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Background Nowadays, the INSTI-based regimens with bictegravir (BIC) and dolutegravir (DTG) represent the cornerstone of antiretroviral treatment (ART). Our study aimed to investigate the durability of bictegravir/emtricitabine/tenofovir alafenamide (B/F/TAF) and DTG-based regimens and their safety in a real-life setting.Methods Consecutive people with HIV (PWH) enrolled in the SCOLTA project who either initiated their first ART with, or switched to a regimen containing BIC or DTG combination were included. DTG-based regimens comprised 2-drug regimens (2DR) with atazanavir, darunavir, rilpivirine or lamivudine (3TC) and 3-drug regimens (3DR) with 3TC/abacavir, F/TAF or F/TDF. PWH were followed up until treatment discontinuation and grade 3-4 adverse events (AE) were recorded. The observation was truncated to 48 months. Hazard ratios (HRs) and 95% confidence intervals (CIs) for discontinuation were estimated using the Cox proportional hazards model. A multivariate model including all variables that differed significantly between treatment groups or were associated with treatment interruptions was run, with a retention criterion set at p=0.20. A competitive model was also performed for each cause of discontinuation.Results Of 2668 enrolled PWH, 2359 were treated with one of the included regimens and had at least one follow-up visit: 1002 in B/F/TAF (42.3%), 595 (25.2%) in DTG-2DR and 762 (32.3%) in DTG-3DR regimens. In the DTG-2DR group, the most represented regimens were DTG/3TC (382, 64.2%) and DTG/RPV (134, 22.6%); in the DTG-3DR group, it was DTG/3TC/ABC (445, 58.4%). The baseline characteristics are reported in table 1.Forty-eight months after the study started, 199 (19.8%), 113 (19.0%) and 256 (33.6%) respectively discontinued the cohort treatment (reference B/F/TAF: HR 0.86, 95% CI 0.68-1.10 for DTG-2DR, HR 1.18, 95% CI 0.98-1.43 for DTG-3DR). In the multivariate model for any cause discontinuation (including sex, CD4, risk factor for HIV acquisition, CDC stage, naïve status, HIVRNA at T0, dyslipidemia and current ART regimen), higher CD4 at T0 were associated with lower risk. In contrast, female sex, past intravenous drug use, naïve status and entering the study with previous ART treatment but detectable HIVRNA were associated with higher risk of discontinuation.In the competitive model, no difference emerged between treatment in the risk of discontinuation due to switch to LA, treatment failure, loss to follow-up or death. On the contrary, risk was higher in the DTG-3DR group (aHR 3.17, 95% CI 2.13-4.70) when discontinuation was due to AEs and lower in the DTG-2DR group when due to simplification (aHR 0.26, 95% CI 0.13-0.54) (table 2).Conclusions In our cohort, a similar durability and safety profile was observed for BIC and DTG. Discontinuations due to adverse events were more frequent in the DTG-3DR group. These findings highlight that regimen composition may influence treatment interruptions beyond the choice of INSTI.Abstract P20 Table 1Main characteristics of 2359 PWH enrolled in the Bictegravir and Dolutegravir SCOLTA cohortsAbstract P20 Table 2Reasons for 568 discontinuations