Real world efficacy of dolutegravir plus lamivudine in people living with HIV with undetectable viral load after previous failures

Background: Dolutegravir (DTG) +lamivudine (3TC) combination has been found to be as effective as triple therapies, and has been extensively prescribed in clinical practice as a maintenance therapy. We aimed to investigate the effect of previous virological failures (VFs) on virological efficacy. Methods: The analysis included data of people living with HIV (PLWH) with HIV-RNA ≤50 copies/mL enrolled in an Italian retrospective multicohort study who were switching to DTG+3TC. Primary endpoint was viral rebound (VR; confirmed HIV-RNA ≥50 copies/mL or single HIV-RNA ≥50 copies/mL followed by change of antiretroviral therapies [ART]). Kaplan-Meier curves were used to estimate probabilities of VR based upon histories of previous VFs (single HIV-RNA ≥1000 copies/mL or confirmed HIV-RNA ≥50 copies/mL). A weighted Cox regression model was fitted to estimate the causal hazard ratio (HR) of history of failure on the risk of VR. Results: A total of 966 PLWH were included; 20.1% had a history of previous VF. VR was detected in 23 PLWH. The one-year probability was 1.2% (95% confidence interval [CI], 0.2%–2.2%) in PLWH without previous VF and 3.3% (95% CI, 0.4%–6.2%) in those with ≥1 VF (log-rank P = 0.042). By multivariate analysis adjusted for CD4+ cell count at nadir, duration of virological suppression, and mode of HIV transmission, PLWH with ≥1 previous VF had a higher risk of virological rebound than those without previous VF (adjusted hazard ratio 3.06 [95% CI, 1.00–9.44], P = 0.051). Conclusion: Despite the low absolute one-year risk in both groups, real-world data confirmed that PLWH with a previous failure have an increased risk of viral rebound.