Background: Dolutegravir (DTG) plus lamivudine (2-DR) is suggested as an initial and switch option in HIV-1 treatment. Objective: To analyze the effectiveness, durability, and safety of 2-DR compared with DTG plus abacavir/lamivudine (3-DR). Methods: This was an observational, ambispective study that included all treatment-naïve (TN) and treatment-experienced (TE) patients who started 2-DR or 3-DR between July 1, 2018, and November 30, 2020. The primary end point was noninferiority, at 24 and 48 weeks, of 2-DR versus 3-DR regarding the percentage of patients with viral load (VL)≥50 and 200 copies/mL in TN (4% margin) and VL<50 and 200 copies/mL in TE (margin 12%). Durability of response, and safety were also measured. Results: 242 patients were included (53 TN and 189 TE). Two TN patients on 2-DR had VL≥50 copies/mL and 1 had VL≥200 copies/mL at week 24. In TE patients on 2-DR, 90.2% achieved VL<200 copies/mL at week 24 (difference: 3.8%; 95% CI = −6.3% to 14%) and 91.8% at week 48 (difference: 0.06%; 95% CI = −9% to 10%), meeting noninferiority criteria. Among the 53 TN patients, only 1 VF was observed in 2-DR. In TN patients, the risk of treatment discontinuation was similar between groups (hazard ratio [HR] = 0.37; P = 0.15); similar rates were also found in TE patients (HR = 0.94; P = 0.85). TE patients on 2-DR showed a better safety profile compared with 3-DR patients ( P<0.001). Conclusion and Relevance: Our results did not show noninferiority in terms of virological effectiveness. Nevertheless, all effectiveness measures support the use of 2-DR in a real-life cohort of TN and TE. Additionally, durability and safety of 2-DR were confirmed to be similar to that of 3-DR.
