Abstract Body

The unboosted integrase inhibitor containing single-tablet regimen (bictegravir/emtricitabine/tenofovir alafenamide, B/F/TAF) has shown efficacy and safety in HIV-1 infected patients. Bictegravir is a novel, unboosted INSTI that has been coformulated with F/TAF in an STR that has shown high rates of suppression with no resistance in phase 3 studies of treatment naïve patients. We now report Week 24 (W24) safety and efficacy of switching to B/F/TAF versus staying on baseline regimen (SBR) [elvitegravir (E)/cobicistat (C)/F/TAF, E/C/F/tenofovir disoproxil fumarate (TDF) or atazanavir (ATV)+ritonavir (RTV)+F/TDF] in an all-women, international multi-centre, randomized, open-label, phase 3 trial.

HIV‑1 infected, virologically suppressed women on a protease inhibitor or boosted elvitegravir-containing regimen were randomized (1:1) to switch to B/F/TAF or stay on baseline regimen (SBR). The primary efficacy endpoint was the proportion of women with HIV‑1 RNA >50 copies (c)/mL at W48 with 4% noninferiority margin (FDA snapshot). A secondary efficacy endpoint of HIV-1 RNA <50 c/mL at W24 is reported here. Other secondary endpoints include safety (adverse events (AEs), laboratory abnormalities). This interim W24 efficacy and safety analysis was pre-specified.

We randomized and treated 470 women (234 B/F/TAF, 236 SBR (E/C/F/TAF n=125; E/C/F/TDF n=98; ATV+RTV+FTC/TDF n=13). Demographic and baseline characteristics were balanced; overall 37% black, 28.3% white, 21.7% Asian, median age was 39 years and CD4 count was 686 cells/μl. At W24 98.7% in the B/F/TAF group vs. 99.2% in the SBR group achieved HIV-1 RNA <50 c/mL (difference -0.4% (95%CI: 3.0% to 1.9%, p=0.68). Two participants, one in each group, had resistance testing; neither developed resistance to any study drug. No participant discontinued treatment due to an AE; there were no differences between groups in grade 3 or 4 treatment-emergent AEs (3.8% B/F/TAF, 5.5% SBR group). Grade 3 or 4 laboratory abnormalities occurred in 17% of participants on B/F/TAF and 18% on SBR.

At W24 women who switched to B/F/TAF maintained high levels of virologic suppression with comparable efficacy to those who remained on a baseline regimen. B/F/TAF was safe and well tolerated. This analysis supports the efficacy and safety of B/F/TAF in women observed in other B/F/TAF phase 2 and 3 studies.