in this era of increasing concern regarding DTG resistance globally.