Efficacy of dolutegravir plus lamivudine in treatment-naive people living with HIV without baseline drug-resistance testing available (D2ARLING): 48-week results of a phase 4, randomised, open-label, non-inferiority trial.

BACKGROUND Dolutegravir plus lamivudine has emerged as a preferred treatment for HIV; however, initiating this regimen without baseline resistance testing raises concerns about the potential presence of pretreatment lamivudine resistance. We aimed to evaluate the efficacy of dolutegravir plus lamivudine in the absence of information on baseline resistance testing in treatment-naive people with HIV. METHODS We did an open-label, non-inferiority, single-centre, phase 4, randomised controlled study (D2ARLING), designed to assess the efficacy and safety of dolutegravir plus lamivudine in treatment-naive people with HIV with no available baseline resistance testing. We included participants aged 18 years or older with HIV-1 diagnosis who were naive to antiretroviral therapy and had no baseline genotypic resistance testing result available. We randomly assigned (1:1) participants to receive dolutegravir 50 mg plus lamivudine 300 mg or a three-drug regimen including dolutegravir 50 mg plus tenofovir disoproxil fumarate 300 mg and either emtricitabine 200 mg or lamivudine 300 mg. Randomisation was stratified by baseline HIV-1 RNA (≤100 000 vs >100 000 copies per mL) and CD4 cell count (<200 vs ≥200 cells per μL). Per protocol, we performed genotypic drug-resistance testing on day 1 and it remained double-masked throughout the study, simulating a scenario of inaccessibility of baseline resistance testing. The primary endpoint was the proportion of participants with plasma HIV-1 RNA less than 50 copies per mL at week 48 (intention-to-treat exposed analysis via the Snapshot algorithm) with prespecified non-inferiority margin of 10%. This trial is registered with ClinicalTrials.gov (NCT04549467). FINDINGS Between Nov 17, 2020, and Aug 31, 2022, 214 participants were randomly assigned to and treated with dolutegravir plus lamivudine (n=106) or dolutegravir plus tenofovir disoproxil fumarate and either emtricitabine or lamivudine (n=108). Median age of participants was 31 years (IQR 26-39) and 49 (23%) were female. At baseline, 66 (31%) of participants had an HIV-1 RNA viral load of more than 100 000 copies per mL, and 44 (21%) had a CD4 T-cell count of less than 200 cells per μL. At week 48, 97 (92%) of 106 participants in the dolutegravir plus lamivudine group and 96 (89%) of 108 participants in the dolutegravir plus tenofovir disoproxil fumarate with either emtricitabine or lamivudine group had HIV-1 RNA of less than 50 copies per mL (difference 2·62%; 95% CI -5·3 to 10·6), showing non-inferiority of dolutegravir plus lamivudine to the three-drug regimen. None of the participants in the dolutegravir plus lamivudine group and two in the control group had protocol-defined virological failure, and none developed treatment-emergent resistance mutations to any of the study drugs. Overall adverse event rates were similar between arms. Less than 1% of participants in both groups were discontinued due to adverse events. INTERPRETATION This study provides evidence supporting the non-inferiority of dolutegravir plus lamivudine compared with a preferred three-drug regimen in treatment-naive individuals without baseline resistance testing. These findings suggest that baseline resistance testing might not be a requirement for initiating treatment with dolutegravir plus lamivudine in settings with low frequency or suspicion of transmitted drug resistance to these drugs. FUNDING ViiV Healthcare.