Incidence of low-level viremia and its impact on virologic failure among people living with HIV-1 who switched to elvitegravir-based antiretroviral therapy.

OBJECTIVES:We aimed to investigate the incidence of low-level viremia (LLV) and its impact on virologic failure (VF) in people living with HIV (PLWH) on stable antiretroviral therapy (ART) who switched to co-formulated elvitegravir, cobicistat, emtricitabine and tenofovir alafenamide (EVG/c/FTC/TAF). METHODS:PLWH aged 18 years or older who had received ART with plasma HIV RNA load (PVL) <50 copies/mL for 6 months or longer and switched to EVG/c/FTC/TAF between March and October 2018 were retrospectively included. The incidence of LLV (defined as PVL of 50-999 copies/mL) and VF (PVL ≥1000 copies/mL) was calculated and represented by Kaplan-Meier plots. The generalised estimating equation model was constructed to identify factors associated with LLV and VF. Resistance-associated mutations were determined using population sequencing. RESULTS:A total of 1078 PLWH were included. The incidence rates of LLV and VF after the switch to EVG/c/FTC/TAF were 3.5 and 0.8 events per 100 person-years of follow-up, respectively, whereas the respective cumulative incidence of LLV and VF reached 11.7% and 2.9% within 3 years of follow-up. LLV was associated with any LLV episode before or after the switch and prior exposure to integrase strand transfer inhibitor-based ART. VF was associated with any LLV before or after the switch and prior exposure to raltegravir, but not the level or frequency of LLV. CONCLUSION:The risks of LLV and VF were low in PLWH who had achieved virologic suppression and switched to EVG/c/FTC/TAF, and the presence of LLV and prior exposure to raltegravir increased the risk of VF.