Emergent resistance-associated mutations at first- or second-line HIV-1 virologic failure with second-generation InSTIs in two- and three-drug regimens: the Virostar-1 study.

Background: Second-generation integrase strand transfer inhibitors (InSTIs) have a high barrier to resistance and potent antiretroviral activity. They are recommended as first- or second-line (FL and SL) options in two- and three-drug regimens (2DR and 3DR) in international treatment guidelines. However, there are limited real-world data on emerging resistance at the time of virological failure (VF) with these regimens.

Objectives: The Virostar-1 study objective is to analyse the emergence of resistance-associated mutations (RAMs) over 3 years with DTG-based 2DRs and DTG- or bictegravir (BIC)-based 3DRs in people living with HIV (PLWH) experiencing a VF (FL or SL).

Methods: Retrospective analysis of genotypic resistance detected at the time of a FL or SL VF with BIC/FTC/TAF, DTG/ABC/3TC, DTG/3TC and DTG/RPV between 2019 and 2022 was conducted from a French multicentre database. VF was defined as two consecutive HIV-1 plasma viral loads > 50 c/mL. Sanger assays were performed at VF within standard clinical care. Resistance mutations were reported using the ANRS algorithm. Selection biases prevent group comparisons.

Results: During the period, N = 5986 PLWH were followed either in FL or SL. The VF rate was overall low: BIC/FTC/TAF, 6.8%; DTG/ABC/3TC, 7.5%; DTG/3TC, 5.1%; and DTG/RPV, 2.1%. Some emergent InSTI or NRTI RAMs were detected with BIC/FTC/TAF 4%, DTG/ABC/3TC 8.5%, DTG/3TC 18% and 39% emergent NNRTI RAMs with DTG/RPV. However, a complete absence of dual resistance against NRTIs and InSTIs was observed.

Conclusions: We detected rare emergent InSTI RAMs and few emergent NRTI RAMs in PLWH failing DTG- or BIC-based regimens in FL or SL. The observed rates of emergent RAMs at VF were 4% with BIC/FTC/TAF, 8.5% with DTG/ABC/3TC, 18% with DTG/3TC and 39% with DTG/RPV.