Virologic efficacy of tenofovir, lamivudine and dolutegravir as second-line in adults failing a tenofovir-based first-line regimen: a prospective cohort study

OBJECTIVE Recycling tenofovir and lamivudine/emtricitabine (XTC) with dolutegravir would provide a more tolerable, affordable, and scalable second-line regimen than dolutegravir with an optimized nucleoside reverse transcriptase inhibitor (NRTI) backbone. We evaluated efficacy of tenofovir/lamivudine/dolutegravir (TLD) in patients failing first-line tenofovir/XTC/efavirenz or nevirapine. DESIGN Single arm, prospective, interventional study. SETTING Two primary care clinics in Khayelitsha, South Africa. PARTICIPANTS 60 adult patients with two viral loads (VL)>1000 copies/mL. INTERVENTION Participants were switched to TLD with additional dolutegravir (50 mg) for two weeks to overcome efavirenz induction. PRIMARY OUTCOME Proportion achieving VL<50 copies/mL at week 24 using the FDA snapshot algorithm. RESULTS Baseline median CD4 count was 248 cells/mm3, VL 10580 copies/mL and 48/54 (89%) had resistance (Stanford score ≥15) to one or both of tenofovir and XTC. No participants were lost to follow-up. At week 24, 51/60 (85%, 95% CI 73-93%) were virologically suppressed, six had VL 50-100 copies/mL, one VL 100-1000 copies/mL, one no VL in window, and one switched due to tenofovir-related adverse event. No integrase mutations were detected in the one participant meeting criteria for resistance testing. Virological suppression was achieved by 29/35 (83%, 95% CI 66-93%) with resistance to tenofovir and XTC, 11/13 (85%, 95% CI 55-98%) with resistance to XTC, and 6/6 (100%, 95% CI 54-100%) with resistance to neither. CONCLUSION A high proportion of adults switching to second-line TLD achieved virologic suppression despite substantial baseline NRTI resistance and most not suppressed had low-level viraemia (≤100 copies/mL). This suggests recycling tenofovir and XTC with dolutegravir could provide an effective second-line option.